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19-2429; Rev 1; 10/02
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
General Description
The MAX6957 compact, serial-interfaced LED display driver general-purpose I/O (GPIO) peripheral provides 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 constantcurrent 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 GPIO can be either a pushpull 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 MAX6957 is controlled through an SPITM-compatible 4-wire serial interface. The MAX6957AAX and MAX6957AGL have 28 ports and are available in 36-pin SSOP and 40-pin QFN packages, respectively. The MAX6957AAI and MAX6957ANI have 20 ports and are available in 28-pin SSOP and 28-pin DIP packages, respectively. For a 2-wire interfaced version, refer to the MAX6956 data sheet. o 2.5V to 5.5V Operation o -40C to +125C Temperature Range o 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 o 11A (max) Shutdown Current o 16-Step Individually Programmable Current Control for Each LED o Logic Transition Detection for Seven I/O Ports
Features
o High-Speed 26MHz SPI-/QSPI-TM/MICROWIRETMCompatible Serial Interface
MAX6957
Ordering Information
PART MAX6957ANI MAX6957AAI MAX6957AAX MAX6957AGL* TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 28 DIP 28 SSOP 36 SSOP 40 QFN
*Future product--contact factory for availability.
Applications
Set-Top Boxes Panel Meters White Goods Automotive Bar Graph Displays Industrial Controllers System Monitoring
TOP VIEW
ISET 1 GND 2 GND 3 DOUT 4 P12 5 P13 6 P14 7 P15 8 P16 9 P17 10 P18 11 P19 12 P20 13
Pin Configurations
28 V+ 27 CS 26 DIN 25 SCLK 24 P31 23 P30
MAX6957
22 P29 21 P28 20 P27 19 P26 18 P25 17 P24 16 P23 15 P22
Typical Operating Circuit appears at end of data sheet. SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corp.
P21 14
SSOP/DIP
Pin Configurations continued at end of data sheet. 1
________________________________________________________________ Maxim Integrated Products
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
ABSOLUTE MAXIMUM RATINGS
Voltage (with Respect to GND) V+ .............................................................................-0.3V to +6V All Other pins................................................-0.3V to (V+ + 0.3V) P4-P31 Current ................................................................30mA GND Current .....................................................................800mA Continuous Power Dissipation (TA = +70C) 28-Pin PDIP (derate 20.8mW/C above +70C)........1667mW 28-Pin SSOP (derate 9.5mW/C above +70C) ..........762mW 36-Pin SSOP (derate 11.8mW/C above +70C) ........941mW 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
(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 SYMBOL V+ ISHDN All digital inputs at V+ or GND TA = +25C TA = -40C to +85C TA = TMIN to TMAX All ports programmed TA = +25C as outputs high, no load, TA = -40C to +85C all other inputs at V+ or TA = TMIN to TMAX GND All ports programmed as outputs low, no load, all other inputs at V+ or GND TA = +25C TA = -40C to +85C TA = TMIN to TMAX 110 180 CONDITIONS MIN 2.5 5.5 TYP MAX 5.5 8 10 11 230 250 270 170 210 230 240 135 140 145 0.7 V+ 0.3 V+ V+ = 2.5V V+ = 5.5V GPIO outputs, ISOURCE = 2mA, TA = -40C to +85C Output High Voltage VOH GPIO outputs, ISOURCE = 1mA, TA = TMIN to TMAX (Note 2) 12 80 V+ 0.7 V+ 0.7 19 120 0.3 30 180 A A A A UNITS V
