19-2414; Rev 3; 3/09 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander The MAX6956 compact, serial-interfaced LED display driver/I/O expander provide microprocessors with up to 28 ports. Each port is individually user configurable to either a logic input, logic output, or common-anode (CA) LED constant-current segment driver. Each port configured as an LED segment driver behaves as a digitally controlled constant-current sink, with 16 equal current steps from 1.5mA to 24mA. The LED drivers are suitable for both discrete LEDs and CA numeric and alphanumeric LED digits. Each port configured as a general-purpose I/O (GPIO) can be either a push-pull logic output capable of sinking 10mA and sourcing 4.5mA, or a Schmitt logic input with optional internal pullup. Seven ports feature configurable transition detection logic, which generates an interrupt upon change of port logic level. The MAX6956 is controlled through an I2C-compatible 2-wire serial interface, and uses four-level logic to allow 16 I 2C addresses from only 2 select pins. The MAX6956AAX and MAX6956ATL have 28 ports and are available in 36-pin SSOP and 40-pin thin QFN packages, respectively. The MAX6956AAI and MAX6956ANI have 20 ports and are available in 28-pin SSOP and 28-pin DIP packages, respectively. For an SPI-interfaced version, refer to the MAX6957 data sheet. For a lower cost pin-compatible port expander without the constant-current LED drive capability, refer to the MAX7300 data sheet. Applications Features 400kbps I C-Compatible Serial Interface 2 2.5V to 5.5V Operation -40°C to +125°C Temperature Range 20 or 28 I/O Ports, Each Configurable as Constant-Current LED Driver Push-Pull Logic Output Schmitt Logic Input Schmitt Logic Input with Internal Pullup 11µA (max) Shutdown Current 16-Step Individually Programmable Current Control for Each LED Logic Transition Detection for Seven I/O Ports Ordering Information PART MAX6956ANI TEMP RANGE PIN-PACKAGE -40°C to +125°C 28 DIP MAX6956AAI -40°C to +125°C 28 SSOP MAX6956AAX -40°C to +125°C 36 SSOP MAX6956ATL -40°C to +125°C *EP = Exposed pad. 40 Thin QFN-EP* Pin Configurations TOP VIEW Set-Top Boxes Bar Graph Displays ISET 1 28 V+ Panel Meters Industrial Controllers GND 2 27 AD1 White Goods System Monitoring GND 3 26 SCL AD0 4 25 SDA Automotive P12 5 P13 6 Typical Operating Circuit appears at end of data sheet. 24 P31 MAX6956 23 P30 P14 7 22 P29 P15 8 21 P28 P16 9 20 P27 P17 10 19 P26 P18 11 18 P25 P19 12 17 P24 P20 13 16 P23 P21 14 15 P22 SSOP/DIP 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 MAX6956 General Description MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander ABSOLUTE MAXIMUM RATINGS Voltage (with Respect to GND) V+ .............................................................................-0.3V to +6V SCL, SDA, AD0, AD1................................................-0.3V to +6V All Other Pins................................................-0.3V to (V+ + 0.3V) P4–P31 Current ................................................................±30mA GND Current .....................................................................800mA Continuous Power Dissipation 28-Pin PDIP (derate 14.3mW/°C above TA = +70°C) 1143mW 28-Pin SSOP (derate 9.1mW/°C above TA = +70°C) ...727mW 36-Pin SSOP (derate 11.8mW/°C above TA = +70°C) ...941mW 40-Pin TQFN (derate 26.3mW/°C above TA = +70°C) 2105mW Operating Temperature Range (TMIN to TMAX) ...............................................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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 (Typical Operating Circuit, V+ = 2.5V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER Operating Supply Voltage Shutdown Supply Current Operating Supply Current Operating Supply Current Operating Supply Current SYMBOL V+ ISHDN IGPOH IGPOL ILED CONDITIONS All digital inputs at V+ or GND All ports programmed as outputs high, no load, all other inputs at V+ or GND All ports programmed as outputs low, no load, all other inputs at V+ or GND MIN 2.5 TA = +25°C TYP MAX 5.5 5.5 8 TA = -40°C to +85°C 10 TA = TMIN to TMAX 11 TA = +25°C 180 250 TA = TMIN to TMAX 270 170 230 TA = TMIN to TMAX 240 110 µA 210 TA = -40°C to +85°C All ports programmed TA = +25°C as LED outputs, all LEDs TA = -40°C to +85°C off, no load, all other inputs at V+ or GND TA = TMIN to TMAX µA 230 TA = -40°C to +85°C TA = +25°C UNITS V µA 135 140 µA 145 INPUTS AND OUTPUTS Logic-High Input Voltage Port Inputs VIH Logic-Low Input Voltage Port Inputs VIL Input Leakage Current IIH, IIL GPIO Input Internal Pullup to V+ IPU Hysteresis Voltage GPIO Inputs ΔVI Output High Voltage Port Sink Current Output Short-Circuit Current 2 VOH IOL IOLSC 0.7 ✕ V+ GPIO inputs without pullup, VPORT = V+ to GND V+ = 2.5V V+ = 5.5V V 0.3 ✕ V+ V -100 ±1 +100 nA 12 80 19 120 30 180 µA 0.3 GPIO outputs, ISOURCE = 2mA, TA = -40°C to +85°C V+ 0.7 GPIO outputs, ISOURCE = 1mA, TA = TMIN to TMAX (Note 2) V+ 0.7 VPORT = 0.6V Port configured output low, shorted to V+ V V 2 10 18 mA 2.75 11 20 mA _______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander (Typical Operating Circuit, V+ = 2.5V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER Port Drive LED Sink Current, Port Configured as LED Driver Port Drive Logic Sink Current, Port Configured as LED Driver Input High-Voltage SDA, SCL, AD0, AD1 Input Low-Voltage SDA, SCL, AD0, AD1 Input Leakage Current SDA, SCL Input Capacitance Output Low-Voltage SDA SYMBOL CONDITIONS V+ = 2.5V, VLED = 2.3V at maximum LED current V+ = 3.3V, VLED = 2.4V at maximum LED IDIGIT current (Note 2) V+ = 5.5V, VLED = 2.4V at maximum LED current V+ = 2.5V, VOUT = 0.6V at maximum sink current IDIGIT_SC V+ = 5.5V, VOUT = 0.6V at maximum sink current MIN TYP MAX 9.5 13.5 18 18.5 24 27.5 19 25 30 18.5 23 28 19 24 28 V VIL IIH, IIL VOL mA mA 0.7 ✕ V+ VIH UNITS -50 (Note 2) ISINK = 6mA 0.3 ✕ V+ 50 10 0.4 nA pF V MAX 400 UNITS kHz V TIMING CHARACTERISTICS (Figure 2) (V+ = 2.5V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1) PARAMETER Serial Clock Frequency Bus Free Time Between a STOP and a START Condition Hold Time (Repeated) START Condition Repeated START Condition Setup Time STOP Condition Setup Time Data Hold Time Data Setup Time SCL Clock Low Period SCL Clock High Period Rise Time of Both SDA and SCL Signals, Receiving Fall Time of Both SDA and SCL Signals, Receiving Fall Time of SDA Transmitting SYMBOL fSCL CONDITIONS MIN TYP tBUF 1.3 µs tHD, STA 0.6 µs tSU, STA 0.6 µs tSU, STO tHD, DAT tSU, DAT tLOW tHIGH (Note 3) tR (Notes 2, 4) tF (Notes 2, 4) tF,TX (Notes 2, 5) 0.6 15 100 1.3 0.7 900 20 + 0.1Cb 20 + 0.1Cb 20 + 0.1Cb µs ns ns µs µs 300 ns 300 ns 250 ns Pulse Width of Spike Suppressed tSP (Notes 2, 6) 0 50 ns Capacitive Load for Each Bus (Note 2) 400 pF Cb Line Note 1: All parameters tested at TA = +25°C. Specifications over temperature are guaranteed by design. Note 2: Guaranteed by design. 