19-0598; Rev 3; 2/08 KIT ATION EVALU E L B A IL AVA 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Features The MAX6946/MAX6947 I 2 C-/SMBus TM-compatible, 2.25V to 3.6V Operation I/O Ports Default to High Impedance (LEDs Off) on Power-Up I/O Port Inputs Are Overvoltage Protected to 7V I/O Port Outputs Are 7V-Rated Open-Drain, 10mA or 20mA Constant-Current Static/PWM LED Drivers, or Open-Drain Logic Outputs I/O Ports Support Hot Insertion Individual 8-Bit PWM Intensity Control for Each LED RST Input Clears Serial Interface and Can Exit Shutdown (Warm Start) MAX6946 OSC Input Allows for External PWM Clock Input MAX6947 AD0 Input Selects from Two Slave Addresses Auto Ramp-Up Out of Shutdown, and Up to 4s Hold-Off Before Ramp-Down into Shutdown 0.8A (typ) Shutdown Current -40C to +125C Temperature Range Tiny WLP Package (4 x 4 Grid) serial-interfaced peripherals provide microprocessors with 10 I/O ports rated to 7V. Each port can be configured as a 2.5mA to 20mA constant-current LED driver (static or PWM), a 1.25mA to 10mA constant-current LED driver (static or PWM), an open-drain logic output, or an overvoltage-protected Schmitt logic input. Analog and switching LED intensity control includes individual 8-bit PWM control per output, individual 1-bit analog current control (half/full scale) per output, and a global 3-bit DAC current control that applies to all LED outputs. The MAX6946/MAX6947 can stagger the PWM timing of the 10-port outputs in consecutively phased 45 increments. Staggering the outputs spreads the PWM load currents over time in eight steps, helping to even out the power-supply current and reduce the RMS current. For a similar part with an SPITM-/QSPITM-/ or MICROWIRETMcompatible interface, refer to the MAX6966/MAX6967 data sheet. Applications Cellular Phones Portable Equipment RGB LED Drivers LCD Backlights Keypad Backlights LED Status Indicators Typical Operating Circuit +3.3V VEXT = +5V VDD C SCL SDA SCL SDA OSC* MAX6946 MAX6947 RST AD0** GND P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 Ordering Information PART PKG CODE PIN-PACKAGE MAX6946ATE+ 16 TQFN-EP* MAX6946CAWE+ 16 WLP MAX6947ATE+ 16 TQFN-EP* T1633-4 W162B2-1 T1633-4 +Denotes a lead-free package. *EP = Exposed pad. Note: All devices are specified over the -40C to +125C operating temperature range.. Pin Configurations LOGIC INPUT LOGIC INPUT LOGIC INPUT LOGIC INPUT LOGIC INPUT LOGIC INPUT LOGIC INPUT *MAX6946 ONLY. **MAX6947 ONLY. SMBus is a trademark of Intel Corp. SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp. TOP VIEW MAX6946C A1 A2 A3 A4 RST VDD SCL SDA B1 B2 B3 B4 P9 OSC P1 P0 C1 C2 C3 C4 P8 P7 P3 P2 D1 D2 D3 D4 P6 P5 GND P4 (BUMPS ON BOTTOM) 16-BUMP, 2.1mm x 2.1mm WLP Pin Configurations continued at end of data sheet. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX6946/MAX6947 General Description MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control ABSOLUTE MAXIMUM RATINGS VDD to GND .............................................................-0.3V to +4V SCL, SDA, AD0, RST, OSC to GND .........................-0.3V to +6V P0 to P9 to GND .......................................................-0.3V to +8V DC Current into P0 to P9 ....................................................24mA DC Current into SDA ...........................................................10mA RST Sink Current.................................................................10mA Total GND Current ............................................................280mA Continuous Power Dissipation (TA = +70C) 16-Pin TQFN (derate 14.7mW/C over +70C) ..........1176mW 16-Bump WLP (derate 13.3mW/C over +70C)........1066mW Operating Temperature Range (TMIN, TMAX) ....-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VDD = 2.25V to 3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 3.3V, TA = +25C.) (Note 1) PARAMETER SYMBOL Operating Supply Voltage VDD Output Load External Supply Voltage P0-P9 VEXT Power-On-Reset Voltage VPOR Power-On-Reset Voltage Hysteresis Standby Current Interface Idle (PWM Disabled, All Ports High Impedance) Standby Current in Reset (PWM Disabled, All Ports High Impedance) Supply Current Interface Active (Reset Run Enabled, PWM Disabled, All Ports High Impedance) PORHYS ISTBY IRST IDD IDD10 CONDITIONS MIN TYP MAX UNITS 3.60 V 7 V VDD rising 1.91 V 16-pin TQFN 128 2.25 16-bump WLP RST at VDD; fSCL = 0Hz; other digital inputs at VDD or GND RST at GND; fSCL = 400kHz; other digital inputs at VDD or GND fSCL = 400kHz; other digital inputs at VDD or GND 33 TA = +25C 1.0 TA = TMIN to +85C TA = +25C 1.3 1.3 TA = TMIN to TMAX 23 24 TA = TMIN to TMAX 25 50 TA = TMIN to +85C 62 TA = TMIN to TMAX 65 One port set to 10mA TA = +25C constant current; all other ports' output registers set TA = TMIN to +85C to 0x00, 0x01, or 0xFF; digital inputs at VDD or TA = TMIN to TMAX GND 1.58 One port set to 20mA TA = +25C constant current; all other ports' output registers set TA = TMIN to +85C to 0x00, 0x01, or 0xFF; digital inputs at VDD or TA = TMIN to TMAX GND 3.2 A 60 A 1.8 1.9 2.0 Delta Supply Current Interface Idle mA IDD20 2 A 1.5 17 TA = TMIN to +85C TA = +25C mV _______________________________________________________________________________________ 3.6 3.8 4.0 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control (VDD = 2.25V to 3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 3.3V, TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS Input High Voltage (P0-P9, SDA, SCL, RST, AD0, OSC) VIH P0-P9: output register set to 0x01 Input Low Voltage (P0-P9, SDA, SCL, RST, AD0, OSC) VIL P0-P9: output register set to 0x01 Input Leakage Current (P0-P9, SDA, SCL, RST, AD0, OSC) IIH, IIL MIN IOUT Output register set to 0x02, TA = TMIN to +85C 16-pin TQFN VDD = 3.3V, VEXT - VLED = 1V (Note 3) T = T A MIN to +85C 16-bump WLP TA = +25C Port Sink Constant-Current Matching Port Logic Output Low Voltage (P0-P9) 0.3 x VDD V +0.2 A 10 IOUT IOUT VOLP_ Output register set to 0x02, TA = TMIN to +85C VDD = 3.3V, 16-pin TQFN VEXT - VLED = 1V (Note 3) TA = TMIN to +85C 16-bump WLP 9.3 10 pF 10.5 9.1 11.0 9.0 11.0 19.00 UNITS V -0.2 TA = +25C 20mA Port Nominal Sink Constant Current (P0-P9) MAX 0.7 x VDD Input Capacitance (P0-P9, SDA, SCL, RST, AD0, OSC) 10mA Port Nominal Sink Constant Current (P0-P9) TYP 20 21.12 18.6 21.8 18.4 22.0 TA = +25C, VDD = 3.3V, VP0 to VP9 = 1.4V, IOUT = 20mA 2.0 TA = +25C, VDD = 3.3V, VP0 to VP9 = 1.4V, IOUT = 10mA 2.0 mA mA 4.0 % Output register set to 0x00, ISINK = 0.5mA 5.0 0.5 V Port Logic Output Low Short-Circuit Current (P0-P9) Output register set to 0x00, VOLP_ = 5V 10 mA Port Slew Time From 20% current to 80% current 2 s Output Low Voltage (SDA) VOLSDA ISINK = 