Operating Supply Current
IGPOH
Operating Supply Current
IGPOL
Operating Supply Current
ILED
All ports programmed TA = +25C as LED outputs, all LEDs TA = -40C to +85C off, no load, all other TA = TMIN to TMAX inputs at V+ or GND
INPUTS AND OUTPUTS Logic-High Input Voltage Port Inputs Logic-Low Input Voltage Port Inputs GPIO Input Internal Pullup to V+ Hysteresis Voltage GPIO Inputs VIH VIL IPU VI V V A V V V
2
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
ELECTRICAL CHARACTERISTICS (continued)
(Typical Operating Circuit, V+ = 2.5V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1)
PARAMETER Port Sink Current Output Short-Circuit Current SYMBOL IOL IOLSC VPORT = 0.6V Port configured output low, shorted to V+ V+ = 2.5V, VLED = 2.3V at maximum LED current Port Drive LED Sink Current, Port Configured as LED Driver IPORT V+ = 3.3V, VLED = 2.4V at maximum LED current (Note 2) V+ = 5.5V, VLED = 2.4V at maximum LED current V+ = 2.5V, VOUT = 0.6V at maximum LED current IPORT_SC V+ = 5.5V, VOUT = 0.6V at maximum LED current V+ 3.3V V+ > 3.3V CONDITIONS MIN 2 2.75 9.5 18.5 19 18.5 19 TYP 10 11 13.5 24 25 23 24 6 1.6 2 0.6 -50 ISOURCE = 1.6mA ISINK = 1.6mA V+ 0.5 0.4 +50 MAX 18 20 18 27.5 30 28.0 mA 28 % V V nA V V mA UNITS mA mA
MAX6957
Port Drive Logic Sink Current, Port Configured as LED Driver Port LED Sink Current Matching Input High-Voltage SCLK, DIN, CS Input Low-Voltage SCLK, DIN, CS Input Leakage Current SCLK, DIN, CS Output High-Voltage DOUT Output Low-Voltage DOUT
IPORT VIH VIL IIH, IIL VOH VOL
TIMING CHARACTERISTICS (Figure 3)
(V+ = 2.5V to 5.5V, TA = TMIN to TMAX, unless otherwise noted.) (Note 1)
PARAMETER CLK Clock Period CLK Pulse Width High CLK Pulse Width Low CS Fall to SCLK Rise Setup Time CLK Rise to CS Rise Hold Time DIN Setup Time DIN Hold Time Output Data Propagation Delay Minimum CS Pulse High SYMBOL tCP tCH tCL tCSS tCSH tDS tDH tDO tCSW CLOAD = 25pF 19 CONDITIONS MIN 38.4 19 19 9.5 0 9.5 0 21 TYP MAX UNITS ns ns ns ns ns ns ns ns ns
Note 1: All parameters tested at TA = +25C. Specifications over temperature are guaranteed by design. Note 2: Guaranteed by design.
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
__________________________________________Typical Operating Characteristics
(RISET = 39k, TA = +25C, unless otherwise noted.)
OPERATING SUPPLY CURRENT vs. TEMPERATURE
0.36 0.32 SUPPLY CURRENT (mA) 0.28 0.24 0.20 0.16 0.12 0.08 0.04 0 -40.0 -12.5 15.0 42.5 70.0 97.5 125.0 TEMPERATURE (C) ALL PORTS LED (OFF) 3 -40.0 -12.5 15.0 42.5 70.0 97.5 125.0 TEMPERATURE (C) 0.01 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 V+ (V) ALL PORTS OUTPUT (1) ALL PORTS OUTPUT (0) V+ = 2.5V TO 5.5V NO LOAD
MAX6957 toc01
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX6957 toc02
OPERATING SUPPLY CURRENT vs. V+ (NO LOADS)
ALL PORTS LED (ON) SUPPLY CURRENT (mA) 10 ALL PORTS OUTPUT (1) 1 ALL PORTS OUTPUT (0)
MAX6957 toc03
0.40
8 V+ = 5.5V 7 SUPPLY CURRENT (A) V+ = 3.3V 6
100
5
V+ = 2.5V
0.1 4 ALL PORTS LED (OFF)
LED DRIVER SINK CURRENT vs. V+
MAX6957 toc04
LED DRIVER SINK CURRENT vs. TEMPERATURE
MAX6957 toc05
GPO SINK CURRENT vs. TEMPERATURE (OUTPUT = 0)
V+ = 2.5V TO 5.5V, VPORT = 0.6V 16 PORT SINK CURRENT (mA) 14 12 10 8 6 4 2
MAX6957 toc06
26 24 PORT SINK CURRENT (mA) 22 20 18 16 14 12 10 8 6 2.0 2.5 3.0 3.5 4.0 4.5 5.0 LED DROP = 1.8V LED DROP = 2.4V
27 VLED = 2.4V 26 PORT SINK CURRENT (mA) 25 24 23 V+ = 3.3V 22 21 20 V+ = 5.5V