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: Cb = total capacitance of one bus line in pF. tR and tF measured between 0.3V+ and 0.7V+. Note 5: ISINK ≤ 6mA. Cb = total capacitance of one bus line in pF. tR and tF measured between 0.3V+ and 0.7V+. Note 6: Input filters on the SDA and SCL inputs suppress noise spikes less than 50ns. _______________________________________________________________________________________ 3 MAX6956 ELECTRICAL CHARACTERISTICS (continued) __________________________________________Typical Operating Characteristics (RISET = 39kΩ, TA = +25°C, unless otherwise noted.) ALL PORTS OUTPUT (0) ALL PORTS OUTPUT (1) 0.20 0.16 0.12 0.08 6 V+ = 2.5V ALL PORTS OUTPUT (1) 1 ALL PORTS OUTPUT (0) ALL PORTS LED (OFF) ALL PORTS LED (OFF) 0 3 -12.5 15.0 42.5 70.0 97.5 125.0 0.01 -40.0 -12.5 15.0 42.5 70.0 97.5 125.0 2.0 3.0 3.5 4.0 4.5 5.0 V+ (V) LED DRIVER SINK CURRENT vs. V+ LED DRIVER SINK CURRENT vs. TEMPERATURE GPO SINK CURRENT vs. TEMPERATURE (OUTPUT = 0) 20 LED DROP = 2.4V 18 16 LED DROP = 1.8V 14 26 PORT SINK CURRENT (mA) 22 VLED = 2.4V 12 V+ = 5.5V 18 V+ = 2.5V TO 5.5V, VPORT = 0.6V 16 PORT SINK CURRENT (mA) 27 MAX6956 toc04 24 25 24 23 V+ = 3.3V 22 10 21 8 2.5 3.0 3.5 4.0 4.5 5.0 12 10 8 6 2 -40.0 5.5 14 4 20 6 -12.5 15.0 42.5 70.0 97.5 -40.0 125.0 -12.5 15.0 42.5 70.0 97.5 V+ (V) TEMPERATURE (°C) TEMPERATURE (°C) GPO SOURCE CURRENT vs. TEMPERATURE (OUTPUT = 1) GPI PULLUP CURRENT vs. TEMPERATURE GPO SHORT-CIRCUIT CURRENT vs. TEMPERATURE PULLUP CURRENT (μA) V+ = 5.5V V+ = 3.3V 6 5 V+ = 2.5V 4 PORT CURRENT (mA) V+ = 5.5V 100 V+ = 3.3V GPO = 0, PORT SHORTED TO V+ 10 V+ = 2.5V 3 2 GPO = 1, PORT SHORTED TO GND 1 10 -12.5 15.0 42.5 70.0 TEMPERATURE (°C) 97.5 125.0 125.0 MAX6956 toc09 8 100 MAX6956 toc08 VPORT = 1.4V 7 1000 MAX6956 toc07 9 -40.0 5.5 TEMPERATURE (°C) 26 2.0 2.5 TEMPERATURE (°C) MAX6956 toc05 -40.0 4 10 0.1 4 0.04 PORT SINK CURRENT (mA) V+ = 3.3V 5 ALL PORTS LED (ON) MAX6956 toc06 0.24 100 SUPPLY CURRENT (mA) 0.28 V+ = 5.5V 7 SUPPLY CURRENT (μA) SUPPLY CURRENT (mA) 0.32 OPERATING SUPPLY CURRENT vs. V+ (NO LOADS) MAX6956 toc02 V+ = 2.5V TO 5.5V NO LOAD 0.36 8 MAX6956 toc01 0.40 SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE MAX6956 toc03 OPERATING SUPPLY CURRENT vs. TEMPERATURE PORT SOURCE CURRENT (mA) MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander -40.0 -12.5 15.0 42.5 70.0 TEMPERATURE (°C) 97.5 125.0 -40.0 -12.5 15.0 42.5 70.0 TEMPERATURE (°C) _______________________________________________________________________________________ 97.5 125.0 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander PIN NAME FUNCTION 36 ISET Segment Current Setting. Connect ISET to GND through a resistor (RISET) to set the maximum segment current. 2, 3 37, 38, 39 GND Ground 4 4 40 AD0 Address Input 0. Sets device slave address. Connect to either GND, V+, SCL, SDA to give four logic combinations. See Table 3. 5–24 — — P12–P31 LED Segment Drivers and GPIO. P12 to P31 can be configured as CA LED drivers, GPIO outputs, CMOS logic inputs, or CMOS logic inputs with weak pullup resistor. — 5–32 1–10, 12–19, 21–30 P4–P31 LED Segment Drivers and GPIO. P4 to P31 can be configured as CA LED drivers, GPIO outputs, CMOS logic inputs, or CMOS logic inputs with weak pullup resistor. SSOP/DIP SSOP TQFN 1 1 2, 3 — — 11, 20, 31 N.C. No Connection 25 33 32 SDA I2C-Compatible Serial Data I/O 26 34 33 SCL I2C-Compatible Serial Clock Input 27 35 34 AD1 Address Input 1. Sets device slave address. Connect to either GND, V+, SCL, SDA to give four logic combinations. See Table 3. 28 36 35 V+ Positive Supply Voltage. Bypass V+ to GND with minimum 0.047µF capacitor. — — — EP Exposed Pad (TQFN Only). Not internally connected. Connect EP to ground plane for maximum thermal performance. Detailed Description The MAX6956 LED driver/GPIO peripheral provides up to 28 I/O ports, P4 to P31, controlled through an I2C-compatible serial interface. The ports can be configured to any combination of constant-current LED drivers, logic inputs and logic outputs, and default to logic inputs on power-up. When fully configured as an LED driver, the MAX6956 controls up to 28 LED segments with individual 16-step adjustment of the constant current through each LED segment. A single resistor sets the maximum segment current for all segments, with a maximum of 24mA per segment. The MAX6956 drives any combination of discrete LEDs and CA digits, including seven-segment and starburst alphanumeric types. Figure 1 is the MAX6956 functional diagram. Any I/O port can be configured as a push-pull output (sinking 10mA, sourcing 4.5mA), or a Schmitt-trigger logic input. Each input has an individually selectable internal pullup resistor. Additionally, transition detection allows seven ports (P24 through P30) to be monitored in any maskable combination for changes in their logic status. A detected transition is flagged through a status register bit, as well as an interrupt pin (port P31), if desired. The Typical Operating Circuit shows two MAX6956s working together controlling three monocolor 16-seg- ment-plus-DP displays, with five ports left available for GPIO (P26–P31 of U2). The port configuration registers set the 28 ports, P4 to P31, individually as either LED drivers or GPIO. A pair of bits in registers 0x09 through 0x0F sets each port’s configuration (Tables 1 and 2). The 36-pin MAX6956AAX has 28 ports, P4 to P31. The 28-pin MAX6956ANI and MAX6956AAI make only 20 ports available, P12 to P31. The eight unused ports should be configured as outputs on power-up by writing 0x55 to registers 0x09 and 0x0A. If this is not done, the eight unused ports remain as floating inputs and quiescent supply current rises, although there is no damage to the