Time-to-Digital Converter Target Specification TDC-GP2 2-channel Universal Time-to-Digital Converter 26th May 2010 Document-No.: DB_GP2_e V2.0 TDC TDC-GP2 Published by acam-messelectronic gmbh (c) acam-messelectronic gmbh 2010 Disclaimer / Notes The information provided by this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by acam for its use, nor for any infringements of patents or other rights of third parties that may result from its use. The information is subject to change without notice and is provided as is" without warranty of any kind (expressed or implied). Picostrain is a registered trademark of acam. All other brand and product names in this document are trademarks or service marks of their respective owners. Support For a complete listing of direct sales, distributors and sales representatives visit the acam website at: http://www.acam.de/company/distributors For technical support you can contact the acam support team in the headquarter in Germany or the Distributor in your country. The contact details of acam in Germany are: sales@acam.de 1 or by phone +49-7244-74190. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 Table of Contents 1-4 1 Overview 2 Characterisitcs & Specifications 2.1 Electrical Characteristics 2-1 2.2 Timings 2-3 2.3 Pin Description 2-6 2.4 Package Drawings 2-7 2.5 Power Supply 2-8 2.6 Register settings 3 Measurement Mode 1 4 Measurement Mode 2 5 Details and Special Functions 2-10 3.1 General Description 3-1 3.2 Measurement Flow 3-2 4.1 General Descriptionweis 4-1 4.2 Measurement Flow 4-2 4.3 Stop Masking 4-7 5.1 Oscillator 5-1 5.2 Fire-pulse Generator 5-4 5.3 Temperature Measurement 5-7 5.4 SPI-interface 5-10 5.5 Fast Initialization 5-11 5.6 Noise Unit 5-11 6 Applications 6-1 7 Miscellaneous 7-1 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2 Time-to-Digital-Converter 3 TDC-GP2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 1 Overview 1.1 Introduction TDC-GP2 is the next generation of acam generalpurpose TDCs. Higher resolution and smaller package size make it ideal for cost sensitive industrial applications. With special functional blocks like a fire-pulse generator, stop-enable, temperature measurement, and clock control it is perfectly suited for ultrasonic flow-meter and heat-meter applications. 1.2 Features Measurement Mode 1 Temperature Measurement 2 channels with typ. 50 ps resolution rms 2 or 4 sensors Measurement range 3.5 ns to 1.8 s (0 to PT500/PT1000 or higher 1.8s between stop channels) 15 ns pulse-pair resolution with 4-fold multihit capability Very high resolution: 16 Bit eff. (0.004 C resolution for platinum sensors) Ultra low current (0.08 A when measuring 4 events can be measured arbitrarily against every 30 seconds) each other Trigger to rising or/and falling edge General Windowing for precise stop enable QFN 32 package I/O voltage 1.8 V to 5.5 V Measurement Mode 2 Core voltage 1.8 V to 3.6 V 1 channel with typ. 50 ps resolution rms 1 MHz continuous data rate max. Measurement range 500 ns to 4 ms Temperature range - 40 C to 125 C 2 x CLKHS pulse-pair resolution with 3-fold 4 wire SPI interface multihit capability Fire pulse generator Trigger to rising or/and falling edge Clock calibration unit Each of the 3 events can be assigned to an Precise stop enable by windowing adjustable measuring window with 10ns reso- Trigger to rising and/or falling edge lution acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 1-4 Time-to-Digital-Converter 1.3 1-5 TDC-GP2 Blockdiagram acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 2 Characterisitcs & Specifications 2.1 Electrical Characteristics Absolute Maximum Ratings Supply voltage Vcc vs. GND - 0.3 to 4.0 V Vio vs. GND - 0.3 to 7.0 V Continous current into Output-Pin (Iout) 30 mA Storage temperature (Tstg) - 65 to 150 C Junction temperature (Tj) max.125 C Recommended Operating Conditions Symbol Parameter Conditions Min Vcc Core supply voltage* Vio > Vcc Vio I/O supply voltage tri Max Unit 1.8 3.6 V 1.8 5.5 V Normal Input Rising Time 50 ns tfa Normal Input Falling Time 50 ns tri Schmitt Trigger Rising Time 5 ms tfa Schmitt Trigger Falling Time 5 ms Ta Ambient Temperature 120 C Tj must not exceed Typ -40 125C *including the oscillator pins XIN, XOUT, Clk32In, Clk32Out DC Characteristics (Vio = Vcc = 3.3 V 0.3 V, Tj = -40 to +85C) Symbol Parameter Conditions I32 Current 32 kHz Icc + Iio, only 32kHz os- Min Typ Max Unit 4.5 A 260 A 15 mA <150 nA cillator running, Vcc = 3.6 V Ihs Current 4 Mhz Icc + Iio, only ClkHS running cont. at 4MHz, Vcc = 3.6 V Itmu Iddq Current time measuring only during active time unit measurement Quiescent current all clocks off, Vio = Vcc = 3.6 V @ 85 C Il Input Leakage Current Voh High Level Output Voltage -1 Ioh= tbd mA Vio=Min. +1 Vio- A V 0.4 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-1 Time-to-Digital-Converter Symbol Parameter Conditions Vol Low Level Output Voltage Iol = tbd mA, Vio=Min Vih High Level Input Voltage LVTTL Level, Vio = Max. Vil Low Level Input Voltage LVTTL Level, Vio = Min. Vth High Level Schmitt Trigger TDC-GP2 Min Typ Max Unit 0.4 V 2.0 V 0.8 V 1.1 2.4 V 0.6 1.8 V Voltage Vtl Low Level Schmitt Trigger Voltage Vh Schmitt Trigger Hysteresis 0.1 V Terminal Capacitance Symbol Terminal Condition Rated Value Min. Typ. Unit Max. Ci Input measured @ Vcc = Vio, 10 Co Output f = 1 MHz, 10 Cio Bidirectional Ta = 25C 10 pF Time Measuring Unit Symbol Terminal LSB Condition Vio = Vcc = 3.3 V Vio = Vcc = 2.5 V Standard Deviation Vio=3.3 V, Vcc =3.3 V Ta = 25C 2-2 Rated Value Unit Min. Typ. Max. -40 C 25 C 85 C 3.6 V 3.3 V 3.0 V 35 63 111 -40 C 25 C 85 C 2.75 V 2.5 V 2.25 V 38 76 156 2.75 V 2.5 V - 50 - acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de ps TDC-GP2 Temperature Measuring Unit Symbol Terminal Condition Rated Value Min. Typ. Unit Max. Resolution RMS Vio = Vcc =3.3 V 16.0 Bit SNR PT1000 96 dB Absolute Gain-Error 150 nF Capacitance 0,1 % Gain-Drift vs. Vio 0,08 %/V Gain-Drift vs. Temp 0,0008 %/K Uncalibrated Offset <0.01 % Offset Drift vs. <0,2 ppm/K >100 dB Temp PSRR 2.2 Timings At Vcc = 3.3 V 0.3 V, ambient temperature -40 C to +85 C unless otherwise specified Oscillator Symbol Parameter Min. Typ. Clk32 32 kHz reference oscillator 32,768 kHz toszst Oscillator start-up time with ceramic resonator 200 s toszst Oscillator start-up time with crystal oscillator 5 ms ClkHS High-speed reference oscillator 2 Max. 8 Unit MHz Serial Interface Symbol Parameter Max. @ Vio = Unit 2.0 V 2.5 V 3.3 V 20 25 fclk Serial clock frequency 10 Symbol Parameter Min. @ Vio = MHz Unit 2.0 V 2.5 V 3.3 V 50 25 20 tpwh Serial clock, pulse width high ns tpwl Serial clock, pulse width low tsussn SSN enable to valid latch clock 20 40 10 ns tpwssn SSN pulse width between write cycles 50 30 20 ns thssn SSN hold time after SCLK falling 70 40 25 ns tsud Data set-up time prior to SCLK falling 10 5 5 ns thd Data hold time before SCLK falling 10 5 5 ns ns acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-3 Time-to-Digital-Converter Symbol tvd TDC-GP2 Parameter Max. @ Vio = Data valid after SCLK rising Unit 1.8 V 2.5 V 3.3 V 30 20 16 Serial Interface (SPI compatible, Clock Phase Bit =1, Clock Polarity Bit =0): Figure 2-1: SPI Write Figure 2-2: SPI Read 8-Bit Opcodes: MSB 2-4 LSB Description 1 0 0 0 0 ADR2 ADR1 ADR0 Write into address ADR 1 0 1 1 0 ADR2 ADR1 ADR0 Read from address ADR 0 1 1 1 0 0 0 0 Init 0 1 0 1 0 0 0 0 Power On Reset 0 0 0 0 0 0 0 1 Start_Cycle 0 0 0 0 0 0 1 0 Start_Temp 0 0 0 0 0 0 1 1 Start_Cal_Resonator 0 0 0 0 0 1 0 0 Start_Cal_TDC acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de ns TDC-GP2 Disable Timings Figure 2-3: Spec Description Min (ns) Max (ns) tS-EN Enable Setup Time 5 ns - tSH-EN Enable Hold Time 5 ns - Min (ns) Max (ns) 50 ns - 200 ns - Reset Timings Figure 2-4: Spec Description tph Reset pulse width trfs Time after rising edge of reset pulse before hits are accepted acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-5 Time-to-Digital-Converter 2.3 No. TDC-GP2 Pin Description Name Description Buffer type Value If not used 1 Xin Oscillator driver in 2 Xout Oscillator driver out 3 Vio I/O - supply voltage 4 GND Ground 5 Fire1 Fire pulse generator output 1 48 mA 6 Fire2 Fire pulse generator output 2 48 mA 7 Fire_In Signal input for quasi "Sing Around" 8 INTN Interrupt flag 12 mA LOW active 9 SSN Slave select Schmitt trigger LOW active 10 SCK Clock serial interface Schmitt trigger 11 SI Data input serial interface Schmitt trigger 12 SO Data output serial interface 12 mA tristate 13 RSTN Reset input Schmitt trigger 14 Vcc