6mA 300 mV _______________________________________________________________________________________ 3 MAX6946/MAX6947 ELECTRICAL CHARACTERISTICS (continued) MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control TIMING CHARACTERISTICS (Figure 8) (VDD = 2.25V to 3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VDD = 3.3V, TA = +25C.) (Note 1) PARAMETER SYMBOL MIN TYP MAX 16-pin TQFN CONDITIONS 23 32 42 16-bump WLP 20 32 45 UNITS Internal PWM Clock Frequency fINT External PWM Clock Frequency fOSC 100 kHz Serial-Clock Frequency fSCL 400 kHz Bus Free Time Between a STOP and a START Condition tBUF 1.3 s Hold Time, (Repeated) START Condition tHD, STA 0.6 s Repeated START Condition Setup Time tSU, STA 0.6 s 0.6 kHz STOP Condition Setup Time tSU, STO Data Hold Time tHD, DAT s Data Setup Time tSU, DAT 180 ns SCL Clock Low Period tLOW 1.3 s SCL Clock High Period tHIGH 0.7 s (Note 3) 0.9 s Rise Time of Both SDA and SCL Signals, Receiving tR (Notes 4, 5) 20 + 0.1Cb 300 ns Fall Time of Both SDA and SCL Signals, Receiving tF (Notes 4, 5) 20 + 0.1Cb 300 ns tF, TX (Notes 4, 6) 20 + 0.1Cb 250 ns 400 pF Fall Time of SDA Transmitting Pulse Width of Spike Supressed tSP (Note 7) Capacitive Load for Each Bus Line Cb (Note 4) RST Pulse Width tW RST Rising Edge to MAX6946/MAX6947 ACK to Cancel Reset Run tRSTRUN RST Rising Edge to MAX6946/MAX6947 ACK to Ensure Reset Run tRSTRUN 50 ns 0.1 Reset Run enabled, internal oscillator enabled s 16-pin TQFN 3.0 16-bump WLP 2.5 ms Reset Run enabled, internal oscillator enabled 5.6 ms Note 1: All parameters are tested at TA = +25C. Specifications over temperature are guaranteed by design. Note 2: Port current is factory trimmed to meet a median sink current of 20mA and 10mA over all ports. The IOUT specification guarantees current matching between parts. Note 3: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) in order to bridge the undefined region of SCL's falling edge. Note 4: Not production tested. Guaranteed by design. Note 5: Cb = total capacitance of one bus line in picoFarads; tR and tF are measured between 0.3 x VDD and 0.7 x VDD. Note 6: ISINK 6mA. Note 7: Guaranteed by design. Input filters on the SDA and SCL inputs suppress noise spikes of less than 50ns. 4 _______________________________________________________________________________________ 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control 0.8 0.4 15 10 VDD = 2.7V -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) DELTA SUPPLY CURRENT (IDD20) vs. TEMPERATURE OUTPUT SINKING CURRENT vs. VEXT - VLED AT 10mA VDD = 2.7V 12 VDD = 3.3V 9 6 3 VDD = 2.7V 14 VDD = 2.25V 2.0 12 10 8 6 4 2 0 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) MAX6946/47 toc06 VDD = 3.6V OUTPUT SINKING CURRENT (mA) 2.8 VDD = 2.25V -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 15 DELTA SUPPLY CURRENT (mA) MAX6946/47 toc04 3.2 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) OUTPUT SINKING CURRENT vs. VEXT - VLED AT 20mA 1 2 3 VEXT - VLED (V) 4 5 STAGGER PWM PORT WAVEFORMS (OUTPUT REGISTERS SET TO 0x80) MAX6946/47 toc08 MAX6946/47 toc07 24 OUTPUT SINKING CURRENT (mA) DELTA SUPPLY CURRENT (mA) VDD = 3.3V VDD = 2.25V 10 0 DELTA SUPPLY CURRENT (IDD20) vs. TEMPERATURE 2.4 15 5 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) VDD = 3.6V VDD = 3.3V VDD = 2.25V 0 3.6 VDD = 3.6V 20 5 VDD = 2.25V 4.0 MAX6946/47 toc02 VDD = 2.7V 25 STANDBY CURRENT (A) VDD = 3.3V VDD = 2.7V VDD = 3.3V 20 SUPPLY CURRENT (A) VDD = 3.6V VDD = 3.6V MAX6946/47 toc05 1.6 STANDBY CURRENT (A) 25 MAX6946/47 toc01 2.0 1.2 STANDBY CURRENT (IRST) vs. TEMPERATURE SUPPLY CURRENT (IDD) vs. TEMPERATURE MAX6946/47 toc03 STANDBY CURRENT (ISTBY) vs. TEMPERATURE 20 PORT P0 2V/div 16 PORT P4 2V/div 12 8 PORT P7 2V/div 4 0 0 1 2 3 VEXT - VLED (V) 4 5 1ms/div _______________________________________________________________________________________ 5 MAX6946/MAX6947 Typical Operating Characteristics (TA = +25C, unless otherwise noted.) 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control MAX6946/MAX6947 Pin Description PIN NAME MAX6946/ MAX6947 MAX6946C 1 B4 P0 2 B3 P1 3 C4 P2 4 C3 P3 5 D4 P4 6 D3 GND 7 D2 P5 8 D1 P6 9 C2 P7 10 C1 P8 11 B1 P9 12 B2 FUNCTION I/O Ports. Configure P0-P4 as open-drain current sink outputs rated at 20mA (max), as CMOS-logic inputs, or as open-drain logic outputs. Connect loads to a supply voltage no higher than 7V. Ground I/O Ports. Configure P5-P9 as open-drain current sink outputs rated at 20mA (max), as CMOS-logic inputs, or as open-drain logic outputs. Connect loads to a supply voltage no higher than 7V. OSC (MAX6946) External Oscillator Input AD0 (MAX6947) Address Input. Sets the device slave address (see Table 10). 13 A1 RST Active-Low Reset Input 14 A2 VDD Positive Supply Voltage. Bypass VDD to GND with a 0.1F ceramic capacitor. 15 A3 SCL I2C-Compatible, Serial-Clock Input 16 A4 SDA I2C-Compatible, Serial-Data I/O -- -- EP Exposed Pad on Package Underside. Connect to GND. Do not use as the main ground connection. Block Diagram CURRENT REFERENCE INTERNAL OSCILLATOR OSC* **MAX6946 ONLY. **MAX6947 ONLY. 6 PWM CONTROLLER I/O PORTS P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 EXTERNAL CLOCK INPUT* MAX6946 MAX6947 ADO** SCL SDA RST RAMP-UP/RAMP-DOWN CONTROLS CONFIGURATION REGISTER I/O REGISTER 2-WIRE SERIAL INTERFACE _______________________________________________________________________________________ 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control The MAX6946/MAX6947 general-purpose input/output (GPIO) peripherals provide 10 I/O ports, P0 to P9, controlled through an I2C-compatible serial interface. Use the 10 I/O ports as logic inputs, open-drain logic outputs, or constant-current sinks in any combination. Ports withstand 7V independent of the MAX6946/ MAX6947s' supply voltage whether used as logic inputs, logic outputs, or constant-current sinks. The MAX6946/MAX6947 feature shutdown and standby modes for low-power dissipation. The I/O ports feature pulse-width modulation (PWM) of the outputs and can stagger the PWM timing of the 10 port outputs in consecutively phased 45 increments. The I/O ports also feature ramp-up and ramp-down controls. The MAX6946/MAX6947 feature a RST input to halt any serial-interface transmission and bring the device out of shutdown. Open-drain logic outputs require external pullup resistors to provide the logic-high reference. Ports configured as open-drain logic outputs have a relatively weak sink capability, but are still adequate for normal logiclevel outputs. The weak drive means that the short-circuit current is low enough that inadvertently driving an LED from a port configured as a logic output is unlikely to damage the LED. The