part. Register Control of I/O Ports and LEDs Across Multiple Drivers The MAX6956 offers 20 or 28 I/O ports, depending on package choice. These can be applied to a variety of combinations of different display types, for example: seven, 7-segment digits (Figure 7). This example requires two MAX6956s, with one digit being driven by both devices, half by one MAX6956, half by the other (digit 4 in this example). The two drivers are static, and therefore do not need to be synchronized. The MAX6956 sees CA digits as multiple discrete LEDs. To _______________________________________________________________________________________ 5 MAX6956 Pin Description MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander Table 1. Port Configuration Map REGISTER DATA ADDRESS CODE (HEX) REGISTER Port Configuration for P7, P6, P5, P4 D7 0x09 D6 D5 P7 D4 D3 P6 D2 P5 D1 D0 P4 Port Configuration for P11, P10, P9, P8 0x0A P11 P10 P9 P8 Port Configuration for P15, P14, P13, P12 0x0B P15 P14 P13 P12 Port Configuration for P19, P18, P17, P16 0x0C P19 P18 P17 P16 Port Configuration for P23, P22, P21, P20 0x0D P23 P22 P21 P20 Port Configuration for P27, P26, P25, P24 0x0E P27 P26 P25 P24 Port Configuration for P31, P30, P29, P28 0x0F P31 P30 P29 P28 Table 2. Port Configuration Matrix MODE FUNCTION Output LED Segment Driver Output GPIO Output Input GPIO Input Without Pullup Input GPIO Input with Pullup PORT REGISTER (0x20–0x5F) PIN BEHAVIOR PORT CONFIGURATION BIT PAIR UPPER LOWER 0x09 to 0x0F 0 0 0x09 to 0x0F 0 1 Schmitt logic input 0x09 to 0x0F 1 0 Schmitt logic input with pullup 0x09 to 0x0F 1 1 Register bit = 0 High impedance Register bit = 1 Open-drain current sink, with sink current (up to 24mA) determined by the appropriate current register Register bit = 0 Active-low logic output Register bit = 1 Active-high logic output Register bit = input logic level ADDRESS CODE (HEX) Note: The logic is inverted between the two output modes; a high makes the output go low in LED segment driver mode (0x00) to turn that segment on; in GPIO output mode (0x01), a high makes the output go high. simplify access to displays that overlap two MAX6956s, the MAX6956 provides four virtual ports, P0 through P3. To update an overlapping digit, send the same code twice as an eight-port write, once to P28 through P35 of the first driver, and again to P0 through P7 of the second driver. The first driver ignores the last 4 bits and the second driver ignores the first 4 bits. Two addressing methods are available. Any single port (bit) can be written (set/cleared) at once; or, any sequence of eight ports can be written (set/cleared) in any combination at once. There are no boundaries; it is equally acceptable to write P0 through P7, P1 through P8, or P31 through P38 (P32 through P38 are nonexistent, so the instructions to these bits are ignored). Using 8-bit control, a seven-segment digit with a decimal point can be updated in a single byte-write, a 146 segment digit with DP can be updated in two bytewrites, and 16-segment digits with DP can be updated in two byte-writes plus a bit write. Also, discrete LEDs and GPIO port bits can be lit and controlled individually without affecting other ports. Shutdown When the MAX6956 is in shutdown mode, all ports are forced to inputs (which an be read), and the pullup current sources are turned off. Data in the port and control registers remain unaltered, so port configuration and output levels are restored when the MAX6956 is taken out of shutdown. The display driver can still be programmed while in shutdown mode. For minimum supply current in shutdown mode, logic inputs should be at GND or V+ potential. Shutdown mode is exited by setting the S bit in the configuration register (Table 8). _______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander MAX6956 INTENSITY REGISTERS INTENSITY TEST REGISTER TEST CONFIGURATION MAX6956 PORT REGISTERS MASK REGISTER P4 TO P31 LED DRIVERS OR GPIO LED DRIVERS AND GPIO CONFIGURATION REGISTERS PORT CHANGE DETECTOR DATA R/W CE 8 SEGMENT OR GPIO DATA R/W 8 AD0 COMMAND REGISTER DECODE ADDRESS MATCHER AD1 7 8 8 DATA BYTE D0 D1 D2 D3 D4 7 COMMAND BYTE D5 D6 D7 D8 D9 D10 TO/FROM DATA REGISTERS 7-BIT DEVICE ADDRESS D11 D12 D13 D14 D15 TO COMMAND REGISTERS R/W SDA SCL SLAVE ADDRESS BYTE DATA BYTE COMMAND BYTE Figure 1. MAX6956 Functional Diagram Shutdown mode is temporarily overridden by the display test function. Serial Interface Serial Addressing The MAX6956 operates 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 MAX6956, and generates the SCL clock that synchronizes the data transfer (Figure 2). The MAX6956 SDA line operates as both an input and an open-drain output. A pullup resistor, typically 4.7kΩ, is required on SDA. The MAX6956 SCL line operates only as an input. A pullup resistor, typically 4.7kΩ, is required on SCL if there are multiple masters on the 2wire interface, or if the master in a single-master system has an open-drain SCL output. Each transmission consists of a START condition (Figure 3) sent by a master, followed by the MAX6956 7-bit slave address plus R/ W bit (Figure 6), a register address byte, one or more data bytes, and finally a STOP condition (Figure 3). 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 _______________________________________________________________________________________________________ 7 MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander SDA tBUF tSU, STA tSU, DAT tHD, STA tLOW tSU, STO tHD, DAT SCL tHIGH tHD, STA tR tF REPEATED START CONDITION START CONDITION STOP CONDITION START CONDITION Figure 2. 2-Wire Serial Interface Timing Details SDA SCL S P START CONDITION STOP CONDITION Figure 3. Standard Stop Conditions SDA SCL DATA LINE STABLE; DATA VALID CHANGE OF DATA ALLOWED Figure 4. Bit Transfer has finished 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 3). Bit Transfer One data bit is transferred during each clock pulse. The data on SDA must remain stable while SCL is high (Figure 4). 