Core supply voltage 15 Clk32Out Output 32 kHz clock generator n. c. 16 Clk32In Input 32 kHz clock generator GND 2-6 GND GND LOW active acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 No. Name Description Buffer type Value If not used 17 SenseT Sense input temperature measure- Schmitt trigger GND 24 mA n.c. ment 18 LoadT Load output temperature measurement 19 PT4 Port 4 temperature measurement 48 mA 20 PT3 Port 3 temperature measurement 48 mA 21 GND Ground 22 Vio I/O - supply voltage 23 PT2 Port 2 temperature measurement 48 mA 24 PT1 Port 1 temperature measurement 48 mA 25 En_Stop2 Enable pin stop input 2 Schmitt trigger HIGH active Vio 26 En_Stop1 Enable pin stop input 1 Schmitt trigger HIGH active Vio 27 Stop2 Stop input 2 28 GND Ground 29 Vcc Core supply voltage 30 Stop1 Stop input 1 31 Start Start input 32 En_Start Enable pin start input 2.4 GND GND Schmitt trigger HIGH active Vio Package Drawings Suitable socket: Plastronics 32QN50S15050D Symbol Dimension in Millimeters Min. Nom. Max. D - 5 - E - 5 - A - - 1 A1 0 - - b 0.17 - 0.3 e - 0.5 - L 0.3 - 0.5 G Center pad shall not be connected to GND. 3.24 Thermal resistance Roughly 40 K/W at 0 m/s air flow, 37 K/W at 1 m/s air flow, 35 K/W at 2m/s air flow (values just for reference). acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-7 Time-to-Digital-Converter TDC-GP2 Soldering Temperature Profile The temperature profile for infrared reflow furnace (in which the temperature is the resin's surface temperature) should be maintained within the range described below. Maximum temperature The maximum temperature requirement for the resin surface, given 260C as the peak temperature of the package body's surface, is that the resin surface temperature must not exceed 250C for more than 10 seconds. This temperature should be kept as low as possible to reduce the load caused by thermal stress on the package, which is why soldering for short periods only is recommended. In addition to using a suitable temperature profile, we also recommend that you check carefully to confirm good soldering results. 2.5 Power Supply Supply voltage Although the TDC-GP2 is a fully digital circuit, some analog measures affect the circuit. The reason is that the TDC is based on the internal analog measure propagation delay time` which is influenced by temperature and supply voltage. A good layout of the supply voltage is essential for good measurement results. It should be high capacitive and of low in-ductance. The TDC-GP2 provides two pairs of power supply terminals: Vio - I/O supply voltage Vcc - Core supply voltage All ground pins should be connected to a ground plane on the printed circuit board. Vio and Vcc should be provided by a battery or fixed linear voltage regulator. Do not use switched regulators to avoid disturbances caused by the I/O supply. 2-8 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 The measurement quality of a time-to-digital converter depends on a good power supply. The chip sees mainly pulsed current and therefore a sufficient bypassing is mandatory: Vcc 100 F (minmum 47 F) Vio 10 F (minimum 1 F) The supply voltage should be provided through analog regulators. We strongly recommend not to use switch mode power supplies. Current consumption The current consumption is the sum from different parties (all data for Vio = Vcc = 3.6V): Iddq < 150 nA Quiescent current, I32 typ. 4.5 A Current into the 32 kHz oscillator, turned on only if the 32 kHz oscillator is connected Ihs typ. 260 A/s Current into the high speed oscillator, * (active runtime) Example: In ultrasonic flow-meters the high-speed oscillator is on for about 2ms only. The average current consumption is 260 A/s * 2 ms = 0.52 A Itmu typ. 15 mA/s Current into the time measuring unit, In measurement range 1 * (active measuring time) the time measuring unit is active for the start-stop time inter val plus the calibration time interval of 2 periods of the refe rence clock per measurement. In measurement range 2 the time measuring unit is on for average 4 periods of the reference clock per measurement, two for the time measurement and two for calibration. Example: With 10 measurements per second in measurement range 2 and a 4 MHz reference clock the time measuring unit is active for only about 10 s. The average current is 15 mA/s * 10 s = 0.150 A. Ialu Current into ALU during data proccesing including typ. 7 nA per calculation a calibration calculation. Example: At 1000 measurements per second with 3 stops per acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-9 Time-to-Digital-Converter IT TDC-GP2 start the ALU average current is 7 nA * 3000 = 21 A. typ. 2.5 As * measure rate The current for a full temperature measurement is typ.2.5As. In heat-meters the temperature is measured typically once every 30 seconds. The average current is about 0.085 A 2.6 Register settings Service bits are for acam testing and security purposes only, Please use the recommended values. 2.6.1 Write registers Default values in second rows Bit Reg0 23 FIRE# (*) Reg1 CONF_FIRE (*) 0 s.c. 0 s.c. 0 0 s.c. 0 s.c. 0 0 21 0 0 1 EN_ERR_VAL 0 s.c. 1 0 20 0 1 RFEDGE2 0 SEL_TIMO_ 1 s.c. 0 EN_STARTNOISE 0 0 RFEDGE1 0 MR2 1 s.c. 0 DIS_PhaseNoise 0 DELVAL1 0 DELVAL2 0 DELVAL3 0 REPEAT_FIRE 0 HIT1 EN_INT (*) Reg5 1 0 0 (*) Reg4 0 DIV_FIRE HIT2 (*) Reg3 22 19 0 (*) Reg2 0 18 0 1 17 0 0 0 0 0 0 16 0 1 0 0 0 0 0 EN_FAST_INIT 0 0 0 0 0 s.c. 1 0 0 0 0 0 HITIN2 0 0 0 0 0 15 CALRES# 14 13 ClkHSDiv PHASE_FIRE 0 12 0 0 0 0 0 0 11 START_ClkHS 0 0 0 0 0 0 10 1 0 0 0 0 0 HITIN1 9 PORT# 1 0 0 0 0 0 8 TCycle 0 0 0 0 0 0 7 No_FAKE 0 n.c 0 0 0 0 0 6 SelClkT 1 n.c 0 0 0 0 0 5 Calibrate 1 n.c 0 0 0 0 0 4 DisAutoCal 0 n.c 0 0 0 0 0 3 MRange2 1 n.c 0 0 0 0 0 2 NEG_STOP2 0 n.c 0 0 0 0 0 1 NEG_STOP1 0 n.c 0 0 0 0 0 0 NEG_START 0 n.c 0 0 0 0 0 s.c. = Special acam configuration bits, n.c. = not in use (*) = Default value after Power On Reset 2-10 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 Short description of the bits: Bits Name Descritpion Value 0 NEG_START Negation start input 0 = non-inverted input signal - rising edge 1 = inverted input signal - falling edge 1 NEG_STOP1 Negation stop 1 input 0 = non-inverted input signal - rising edge 1 = inverted input signal - falling edge 2 NEG_STOP2 Negation stop 2 input 0 = non-inverted input signal - rising edge 1 = inverted input signal - falling edge 3 MRange2 Switch to measurement range 2 0 = measurement range 1 1 = measurement range 2 4 DisAutoCal Enables/disables auto-calibration run in the TDC 0 = auto-calibration after measurement 1 = auto-calibration disabled 5 Calibrate Enables/disables calibration calculation in the ALU 0 = calibration off (only MR 1) 1 = calibration on 6 SelClkT Select reference signal for internal 0 = use 32,768 kHz as cycle clock 1 = use 128 * CLKHS as period for cycle clock cycle clock for tem-perature (32s with 4 MHZ high speed clock signal ) measurement 7 FAKE# Number of dummy cycles at the beginning of a tempera-ture measurement 0 = 2 Fake measurements 1 = 7 Fake measurements 8 TCycle Sets cycle time for tempera-ture measurement 0 = 128 s cycle time @ 4 MHz 1 = 512 s cycle time @ 4 MHz (recommended) 9 PORT# Sets number of ports used for temperature measure-ment 0 = 2 temperature ports (PT1 and PT2) 1 = 4 temperature ports 10-11 START_CLKHS Switch on high-speed oscilla-tor 0 1 2 3 = = = = Oscillator off Oscillator on settling time = 640 s settling time = 1280 s (see Bug Report) 12-13 ClkHSDiv Sets predivider for CLKHS 0 1 2 3 = = = = divided divided divided divided 14-15 CALRES# Sets number of periods used for calibrating the ceramic resonator 0 1 2 3 = = = = 2 periods = 61.035 s 4 periods = 122.07 s 8 periods = 244.14 s 16 periods = 488.281 s 16-19 DIV_FIRE Sets predivider for internal clock signal of fire pulse generator 0 = not permitted1 = divided by 2 2 = divided by 3 3.= divided by 4 ... 15 = divided by 16 Reg 0 by by by by 1 2 4 4 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-11 Time-to-Digital-Converter 20-23 TDC-GP2 FIRE# Sets number of pulses gen-erated by fire pulse generator 0 = off 1 = 1 pulse 2 = 2 pulses 3 = 3 pulses ... 