MAX6946 features a fixed I 2C slave address of 010 0000 and provides an OSC input to accept an external PWM clock input as an alternative to the internal PWM clock. The MAX6947 features an AD0 input that uses two-level logic to select from two I 2 C slave addresses. The MAX6947 always uses the internal PWM clock. Register Structure The MAX6946/MAX6947 contain 22 internal registers (see Table 1). Use registers 0x00 to 0x09 to individually control ports P0 to P9. Registers 0x0A to 0x0D allow more than one port control register to be written with the same data to simplify software. Registers 0x0E and 0x0F do not store data, but return the port input status when read. Registers 0x10 to 0x15 configure and control the device operation. Table 1. Register Address Map ADDRESS CODE (HEX) AUTOINCREMENT ADDRESS Port P0 output level or PWM 0x00 0x01 Port P1 output level or PWM 0x01 0x02 Port P2 output level or PWM 0x02 0x03 Port P3 output level or PWM 0x03 0x04 Port P4 output level or PWM 0x04 0x05 Port P5 output level or PWM 0x05 0x06 Port P6 output level or PWM 0x06 0x07 Port P7 output level or PWM 0x07 0x08 Port P8 output level or PWM 0x08 0x09 Port P9 output level or PWM 0x09 0x10 Write ports P0-P9 with same output level or PWM 0x0A 0x10 0x0B 0x10 0x0C 0x10 0x0D 0x10 DESCRIPTION Read port P0 output level or PWM Write ports P0-P3 with same output level or PWM Read port P0 output level or PWM Write ports P4-P7 with same output level or PWM Read port P4 output level or PWM Write ports P8 or P9 with same output level or PWM Read port P8 output level or PWM Read ports P7-P0 inputs 0x0E 0x0F Read ports P9 and P8 inputs 0x0F 0x0E Configuration 0x10 0x11 Ramp-down 0x11 0x12 Ramp-up 0x12 0x13 Output current ISET70 0x13 0x14 Output current ISET98 0x14 0x15 Global current 0x15 0x10 Factory reserved; do not write to this register 0x7D -- _______________________________________________________________________________________ 7 MAX6946/MAX6947 Detailed Description MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Configuration Register (0x10) Initial Power-Up Use the configuration register to select PWM phasing between outputs, test fade status, enable hardware startup from shutdown, and select shutdown or run mode (Table 2). All control registers reset upon power-up (Table 3). Power-up status sets I/O ports P0 to P9 to high impedance, and puts the device into shutdown. The MAX6946/MAX6947 powers up in shutdown. Table 2. Configuration Register (0x10) REGISTER BIT DESCRIPTION D7 OSC enable* D6 RSTPOR options D5 PWM stagger D4 Hold-off status** D3 Fade-off status** D2 D1 D0 VALUE Ramp-up status** RST RUN enable RUN enable FUNCTION 0 Internal oscillator enabled as PWM clock source 1 External oscillator input enabled as PWM clock source 0 RST does not change register data 1 RST resets registers to POR (power-on reset) state 0 PWM outputs are in phase 1 PWM outputs stagger phase 0 Device not in hold-off 1 Device in hold-off 0 Device not in fade-off 1 Device in fade-off 0 Device not in ramp-up 1 Device in ramp-up 0 Reset Run disabled 1 Reset Run enabled 0 Shutdown mode 1 Run mode *The OSCEN bit applies only to the MAX6946. OSCEN is always 0 for the MAX6947, and the MAX6947 ignores writes to the OSCEN bit. **Read-only bits. Table 3. Initial Power-Up Register Status DESCRIPTION POWER-UP CONDITION REGISTER BIT ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 0x00-0x09 1 1 1 1 1 1 1 1 Port P0-P9 output level or PWM Port 0-9 high impedance Configuration Shutdown mode, Reset Run disabled 0x10 0/1* 0 0 0 0 0 0 0 Ramp-down/hold-off Fade/hold-off disabled 0x11 0 0 0 0 0 0 0 0 Ramp-up Disabled 0x12 0 0 0 0 0 0 0 0 Output current ISET70 IPEAK = 10mA for ports P7-P0 0x13 0 0 0 0 0 0 0 0 Output current ISET98 IPEAK = 10mA for ports P9, P8 0x14 0 0 0 0 0 0 0 0 Global current Full current 0x15 0 0 0 0 0 1 1 1 *Value is 0 for MAX6947 and 1 for MAX6946 bit. 8 _______________________________________________________________________________________ 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Phasing section). The I/O ports are high impedance without VDD applied and remain high impedance upon power-up. Figure 1 shows the I/O port structure of the MAX6946/ MAX6947. I/O ports P0 to P9 default to high impedance on power-up, so LEDs or other port loads connected draw no current. Ports used as inputs do not load their source signals. I/O PORT A POSITION A: 0x00-0x01 B ENABLE = 0x00 POSITION B: 0x02-0xFF CLOSE SWITCH: 0x02-0xFE 8-BIT LATCH OUTPUT PORT REGISTER PWM GENERATOR ENABLE TO/FROM SERIAL INTERFACE 1-BIT LATCH OUTPUT CURRENT REGISTER SET CURRENT MSB N 4-BIT DAC 3-BIT LATCH GLOBAL CURRENT REGISTER READ I/O PORT COMMAND Figure 1. Simplified Schematic of I/O Ports Table 4. Individual Port Configuration Options (Port Output Registers 0x00-0x09) PORT TYPE Low-logic output High-logic output OUTPUT REGISTER CODE SHUTDOWN (CONFIGURATION REGISTER BIT D0 = 0) 0x00 Logic-low output, not constant current 0x01 Logic-high output with external pullup resistor; otherwise, high impedance Logic input Constantcurrent static sink output RUN MODE (CONFIGURATION REGISTER BIT D0 = 1) APPLICATION NOTES Lowest supply current, unaffected by shutdown CMOS logic input 0x02 Static constant-current sink output Full constant-current drive with no PWM High impedance Constantcurrent PWM output LED off 0x03-0xFE 0xFF 0x03 = 3/256 PWM duty cycle 0xFE = 254/256 PWM duty cycle Logic-high output with external pullup resistor; otherwise, high impedance Adjustable constant current LED off _______________________________________________________________________________________ 9 MAX6946/MAX6947 I/O Ports The MAX6946/MAX6947 contain 10 I/O ports. Configure the 10 I/O ports as logic inputs, open-drain logic outputs, or constant-current sinks in any combination. Table 4 shows a detailed description of the individual port configuration registers 0x00 through 0x09. Use registers 0x00-0x09 to individually assign each port as a logic input, open-drain logic output or constant-current sink (see the PWM Intensity Control and MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Ports Configured as Outputs The global-current register sets the full (maximum) constant-current sink into an I/O port configured as an output (Table 5). Each output port's individual constantcurrent sink can set to either half or full scale of the global current by the output-current registers (Table 6). By default, maximum current is 20mA, hence the default maximum half current is 10mA. Set each output port's individual constant-current sink to either half scale or full scale of the global current. Use the output-current registers to set the individual currents (Table 6). Set the