8 Acknowledge The acknowledge bit is a clocked 9th bit, which the recipient uses to handshake receipt of each byte of data (Figure 5). Thus, each byte transferred effectively requires 9 bits. The master generates the 9th clock pulse, and the recipient pulls down SDA during the acknowledge clock pulse, such that the SDA line is stable low during the high period of the clock pulse. When the master is transmitting to the MAX6956, the MAX6956 generates the acknowledge bit because the _______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander MAX6956 START CONDITION CLOCK PULSE FOR ACKNOWLEDGMENT SCL 1 2 8 9 SDA BY TRANSMITTER S SDA BY RECEIVER Figure 5. Acknowledge SDA 1 0 0 A3 A2 A1 A0 R/W ACK LSB MSB SCL Figure 6. Slave Address MAX6956 is the recipient. When the MAX6956 is transmitting to the master, the master generates the acknowledge bit because the master is the recipient. Slave Address The MAX6956 has a 7-bit-long slave address (Figure 6). The eighth bit following the 7-bit slave address is the R/ W bit. It is low for a write command, high for a read command. The first 3 bits (MSBs) of the MAX6956 slave address are always 100. Slave address bits A3, A2, A1, and A0 are selected by address inputs, AD1 and AD0. These two input pins may be connected to GND, V+, SDA, or SCL. The MAX6956 has 16 possible slave addresses (Table 3) and therefore, a maximum of 16 MAX6956 devices may share the same interface. Message Format for Writing the MAX6956 A write to the MAX6956 comprises the transmission of the MAX6956’s slave address with the R/ W bit set to zero, followed by at least 1 byte of information. The first byte of information is the command byte. The command byte determines which register of the MAX6956 is to be written by the next byte, if received. If a STOP condition is detected after the command byte is received, then the MAX6956 takes no further action (Figure 8) beyond storing the command byte. Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MAX6956 selected by the command byte (Figure 9). If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent MAX6956 internal registers because the command byte address generally autoincrements (Table 4). Message Format for Reading The MAX6956 is read using the MAX6956’s internally stored command byte as address pointer, the same way the stored command byte is used as address pointer for a write. The pointer generally autoincrements after each data byte is read using the same rules as for a write (Table 4). Thus, a read is initiated by first configuring the MAX6956’s command byte by perform- _______________________________________________________________________________________ 9 MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander 7-SEGMENT DIGIT 1 7-SEGMENT DIGIT 2 7-SEGMENT DIGIT 3 V+ 7-SEGMENT DIGIT 4 VIRTUAL SEGMENTS P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31 7-SEGMENT DIGIT 5 7-SEGMENT DIGIT 6 V+ 7-SEGMENT DIGIT 7 VIRTUAL SEGMENTS P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24 P25 P26 P27 P28 P29 P30 P31 Figure 7. Two MAX6956s Controlling Seven 7-Segment Displays D15 D14 D13 D12 D11 D10 D9 COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION ACKNOWLEDGE FROM MAX6956 SLAVE ADDRESS S 0 COMMAND BYTE RECEIVED A D8 A COMMAND BYTE P ACKNOWLEDGE FROM MAX6956 R/W Figure 8. Command Byte Received ACKNOWLEDGE FROM MAX6956 D15 D14 D13 D12 D11 D10 HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6956's REGISTER ACKNOWLEDGE FROM MAX6956 S SLAVE ADDRESS 0 R/W A COMMAND BYTE D9 ACKNOWLEDGE FROM MAX6956 D8 D7 A D6 D5 D4 D3 D2 DATA BYTE 1 BYTE Figure 9. Command and Single Data Byte Received 10 ______________________________________________________________________________________ D1 D0 A P 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander D15 D14 D13 D12 D11 D10 D9 MAX6956 ACKNOWLEDGE FROM MAX6956 ACKNOWLEDGE FROM MAX6956 HOW COMMAND BYTE AND DATA BYTE MAP INTO MAX6956's REGISTER D8 D7 D6 D5 D4 D3 D2 D1 D0 ACKNOWLEDGE FROM MAX6956 SLAVE ADDRESS S 0 COMMAND BYTE A DATA BYTE A A P n BYTES R/W AUTOINCREMENT MEMORY WORD ADDRESS Figure 10. n Data Bytes Received Table 3. MAX6956 Address Map PIN CONNECTION DEVICE ADDRESS AD1 AD0 A6 A5 A4 A3 A2 A1 A0 GND GND 1 0 0 0 0 0 0 GND V+ 1 0 0 0 0 0 1 GND SDA 1 0 0 0 0 1 0 GND SCL 1 0 0 0 0 1 1 V+ GND 1 0 0 0 1 0 0 V+ V+ 1 0 0 0 1 0 1 V+ SDA 1 0 0 0 1 1 0 V+ SCL 1 0 0 0 1 1 1 SDA GND 1 0 0 1 0 0 0 SDA V+ 1 0 0 1 0 0 1 SDA SDA 1 0 0 1 0 1 0 SDA SCL 1 0 0 1 0 1 1 SCL GND 1 0 0 1 1 0 0 SCL V+ 1 0 0 1 1 0 1 SCL SDA 1 0 0 1 1 1 0 SCL SCL 1 0 0 1 1 1 1 Table 4. Autoincrement Rules COMMAND BYTE ADDRESS RANGE x0000000 to x1111110 x1111111 AUTOINCREMENT BEHAVIOR Command address autoincrements after byte read or written Command address remains at x1111111 after byte written or read ing a write (Figure 8). The master can now read n consecutive bytes from the MAX6956, with the first data byte being read from the register addressed by the initialized command byte. When performing read-afterwrite verification, remember to reset the command byte’s address because the stored control byte address generally has been autoincremented after the write (Table 4). Table 5 is the register address map. Operation with Multiple Masters If the MAX6956 is operated on a 2-wire interface with multiple masters, a master reading the MAX6956 should use a repeated start between the write, which sets the MAX6956’s address pointer, and the read(s) that takes the data from the location(s). This is because it is possible for master 2 to take over the bus after master 1 has set up the MAX6956’s address pointer but before master 1 has read the data. If master 2 subse- ______________________________________________________________________________________ 11 MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander Table 5. Register Address Map COMMAND ADDRESS D15 D14 D13 D12 D11 D10 D9 D8 HEX CODE No-Op X 0 0 0 0 0 0 0 0x00 Global Current X 0 0 0 0 0 1 0 0x02 REGISTER Configuration X 0 0 0 0 1 0 0 0x04 Transition Detect Mask X 0 0 0 0 1 1 0 0x06 Display Test X 0 0 0 0 1 1 1 0x07 Port Configuration P7, P6, P5, P4 X 0 0 0 1 0 0 1 0x09 Port Configuration P11, P10, P9, P8 X 0 0 0 1 0 1 0 0x0A Port Configuration P15, P14, P13, P12 X 0 0 0 1 0 1 1 0x0B Port Configuration P19, P18, P17, P16 X 0 0 0 1 1 0 0 0x0C Port Configuration P23, P22, P21, P20 X 0 0 0 1 1 0 1 0x0D Port Configuration P27, P26, P25, P24 X 0 0 0 1 1 1 0 0x0E Port Configuration P31, P30, P29, P28 Current054 X X 0 0 0 0 0 1 1 0 1 0 1 1 1 0 0x0F 0x12 Current076 X 0 0 1 0 0 1 1 0x13 Current098 X 0 0 1 0 1 0 0 0x14 Current0BA X 0 0 1 0 1 0 1 0x15 Current0DC X 0 0 1 0 1 1 0 0x16 Current0FE X 0 0 