15 = 15 pulses 8-10 HITIN1 Number of expected hits on channel 1 0 1 2 3 4 5 = stop channel 1 disabled = 1 hit = 2 hits = 3 hits = 4 hits to 7 = not permitted 11-13 HITIN2 Number of expected hits on channel 2 0 1 2 3 4 5 = stop channel 2 disabled = 1 hit = 2 hits = 3 hits = 4 hits to 7 = not permitted 15 EN_FAST_INIT Enables fast init operation 0 = Fast init mode disabled 1 = Fast init mode enabled 16-19 HIT1 Defines operator for ALU data post-processing MRange1: HIT1-HIT2 MRange2: HIT2-Start MRange1: 0 = Start 1 = 1. Stop Ch1 2 = 2. Stop Ch1 3 = 3. Stop Ch1 4 = 4. Stop Ch1 5 = no action 6 = Cal1 Ch1 7 = Cal2 Ch1 9 = 1. Stop Ch2 A = 2. Stop Ch2 B = 3. Stop Ch2 C = 4. Stop Ch2 MRange2: 1 = Start 20-23 HIT2 Defines operator for ALU data post-processing MRange1: HIT1-HIT2 MRange2: HIT2-Start MRange1: 0 = Start 1 = 1. Stop Ch1 2 = 2. Stop Ch1 3 = 3. Stop Ch1 4 = 4. Stop Ch1 5 = no action 6 = Cal1 Ch1 7 = Cal2 Ch1 9 = 1. Stop Ch2 A = 2. Stop Ch2 B = 3. Stop Ch2 C = 4. Stop Ch2 MRange2: 2 = 1. Stop Ch1 3 = 2. Stop Ch1 4 = 3. Stop Ch1 Reg 1 2-12 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 Reg 2 0-18 DELVAL1 Delay value for internal stop enable unit, hit 1 channel 1. Fixed point number with 14 integer and 5 fractional digits in multiples of Tref DELVAL1 = 0 to 16383.96875 19 RFEDGE1 Edge sensitivity channel 1 0 = rising or falling edge 1 = rising and falling edge 20 RFEDGE2 Edge sensitivity channel 1 0 = rising or falling edge 1 = rising and falling edge 21-23 EN_INT Activates interrupt sources wired Bit 23 = Timeout interrupt enable by OR Bit 22 = End Hits interrupt enable Bit 21 = ALU interrupt enable Reg 3 DELVAL1 = 0 to 16383.96875 0-18 DELVAL2 Delay value for internal stop enable unit, hit 2 channel 1. Fixed point number with 14 integer and 5 fractional digits in multiples of Tref 19-20 SEL_TIMO_MR2 Select predivider for timeout in 0 = 64 s measurement range 2 1 = 256 s 2 = 1024 s 3 = 4096 s @ 4 MHz ClkHS 21 EN_ERR_VAL Timeout forces ALU to write 0xFFFFFFFF into the output register 0 = disabled 1 = enabled Reg 4 0-18 DELVAL1 Delay value for internal stop enable unit, hit 3 channel 1. Fixed point number with 14 integer and 5 fractional digits in multiples of Tref DELVAL1 = 0 to 16383.96875 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-13 Time-to-Digital-Converter TDC-GP2 Reg 5 0-15 PHASE_FIRE Enables phase reversing for each 0 = no inversion 1 = inversion pulse of a sequence of up to 15 possible pulses 16-18 REPEAT_FIRE Number of pulse sequnce repetition for "quasi-sing-arround" 0= 1= 2= ... 7= no signal repetition 1 signal repetition 2 signal repetition 7 signal repetition 19 DIS_PHASENOISE Phase noise unit, has to be disabled, See bug report section 7.2 1 = disable phase shift Setting 1 is mandatory 20 EN_STARTNOISE Enables additional noise for start channel 1 = switch on noise unit 21-23 CONF_FIRE Output configuration for pulse generator Bit 23 = 1: negate output Fire2 Bit 22 = 1: disable output Fire2 Bit 21 = 1: disable output Fire1 2.6.2 Read registers / Output data format ADR Symbol Bits Description 0 RES_0 32 Measurement result 1, fixed-point number with 16 integer and 16 fractional digits 20,2-1 215 2-16 1 RES_1 32 Measurement result 2, fixed-point number with 16 integer and 16 fractional digits 2 RES_2 32 Measurement result 3, fixed-point number with 16 integer and 16 fractional digits 3 RES_3 32 Measurement result 4, fixed-point number with 16 integer and 16 fractional digits 4 STAT 16 15 - 13 12 11 10 9 8-6 5-3 2-0 n.c. Error short Error open Timeout Precounter Timeout TDC # of hits Ch2 # of hits Ch1 Pointer result register 5 REG_1 8 Content of highest 8 Bits of write register 1, to be used for testing the communication The data structure and the occupancy of the result registers depends on the operation mode and whether calibrated or non-calibrated data are stored. Several cases must be distinguished: Only in measurement range 1 negative results are possible. In measurement range 2 only positive results are possible, given as unsigned numbers. A non-calibrated measurement is only possible in measurement range 1. In measurement range 1 with calibrated data (ALU) the time intervals that have to be measured can not exceed twice the period of the calibration clock. When measuring bigger time intervals an ALU - overflow will occur and 0xFFFFFFFF is written in the appropriate result register. 2-14 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 a. Measurement range 1 with calibrated data (Calibrate = 1) The results are given in multiples of the internal reference clock (= external reference clock divided by 1, 2 or 4 (DIV_CLKHS)). Calibrated data are 32 bit fixed point numbers with 16 integer bits and 16 fractional bits. Any calibrated result covers therefore 1 result register. The serial output begins with the highest bit (215) and ends with the lowest one (2-16). The numbers are available in complements of 2. Time = RES_X * Tref * 2ClkHSDiv = RES_X * Tref * N , with N = 1, 2 or 4 Time < 2 * Tref * 2ClkHSDiv b. Measurement range 1 without calibration (Calibrate = 0) Non-calibrated data are of the type Signed Integer` and are stored as a 16 bit value in the high word of the result registers. The bits of the low word are set to zero. The result is represented as number of LSB and is available in complements of 2. Time = RES_X * LSB ~ RES_X * 65 ps c. Measurement range 2 In measurement range 2 the TDC-GP2 only supports calibrated measurement. The results are given in multiples of the internal reference clock (= external reference clock divided by 1, 2 or 4 (DIV_CLKHS)). Calibrated data are 32 bit fixed point numbers with 16 integer bits and 16 fractional bits. Any calibrated result covers therefore 1 result register. The serial output begins with the highest bit (215) and ends with the lowest one (2-16). The numbers are available in complements of 2. Time = RES_X * Tref * 2ClkHSDiv = RES_X * Tref * N , with N = 1, 2 or 4 d. Temperature measurement Discharge tiem in the same format as in c. measurement mode 2. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 2-15 Time-to-Digital-Converter 2.6.3 TDC-GP2 Status register Bits Name Description 2-0 Pointer result register Pointer to the next free result register 5-3 # of hits Ch 1 Number of hits registered on channel 1 8-6 # of hits Ch 2 Number of hits registered on channel 2 9 Timeout TDC Indicates an overflow of the TDC unit Values 1 = overflow 10 Timeout Precounter Indicates an overflow of the 14 bit precounter in MR 2 1 = overflow 11 Error open Indicates an open sensor at temperature measurement 1 = open 12 Error short Indicates a shorted sensor at temperature measurement 1 = short 2-16 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 3 Measurement Mode 1 3.1 General Description 2 stop channels referring to one start channel Each of typ. 50 ps RMS resolution LSB width typ. 65 ps 15 ns pulse pair resolution 4-fold multihit capability for each stop channel Measurement range 3.5 to 1.8 s (0 to 1.8s between stop channels) Selectable rising/falling edge sensitivity for each channel Enable pins for powerful windowing functionality The possibility to arbitrarily measure all events against each other Digital TDCs use internal propagation delays of signals through gates to measure time intervals with very high precision. Figure 5 clarifies the principal structure of such an absolute-time TDC. Intelligent circuit structures, redundant circuitry and special methods of layout on the chip make it possible to reconstruct the exact number of gates passed by the signal. The maximum possible resolution strongly depends on the maximum possible gate propagation delay on the chip. Figure 3-1 The measuring unit is actuated by a START signal and stopped by a STOP signal. Based on the position of the ring oscillator and the coarse counter the time interval between START and STOP is calculated with a 20 Bit measurement range. The BIN size (LSB) is typically 65 ps at 3.3 V and 25 C ambient temperature. The RMS noise is about 50 ps (0.7 LSB). The gate propagation delay times strongly depend on temperature and voltage. Usually this is solved doing a calibration. During such a calibration the TDC measures 1 and 2 periods of the reference clock. The measurement range is limited by size of the counter: tyy = BIN x 26224 ~ 1.8 s acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 3-1 Time-to-Digital-Converter Time (Condition) Description tph 2,5 ns (min.) Minimum pulse width tpl 2,5 ns (min.) Minimum pulse width tss 3.5 ns ns (min) Start to Stop TDC-GP2 1.8 s (max.) trr 15 ns (typ.) tff 15 ns (typ.) tva 560 ns uncalibrated Rising edge to rising edge Last hit to data valid 4.6 s calibrated txx No timing limits tyy 1,8 s (max) Figure 3-2 Max. measuring range Input circuitry Each input separately can be set to be sensitive to rising or falling edge or both edges. This is done in register 0, Bits 0 to 2. (NEG_START, NEG_STOP1, NEG_STOP2) and register 2, Bit 19&20, RFEDGEx. Furthermore all