global current by the globalcurrent register (Table 5). Set each output current individually to best suit the maximum operating current of an LED load, or even adjust on the fly to double the effective intensity control range of each output. The individual current selection is 10mA (half) or 20mA (full) when setting the global-current register to its maximum value. Table 5. Global-Current Register Format (0x15) DESCRIPTION Full current is 2.5mA; half current is 1.25mA Full current is 5mA; half current is 2.5mA Full current is 7.5mA; half current is 3.75mA Full current is 10mA; half current is 5mA Full current is 12.5mA; half current is 6.25mA Full current is 15mA; half current is 7.5mA Full current is 17.5mA; half current is 8.75mA Full current is 20mA; half current is 10mA D7 D6 D5 X X X X X X X X X X X X X X X X X X X X X X X X REGISTER BIT D4 D3 X X X X X X X X X X X X X X X X D2 D1 D0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 Table 6. Output-Current Register Format DESCRIPTION Output P0 is set to half constant current Output P0 is set to full constant current Output P1 is set to half constant current Output P1 is set to full constant current Output P2 is set to half constant current Output P2 is set to full constant current Output P3 is set to half constant current Output P3 is set to full constant current Output P4 is set to half constant current Output P4 is set to full constant current Output P5 is set to half constant current Output P5 is set to full constant current Output P6 is set to half constant current Output P6 is set to full constant current Output P7 is set to half constant current Output P7 is set to full constant current Output P8 is set to half constant current Output P8 is set to full constant current Output P9 is set to half constant current Output P9 is set to full constant current 10 ADDRESS CODE (HEX) 0x13 0x14 D7 X X X X X X X X X X X X X X 0 1 X X X X D6 X X X X X X X X X X X X 0 1 X X X X X X D5 X X X X X X X X X X 0 1 X X X X X X X X REGISTER BIT D4 D3 X X X X X X X X X X X X X 0 X 1 0 X 1 X X X X X X X X X X X X X X X X X X X X X D2 X X X X 0 1 X X X X X X X X X X X X X X ______________________________________________________________________________________ D1 X X 0 1 X X X X X X X X X X X X X X 0 1 D0 0 1 X X X X X X X X X X X X X X 0 1 X X 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Configure PWM timing by setting the stagger bit in the configuration register (Table 2), either with output staggering or without. Clearing the stagger bit causes all outputs using PWM to switch at the same time using the timing shown in Figure 2. All outputs, therefore, draw load current at the exactly same time for the same PWM setting. This means that if, for example, all outputs are set to 0x80 (128/256 duty cycle), the current draw would be zero (all loads off) for half the time, and full (all loads on) for the other half. Setting the stagger bit causes the PWM timing of the 10 port outputs to stagger by 32 counts of the 256-count PWM period (i.e., 1/8th), distributing the port output switching points across the PWM period (Figure 3). Staggering reduces the di/dt output-switching transient on the supply and also reduces the peak/mean current requirement. Set or clear the stagger bit during shutdown. Changing the stagger bit during normal operation can cause a transient flicker in any PWM-controlled LEDs because of the fundamental PWM timing changes. OUTPUT REGISTER VALUE 0x00 7.8125ms NOMINAL PWM PERIOD HIGH-Z OUTPUT STATIC-LOW LOGIC DRIVE WITH INPUT BUFFER ENABLED (GPI) LOW HIGH-Z 0x01 OUTPUT STATIC-HIGH LOGIC DRIVE WITH INPUT BUFFER ENABLED (GPI) LOW HIGH-Z 0x02 OUTPUT STATIC-LOW CONSTANT CURRENT WITH INPUT BUFFER DISABLED (STATIC LED DRIVE ON) LOW HIGH-Z 0x03 OUTPUT LOW 3/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE) LOW HIGH-Z 0x04 0xFC OUTPUT LOW 4/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE) OUTPUT LOW 252/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE) HIGH-Z LOW OUTPUT LOW 253/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE) 0xFD 0xFE LOW HIGH-Z LOW OUTPUT LOW 254/256 DUTY CONSTANT CURRENT WITH INPUT BUFFER DISABLED (PWM LED DRIVE) HIGH-Z LOW HIGH-Z 0xFF OUTPUT STATIC HIGH IMPEDANCE WITH INPUT BUFFER DISABLED (STATIC LED DRIVE OFF) LOW Figure 2. Static and PWM Constant-Current Waveforms ______________________________________________________________________________________ 11 MAX6946/MAX6947 PWM Intensity Control and Phasing The MAX6946/MAX6947 use an internal 32kHz oscillator to generate PWM timing for LED intensity control. The MAX6946 also features an OSC input to allow for an external clock for generating PWM timing for LED intensity control. Select the PWM clock source for the MAX6946 with configuration register bit D7 (Table 2). The MAX6947 powers up configured to use the internal 32kHz oscillator by default. The MAX6946 powers up configured to use the external clock source by default. A PWM period comprises 256 cycles of the nominal 32kHz PWM clock (Figure 2). Individually set the ports' PWM duty cycle between 3/256 and 254/256. See Table 4 for port register settings. MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Ports Configured as Inputs Configure a port as a logic input by writing 0x01 to the port's output register (Table 4). Reading an input port register returns the logic levels from the I/O ports configured as a logic input (Table 7). The input port register returns logic 0 in the appropriate bit position for a port not configured as a logic input. The input port's registers are read only. The MAX6946/ MAX6947 ignore a write to input ports register. RST Input The active-low RST input operates as a reset that voids any current I2C transaction involving the MAX6946/ MAX6947, forcing the devices into the I2C stop condition. Use the D6 bit in the configuration register to configure RST to reset all the internal registers to the power-on reset state (Tables 2 and 3). The RST input is overvoltage tolerant to 6V. The MAX6946/MAX6947 ignore all I2C bus activity while RST remains low. The MAX6946/MAX6947 use this feature to minimize supply current in power-critical applications by effectively disconnecting the MAX6946/ MAX6947 from the bus during idle periods. RST also operates as a bus multiplexer, allowing multiple MAX6946/MAX6947s to use the same I2C slave address. Drive only one MAX6946/MAX6947 RST input high at any time to use RST as a bus multiplexer. 