LinearTechnologyChronicle A Showcase of Linear Technology's Focus Products September 1997 Product of the Month Dual Current Feedback Amplifier Delivers 125mA Output Current and 900V/s Slew Rate The LT(R)1497 is a dual Current Feedback Amplifier (CFA) that features a 900V/ s slew rate, 50MHz gain-bandwidth and a guaranteed 125mA minimum output current over temperature using 15V supplies. Maximum supply current per amplifier is only 9mA for 15V operation and just 7mA for 5V operation. High output drive and slew rate combine to provide low distortion transmission of either analog or digital information down long distances of twisted pair, shielded coax or other transmission media. The LT1497 is shown below as an HDSL line driver in just one of the many line driving applications it performs. Any application that requires delivery of a fast signal into a low impedance load, such as ISDN or video distribution, can benefit from the LT1497. The LT1497 can drive a twisted pair with a 1MHz, 40mA peak signal at - 70dBc. Settling time for a 5V step input for the LT1497 is just 55ns. The LT1497 is offered in a low thermal resistance SO-8 package (JA = 80C/W) for operation with 5V supplies and an enhanced 16-pin SO (JA = 40C/W) package for operation with 15V supplies. Thermal shutdown protects against excessive internal (junction) temperatures by cycling between normal operation and an off-state. For a data sheet and evaluation samples, contact your local Linear Technology sales office or for more information, visit our web site at www.linear-tech.com. Synchronous Buck Switching Regulator in SO-8 Offers High Output Accuracy The LTC (R)1504 is a high efficiency synchronous buck switching regulator for use as a board-level 5V to 3.3V converter in mixed voltage systems. A pair of on-chip 1.3 power switches enable it to supply an output current of up to 500mA. Its 200kHz operating frequency and fast transient response reduce the number of output capacitors required for most applications. Peak efficiency of 92% is possible. The LTC1504 is ideal in space limited designs requiring localized voltage regulation, such as in SCSI-II termination supplies, I/O supply for split-plane CPUs and as a supply for low power digital signal processors. 5V 560 NC SHUTDOWN IMAX SHDN VCC + CIN 560 Vol. 6 No. 9 SS 68.1 1/2 LT1497 VIN + NC 1:1* 560 135 560 CIN: AVX TPSC226M016R0375 COUT: AVX TAJC476M010 LEXT: COILTRONICS CTX50-1P SENSE + COMP COUT 1000pF 1504 * TA01 Figure 1. LTC1504 in Synchronous Buck Architecture Operates over a 4V to 10V Input Voltage Range and Requires Only Four External Components - 68.1 3.3V AT 500mA LTC1504-3.3 GND - LEXT SW *MIDCOM 671-7807 1/2 LT1497 + 1497 TA01 Figure 1. HDSL Line Driver Has Thermal and Current Limit Circuits that Protect Against Fault Conditions Inside This Issue: DC/DC Step-Up Controller Meets High Power Demands ........................................................ 2 SIM Power Supply and Level Translator Compatible with 3V and 5V Cards ........................... 2 3.3V Powered Barometric Pressure Signal Conditioner .......................................................... 3 2.5V Micropower Shunt Reference in SO-8 Guarantees 25ppm/C and 0.05% Initial Accuracy ......................................................................................................... 3 Fixed Voltage Output Step-Down Converters Draw Only 10A in Standby ............................. 4 Linear Technology Chronicle * September 1997 The LTC1504 has an internal 1% reference combined with a sophisticated voltage feedback loop that provides optimum output voltage accuracy and fast load transient response and requires no current sense resistor. Synchronous operation allows it to sink or source current for use in an active Continued on page 4 , LTC and LT are registered trademarks of Linear Technology Corporation. 