Start/Stop-inputs support a high active enable pin. 3.2 Measurement Flow Figure 3-3 3.2.1 Configuration At the beginning the TDC-GP2 has to be configured. The main settings for measurement range 1 are: a. Select measurement range1 setting register 0, Bit3, MRange2 = 0. b. Select the reference clock (see also section 5.1) Register 0, Bits 10&11, START_CLKHS defines the switch-on behavior of the high-speed clock. If only the 32kHz is used this is be set to 0". If only the high-speed clock is used this is be set to 1"(conti- 3-2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 nuously on). In case both oscillators are used for current saving reasons this should be set to 2" for ceramic oscillators and to 3" for quartz oscillators". Register 0, Bits 12&13, ClkHSDiv sets an additional internal divider for the reference clock (1,2 or 4). This is important for calibrated measurements in measurement range 1 because the ALU works correctly only if 2*Tref(intern) is bigger than the maximum time interval to be measured. Otherwise the ALU output is 0xFFFFFFFF. Make also sure that 2*Tref(intern) < 1.8 s to avoid a timeout during calibration. c. Set the number of expected hits In register 1, Bits 8 to 10 and 11 to 13, HITIN1 and HITIN2 the user has to define the number of hits the TDC-GP2 has to wait for. A maximum of 4 on each channel is possible. The TDC-GP2 measures until the set number of hits is registered or a timeout occurs. d. Select calibration As the BIN size varies with temperature and voltage the TDC-GP2 ALU can internally calibrate the results. This option is switched on by setting register 0, Bit5, Calibrate = 1". It is recommended to do this. For the calibration the TDC measures 1 and 2 cycles of the reference clock. The two data are stored as Cal1 and Cal2. There are two ways to update the calibration data Cal1 and Cal2: - Separate calibration by sending opcode Start_Cal_TDC via the SPI interface - Automatic update by setting register 0, Bit 4, DisAutoCal = 0". In most applications this will be the preferred setting. e. Define ALU data processing While the TDC unit can measure up to 4 hits on each channel the user is free in his definition what the ALU shall calculate. The settings are done in register 1, Bits 16 to 19 and 20 to 23, HIT1 and HIT2. Both parameters can be set to: 0 = Start 1 = 1. Stop Ch1 9 = 1. Stop Ch2 2 = 2. Stop Ch1 A = 2. Stop Ch2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 3-3 Time-to-Digital-Converter 3 = 3. Stop Ch1 B = 3. Stop Ch2 4 = 4. Stop Ch1 C = 4. Stop Ch2 6 = Cal1 Ch1 7 = Cal2 Ch1 The ALU calculates Hit1 - Hit2. TDC-GP2 Examples: Reg1 = 0x01xxxx - 1st Stop Ch1-Start Reg1 = 0x2Bxxxx - 3rd Stop Ch2-2nd Stop Ch1 Reg1 = 0x06xxxx - Cal1 In case calibration is active the ALU does the full calibration calculation (except when reading the calibration values. In this case the ALU writes the Cal1/Cal2 raw data to the output register). N = 1, 2 or 4. Figure 3-4 f. Select input sensitivity In register 2, Bits 19 & 20, RFEDGE1 and RFEDGE2, the user can select whether the stop inputs are sensitive to either rising or falling edges (RFEDGE = 0") or to both rising and falling edges (RFEDGE = 1"). In register 0, Bits 0 to 2 the user can add an internal inverter to each input, Start, Stop1 and Stop2. With RFEDGE = 0" this is the same as rising edge (NEG_X = 0") or falling edge (NEG_X = 1"). g. Interrupt behavior The interrupt pin 8, INT can have different sources. They are selected in register 2, Bits 21 to 23, EN_INT. 3-4 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 EN_INT = 0 no Interrupt source 1 ALU ready 2 The set number of hits is there 4 Timeout of the TDC unit The different options are wired by OR to enable more than one source. There are further configuration options that will be described later in this chapter. After the configuration the user has to initialize the TDC-GP2 by sending opcode Init" so that the TDC accepts Start and Stop hits. 3.2.2 Measurement After an initialization the TDC unit will start with the first pulse on the Start input. It will run until: the set number of hits has been seen (maximum 4 on both stop channels in MR1) or until a timeout occurs at the end of the measurement range (at about1.8s in ,MR1). The time measurement raw data are internally stored. The number of hits can be seen from the status register, bits 3 to 8. In case calibration is active the TDC now measures one and two periods of the internal reference clock (Tref * 1,2 or 4). The calibration raw data Cal1 and Cal2 are also internally stored. Figure 3-5 3.2.3 Data Processing At the end of the measurement the ALU starts to process the data according to the HIT1, HIT2 settings and transfers the result to the output register. In case calibration is off the ALU transfers the 16 Bit raw data to the output register. With calibration the ALU calculates according to 3.1.1.d and transfers the 32Bit fixed point number to the output register. The ALU can be switched off configuring HIT1=HIT2=5. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 3-5 Time-to-Digital-Converter TDC-GP2 The time it takes the ALU depends on whether calibration is on or not and the supply voltage. Table 3-1: ALU timings As soon as the data is available from the output un-calibrated calibrated register the interrupt flag is set (assumed that the 3.3 V 220 ns 2.3 s ALU interrupt is enabled, see reg 2, EN_INT). Further 2.5 V 310 ns 2.5 s 2.0 V 580 ns 2.8 s the load pointer of the output register is increased by 1 and points to the next free memory. The actual position of the load pointer can be seen in the status 3.2.4 Reading Data register, Bits 0 to 2. Now the user can read the data sending the opcode 10110ADR. With the next 16 cycles (un-calibrated data) or 32 cycles (calibrated data) the TDC-GP2 will send the result, beginning with the most significant Bit (MSB). a. Un-calibrated data format: 16 Bit Signed integer in complements of 2. 1BIN = uncalibrated gate delay is about 65ps at 5V and 25C. Time = RES_X x 65ps Example: configuration b. Calibrated data format: ... 32 Bit fixed-point number in complements of 2. write reg1=0x104400 4 hits on channel 1, Given in multiples of the reference clock. calculate Hit1-Start Time = RES_X * Tref * N, N = 1, 2 or 4 ... The measured time interval may not exceed , Initialize otherwise the ALU will go into overflow and will ... write the data 0xFFFFFFFF to the output regis- while(Check interrupt flag) ter. write reg1=0x204400 The configuration of the ALU allows only one wait(4.6s) hit calculation at the time. In case more than write reg1=0x304400 one hit has been measured it is necessary to wait(4.6s) write new commands to HIT1/HIT2 to instruct write reg1=0x404400 the ALU for calculating the other hits. After wait(4.6s) writing to HIT1/HIT2 it is necessary to wait for Now all Hit data are available from registers 0 to 3. minimum 4.6s (calibrated data) or 580ns (un- The load pointer value is 4. calculate Hit2-Start calculate Hit3-Start calculate Hit4-Start calibrated data) before reading or writing again to HIT1/HIT2. At the end the TDC-GP2 has to be initialized again to be ready for the next measurement. This is done by sending the opcode Init" so that the TDC accepts new Start and Stop hits. 3-6 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 4 Measurement Mode 2 4.1 General Description 1 stop channels referring to one start channel Typ. 50 ps RMS resolution LSB width typ. 65 ps 2 x Tref pulse pair resolution 3-fold multihit capability Measurement range 2 x Tref to 4 ms @ 4MHz Selectable rising/falling edge sensitivity Integrated programmable windowing for each single stop with 10 ns precision Digital TDCs use internal propagation delays of signals through gates to measure time intervals with very high precision (see also measurement range 1, section 4). In measurement range 2 the maximum time interval is extended using a pre-divider. The resolution in LSB remains unchanged by that. In this mode the high-speed unit of the TDC does not measure the whole time interval but only time intervals from START and STOP to the next rising edge of the reference clock (fine-counts). In between the fine-counts the TDC counts the number of periods of the reference clock (coarse-count). Figure 4-1 The BIN size (LSB) is typically 65 ps at 3.3 V and 25 C ambient temperature. The RMS Noise is approx. 