1 0 1 1 1 0x17 Current110 X 0 0 1 1 0 0 0 0x18 Current132 X 0 0 1 1 0 0 1 0x19 Current154 X 0 0 1 1 0 1 0 0x1A Current176 X 0 0 1 1 0 1 1 0x1B Current198 X 0 0 1 1 1 0 0 0x1C Current1BA X 0 0 1 1 1 0 1 0x1D Current1DC X 0 0 1 1 1 1 0 0x1E Current1FE X 0 0 1 1 1 1 1 0x1F Port 0 only (virtual port, no action) X 0 1 0 0 0 0 0 0x20 Port 1 only (virtual port, no action) X 0 1 0 0 0 0 1 0x21 Port 2 only (virtual port, no action) X 0 1 0 0 0 1 0 0x22 Port 3 only (virtual port, no action) X 0 1 0 0 0 1 1 0x23 Port 4 only (data bit D0; D7–D1 read as 0) X 0 1 0 0 1 0 0 0x24 Port 5 only (data bit D0; D7–D1 read as 0) X 0 1 0 0 1 0 1 0x25 Port 6 only (data bit D0; D7–D1 read as 0) X 0 1 0 0 1 1 0 0x26 Port 7 only (data bit D0; D7–D1 read as 0) X 0 1 0 0 1 1 1 0x27 Port 8 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 0 0 0 0x28 Port 9 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 0 0 1 0x29 Port 10 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 0 1 0 0x2A 12 ______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander REGISTER COMMAND ADDRESS HEX CODE D15 D14 D13 D12 D11 D10 D9 D8 Port 11 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 0 1 1 0x2B Port 12 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 1 0 0 0x2C Port 13 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 1 0 1 0x2D Port 14 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 1 1 0 0x2E Port 15 only (data bit D0; D7–D1 read as 0) X 0 1 0 1 1 1 1 0x2F Port 16 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 0 0 0 0x30 Port 17 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 0 0 1 0x31 Port 18 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 0 1 0 0x32 Port 19 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 0 1 1 0x33 Port 20 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 1 0 0 0x34 Port 21 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 1 0 1 0x35 Port 22 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 1 1 0 0x36 Port 23 only (data bit D0; D7–D1 read as 0) X 0 1 1 0 1 1 1 0x37 Port 24 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 0 0 0 0x38 Port 25 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 0 0 1 0x39 Port 26 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 0 1 0 0x3A Port 27 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 0 1 1 0x3B Port 28 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 1 0 0 0x3C Port 29 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 1 0 1 0x3D Port 30 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 1 1 0 0x3E Port 31 only (data bit D0; D7–D1 read as 0) X 0 1 1 1 1 1 1 0x3F 4 ports 4–7 (data bits D0–D3; D4–D7 read as 0) X 1 0 0 0 0 0 0 0x40 5 ports 4–8 (data bits D0–D4; D5–D7 read as 0) X 1 0 0 0 0 0 1 0x41 6 ports 4–9 (data bits D0–D5; D6–D7 read as 0) X 1 0 0 0 0 1 0 0x42 7 ports 4–10 (data bits D0–D6; D7 reads as 0) X 1 0 0 0 0 1 1 0x43 8 ports 4–11 (data bits D0–D7) X 1 0 0 0 1 0 0 0x44 8 ports 5–12 (data bits D0–D7) X 1 0 0 0 1 0 1 0x45 8 ports 6–13 (data bits D0–D7) X 1 0 0 0 1 1 0 0x46 8 ports 7–14 (data bits D0–D7) X 1 0 0 0 1 1 1 0x47 8 ports 8–15 (data bits D0–D7) X 1 0 0 1 0 0 0 0x48 8 ports 9–16 (data bits D0–D7) X 1 0 0 1 0 0 1 0x49 8 ports 10–17 (data bits D0–D7) X 1 0 0 1 0 1 0 0x4A 8 ports 11–18 (data bits D0–D7) X 1 0 0 1 0 1 1 0x4B 8 ports 12–19 (data bits D0–D7) X 1 0 0 1 1 0 0 0x4C 8 ports 13–20 (data bits D0–D7) X 1 0 0 1 1 0 1 0x4D 8 ports 14–21 (data bits D0–D7) X 1 0 0 1 1 1 0 0x4E 8 ports 15–22 (data bits D0–D7) X 1 0 0 1 1 1 1 0x4F ______________________________________________________________________________________ 13 MAX6956 Table 5. Register Address Map (continued) MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander Table 5. Register Address Map (continued) COMMAND ADDRESS D15 D14 D13 D12 D11 D10 D9 D8 HEX CODE 8 ports 16–23 (data bits D0–D7) X 1 0 1 0 0 0 0 0x50 8 ports 17–24 (data bits D0–D7) X 1 0 1 0 0 0 1 0x51 8 ports 18–25 (data bits D0–D7) X 1 0 1 0 0 1 0 0x52 8 ports 19–26 (data bits D0–D7) X 1 0 1 0 0 1 1 0x53 8 ports 20–27 (data bits D0–D7) X 1 0 1 0 1 0 0 0x54 8 ports 21–28 (data bits D0–D7) X 1 0 1 0 1 0 1 0x55 8 ports 22–29 (data bits D0–D7) X 1 0 1 0 1 1 0 0x56 8 ports 23–30 (data bits D0–D7) X 1 0 1 0 1 1 1 0x57 8 ports 24–31 (data bits D0–D7) X 1 0 1 1 0 0 0 0x58 7 ports 25–31 (data bits D0–D6; D7 reads as 0) X 1 0 1 1 0 0 1 0x59 6 ports 26–31 (data bits D0–D5; D6–D7 read as 0) X 1 0 1 1 0 1 0 0x5A 5 ports 27–31 (data bits D0–D4; D5–D7 read as 0) X 1 0 1 1 0 1 1 0x5B 4 ports 28–31 (data bits D0–D3; D4–D7 read as 0) X 1 0 1 1 1 0 0 0x5C 3 ports 29–31 (data bits D0–D2; D3–D7 read as 0) X 1 0 1 1 1 0 1 0x5D 2 ports 30–31 (data bits D0–D1; D2–D7 read as 0) X 1 0 1 1 1 1 0 0x5E 1 port 31 only (data bit D0; D1–D7 read as 0) X 1 0 1 1 1 1 1 0x5F REGISTER Note: Unused bits read as 0. quently changes, the MAX6956’s address pointer, then master 1’s delayed read may be from an unexpected location. Command Address Autoincrementing Address autoincrementing allows the MAX6956 to be configured with the shortest number of transmissions by minimizing the number of times the command address needs to be sent. The command address stored in the MAX6956 generally increments after each data byte is written or read (Table 4). Initial Power-Up On initial power-up, all control registers are reset, the current registers are set to minimum value, and the MAX6956 enters shutdown mode (Table 6). LED Current Control LED segment drive current can be set either globally or individually. Global control simplifies the operation when all LEDs are set to the same current level, because writing just the global current register sets the current for all ports configured as LED segment drivers. It is also possible to individually control the current 14 drive of each LED segment driver. Individual/global brightness control is selected by setting the configuration register I bit (Table 9). The global current register (0x02) data are then ignored, and segment currents are set using register addresses 0x12 through 0x1F (Tables 12, 13, and 14). Each segment is controlled by a nibble of one of the 16 current registers. Transition (Port Data Change) Detection Port transition detection allows any combination of the seven ports P24–P30 to be continuously monitored for changes in their logic status (Figure 11). A detected change is flagged on the transition detection mask register INT status bit, D7 (Table 15). If port P31 is configured as an output (Tables 1 and 2), then P31 also automatically becomes an active-high interrupt output (INT), which follows the condition of the INT status bit. Port P31 is set as output by writing bit D7 = 0 and bit D6 = 1 to the port configuration register (Table 1). Note that the MAX6956 does not identify which specific port(s) caused the interrupt, but provides an alert that one or more port levels have changed. ______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander POWER-UP CONDITION ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 LED Off; GPIO Output Low 0x24 to 0x3F X X X X X X X 0 1/16 (minimum on) 0x02 X X X X 0 0 0 0 Shutdown Enabled Current Control = Global Transition Detection Disabled 0x04 0 0 X X X X X 0 Input Mask Register All Clear (Masked Off) 0x06 X 0 0 0 0 0 0 0 Display Test Normal Operation 0x07 X X X X X X X 0 Port Configuration P7, P6, P5, P4: GPIO Inputs Without Pullup 0x09 1 0 1 0 1 0 1 0 Port Configuration P11, P10, P9, P8: GPIO Inputs Without Pullup 0x0A 1 0 1 0 1 0 1 0 Port Configuration P15, P14, P13, P12: GPIO Inputs Without Pullup 0x0B 1 0 1 0 1 0 1 0 Port Configuration P19, P18, P17, P16: GPIO Inputs Without Pullup 0x0C 1 0 1 0 1 0 1 0 Port Configuration P23, P22, P21, P20: GPIO Inputs Without Pullup 0x0D 1 0 1 0 1 0 1 0 Port Configuration P27, P26, P25, P24: GPIO Inputs Without Pullup 0x0E 1 0 1 0 1 0 1 0 Port Configuration P31, P30, P29, P28: GPIO Inputs Without Pullup 0x0F 1 0 1 0 1 0 1 0 Current054 1/16 (minimum on) 0x12 0 0 0 0 0 0 0 0 Current076 1/16 (minimum on) 0x13 0 0 0 0 0 0 0 0 Current098 1/16 (minimum on) 0x14 0 0 0 0 0 0 0 0 Current0BA 1/16 (minimum on) 0x15 0 0 0 0 0 0 0 0 Current0DC 1/16 (minimum on) 0x16 0 0 0 0 0 0 0 0 Current0FE 1/16 (minimum on) 0x17 0 0 0 0 0 0 0 0 Current110 1/16 (minimum on) 0x18 0 0 0 0 0 0 0 0 Current132 1/16 (minimum on) 0x19 0 0 0 0 0 0 0 0 Current154 1/16 (minimum on) 0x1A 0 0 0 0 0 0 0 0 Current176 1/16 (minimum on) 0x1B 0 0 0 0 0 0 0 0 REGISTER FUNCTION Port Register Bits 4 to 31 Global Current Configuration Register REGISTER DATA Current198 1/16 (minimum on) 0x1C 0 0 0 0 0 0 0 0 Current1BA 1/16 (minimum on) 0x1D 0 0 0 0 0 0 0 0 Current1DC 1/16 (minimum on) 0x1E 0 0 0 0 0 0 0 0 Current1FE 1/16 (minimum on) 0x1F 0 0 0 0 0 0 0 0 X = unused bits; if read, zero results. ______________________________________________________________________________________ 15 MAX6956 Table 6. Power-Up Configuration MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander Table 7. Configuration Register Format REGISTER DATA FUNCTION ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Configuration Register 0x04 M I X X X X X S Table 8. Shutdown Control (S Data Bit D0) Format REGISTER DATA FUNCTION ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Shutdown 0x04 M I X X X X X 0 Normal Operation 0x04 M I X X X X X 1 Table 9. Global Current Control (I Data Bit D6) Format REGISTER DATA ADDRESS CODE (HEX) FUNCTION D7 D6 D5 D4 D3 D2 D1 D0 Global Constant-current limits for all digits are controlled by one setting in the Global Current register, 0x02 0x04 M 0 X X X X X S Individual Segment Constant-current limit for each digit is individually controlled by the settings in the Current054 through Current1FE registers 0x04 M 1 X X X X X S Table 10. Transition Detection Control (M-Data Bit D7) Format REGISTER DATA FUNCTION ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 Disabled 0x04 0 I X X X X X S Enabled 0x04 1 I X X X X X S The mask register contains 7 mask bits, which select which of the seven ports P24–P30 are to be monitored (Table 15). Set the appropriate mask bit to enable that port for transition detect. Clear the mask bit if transitions on that port are to be ignored. Transition detection works regardless of whether the port being monitored is set to input or output, but generally, it is not particularly useful to enable transition detection for outputs. To use transition detection, first set up the mask register and configure port P31 as an output, as described above. Then enable transition detection by setting the 16 M bit in the configuration register (Table 10). Whenever the configuration register is written with the M bit set, the MAX6956 updates an internal 7-bit snapshot register, which holds the comparison copy of the logic states of ports P24 through P30. The update action occurs regardless of the previous state of the M bit, so that it is not necessary to clear the M bit and then set it again to update the snapshot register. When the configuration register is written with the M bit set, transition detection is enabled and remains enabled until either the configuration register is written ______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander LED DRIVE FRACTION TYPICAL SEGMENT CURRENT (mA) ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE 1/16 1.5 0x02 X X X X 0 0 0 0 0xX0 2/16 3 0x02 X X X X 0 0 0 1 0xX1 3/16 4.5 0x02 X X X X 0 0 1 0 0xX2 4/16 6 0x02 X X X X 0 0 1 1 0xX3 5/16 7.5 0x02 X X X X 0 1 0 0 0xX4 6/16 9 0x02 X X X X 0 1 0 1 0xX5 7/16 10.5 0x02 X X X X 0 1 1 0 0xX6 8/16 12 0x02 X X X X 0 1 1 1 0xX7 9/16 13.5 0x02 X X X X 1 0 0 0 0xX8 10/16 15 0x02 X X X X 1 0 0 1 0xX9 11/16 16.5 0x02 X X X X 1 0 1 0 0xXA 12/16 18 0x02 X X X X 1 0 1 1 0xXB 13/16 19.5 0x02 X X X X 1 1 0 0 0xXC 14/16 21 0x02 X X X X 1 1 0 1 0xXD 15/16 22.5 0x02 X X X X 1 1 1 0 0xXE 16/16 24 0x02 X X X X 1 1 1 1 0xXF X = Don’t care bit. with the M bit clear, or a transition is detected. The INT status bit (transition detection mask register bit D7) goes low. Port P31 (if enabled as INT output) also goes low, if it was not already low. M bit set, to take a new snapshot of the seven ports P24 to P30. Once transition detection is enabled, the MAX6956 continuously compares the snapshot register against the changing states of P24 through P31. If a change on any of the monitored ports is detected, even for a short time (like a pulse), the INT status bit (transition detection mask register bit D7) is set. Port P31 (if enabled as INT output) also goes high. The INT output and INT status bit are not cleared if more changes occur or if the data pattern returns to its original snapshot condition. The only