1 DC/DC Step-Up Controller Meets High Power Demands The LT1680 is a high power current mode step-up switching regulator controller that drives N-channel MOSFETs with a source voltage up to 60V and gate capacitance up to 10,000pF. Its high power capability makes it ideal for high voltage, high current step-up applications (Figure 1) that require hundreds of watts of output power at very high efficiency (Figure 2). PWM operating frequency is programmable and can be synchronized up to 200kHz to an external system clock for lower EMI. The LT1680 is ideal as a switcher in the high power industrial/automotive and telecom areas. The LT1680 incorporates programmable average current limiting allowing accurate limiting of DC current in the magnetics, independent of ripple current. User adjustable slope compensation provides stable operation at duty cycles up to 90%. Its current sense common mode range up to 60V allows current sensing to be referenced to the input supply, eliminating the need for sense blanking circuits. Its 5V reference with 10mA sourcing capability provides a local 5V supply for micropower ancillary circuits. The LT1680 is available in 16-lead PDIP or wide SO packages over the commercial and industrial temperature ranges. For a data sheet and evaluation samples, contact your local Linear Technology sales office or for more information, visit our web site at www.linear-tech.com . Kool M is a registered trademark of Magnetics, Inc. 12VIN 10V TO 15V 24A (DC) RSENSE 0.005 R1 15k C1 1nF 1 2 C3, 2.2nF C4, 0.22F 3 4 5 C5, 4.7nF R2, 4.7k 6 C6 0.1F 7 8 R7 2k + LT1680 SL/ADJ 5VREF CT SYNC IAVG 12VIN SS GATE VC 16 15 11 10 SENSE - 9 SENSE + M1 IRFZ44 x3 R9 100k C11, 1nF R6 75k VOUT = 48V 95 C12 1F 12 PGND VREF 100 L1 25H 13 SGND RUN/SHDN VFB + 14 CIN 680F 25V x4 EFFICIENCY (%) C2 1F 90 85 80 D1 MBR20100CT x2 + (R) L1: Kool M , 18T #14 ON 77314-A7 VOUT 48V COUT 5.2A 680F 63V 1680 TA01 x3 75 0 50 150 200 100 OUTPUT POWER (W) 250 1680 TA02 Figure 1. The LT1680 as a Step-Up Converter Generates High Current 48V Bus Voltages Figure 2. Efficiencies Approach 95% in 12V to 48V Boost Applications SIM Power Supply and Level Translator Compatible with 3V and 5V Cards 5V to the SIM card. Output voltage can also be programmed to 3V, 5V or be directly connected to the VIN pin--useful when VIN = 3V to pass through the SIM card supply voltage. The input voltage to these devices may range from 2.7V to 10V, permitting a direct connection to the battery. The LTC1555's output current is 10mA when VIN 2.7V and 20mA when VIN 3V. It is short-circuit protected and in The LTC1555/ LTC1556 are integrated solutions providing the power conversion, digital signal level-shifting and 10kV ESD protection needed for 3V or 5V GSM cellular telephone SIMs (Subscriber Identity Modules). This permits new phones to maintain compatibility with older 5V SIM cards as well as the newer 3V versions. The LTC1555/LTC1556 have a step-up/stepdown charge pump that delivers a regulated 3V GSM CONTROLLER 3V 1 2 3 4 VCC VIN 2.7V TO 10V LTC1555 5 6 7 8 CIN CLK RIN RST DATA I/O DDRV VCC DVCC VIN SIM 16 CLK 15 RST 14 I/O 13 12 SS C1 + 11 M1 C1 - 10 M0 GND 9 + 10F + 0.1F VCC 5V 5% IVCC 10mA 10F GND addition has a soft start feature to control inrush current at turn-on and tolerates indefinite short-circuit conditions. The switchedcapacitor charge pump operates at a switching frequency of 650kHz. All SIM contact pins on the LTC1555/LTC1556 are ESD protected to 10kV-- essential during insertion and removal of the SIM card in normal use. The LTC1556 includes all of the features of the LTC1555 plus an internal 4.3V low dropout linear regulator with 5mA to 10mA output current capability. The LTC1555 is available in a 16-lead narrow SSOP package and the LTC1556 in a 20lead narrow SSOP package. Contact your local Linear Technology sales office for a data sheet and evaluation samples or visit our web site at www.linear-tech.com for more information. 