50 ps (0.7 LSB). The gate propagation delay times strongly depend on temperature and voltage. In measuring range 2 the result is the sum of different fine and coarse-count results. Therefore it is necessary in measuring range 2 to make a calibration. During a calibration the TDC measures 1 and 2 periods of the reference clock. The measurement range is limited by size of the coarse counter: tyy = Tref x 214 = 4.1ms @ 4MHz The time interval between START and STOP is calculated with a 26 Bit measurement range. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 4-1 Time-to-Digital-Converter TDC-GP2 Figure 4-2 Time (Condition) Description tph 2,5 ns (min.) Minimum pulse width tpl 2,5 ns (min.) Minimum pulse width tss 2*Tref Start to Stop @ Dis_Phasenoise=1 trr 2*Tref Rising edge to rising edge tff 2*Tref Falling edge to falling edge tva 4.6 s (max.) ALU start to data valid tyy 4 ms (max) Max. measuring range Input circuitry Each input separately can be set to be sensitive to rising or falling edge. This is done in register 0, Bits 0 to 2. (NEG_START, NEG_STOP1). Further all Start/Stop-inputs support a high active enable pin. Note: In case the Start-Stop interval is less than the lower limit tzz the TDC will ignore more and more events the smaller it is. In no case there will be wrong results. 4.2 Measurement Flow Figure 4-3 4.2.1 Configuration At the beginning the TDC-GP2 has to be configured. The main settings for measurement range 2 are: a. Select measurement range2 setting register 0, Bit3, MRange2 = 1. b. Select the reference clock (see also section 5.1) In measurement range 2 the TDC-GP2 needs the high-speed clock for the time measurement. In case of low-power applications this clock can be switched of in between measurements. The a 32.768 kHz clock is necessary for the timing control during the oscillator power-on. 4-2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 Register 0, Bits 10&11, START_CLKHS defines the switch-on behavior of the high-speed clock. If only the high-speed clock is used this is be set to 1"(continuously on). In case both oscillators are used for current saving reasons this should be set to 2" for ceramic oscillators and to 3" for quartz oscillators". Register 0, Bits 12&13, ClkHSDiv sets an additional internal divider for the reference clock (1,2 or 4). The choice has an influence on the minimum time interval tmin = 2 * Tref * 2ClkHDiv and the maximum time interval tmax = 214 * Tref * 2ClkHDiv Further, it is necessary that 2 * Tref * 2ClkHDiv < 1.8 s. Otherwise the ALU will go into an overflow during calibration and write 0xFFFFFFFF as output data. c. Set the number of expected hits In register 1, Bits 8 to 10, HITIN1 the user has to define the number of hits the TDC-GP2 has to wait for. A maximum of 3 on channel 1 is possible. The number HITIN1 always has to be higher by 1 than the number of expected hits. The reason is that the Start is also counted as a hit. The TDC-GP2 measures until the set number of hits is registered or a timeout occurs. register 0, Bits 11 to 13, HITIN2 have to be set to 0". Example: 2 stop pulses are expected: HITIN1 = 3, HITIN2 = 0 d. Select calibration The calibration is switched on by setting register 0, Bit5, Calibrate = 1". It is mandatory to do this. For the calibration the TDC measures 1 and 2 cycles of the reference clock. The two data are stored as Cal1 and Cal2. There are two ways to update the calibration data Cal1 and Cal2: Separate calibration by sending opcode Start_Cal_TDC via the SPI interface Automatic update by setting register 0, Bit 4, DisAutoCal = 0". In most applications this will be the preferred setting. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 4-3 Time-to-Digital-Converter TDC-GP2 e. Define ALU data processing While the TDC unit can measure up to 3 hits the ALU can calculate only one hit at once. The settings are done in register 1, Bits 16 to 19 and 20 to 23, HIT1 and HIT2. The Start pulse is internally handled like a Stop pulse because of the special measuring method in measurement range 2. Reg1 = 0x21xxxx = Calculate 1st Stop Ch1-Start Reg1 = 0x31xxxx = Calculate 2nd Stop Ch1-Start Reg1 = 0x41xxxx = Calculate 3rd Stop Ch1-Start The ALU calculates the time interval as: Time = RES_X * Tref * 2ClkHSDiv f. Select input sensitivity In register 2, Bits 19 & 20, RFEDGE1 and RFEDGE2, the user can select whether the stop inputs are sensitive to either rising or falling edges (RFEDGE = 0") or to both rising and falling edges (RFEDGE = 1"). In register 0, Bits 0 to 2 the user can add an internal inverter to each input, Start, Stop1 and Stop2. With RFEDGE = 0" this is the same as rising edge (NEG_X = 0") or falling edge (NEG_X = 1"). g. Interrupt behavior The INT pin can have various sources, to be selected in register 2, Bits 21 to 23, EN_INT. EN_INT = 0 no Interrupt source 1 ALU ready 2 The set number of hits is there 4 Timeout of the TDC unit The different options are wired by OR. After the configuration the user has to initialize the TDC-GP2 by sending opcode Init" so that the TDC accepts Start and Stop hits. 4-4 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 4.2.2 Measurement After an initialization the TDC unit will start with the first pulse on the Start input. It will run until: the set number of hits has been seen (maximum 3 on channel 1 in measurement range 2) or until a timeout occurs. The timeout can be programmed in multiples of the reference clock setting Reg 3, Bits 19&20, SEL_TIMO_MR2. At 4 MHz the values are: SEL_TIMO_MR2 (@ 4 MHz, ClkHSDiv = 0) = 0 = 64 s = 1 = 256 s = 2 = 1024 s = 3 = 4096 s At the end of the time measurement the TDC measures 2 periods of the reference clock for calibration. 4.2.3 Data processing At the end of the measurement the ALU starts to process the data according to the HIT1, HIT2 settings and transfers the result to the output register. The ALU calculates according to 4.1.2.e and transfers the 32Bit fixed point number to the output register. The time it takes the ALU depends on the supply voltage: Table 4-1: ALU timings calibrated 3.3 V 2.3 s 2.5 V 2.8 s 2.0 V 3.1 s As soon as the data is available from the output register the interrupt flag is set (assumed that the ALU interrupt is enabled, see reg 2, EN_INT). Further the load pointer of the output register is increased by 1 and points to the next free memory. The actual position of the load pointer can be seen in the status register, Bits 0 to 2. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 4-5 Time-to-Digital-Converter 4.2.4 TDC-GP2 Reading Data Now the user can read the data sending the opcode 10110ADR. With the next 32 cycles (calibrated data) the TDC-GP2 will send the result, beginning with the main significant Bit (MSB). The 32 Bit fixed-point number in complements of 2 represent the time interval in multiples of the reference clock. Time = RES_X * Tref * 2ClkHSDiv The configuration of the ALU allows only one hit calculation at the time. In case more than one hit has been measured it is necessary to write new commands to HIT1/HIT2 to instruct the ALU for calculating the other hits. After writing to HIT1/HIT2 it is necessary to wait for minimum 4.6s (calibrated data) or 580ns (un-calibrated data) before reading or writing again to HIT1/HIT2. Example: configuration ... write reg1=0x214400 3 hits on channel 1, calculate Hit1-Start ... Initialize ... while(Check interrupt flag) write reg1=0x314400 calculate Hit2-Start wait(4.6s) write reg1=0x414400 calculate Hit3-Start wait(4.6s) Now all hit data are available from registers 0 to 2. The load pointer value is 3. At the end the TDC-GP2 has to be initialized again to be ready for the next measurement. This is done by sending the opcode Init" so that the TDC accepts new Start and Stop hits. 4-6 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 4.3 Stop Masking The TDC-GP2 can set time-based masking windows for each of the 3 hits on Stop1 input when no hits are accepted. The masking refers to the start event and has an accuracy of less than 10 ns. The internal enable unit is connected to the external enable pin by a logical AND. The external enable pin must be set to "1" to use the internal masking unit. The configuration settings are made in registers 2 to 4, DELVAL1, DELVAL2 and DELVAL3: DELVAL1 ... DELVAL3 are fixed point numbers with 14 bit integer and 5 bit fractional digits, in multiples of the internal reference clock Delaymin = DELVALX / 25 * Tref * 2ClkHSDiv The minimum mask size is 3 clock cycles The mask values must have an ascending order. Each mask value must be 3 clock cycles bigger than the previous value It is mandatory that if not all registers are used the mask values that are not required are set to "0". When all DELVAL registers are set to 0, the complete unit is disabled. Example: 4 Mhz reference, ClkHSDiv = 1 DELVAL1 = 0x3200 1st Stop not accepted before 200 s after Start (128000/32 * 250ns * 21 = 200 s) DELVAL2 = 0x3300 2nd Stop not accepted before 204 s after Start (13056/32 * 250ns * 21 = 204 s) DELVAL1 = 0x3400 3rd Stop not accepted before 208 s after Start (13312/32 * 250ns * 21 = 208 s) acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 4-7 Time-to-Digital-Converter 4-8 TDC-GP2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 5 Details and Special Functions 5.1 Oscillator The TDC-GP2 uses up to 2 clock signals depending on the operating mode: High-speed clock, typically 4 MHz, for calibration and as a predivider for the TDC measuring unit in measurement range 2 32 kHz clock signal used for internal timer functions. 