way to clear INT is to access (read or write) the transition detection mask register (Table 15). So if the transition detection mask register is read twice in succession after a transition event, the first time reads with bit D7 set (identifying the event), and the second time reads with bit D7 clear. Display test mode turns on all ports configured as LED drivers by overriding, but not altering, all controls and port registers, except the port configuration register (Table 16). Only ports configured as LED drivers are affected. Ports configured as GPIO push-pull outputs do not change state. In display test mode, each port’s current is temporarily set to 1/2 the maximum current limit as controlled by RISET. Transition detection is a one-shot event. When INT has been cleared after responding to a transition event, transition detection is automatically disabled, even though the M bit in the configuration register remains set (unless cleared by the user). Reenable transition detection by writing the configuration register with the Display Test Register Selecting External Component RISET to Set Maximum Segment Current The MAX6956 uses an external resistor RISET to set the maximum segment current. The recommended value, 39kΩ, sets the maximum current to 24mA, which makes the segment current adjustable from 1.5mA to 24mA in 1.5mA steps. To set a different segment current, use the formula: RISET = 936kΩ / ISEG where ISEG is the desired maximum segment current. ______________________________________________________________________________________ 17 MAX6956 Table 11. Global Segment Current Register Format MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander Table 12. Individual Segment Current Registers REGISTER FUNCTION ADDRESS CODE (HEX) Current054 register 0x12 Segment 5 Segment 4 Current076 register 0x13 Segment 7 Segment 6 Current098 register 0x14 Segment 9 Segment 8 Current0BA register 0x15 Segment 11 Segment 10 Current0DC register 0x16 Segment 13 Segment 12 D7 D6 D5 D4 D3 D2 D1 Current0FE register 0x17 Segment 15 Segment 14 Current110 register 0x18 Segment 17 Segment 16 Current132 register 0x19 Segment 19 Segment 18 Current154 register 0x1A Segment 21 Segment 20 Current176 register 0x1B Segment 23 Segment 22 Current198 register 0x1C Segment 25 Segment 24 Current1BA register 0x1D Segment 27 Segment 26 Current1DC register 0x1E Segment 29 Segment 28 Current1FE register 0x1F Segment 31 Segment 30 D0 Table 13. Even Individual Segment Current Format LED DRIVE FRACTION SEGMENT CONSTANT CURRENT WITH RISET = 39kΩ (mA) ADDRESS CODE (HEX) 1/16 1.5 2/16 3 3/16 4.5 18 D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE 0x12 to 0x1F 0 0 0 0 0xX0 0x12 to 0x1F 0 0 0 1 0xX1 0x12 to 0x1F 0 0 1 0 0xX2 4/16 6 0x12 to 0x1F 0 0 1 1 0xX3 5/16 7.5 0x12 to 0x1F 0 1 0 0 0xX4 6/16 9 0x12 to 0x1F 0 1 0 1 0xX5 7/16 10.5 0x12 to 0x1F 0 1 1 0 0xX6 8/16 12 0x12 to 0x1F 0 1 1 1 0xX7 9/16 13.5 0x12 to 0x1F 1 0 0 0 0xX8 10/16 15 0x12 to 0x1F 1 0 0 1 0xX9 11/16 16.5 0x12 to 0x1F 1 0 1 0 0xXA 12/16 18 0x12 to 0x1F 1 0 1 1 0xXB 13/16 19.5 0x12 to 0x1F 1 1 0 0 0xXC 14/16 21 0x12 to 0x1F 1 1 0 1 0xXD 15/16 22.5 0x12 to 0x1F 1 1 1 0 0xXE 16/16 24 0x12 to 0x1F 1 1 1 1 0xXF See Table 14. ______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander LED DRIVE FRACTION SEGMENT CONSTANT CURRENT WITH RISET = 39kΩ (mA) ADDRESS CODE (HEX) D7 D6 D5 D4 1/16 1.5 0x12 to 0x1F 0 0 0 0 0x0X 2/16 3 0x12 to 0x1F 0 0 0 1 0x1X 3/16 4.5 0x12 to 0x1F 0 0 1 0 0x2X D3 D2 D1 D0 HEX CODE 4/16 6 0x12 to 0x1F 0 0 1 1 0x3X 5/16 7.5 0x12 to 0x1F 0 1 0 0 0x4X 6/16 9 0x12 to 0x1F 0 1 0 1 0x5X 7/16 10.5 0x12 to 0x1F 0 1 1 0 8/16 12 0x12 to 0x1F 0 1 1 1 0x7X 9/16 13.5 0x12 to 0x1F 1 0 0 0 0x8X 10/16 15 0x12 to 0x1F 1 0 0 1 0x9X 11/16 16.5 0x12 to 0x1F 1 0 1 0 0xAX 12/16 18 0x12 to 0x1F 1 0 1 1 0xBX 13/16 19.5 0x12 to 0x1F 1 1 0 0 0xCX 14/16 21 0x12 to 0x1F 1 1 0 1 0xDX 15/16 22.5 0x12 to 0x1F 1 1 1 0 0xEX 16/16 24 0x12 to 0x1F 1 1 1 1 0xFX The recommended value of RISET is 39kΩ. The recommended value of R ISET is the minimum allowed value, since it sets the display driver to the maximum allowed segment current. RISET can be a higher value to set the segment current to a lower maximum value where desired. The user must also ensure that the maximum current specifications of the LEDs connected to the driver are not exceeded. The drive current for each segment can be controlled through programming either the Global Current register (Table 11) or Individual Segment Current registers (Tables 12, 13, and 14), according to the setting of the Current Control bit of the Configuration register (Table 9). These registers select the LED’s constant-current drive from 16 equal fractions of the maximum segment current. The current difference between successive current steps, ISTEP, is therefore determined by the formula: ISTEP = ISEG / 16 If ISEG = 24mA, then ISTEP = 24mA / 16 = 1.5mA. See Table 13. 0x6X Applications Information Driving Bicolor and Tricolor LEDs Bicolor digits group a red and a green die together for each display element, so that the element can be lit red, green (or orange), depending on which die (or both) is lit. The MAX6956 allows each segment’s current to be set individually from 1/16th (minimum current and LED intensity) to 16/16th (maximum current and LED intensity), as well as off (zero current). Thus, a bicolor (red-green) segment pair can be set to 289 color/intensity combinations. A discrete or CA tricolor (red-green-yellow or red-green-blue) segment triad can be set to 4913 color/intensity combinations. Power Dissipation Issues Each MAX6956 port can sink a current of 24mA into an LED with a 2.4V forward-voltage drop when operated from a supply voltage of at least 3.0V. The minimum voltage drop across the internal LED drivers is therefore (3.0V - 2.4V) = 0.6V. The MAX6956 can sink 28 x 24mA = 672mA when all outputs are operating as LED ______________________________________________________________________________________ 19 MAX6956 Table 14. Odd Individual Segment Current Format MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander GPIO INPUT CONDITIONING GPIO IN GPIO/PORT OUTPUT LATCH GPIO/PORT OUT INT STATUS STORED AS MSB OF MASK REGISTER P31 INT OUTPUT LATCH CLOCK PULSE AFTER EACH READ ACCESS TO MASK REGISTER R S CONFIGURATION REGISTER M BIT = 