1555/56 TA01 Figure 1. LTC1555 in the GSM Cellular Phone SIM Interface 2 Linear Technology Chronicle * September 1997 Application of the Month 3.3V Powered Barometric Pressure Signal Conditioner The move to 3.3V digital supply voltage creates problems for analog signal conditioning. In particular, transducerbased circuits often require higher voltage for proper transducer excitation. DC/DC converters in standard configurations can address this issue but increase power consumption. Figure 1 shows a way to provide proper transducer excitation for a barometric pressure sensor while minimizing power requirements. The 6k transducer T1 requires precisely 1.5mA of excitation, necessitating a relatively high voltage drive. A1 senses T1's current by monitoring the voltage drop across the resistor string in T1's return path. A1's output biases the LT1172 switching regulator's operating point, producing a stepped-up DC voltage which appears as T1's drive and A2's supply voltage. T1's return current out of Pin 6 closes a loop back at A1 which is slaved to the 1.2V reference. This arrangement provides the required high voltage drive (10V) while minimizing power consumption. This is so because the switching regulator produces only enough voltage to satisfy T1's current requirements. Instrumentation amplifiers A2 and A3 provide gain and the LTC1287 A/D converter gives a 12-bit digital output. A2 is bootstrapped off the transducer supply, enabling it to accept T1's common the "bridge current trim" for exactly 0.1500V at the indicated point. This sets T1's current to the manufacturers specified point. Next, adjust A3's trim so that the digital output corresponds to the known ambient barometric pressure. If a pressure standard is not available, the transducer is supplied with individual calibration data, permitting circuit calibration. mode voltage. Circuit current consumption is about 14mA. If the shutdown pin is driven high, the switching regulator turns off, reducing total power consumption to about 1mA. In shutdown the 3.3V powered A/D's output data remains valid. In practice, the circuit provides a 12-bit representation of ambient barometric pressure after calibration. To calibrate, adjust T1 PRESSURE TRANSDUCER 10V DURING OPERATION TO PROCESSOR 3.3V 5 A = 10 - A2 1F LT1101 10 4 3.3V 1/2 LT1078 + 6 +IN LTC1287 VCC - 10k* BRIDGE CURRENT TRIM 50 BRIDGE CURRENT MONITOR (0.1500V) 100** GND VREF 3.3V 1N4148 L1 150H MUR110 3.3V - A1 1N4148 1/2 LT1078 2.2F + + * = 1% FILM RESISTOR ** = 0.1% FILM RESISTOR L1 = TOKO 262-LYF-0095K T1 = NOVASENSOR (FREMONT, CA) NPH-8-100AH -IN 22F 1M CALIB 1F 100k 1N752 5.6V + 0.05F 700* DOUT CLK CS + A3 VIN VSW VC LT1172 LT1034 1.2V 100k 10k 2N3904 SHUTDOWN E1 E2 FB NC GND 3.3V Figure 1. 3.3V Powered, Digital Output, Barometric Pressure Signal Conditioner 2.5V Micropower Shunt Reference in SO-8 Guarantees 25ppm/ C and 0.05% Initial Accuracy 4 IR = 10A REVERSE VOLTAGE CHANGE (mV) The LT1634-2.5 is a precision 2.5V output shunt reference with an initial accuracy of 0.05% and a maximum guaranteed drift of 25ppm/C. The initial release in this family, a 1.2V output device, was introduced in the August issue of Chronicle. The LT1634 is stable with any value of output capacitor, including none, saving components and board space. These features make it an excellent reference for use in portable meters, precision regulators and in data conversion applications. Advances in design, processing and packaging techniques guarantee an oper- 3 2 1 0 -1 -2 -3 -4 - 40 -20 20 40 60 0 TEMPERATURE (C) 80 100 ating current of only 10A and low temperature cycling hysteresis. The compactness of the product makes it ideal for space limited applications. The LT1634-2.5 is immediately available in volume from stock in 8-lead SO or MSOP surface mount packages. Contact your local Linear Technology sales office for a data sheet and evaluation samples. Visit our web site at www.linear-tech.com for more information. 