5.1.1 High-Speed Oscillator Generally the TDC-GP2 needs a 2 to 8 MHz high-speed clock for calibration. Operating in measurement range 2 the TDC-GP2 needs the high-speed clock signal also as a part of the time measuring unit. The oscillator takes an average current of 260 A when running all the time. Because it is needed only during the time measurement the TDC-GP2 has the capability to control the on-time by itself. The high-speed clock can be switched on automatically with a INIT opcode only for the period of time measurement. An additional delay cares for the settling time of the oscillator. The settings are done in register 0, Bits 10 & 11, START_CLKHS: START_CLKHS =0 Figure 5-1 Oscillator off = 1 Oscillator on =2 The measurement is started with 640 s delay. = 3 same as `2', but with 1280 s delay The programmable delay guarantees that the oscillator has settled before the measurement starts. For ceramic resonators 640 s will be sufficient. Note: Notice the Bug report in section 7 when using Start_CLKHS with quartz oscillators. By this measure the average current consumption can be drastically reduced. Example: At one ToF measurement in an ultrasonic flowmeter (forth/back) per second the high-speed oscillator is active only for about 2 ms. The average current consumption is 260 As * 2 ms = 0.52 A. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 5-1 Time-to-Digital-Converter 5.1.2 TDC-GP2 32.768 kHz Oscillator The TDC-GP2 needs a 32.768 kHz reference for the start-up control of the high-speed clock and the clock calibration. It therefore offers a an integrated driver: There is no need for the 32.768 kHz clock if the high speed clock is permanently running (START_ CLKSHS = 1) and the high speed clock calibration is not used (e.g. in case of a quartz oscillator). 3.6 V. It is also to is provide an external low-and has a current consumption of about 4.5 A at The 32.768 kHzpossible oscillator permanently running frequency rectangular clock at the CLK32Out pin (3.6 V max.). This signal could be generated by an external microprocessor. It will reduce the current consumption down to 1.2 A. For this reason the 32 kHz oscillator should only be used if no external low-current 32.768 kHz clock is available. The settling time of this oscillator is about 2 s. Figure 5-2 The external circuit is necessary only if the 32.768 kHz oscillator is used. Otherwise CLK32In has to be connected to GND. 5.1.3 Calibrating a Ceramic High-speed Oscillator Using a ceramic oscillator for the 2 to 8 MHz clock will be attractive because it is of low cost and has a fast settling time. Unfortunately it has a poor tolerance of 0.3 to 0.5 % and shows a temperature drift. For this reason the TDC-GP2 allows to execute a calibration measurement that allows to compensate this behavior. This measurement is based on the very precise 32.768 kHz clock. The TDC-GP2 generates start/stop pulses from the 32.768 kHz and measures this time interval with its TDC unit. The result is stored in the result register and the interrupt flag is set. The frequency error of the ceramic resonator can be calculated by the microprocessor. The calibration is configured by setting register 0, CALRES# and is started with START_Cal_Resonator" - instruction by the microprocessor. The time interval to be measured is set by CALRES# which defines the number of periods of the 32.768kHz clock: CALRES# =0 2 periods = 61.035 s =1 4 periods = 122.07 s =2 8 periods = 244.14 s =3 16 periods = 488.281s 5-2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 The results is given in multiples of the high-speed clock and (divided by 1, 2 or 4 (DIV_CLKHS)) as 32 bit fixed point numbers with 16 integer bits and 16 fractional bits. The microcontroller can compare this measured value to the theoretical value and calculate the correction factor RES_X/REStheor. Example: The system shall work with a 4 MHz resonator. With CLKHSDIV=0 and CALRES#=1 the theoretical result is 122.0703125s/250ns = 488.28125 (RES_0 = 0x01E84800). If the ceramic resonator in use is not exactly at 4MHz but only 3.98MHz the calibration measurement will show 485,83984375 (RES_0 = 1E5D700). The correction factor for the microcontroller is 1.005. Note: During clock calibration the start input has to be enabled. 5.1.4 How to use Clock Calibration a. Application This option is dedicated especially to ultrasonic flow and heat meters. In those applications the use of ceramic oscillators shows two main advantages: lower cost and less current consumption. Mainly because of the short oszillation start up time of the ceramic oscillator the operating current can be reduced by several A. Referring to 10 years of operation this saves several 100 mAh in battery capacitance. There is no negative effect on the resolution when using this option the correct way. b. Jitter of the 32 kHz clock and consequences The 32 kHz clock is very precise in frequency with only a few ppm error. However the phase jitter is about 3 to 5 ns peak-peak. For this reason also a calibration measurement (Start_Cal_Resonator) has this error. When multiplying a measurement result with the calibration result, the jitter of the calibration is transferred to the result by the ratio calibration measurement time (see CALRES#) to measurement time. Using a permanently updated calibration value will add a considerable jitter to the measurement result. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 5-3 Time-to-Digital-Converter TDC-GP2 c. Application of this option in ultrasonic flow meters A measurement result is always made of two single time-of-flight measurements in ultrasonic flow meters, with and against the flow direction. The difference between those measurements is a measure for the flow. To avoid an influence of the calibration jitter on this measurement result it is necessary only to use the same calibration for both ToF measurements. Following this the differenc between the two ToF measurements will be free of the jitter of the clock calibration measurement. The clock can be calibrated only between measurements that are not directly substracted from each other. 5.2 5.2.1 Fire-pulse Generator General Description The fire-pulse generator generates a sequence of pulses which is highly programmable in frequency, phase and number of pulses. The high-speed oscillator frequency divided by the factor selected for ClkHSDiv is used as the basic frequency. This frequency is internally doubled and can freely be divided by a factor of 2 to 15. It is possible to generate 1 to 15 pulses. For each pulse the phase can be adjusted per register configuration. The fire-pulse generator is activated by sending opcode Start_Cycle. The fire-pulse generator provides 2 outputs, Fire1 and Fire2. The driver strength of each output is 48mA @5V. These 2 outputs can be paralleled to increase the driver strength up to 96 mA. Furthermore Fire2 output signal can be inverted to double the signal amplitude. The outputs can be set individually high-Z. The fire-pulse generator allows to generate and send pulse sequences multiple times for use in a quasi "sing-around" method. Using this feature the received pulse sequence is fed into TDC-GP2 Fire_In input. It is digitally amplified and directly forwarded to the output buffer for an immediate re-emittance without any clock delay. Note: When the fire pulse generator is use it is mandatory to send a start pulse. 5.2.2 Configuration Number of pulses: FIRE# = 0 Switch off fire-pulse generator 1 1 pulse 2 2 pulses ... ... 