7.8125ms NOMINAL PWM PERIOD 0 32 64 96 128 160 192 The MAX6946/MAX6947 feature a Reset Run option so that simply taking the RST input high brings the driver out of shutdown in addition to its normal function of enabling the devices' I2C interface. Standby Mode and Operating Current Configuring all the ports as logic inputs or outputs (all output registers set to value 0x00 or 0x01) or LED off (output register set to value 0xFF) puts the MAX6946/ MAX6947 into standby mode. Put the MAX6946/ MAX6947 into standby mode for lowest supply-current consumption. Setting a port as a constant-current output increases the operating current (output register set to a value between 0x02 and 0xFE), even if a load is not applied to the port. The MAX6946/MAX6947 enable an internal current mirror to provide the accurate constant-current sink. Enabling the internal current mirror increases the devices' supply current. Each output contains a gated mirror, and each mirror is only enabled when required. In PWM mode, the current mirror is only turned on for the output's on-time. This means that the operating current varies as constant-current outputs are turned on and off through the serial interface, as well as by the PWM intensity control. NEXT PWM PERIOD 224 NEXT PWM PERIOD 256 OUTPUTS P0, O8 IN-PHASE PWM PERIOD OUTPUTS P0, O8 IN-PHASE PWM PERIOD OUTPUTS P0, O8 IN-PHASE PWM PERIOD OUTPUT P1, O9 STAGGERED PWM PERIOD OUTPUT P1, O9 STAGGERED PWM PERIOD OUTPUT P1, O9 STAGGERED PWM PERIOD OUTPUT P2 STAGGERED PWM PERIOD OUTPUT P2 STAGGERED PWM PERIOD OUTPUT P3 STAGGERED PWM PERIOD OUTPUT P3 STAGGERED PWM PERIOD OUTPUT P4 STAGGERED PWM PERIOD OUTPUT P4 STAGGERED PWM PERIOD OUTPUT P5 STAGGERED PWM PERIOD OUTPUT P5 STAGGERED PWM PERIOD OUTPUT P6 STAGGERED PWM PERIOD OUTPUT P6 STAGGERED PWM PERIOD OUTPUT P7 STAGGERED PWM PERIOD OUTPUT P7 STAGGERED PWM PERIOD Figure 3. Staggered PWM Waveform Table 7. Input Ports Registers 12 REGISTER BIT DESCRIPTION ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Input ports P7-P0 0x0E Port P7 Port P6 Port P5 Port P4 Port P3 Port P2 Port P1 Port P0 Input ports P9 and P8 0x0F 0 0 0 0 0 0 Port P9 Port P8 ______________________________________________________________________________________ 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Ramp-Up and Ramp-Down Controls The MAX6946/MAX6947 provide controls that allow the output currents to ramp down into shutdown (rampdown), and ramp up again out of shutdown (ramp-up) (Figures 4 and 5). Ramp-down comprises a programmable hold-off delay that also maintains the outputs at full current for a time before the programmed fade-off time. After the hold-off delay, the output currents ramp down. ZERO TO 4s CURRENT RAMP-UP AFTER CS RUN 1/8s 1/16s 1/4s 1/2s 1s 4s 2s FULL CURRENT/ HALF CURRENT 0 EXIT SHUTDOWN COMMAND Figure 4. Ramp-Up Behavior ZERO TO 8s CURRENT RAMP-DOWN ZERO TO 4s CURRENT FADE-OFF AFTER HOLD-OFF DELAY ZERO TO 4s HOLD-OFF DELAY BEFORE FADE-OFF FULL CURRENT/ HALF CURRENT 0 1/4s 1/2s 1s 2s 1/8s 1/16s 4s 1/4s 1/2s 1s 2s 4s 1/8s 1/16s Figure 5. Ramp-Down, Hold-Off, and Fade-Off Behavior ______________________________________________________________________________________ 13 MAX6946/MAX6947 Changing a port from static logic-low (0x00) or static logic-high (0x01) to a constant-current value (0x02-0xFE) in shutdown mode turns that output off (logic-high or high impedance) like any other constantcurrent outputs in shutdown. The new constant-current output starts just like any other constant-current outputs when exiting shutdown. Changing a port from a constant-current value (0x02-0xFE) to static logic-low (0x00) or static logichigh (0x01) in shutdown causes that output to set to the value as a GPIO output. The new GPIO output is unaffected just like any other GPIO output when exiting shutdown. Shutdown Mode In shutdown mode, all ports configured as constantcurrent outputs (output register set to a value between 0x02 and 0xFE) are switched off, and these outputs go high impedance as if their registers were set to value 0xFF. Ports configured as logic inputs or outputs (output registers set to value 0x00 or 0x01) are unaffected (Table 4). This means that any ports used for GPIOs are still fully operational in shutdown mode, and port inputs can be read and output ports can be toggled at any time using the serial interface. Use the MAX6946/ MAX6947 for a mix of logic inputs, logic outputs, and PWM LED drivers, and only the LED drivers turn off automatically in shutdown. Put the MAX6946/MAX6947 into shutdown mode by clearing the run bit (bit D0) in the configuration register (0x10) (Table 2). Exit shutdown by setting the run bit high through the serial interface or by using the Reset Run option (see the Reset Run Option section). Configure and control the MAX6946/MAX6947 normally through the serial interface in shutdown mode. All registers are accessible in shutdown mode, and shutdown mode does not change any register values. MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control The ramp-down register sets the hold-off and fade-off times and allows disabling of hold-off and fade-off (zero delay), if desired (Table 8). The ramp-up register sets the ramp-up time and allows disabling of ramp-up (zero delay), if desired (Table 9). The configuration register contains three status bits that identify the condition of the MAX6946/MAX6947, hold-off, fade-off, or ramp-up (Table 2). The configuration register also enables or disables ramp-up. One write command to the configuration register can put the MAX6946/MAX6947 into shutdown (using hold-off and fade-off settings in the fade register) and one read command to the configuration register can determine whether the Reset Run is enabled for restart, and whether the MAX6946/MAX6947 will use ramp-up on restart. CURRENT PORT CURRENT = FULL 20mA 17.5mA 15mA 12.5mA PORT CURRENT = HALF 10mA 7.5mA 5mA 2.5mA 0mA FULL CURRENT 7/8 CURRENT 6/8 CURRENT 5/8 CURRENT 4/8 CURRENT 3/8 CURRENT 2/8 CURRENT 1/8 ZERO CURRENT CURRENT FADE-UP FADE-OFF Figure 6. Output Fade DAC (Global Current = 0x07) Table 8. Ramp-Down Register Format (0X11) DESCRIPTION Instant going into shutdown after hold-off delay REGISTER BIT D7 D6 D5 D4 D3 D2 D1 D0 X X X X X 0 0 0 1/16s ramp-down from full current before shutdown after hold-off delay X X X X X 0 0 1 1/8s ramp-down from full current before shutdown after hold-off delay X X X X X 0 1 0 1/4s ramp-down from full current before shutdown after hold-off delay X X X X X 0 1 1 1/2s ramp-down from full current before shutdown after hold-off delay X X X X X 1 0 0 1s ramp-down from full current before shutdown after hold-off delay X X X X X 1 0 1 2s ramp-down from full current before shutdown after hold-off delay X X X X X 1 1 0 4s ramp-down from full current before shutdown after hold-off delay X X X X X 1 1 1 Zero hold-off delay before fade-off going into shutdown X X 0 0 0 X X X 1/16s hold-off delay before