1634-2.5 TA02 Figure 1. LT1634-2.5 Reference Has Low Drift over a Wide Temperature Range Linear Technology Chronicle * September 1997 3 Fixed Voltage Output Step-Down Converters Draw Only 10A in Standby Absolute Maximum). They have an adjustable output voltage and are short-circuit protected. Their 100% duty cycle capability ensures low dropout operation and allows maximum energy to be extracted from the batteries. Burst ModeTM operation maintains high efficiency over a wide range of load currents. A low-battery comparator is included and is functional during shutdown. The LTC1475 is identical to the LTC1474 except that it has a push-button ON/OFF operation. Momentarily pushing the ON button pin latches the LTC1475 on and pushing the OFF button pin turns it off (shutdown to 6A IQ). This user interface permits two-button operation without the need for an external microcontroller or one- VIN 4V TO 18V + 10F 25V 0.1F 7 6 3 LOW BATTERY IN RUN SHDN 100k 8 SENSE LBI RUN VIN LOW BATTERY OUT VOUT LTC1474-3.3 LBO GND SW 1 2 L1 100H + VOUT 3.3V AT 300mA 100F 6.3V 5 D1 MBR0530 4 100 90 VIN = 5V VIN = 10V EFFICIENCY (%) Fixed 3.3V and 5V output voltage versions of the LTC1474/LTC1475 micropower converters are now available in 8-lead MSOP and SO packages. These high efficiency (up to 92%) step-down DC/DC converters draw only 10A of standby current while regulating the output voltage. They have an on-chip power switch with programmable peak current control to maximize the life of alkaline batteries for loads ranging from 1mA to 300mA. These features permit a minimum area solution ideally suited for battery-powered, handheld products. The LTC1474-3.3/ LTC1474-5/ LTC1475-3.3/LTC1475-5 operate over a wide input voltage range of 3V to 18V (20V 80 VIN = 15V 70 60 50 0.03 L = 100H VOUT = 3.3V RSENSE = 0 0.3 30 3 LOAD CURRENT (mA) 300 1474/75 TA01 Figure 2. Efficiencies over 92% Are Possible for Various Load Currents button operation with a microcontroller, greatly simplifying ON/OFF control of handheld products. The LTC1474/LTC1475 are immediately available in 8-lead MSOP and SO packages and are screened over both the commercial and industrial temperature ranges. Contact your local Linear Technology sales office for a data sheet and evaluation samples. Visit our web site at www.linear-tech.com for more information. 1474/75 FIX F01 L1 = SUMIDA CDRH74 Figure 1. The LTC1474-3.3 High Efficiency Step-Down Converter Operates over a 4V to 18V Input Range Burst Mode is a trademark of Linear Technology Corporation. LTC1504 from page 1 100 90 80 70 EFFICIENCY (%) termination. An adjustable current limit circuit provides protection from overloads. The LTC1504 fills the need for a low cost 5V to 3.3V switching regulator where high efficiency at light load currents is not critical. The LTC1504 is available in adjustable and fixed 3.3V output versions--the latter (LTC1504-3.3) uses an internal resistor pair for improved space efficiency. Both devices are offered in an 8-lead SO surface mount package. Contact your local Linear Technology sales office for a data sheet and evaluation samples. Visit our web site at www.linear-tech.com for more information. 60 50 40 Linear Technology Products Are Distributed By: 30 20 10 0 10 100 LOAD CURRENT (mA) 500 1504 * TA02 Figure 2. LTC1504 Self-Contained Switching Regulator Offers Up to 92% Peak Efficiency over a Wide Range of Load Current Almac/Arrow Arrow/Schweber Arrow/Zeus Digi-Key Electrosonic Gerber Electronics Farnell Electronics Marshall Industries Phase 1 (c) 1997 Linear Technology Corporation/Printed in USA 4 Technology Corporation * 1630 McCarthy Blvd. * Milpitas, CA 95035-7417 * (408) 432-1900 * FAX: (408) 434-0507 Linear * www.linear-tech.com * For Literature Only: 1-800-4-LINEAR Linear Technology Chronicle * September 1997