15 15 pulses 5-4 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 Phase: The phase of each pulse can be defined in register 5, Bits 0 to 15, PHASE_FIRE. 0" stands for HIGH-LOW and 1" for LOW-HIGH. The pulse sequence begins with the LSB and ends with the MSB Example: Fire# = 7, PHASE_FIRE = 0x0055 Fire-pulse frequency: The input signal fireclk1 for the fire pulse generator is derived from the high speed clock CLKHS and the selected value for the high speed clock divider CLKHS_DIV. Figure 5-3 This Signal is internally doubled and divided by DIV_FIRE. DIV_FIRE = 0 not permitted 1 divided by 2 2 divided by 3 ... ... 15 divided by 16 Register 5, Bit 19, DIS_PHASESHIFT actives the phase shift, which introduces additional noise to improve statistical behaviour when averaging. DIS_PHASESHIFT = 0 Phase shift on acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 5-5 Time-to-Digital-Converter TDC-GP2 DIS_PHASESHIFT = 1 Phase shift off fireclk2 is used as reference signal for the Fire1 / Fire2 - signal which is emitted by the output buffers Fire1 / Fire 2 of the fire pulse generator. Figure 5-4 As shown in Figure 16 at least 2 clock periods Tfireclk2 are required to send one Fire_Pulse. One for the high phase and one for the low phase of the Fire1/Fire2 output signal. Example: CLKHS = 4 MHz, CLKHS_DIV = 1, DIV_FIRE = 1 Max. frequency of the Fire1 / Fire2 output signal: Driver outputs: The output drivers are configured in register 5, Bits 21 to 23, CONF_FIRE: Bit 23 = 1 Inverted output on FIRE2 Bit 22 = 1 FIRE2 disabled (High-Z) Bit 21 = 2 FIRE1 disabled (High-Z) Pulse-burst repetition (quasi sing-around): In register 5, Bits 16 to 18, REPEAT_FIRE the number of repetitions of the pulse sequence is defined. REPEAT_FIRE = 0 no repetition = 1 1 repetition ... ... = 7 7 repetitions Only the number of pulses set under FIRE# will be repeated. With a period of 5 s without a pulse the TDC-GP2 detects the end of a pulse sequence. Note: It is strongly recommend that the summarized time of flight of the up to 7 repetitions does not exceed the measurement range of the GP2!!! 5-6 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 5.3 Temperature Measurement Especially for heat meter applications the TDC-GP2 has a PICOSTRAIN based temperature measuring unit that offers high resolution and very low current consumption. The measurement is based on measuring discharge times. Therefore a capacitor is discharged alternately through the sense resistors and the reference resistors. Figure 5-5 Figure 5-6 The unit has 4 resistor ports with the following function: PT1 reference resistor lower temperature PT2 sense resistor lower temperature PT3 sense resistor higher temperature PT4 reference resistor higher temperature The temperature sensor should have a minimum resistance of 500 Ohm. The TDC-GP2 measures the discharge times of the RC-networks made of each resistor and the capacitor. The precision of the temperature measurement is about 0.004C several times better than needed for heat meters. The temperature measurement is fully automated. It is triggered by the C sending the opcode Start_Temp". The TDC-GP2 controls the 4 measurements by itself. After the 4 measurements have finished the interrupt flag is set. The four data are found in registers 0 to 3. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 5-7 Time-to-Digital-Converter TDC-GP2 From Res_2/RES_1 and RES_3/RES_4 the microcontroller can calculate the ratio Rtemp/Rref. By means of a look-up table it can calculate the temperature for the special type of sensor in use. It is not possible with TDC-GP2 to use 4-wire temperature sensors. Configuration Register 0, Bit 8, Tcycle sets the cycle time for the temperature measurement. Tcycle = 0 128 s cycle time @ 4MHz Tcycle = 1 512 s cycle time @ 4MHz Register 0, Bit9, Port# sets the number of ports that will be used. Port# = 0 2 ports = 1 sensor Port# = 1 4 ports = 2 sensors Register 0, Bit 7, Fake# sets the number of dummy measurements at the beginning of a temperature measurement. This is necessary to overcome mechanical effects of the load capacitor. Fake# = 0 2 dummy measurements Fake# = 1 8 dummy measurements A full temperature measurement last for 2 x (# of ports) + (# of fakes) cycles. Recommended Capacitor Values The discharge time should be about 150 s. Therefore the capacitor should have the following value: PT500: 220 nF PT1000: 100 nF Please set Tcycle = 1 to avoid Timeout Error. Recommended Capacitor Type To get accurate results we recommend capacitor types with very low dC/dU. We recommend: CfCap Series from Tayo Yuden For heatmeter application please do note use X7R or similar capacitors. Current consumption By means of the TDC technology the temperature measurement needs an extremely low current, much less than an A/D converter does. 5-8 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 A full temperature measurement with 2 sensors, 2 references am PT1000 sensor type, including all calculations takes less than 2.5As. With one temperature measurement in 30 seconds (typical for heatmeters) the average current consumption is 0.08 A only. This is about 50 times less than other solutions. A PT500 sensor doubles the current. Note:During temperature measurement the start input has to be enabled. Error detection Additionally the temperature unit checks the plausibility of the results. It is able to detect a short circuit of the sensor or an open sensor. The TDC-GP2 provides in the relevant output register an error code instead of a measurement value. 1. Short circuit: equivalent to a very short time interval (< 8 x Tref = 2 s @ 4 MHz). The TDC-GP2 writes a 0x0 to the output register of the shorted sensor. 2. Broken sensor: equivalent to no stop signal or timeout. The TDC-GP2 writes a 0xFFFFFFFF into the output register of the open sensor. Table 5-1: Analog specifikation Parameter Value (typ.) Unit Resolution RMS SNR 16.0 Bit 96 dB Absolut Gain-Error Gain-Drift vs. Vio 0,1 % 0,08 %/V Gain-Drift vs. Temp 0,0008 %/C Uncalibrated Offset <0.01 % Offset Drift vs. Temp PSRR <0,2 ppm/C >100 dB Condition: Vio = Vcc = 3.3 V, PT1000, 150nF charging capacitor acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 5-9 Time-to-Digital-Converter 5.4 TDC-GP2 SPI-interface The serial interface is compatible with the 4-wire SPI standard. It needs the SerialSelectNot (SSN) and can not operated as 3-wire interface. SSN - Slave Select SCK - SPI Clock SI - SPI Data In SO - SPI Data Out The TDC-GP2 does only support the following SPI mode: Clock Phase Bit =1 Clock Polarity Bit =0 The timings are shown in fiures setion 2.2. It is mandatory to set the SSN - line to High-state for at least 50ns between each Read-/Write sequence. SSN as Reset The SerialSelectNot (SSN) line is the HIGH-active reset for the serial interface. After SSN is set to LOW different operations can be addressed, not depending on the status of the interface before the reset. OPCodes MSB 1 LSB 0 0 0 0 ADR2 ADR1 Description ADR0 Write into address ADR 1 0 1 1 0 ADR2 ADR1 ADR0 Read from address ADR 0 1 1 1 0 0 0 0 Init 0 1 0 1 0 0 0 0 Power On Reset 0 0 0 0 0 0 0 1 Start_Cycle 0 0 0 0 0 0 1 0 Start_Temp 0 0 0 0 0 0 1 1 Start_Cal_Resonator 0 0 0 0 0 1 0 0 Start_Cal_TDC 5-10 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de followed by 24 bit data TDC-GP2 The transfer starts with the MSB and is finished sending the LSB. After sending the last Bit TDC-GP2 transfers the data into the target register or executes the command. It is not possible to do incremental writing. Each register must be addressed separately. When reading from the chip it is necessary to send the opcode first, too. With the first positive edge of the clock following the opcode the TDC-GP2 sends the MSB of the addressed register to SO output. Each positive edge transfers the next lower Bit to the output. 