fade-off going into shutdown X X 0 0 1 X X X 1/8s hold-off delay before fade-off going into shutdown X X 0 1 0 X X X 1/4s hold-off delay before fade-off going into shutdown X X 0 1 1 X X X 1/2s hold-off delay before fade-off going into shutdown X X 1 0 0 X X X 1s hold-off delay before fade-off going into shutdown X X 1 0 1 X X X 2s hold-off delay before fade-off going into shutdown X X 1 1 0 X X X 4s hold-off delay before fade-off going into shutdown X X 1 1 1 X X X 14 ______________________________________________________________________________________ 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control DESCRIPTION Instant full current coming out from shutdown 1/16s ramp-up to full current coming out from shutdown 1/8s ramp-up to full current coming out from shutdown 1/4s ramp-up to full current coming out from shutdown 1/2s ramp-up to full current coming out from shutdown 1s ramp-up to full current coming out from shutdown 2s ramp-up to full current coming out from shutdown 4s ramp-up to full current coming out from shutdown Ramp-up and ramp-down use the PWM clock for timing. When using the external oscillator make sure the oscillator runs until the end of the sequence. The internal oscillator always runs during a fade sequence, even if none of the ports use PWM. The ramp-up and ramp-down circuit operates a 3-bit DAC. The DAC adjusts the internal current reference used to set the constant-current outputs in a similar manner to the global-current register (Table 5). The MAX6946/MAX6947 scale the master current reference so all output constant-current and PWM settings adjust at the same ratio with respect to each other. This means the LEDs always fade at the same rate even if with different intensity settings. The maximum port output current set by the global-current register (Table 5) also sets the point during rampdown that the current starts falling, and the point during ramp-up that the current stops rising. Figure 7 shows the ramp waveforms that occur with different globalcurrent register settings. REGISTER BIT D7 X X X X X X X X D6 X X X X X X X X D5 X X X X X X X X D4 X X X X X X X X D3 X X X X X X X X D2 0 0 0 0 1 1 1 1 D1 0 0 1 1 0 0 1 1 D0 0 1 0 1 0 1 0 1 CURRENT GLOBAL CURRENT = 0x07 20mA 17.5mA 15mA 12.5mA 10mA 7.5mA 5mA 2.5mA 0mA GLOBAL CURRENT = 0x06 GLOBAL CURRENT = 0x05 GLOBAL CURRENT = 0x04 GLOBAL CURRENT = 0x03 GLOBAL CURRENT = 0x02 GLOBAL CURRENT = 0x01 GLOBAL CURRENT = 0x00 ZERO 4/8 2/8 3/8 1/8 6/8 7/8 5/8 FULL CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT CURRENT RAMP-UP RAMP-DOWN Reset Run Option The MAX6946/MAX6947 feature a Reset Run option so that simply taking the RST input high brings the driver out of shutdown in addition to its normal function of enabling the MAX6946/MAX6947s' I2C interface. This provides an alternative method of bringing the driver out of shutdown to writing to the configuration register through the serial interface. The Reset Run timing uses the PWM clock, either the internal nominal 32kHz oscillator or a user-provided clock fed into the OSC input (MAX6946 only). After enabling the Reset Run option, the MAX6946/ MAX6947 use the rising edge on RST, followed by no I2C interface activity to the MAX6946/MAX6947 for 128 to 129 periods of the PWM clock to trigger the Reset Figure 7. Global Current Modifies Fade Behavior Run option. If this timeout period elapses without the MAX6946/MAX6947 acknowledging an I2C transaction, the run bit (D0) in the configuration register sets, bringing the driver out of shutdown and activating any programmed ramp-up. If RST pulses high for less than this timeout period to trigger a Reset Run, the MAX6946/ MAX6947 ignore the pulse, and the MAX6946/MAX6947 continue to wait for a suitable trigger. Cancel the Reset Run trigger by transmitting an I2C communication to the MAX6946/MAX6947 before the timeout period elapses. The trigger cancels when the MAX6946/MAX6947 acknowledge the I2C transaction ______________________________________________________________________________________ 15 MAX6946/MAX6947 Table 9. Ramp-Up Register Format (0x12) MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control and requires sending at least the MAX6946/MAX6947s' I2C slave address. When using the internal oscillator, the minimum timeout period is 127/45000 equal to 2.822ms. When using an external oscillator for the PWM clock, the timeout period is 127/OSC. The shortest time period allowed is 1.27ms; this number corresponds to the maximum OSC frequency of 100kHz. When using the internal oscillator, the minimum I2C clock speed that guarantees a successful start bit and eight data bits (9 bits total) within the minimum timeout period is 9/5.66ms equal to 1590Hz. Canceling the Reset Run trigger clears the Reset Run bit (D1) in the configuration register, disabling Reset Run. The run bit (D0) in the configuration register remains cleared, so the driver remains in shutdown. OSC Input The MAX6946 can use an external clock of up to 100kHz instead of the internal 32kHz oscillator. Connect the external clock to the OSC input and set the OSC bit in the configuration register to enable the MAX6946 to use the external clock (Table 2). Serial Interface Serial Addressing The MAX6946/MAX6947 operate as a slave that sends and receives data through an I2C-compatible, 2-wire interface. The interface uses a serial-data line (SDA) and a serial-clock line (SCL) to achieve bidirectional communication between master(s) and slave(s). A master (typically a microcontroller) initiates all data transfers to and from the MAX6946/MAX6947 and generates the SCL clock that synchronizes the data transfer (Figure 8). The MAX6946/MAX6947 SDA line operates as both an input and an open-drain output. A pullup resistor, typically 4.7k, is required on SDA. The MAX6946/ MAX6947 SCL line operates as an input. A pullup resistor, typically 4.7k, is required on SCL if there are multiple masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output. Each transmission consists of a START condition (Figure 9) sent by a master, followed by the MAX6946/ MAX6947 7-bit slave address plus the R/W bit, a register address byte, one or more data bytes, and finally a STOP condition (Figure 9). SDA tSU,STA tSU,DAT tLOW tBUF tHD,STA tSU,STO tHD,DAT tHIGH SCL tHD,STA tR tF START CONDITION REPEATED START CONDITION STOP CONDITION Figure 8. 