1 GPIO INPUT CONDITIONING P30 GPIO IN D Q GPIO/PORT OUT MASK REGISTER BIT 6 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P29 GPIO IN D Q GPIO/PORT OUT MASK REGISTER BIT 5 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P28 GPIO IN D Q GPIO/PORT OUT MASK REGISTER BIT 4 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P27 GPIO IN D Q OR MASK REGISTER BIT 3 GPIO/PORT OUT GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P26 GPIO IN D Q GPIO/PORT OUT MASK REGISTER BIT 2 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P25 GPIO IN D Q GPIO/PORT OUT MASK REGISTER BIT 1 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P24 GPIO IN D GPIO/PORT OUT GPIO/PORT OUTPUT LATCH Q MASK REGISTER LSB CLOCK PULSE WHEN WRITING CONFIGURATION REGISTER WITH M BIT SET Figure 11. Maskable GPIO Ports P24 Through P31 20 ______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander FUNCTION REGISTER ADDRESS (HEX) Mask Register REGISTER DATA READ/ WRITE D7 D6 D5 D4 D3 D2 D1 D0 Read INT Status* Write Unchanged Port 30 mask Port 29 mask Port 28 mask Port 27 mask Port 26 mask Port 25 mask Port 24 mask D0 0x06 *INT is automatically cleared after it is read. Table 16. Display Test Register REGISTER DATA MODE ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 Normal Operation 0x07 X X X X X X X 0 Display Test Mode 0x07 X X X X X X X 1 X = Don’t care bit segment drivers at full current. On a 3.3V supply, a MAX6956 dissipates (3.3V - 2.4V) 672mA = 0.6W when driving 28 of these 2.4V forward-voltage drop LEDs at full current. This dissipation is within the ratings of the 36-pin SSOP package with an ambient temperature up to +98°C. If a higher supply voltage is used or the LEDs used have a lower forward-voltage drop than 2.4V, the MAX6956 absorbs a higher voltage, and the MAX6956’s power dissipation increases. If the application requires high drive current and high supply voltage, consider adding a series resistor to each LED to drop excessive drive voltage off-chip. For example, consider the requirement that the MAX6956 must drive LEDs with a 2.0V to 2.4V specified forwardvoltage drop, from an input supply range is 5V ±5% with a maximum LED current of 20mA. Minimum input supply voltage is 4.75V. Maximum LED series resistor value is (4.75V - 2.4V - 0.6V)/0.020A = 87.5Ω. We choose 82Ω ±2%. Worst-case resistor dissipation is at maximum toleranced resistance, i.e., (0.020A)2 (82Ω 1.02) = 34mW. The maximum MAX6956 dissipation per LED is at maximum input supply voltage, minimum toleranced resistance, minimum toleranced LED forward-voltage drop, i.e., 0.020 x (5.25V - 2.0V - (0.020A 82Ω x 0.98)) = 32.86mW. Worst-case MAX6956 dissipation is 920mW driving all 28 LEDs at 20mA full current at once, which meets the 941mW dissipation ratings of the 36-pin SSOP package. Low-Voltage Operation The MAX6956 operates down to 2V supply voltage (although the sourcing and sinking currents are not guaranteed), providing that the MAX6956 is powered up initially to at least 2.5V to trigger the device’s internal reset. Serial Interface Latency When a MAX6956 register is written through the I2C interface, the register is updated on the rising edge of SCL during the data byte’s acknowledge bit (Figure 5). The delay from the rising edge of SCL to the internal register being updated can range from 50ns to 350ns. PC Board Layout Considerations Ensure that all of the MAX6956 GND connections are used. A ground plane is not necessary, but may be useful to reduce supply impedance if the MAX6956 outputs are to be heavily loaded. Keep the track length from the ISET pin to the RISET resistor as short as possible, and take the GND end of the resistor either to the ground plane or directly to the GND pins. Power-Supply Considerations The MAX6956 operates with power-supply voltages of 2.5V to 5.5V. Bypass the power supply to GND with a 0.047µF capacitor as close to the device as possible. Add a 1µF capacitor if the MAX6956 is far away from the board’s input bulk decoupling capacitor. ______________________________________________________________________________________ 21 MAX6956 Table 15. Transition Detection Mask Register 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander MAX6956 Typical Operating Circuit 3V 3V 36 47nF V+ 3 GND 2 GND 1 ISET U1 MAX6956AAX 39kΩ 35 AD1 4 AD0 33 SDA 34 SCL DATA CLOCK 31 P31 29 P30 27 P29 25 P28 24 P27 23 P26 22 P25 21 P24 32 P4 30 P5 28 P6 26 P7 5 P8 7 P9 P10 9 11 P11 6 P12 8 P13 10 P14 P15 12 13 P16 14 P17 15 P18 16 P19 P20 17 18 P21 P22 19 20 P23 a1 a2 LED1 b c d1 d2 e f g1 g2 h i j k l m dp ca a1 a2 LED2 b c d1 d2 e f g1 g2 h i 3V 36 V+ U2 47nF 3 GND 2 GND 1 ISET 39kΩ 35 AD1 4 AD0 33 SDA 34 SCL 31 IRQ OUT 1 SW1 22 SW2 2 SW3 P31 29 P30 27 P29 25 P28 24 P27 23 P26 22 P25 21 P24 MAX6956AAX 32 P4 30 P5 28 P6 26 P7 5 P8 7 P9 P10 9 11 P11 6 P12 P13 8 10 P14 P15 12 13 P16 14 P17 15 P18 P19 16 P20 17 18 P21 P22 19 20 P23 j k l m dp ca a1 a2 LED3 b c d1 d2 e f g1 g2 h i j k l m dp ca ______________________________________________________________________________________ 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander MAX6956 31 P31 P9 7 30 P5 P13 8 29 P30 P10 9 28 P6 N.C. 31 32 6 33 P12 34 32 P4 35 33 SDA 5 GND ISET V+ AD1 SCL SDA 4 P8 36 AD0 37 34 SCL GND GND 3 38 35 AD1 GND AD0 36 V+ 2 39 ISET 1 GND 40 TOP VIEW P4 P31 P8 P12 1 30 2 29 P9 P13 P10 P14 3 28 4 27 7 24 8 23 P29 P7 P28 9 22 P27 10 21 P26 20 P23 P21 18 19 P22 20 P20 17 16 21 P24 15 22 P25 P19 16 14 23 P26 P18 15 13 P17 14 19 P17 P25 N.C. 24 P27 18 P16 13 P24 25 P28 17 P15 12 12 26 P7 25 11 P11 11 P11 P15 P16 P18 P19 P20 P21 P22 P23 27 P29 26 MAX6956 6 N.C. P14 10 5 P5 P30 P6 TQFN SSOP Package Information Chip Information PROCESS: CMOS For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 28 DIP N28-2 21-0043 28 SSOP A28-1 21-0056 36 SSOP A36-4 21-0040 40 Thin QFN-EP T4066-5 21-0141 ______________________________________________________________________________________ 23 MAX6956 Pin Configurations (continued) MAX6956 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander Revision History REVISION NUMBER REVISION DATE 2 11/03 — 3 3/09 Added exposed pad information and updated packaging information DESCRIPTION PAGES CHANGED — 1, 2, 5, 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 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.