5.5 Fast Initialization In measurement range 1 the TDC-GP2 offers the possibility of a fast initialization. Activated by setting register 1, Bit 15, EN_FAST_INIT = 1" the interrupt flag automatically initializes the TDC. So the TDC is already prepared for the next measurement while the data can be read out. This mode is for highest speed applications only. It is most reasonable for un-calibrated measurements with only one stop. 5.6 Noise Unit In case the user wants to improve the measuring results by averaging it is necessary that the values do not always display exactly the same time difference. Instead the user should provide some noise` so that different quantization steps of the characteristic curve of the TDC are involved. This can not happen with very constant time differences. One would constantly hit the same LSB. The noise unit enables the use of weighted averaging even for constant time differences. The noise unit adds a random offset to the start. It is dedicated to applications where the TDC gets a dummy start and measures the time difference between STOP1 and STOP2 (e.g. laser range finders). The noise unit is switched on by setting register 5, Bit 20, EN_STARTNOISE = 1" acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 5-11 Time-to-Digital-Converter 5-12 TDC-GP2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 6 Applications 6.1 6.1.1 Ultrasonic Heatmeter General Description The TDC-GP2 is perfectly suited for low-cost ultrasonic heatmeter designs. Thanks to the implemented functionality, including precision temperature measurement, fire pulse generation, windowing and clock calibration it is sufficient to add a simple microprocessor (without A/D converter) and a transducer dependant driver and receiver. The extremely low current consumption guarantees the necessary long battery lifetime in such applications. The measurement is fairly automated by the TDC-GP2. The microprocessor just sends a start command. The TDC then fires the transducers and measures the time of flight. It calibrates the results and provides them to the microprocessor. Figure 6-1 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 6-1 Time-to-Digital-Converter 6.1.2 TDC-GP2 Configuration A typical configuration could look like: Register 0: 0x338AE8 Fire# = 3, DIV_FIRE=3, CalRes# = 8, ClkHSDiv = 0,START_CLKHS = 2, Port# = 4, TCycle = 0, Fake# = 2, SelClkT = 1, Calibrate = 1, DisAutoCal = 0, MRange2 = 1, NEG_STOP2 = 1, NEG_STOP1 = 1, NEG_START = 1 Register 1: 0x214400 HIT2 = 1, HIT1 = 2, EN_FASTINT = 0, HITIN2 = 0, HITIN1 = 4 Register 2: 0xE03200 TimeOut =1, Endhits = 1, ALU = 1, REFEDGE2 = 0, REFEDGE1 = 0 DELVAL1 = 400 Register 3: 0x083300 EN_ERR_VAL = 0, SEL_TIMO_MB2 = 1DELVAL2 = 408 Register 4: 0x203400 DELVAL3 = 416 Register 5: 0x080000 CONF_FIRE = 0, EN_STARTNOISE = 0, DIS_Phasenoise = 1, REPEAT_FIRE = 0, PHASE_FIRE = 0 All inputs are set to rising edges Measurement range 2 is used with Auto-calibration. The temperature measurement uses the high-speed clock with 128s cycle time and 2 fake measurements on 4 ports (2 sensors, for cold and hot water) The high-speed clock is switched on only for the time measurement with 640s delay The 4 MHz high-speed clock is used without a divider The 4 MHz clock calibration is based on 8 periods of the 32.768 kHz clock (244.14 s) For the fire-pulse generation the 4 MHz is internally doubled and the divided by 4 making 1 MHz. The generator sends 3 pulses The first stop is accepted after 100 s, the second one after 102 s and the third one after 104 s. The TDC is set to measure 3 hits on STOP1. The ALU is set to calculate first Hit1 - Start All interrupt options are activated, timeout will be given after 1024 s Phase-shifting is disabled 6-2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 6.1.3 Measurement Flow Power-on reset: Send SO = 0x50 Configuration: Send SO = 0x80338AE8 Send SO = 0x82114000 Send SO = 0x82E03200 Send SO = 0x83083300 Send SO = 0x84203400 Send SO = 0x85080000 Calibrate Clock: Send SO = 0x03 Start_Cal_Resonator Check-loop INTN = 0? Send SO = 0xB0, Read SI = RES_0 Correction factor = 488.28125/RES_0 Time-of-flight measurement every half second: Send SO = 0x70 Initialize TDC Send SO = 0x01 Start_Cycle triggers fire-pulse generator. Check-loop INTN = 0? Send SO = 0xB4, Read SI = STAT STAT&0x0600 > 0: -> Error routine Send SO = 0x81314000 calculate HIT2-Start Wait for 4.6s (ALU time) Send SO = 0x81414000 calculate HIT3-Start Wait for 4.6s (ALU time) Send SO = 0xB0, Read SI = RES_0 Send SO = 0xB1, Read SI = RES_1 Send SO = 0xB2, Read SI = RES_2 P can now start the data post-processing and calculate the flow and the heat. Measurement loop: Temperature measurement every 30 seconds: Send SO = 0x02 Start_Temp Check-loop INTN = 0? Send SO = 0xB4, Read SI = STAT STAT&0x1E00 > 0: -> Error routine Send SO = 0xB0, Read SI = RES_0 Send SO = 0xB1, Read SI = RES_1 Send SO = 0xB2, Read SI = RES_2 Send SO = 0xB3, Read SI = RES_3 Rhot/Rref = RES_0/RES_1 Rcold/Rref = RES_3/RES_2 Go to look-up table to get the temperatures acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 6-3 Time-to-Digital-Converter 6.1.4 TDC-GP2 Current consumption a. Time measurement 32.768kHz: are provided by the P: < 1.3 A 4 MHz: 0 A in power down, 270 A when active TDC: < 150 nA if not active, 15 mA during active time of the high-speed unit With 2 measurements per second (forth and back flow) the total consumption is < 3 A. b. Temperature measurement A full measurement over all four ports takes less than 2.5 As current. Typically the temperature is measured once in 30 seconds. The average current then is about 0.085 A. This is about 50 times less than with solutions without a TDC. c. Quiescent current Thanks to the current optimized 0.35 technology the quiescent current is less than 150 nA typ. d. Total system current The complete current for the measuring unit (TDC, analog part, Transducer) will depend on the analog circuit part. It will be in the range of 4 to 6 A. With a low-power P (e.g. MSP430 series from TI) the average current consumption of the total device might be in the range of 11 to 16 A. It is possible to operate the system from a lithium-thionylchloride AA cell for 10 years without changing the battery. At 6 years runtime it maybe even possible to work with a low-cost 3V CR2450 coin cell battery. 6-4 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 7 Miscellaneous 7.1 Bug Report 7.1.1 Quartz Oscillator Start Up time Bug: When using a quartz resonator for the oscillator the oscillation start up time is about 3 ms even with an optimized circuit. The TDC-GP2`s automatic on-time control for the high speed clock is based on 640 s or 1280 s delay without any activity. In case of a quartz resonator this delay is too short and will cause malfunction. Corrective: There are several options to deal with. 1.Oscillator permanently on The possibility of switching off the high speed oscillator is added only for current saving. This oscillator needs about 270 A when running continuously. In all application without attention to current consumption we recommend to run the high speed oscillator continuously (START_CLKHS=1). 2.Ceramic Resonator With a ceramic resonator the oscillation start up time is about 200 s. There is no problem with TDC-GP2`s internal delays. We recommend the use of ceramic resonators in all applications targeting ratio measurements (like ultrasonic flow metering). In all applications that need a quartz resonator and the switch-off functionality we recommend the following measures: 3.Lower Clock Frequency at CLK32In A clock with lower frequency increases the internal timer delays. In this case we recommend about 4 kHz. The timer delay is increased to 10 ms then. This is enough for a save oscillation start up time of the quartz. 4.Start/Stop Oscillator by Software Writing a 1" or 0" into Start_CLKHS starts or stops the oscillator by software. This way a P can start the oscillator by command and then after 10 ms can send a measurement opcode like START_CYCLE. At the end of the measurement the P has to switch off the oscillator by a further command. acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 7-1 Time-to-Digital-Converter 7.1.2 Bug: TDC-GP2 DIS_PHASENOISE The TDC-GP2 offers a Phase-Noise function that decouples the calibration clock from the fire pulse generator. This option was implemented to provide the necessary statistics for averaging in case the user is looking for a resolution much better than 1 LSB (about 65 ps) and has a a very strong coupling between the start and the reference clock. Because of a design bug the phase noise unit might fail in case of distortions on the power supply. This is relevant only in measurement range 2. Corrective: The phase noise unit has to be switched off by setting DIS_PHASE_NOISE = 1. In case the start is already asynchronous to the referenceclock this has no effect on the capability of averaging. 7.2 Last Changes 05.10.2006 3.2.1b&c, 5.1.3, DIS_PHASENOISE=1 required 27.11.2006 5.2.2 Additional corrections 3.2.1 Corrections Example 01.02.2007 5.3 Additional corrections for temp. measurement 26.05.2010 Various smaller error fixes. General layout change 7-2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de TDC-GP2 acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de 7-3 Data Sheet acam-messelectronic gmbh Am Hasenbiel 27 76297 Stutensee-Blankenloch Germany / Allemagne ph. +49 7244 7419 - 0 fax +49 7244 7419 - 29 e-mail: support@acam.de www.acam.de