2-Wire Serial Interface Timing Details 16 ______________________________________________________________________________________ START CONDITION 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control SDA MAX6947 SLAVE ADDRESS AD0 = GND 010 0000 AD0 = VDD 010 0100 MAX6946 010 0000 Start and Stop Conditions Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a START (S) condition by transitioning SDA from high to low while SCL is high. When the master finishes communicating with the slave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is high. The bus is then free for another transmission (Figure 9). SCL S P START CONDITION STOP CONDITION Figure 9. Start and Stop Conditions SDA SCL DATA LINE STABLE; CHANGE OF DATA DATA VALID ALLOWED Bit Transfer One data bit is transferred during each clock pulse. The data on SDA must remain stable while SCL is high (Figure 10). Figure 10. Bit Transfer Acknowledge Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MAX6946/MAX6947 selected by the command byte (Figure 11). If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent MAX6946/MAX6947 internal registers because the command byte autoincrements (Table 1). Message Format for Reading Read from the MAX6946/MAX6947 using the MAX6946/MAX6947s' internally stored command byte as an address pointer the same way the stored command byte is used as an address pointer for a write. The pointer autoincrements after each data byte is read using the same rules as for a write (Table 1). Thus, a read is initiated by first configuring the MAX6946/ MAX6947s' command byte by performing a write (Figures 12 and 13). The master can now read n con- CLOCK PULSE FOR ACKNOWLEDGE START CONDITION SCL 1 2 8 9 SDA BY TRANSMITTER SDA BY RECEIVER S Figure 11. Acknowledge secutive bytes from the MAX6946/MAX6947 with the first data byte being read from the register addressed by the initialized command byte (Figure 14). When performing read-after-write verification, remember to reset the command byte's address because the stored command byte address has been autoincremented after the write (Table 1). ______________________________________________________________________________________ 17 MAX6946/MAX6947 Table 10. MAX6946/MAX6947 Slave Addresses MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION ACKNOWLEDGE FROM MAX6946/MAX6947 S SLAVE ADDRESS 0 D15 D14 D13 A D12 D11 D10 D9 D8 COMMAND BYTE R/W A P ACKNOWLEDGE FROM MAX6946/MAX6947 Figure 12. Command Byte Received ACKNOWLEDGE FROM MAX6946/MAX6947 HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6946/MAX6947s' REGISTERS D15 D14 D13 D12 D11 D10 D9 ACKNOWLEDGE FROM MAX6946/MAX6947 D8 D7 D6 D5 D4 D3 D2 D1 D0 ACKNOWLEDGE FROM MAX6946/MAX6947 S SLAVE ADDRESS 0 A COMMAND BYTE A DATA BYTE A P 1 BYTE R/W AUTOINCREMENT MEMORY ADDRESS Figure 13. Command and Single Data Byte Received ACKNOWLEDGE FROM MAX6946/MAX6947 HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6946/MAX6947s' REGISTERS D15 D14 D13 D12 D11 D10 D9 ACKNOWLEDGE FROM MAX6946/MAX6947 D8 D7 D6 D5 D4 D3 D2 D1 D0 ACKNOWLEDGE FROM MAX6946/MAX6947 S SLAVE ADDRESS 0 A COMMAND BYTE R/W A DATA BYTE A P N BYTES AUTOINCREMENT MEMORY ADDRESS Figure 14. n Data Bytes Received Operation with Multiple Masters If the MAX6946/MAX6947 operates on a 2-wire interface with multiple masters, a master reading the MAX6946/MAX6947 should use a repeated start between the write. This sets the MAX6946/MAX6947 address pointer, and the read(s) that takes the data from the location(s) (Table 1). This is because it is possible for master 2 to take over the bus after master 1 has set up the MAX6946/MAX6947s' address pointer, then master 1's delayed read can be from an unexpected location. Command Address Autoincrementing The command address stored in the MAX6946/ MAX6947 increments through the grouped register functions after each data byte is written or read (Table 1). 18 Applications Information Port Input and I2C Interface-Level Translation from Higher or Lower Logic Voltages The MAX6946/MAX6947s' I2C interface (SDA, SCL) and I2C slave address select input AD0 (MAX6947 only), PWM clock input OSC (MAX6946 only), and reset input RST are overvoltage protected to +6V, independent of VDD. The 10 I/O ports P0-P9 are overvoltage protected to +8V independent of VDD. This allows the MAX6946/ MAX6947 to operate from one supply voltage, such as 3.3V, while driving the I2C interface and/or some of the 10 I/O as inputs from a higher logic level, such as 5V. ______________________________________________________________________________________ 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Differences Between the MAX6946 and MAX6947 The MAX6946 features the OSC input, allowing the device to use an external clock as the PWM clock source. The MAX6946 features a fixed I 2 C slave address of 0100000. The MAX6947 features an AD0 input, allowing two unique I2C addresses (Table 10). The MAX6947 always uses the internal 32kHz oscillator as the PWM clock source. Driving LEDs into Brownout The MAX6946/MAX6947 correctly regulate the constant-current outputs, provided there is a minimum voltage drop across the port output. This port output voltage is the difference between the load (typically LED) supply and the load voltage drop (LED forward voltage). If the LED supply drops so that the minimum port output voltage is not maintained, the driver output stages brownout and the load current falls. The minimum port voltage is approximately 0.5V at 10mA sink current and approximately 1V at 20mA sink current. Operating the LEDs directly from a battery supply can cause brownouts. For example, the LED supply voltage is a single rechargeable lithium-ion battery with a maximum terminal voltage of 4.2V on charge, 3.4V to 3.7V most of the time, and down to 3V when discharged. In this scenario, the LED supply falls significantly below the brownout point when the battery is at end-of-life voltage (3V). Figure 15 shows the typical current sink by a LITEON LTST-C170TBKT 3.0V blue LED as the LED supply voltage is varied from 2.5V to 7V. The LED currents shown are for ports programmed for 10mA and 20mA constant current, swept over a 2.5V to 7V LED supply voltage range. It can be seen that the LED forward voltage falls with current, allowing the LED current to fall gracefully, not abruptly, in brownout. In practice, the LED current drops to 6mA to 7mA at a 3V LED supply voltage, this is acceptable performance at end-of-life in many backlight applications. Output-Level Translation The open-drain output architecture allows the ports to level translate the outputs to higher or lower voltages than the MAX6946/MAX6947 supply. Use an external pullup resistor on any output to convert the high-impedance, logic-high condition to a positive voltage level. Connect the resistor to any voltage up to 7V. When using a pullup on a constant-current output, select the resistor value to sink no more than a few hundred micramps in logic-low condition. This ensures that the current sink output saturates close to GND. For interfacing CMOS inputs, a pullup resistor value of 220k is a good starting point. Use a lower resistance to improve noise immunity in applications where power consumption is less critical, or where a faster rise time is needed for a given capacitive load. VLED vs. VLED SUPPLY ILED vs. VLED SUPPLY 3.05 20 3.00 18 2.95 16 2.90 14 ILED (mA) VLED (V) 2.85 2.80 2.75 12 10 2.70 8 2.65 6 2.60 4 2.55 2 0 2.50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 VLED SUPPLY (V) VLED SUPPLY (V) Figure 15. LED Brownout ______________________________________________________________________________________ 19 MAX6946/MAX6947 Hot Insertion The RST, SCL, and AD0 inputs and SDA remain high impedance with up to +6V asserted on them when the MAX6946/MAX6947 power down (VDD = 0V). I/O ports P0 to P9 remain high impedance with up to +8V asserted on them when the MAX6946/MAX6947 power down. Use the MAX6946/MAX6947 in hot-swap applications. Using Stagger with Fewer Ports The stagger option, when selected, applies to all ports configured as constant-current outputs. The 10 ports' PWM cycles are separated to eight evenly spaced start positions (Figure 3). Optimize phasing when using fewer than 10 ports as constant-current outputs by allocating the ports with the most appropriate start positions. If using eight constant-current outputs, choose P0-P7 because these all have different PWM start positions. If using four constant-current outputs, choose P0, P2, P4, P6 or P1, P3, P5, P7 because their PWM start positions are evenly spaced. In general, choose the ports that spread the PWM start positions as evenly as possible. This optimally spreads out the current demand from the ports' load supply. Generating a Shutdown/Run Output The MAX6946/MAX6947 can use an I/O port to automatically generate a shutdown/run output. The shutdown/run output is active low when the MAX6946/ MAX6947 are in run mode, hold-off, fade-off, or rampup, and goes high automatically when the devices finally enter shutdown after fade-off. Programming the port's output register to value 0x02 puts the output into static constant-current mode (Table 4). Program the port's output current register to half current (Table 6) to minimize operating current. Connect a 220k pullup resistor to this port. In run mode, the output port goes low, approaching 0V, as the port's static constant current saturates trying to sink a higher current than the 220k pullup resistor can source. In shutdown mode, the output goes high impedance together with any other constant-current outputs. This output remains low during ramp-up and fade-down sequences because the current drawn by the 220k pullup resistor is much smaller than the available output constant current, even at the lowest fade current step. Driving Load Currents Higher than 20mA The MAX6946/MAX6947 can drive loads needing more than 20mA, like high-current white LEDs, by paralleling outputs. For example, consider a white LED that requires 70mA. Drive this LED using the ports P0-P3 connected in parallel (shorted together). Configure three of the ports for full current (20mA) and configure the last port for half current (10mA) to meet the 70mA requirement. Control the four ports simultaneously with one write access using register 0x0B (Table 1). Note that because the output ports are current limiting, they do not need to switch simultaneously to ensure safe current sharing. Power-Supply Considerations The MAX6946/MAX6947 operate with a power-supply voltage of 2.25V to 3.6V. Bypass the power supply to GND with a 0.1F ceramic capacitor as close as possible to the device. Chip Information PROCESS: BiCMOS P9 P8 P7 TOP VIEW OSC(AD0) Pin Configurations (continued) 12 11 10 9 RST 13 VDD 14 MAX6946 MAX6947 SCL 15 1 2 3 4 P2 P3 + P1 SDA 16 P0 MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control TQFN (3mm x 3mm) () MAX6947 ONLY 20 ______________________________________________________________________________________ 8 P6 7 P5 6 GND 5 P4 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control 12x16L QFN THIN.EPS (NE - 1) X e E MARKING E/2 D2/2 (ND - 1) X e D/2 AAAA e CL D D2 k CL b 0.10 M C A B E2/2 L E2 0.10 C C L C L 0.08 C A A2 A1 L L e e PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.8mm 21-0136 I 1 2 ______________________________________________________________________________________ 21 MAX6946/MAX6947 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) PKG 8L 3x3 12L 3x3 16L 3x3 REF. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 b 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 D 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 E 2.90 3.00 3.10 2.90 3.00 3.10 2.90 3.00 3.10 0.75 0.45 0.65 0.30 e L 0.65 BSC. 0.35 0.55 0.50 BSC. 0.50 BSC. 0.55 0.40 N 8 12 16 ND 2 3 4 2 NE 0 A1 A2 k 0.02 3 0.05 0 0.20 REF 0.25 - 0.02 0.25 - 0.50 4 0.05 0 0.02 0.05 0.20 REF 0.20 REF - EXPOSED PAD VARIATIONS - 0.25 - PKG. CODES D2 MIN. E2 NOM. MAX. MIN. NOM. MAX. PIN ID JEDEC TQ833-1 0.25 0.70 1.25 0.25 0.70 1.25 0.35 x 45 T1233-1 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45 WEEC WEED-1 T1233-3 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45 WEED-1 T1233-4 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45 WEED-1 T1633-2 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45 WEED-2 T1633F-3 0.65 0.80 0.95 0.65 0.80 0.95 0.225 x 45 WEED-2 T1633FH-3 0.65 0.80 0.95 0.65 0.80 0.95 0.225 x 45 WEED-2 T1633-4 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45 WEED-2 T1633-5 0.95 1.10 1.25 0.95 1.10 1.25 0.35 x 45 WEED-2 - NOTES: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. N IS THE TOTAL NUMBER OF TERMINALS. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm FROM TERMINAL TIP. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS . DRAWING CONFORMS TO JEDEC MO220 REVISION C. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY. WARPAGE NOT TO EXCEED 0.10mm. PACKAGE OUTLINE 8, 12, 16L THIN QFN, 3x3x0.8mm 21-0136 22 ______________________________________________________________________________________ I 2 2 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control ______________________________________________________________________________________ 23 MAX6946/MAX6947 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) MAX6946/MAX6947 10-Port, Constant-Current LED Driver and I/O Expander with PWM Intensity Control Revision History REVISION NUMBER REVISION DATE 2 10/06 -- 3 1/08 Added MAX6946C (WLP package) to the data sheet. DESCRIPTION PAGES CHANGED 1, 7, 11, 17, 19 1-6, 20, 23 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2008 Maxim Integrated Products Heaney is a registered trademark of Maxim Integrated Products, Inc.