18
5.5
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
-40.0
-12.5
15.0
42.5
70.0
97.5
125.0
V+ (V)
TEMPERATURE (C)
TEMPERATURE (C)
GPO SOURCE CURRENT vs. TEMPERATURE (OUTPUT = 1)
MAX6957 toc07
GPI PULLUP CURRENT vs. TEMPERATURE
MAX6957 toc08
GPO SHORT-CIRCUIT CURRENT vs. TEMPERATURE
MAX6957 toc09
9 VPORT = 1.4V 8 PORT SOURCE CURRENT (mA) 7 6 5 4 3 2 -40.0 -12.5 15.0 42.5 70.0 97.5 V+ = 5.5V V+ = 3.3V V+ = 2.5V
1000
100
PULLUP CURRENT (A)
V+ = 5.5V
PORT CURRENT (mA)
GPO = 0, PORT SHORTED TO V+ 10
100 V+ = 3.3V
V+ = 2.5V 10 125.0 -40.0 -12.5 15.0 42.5 70.0 97.5 125.0 TEMPERATURE (C) TEMPERATURE (C)
GPO = 1, PORT SHORTED TO GND 1 -40.0 -12.5 15.0 42.5 70.0 97.5 125.0 TEMPERATURE (C)
4
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
Pin Description
PIN SSOP DIP 1 2, 3 4 5-24 -- 25 26 27 28 NAME SSOP 1 2, 3 4 -- 5-32 33 34 35 36 ISET GND DOUT P12-P31 P4-P31 SCLK DIN CS V+ Segment Current Setting. Connect ISET to GND through a resistor (RISET) to set the maximum segment current. Ground 4-Wire Serial Data Output Port 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. 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. 4-Wire Serial Clock Input Port 4-Wire Serial Data Input Port 4-Wire Chip-Select Input, Active Low Positive Supply Voltage. Bypass V+ to GND with a minimum 0.047F capacitor. FUNCTION
MAX6957
Detailed Description
The MAX6957 LED driver/GPIO peripheral provides up to 28 I/O ports, P4 to P31, controlled through an SPIcompatible 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 MAX6957 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 MAX6957 drives any combination of discrete LEDs and CA digits, including seven-segment and starburst alphanumeric types. Figure 1 is the MAX6957 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 MAX6957s working together controlling three monocolor 16-segment-plus-DP displays, with five ports left available for GPIO (P27-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 MAX6957AAX has 28 ports, P4 to P31. The 28-pin MAX6957ANI and MAX6957AAI make only 20 ports available. 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 MAX6957 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 2). This example requires two MAX6957s, with one digit being driven by both devices, half by one MAX6957, half by the other (digit 4 in this example). The two drivers are static, and therefore do not need to be synchronized. The MAX6957 sees CA digits as multiple discrete LEDs. To simplify access to displays that overlap two MAX6957s, the MAX6957 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 sec5
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 1. Port Configuration Map
REGISTER Port Configuration for P7, P6, P5, P4 Port Configuration for P11, P10, P9, P8 Port Configuration for P15, P14, P13, P12 Port Configuration for P19, P18, P17, P16 Port Configuration for P23, P22, P21, P20 Port Configuration for P27, P26, P25, P24 Port Configuration for P31, P30, P29, P28 ADDRESS CODE (HEX) 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F REGISTER DATA D7 P7 P11 P15 P19 P23 P27 P31 D6 D5 P6 P10 P14 P18 P22 P26 P30 D4 D3 P5 P9 P13 P17 P21 P25 P29 D2 D1 P4 P8 P12 P16 P20 P24 P28 D0
Table 2. Port Configuration Matrix
MODE FUNCTION PORT REGISTER Written Low Output LED Segment Driver Written High PIN BEHAVIOR ADDRESS CODE (HEX) PORT CONFIGURATION BIT PAIR UPPER High impedance Open-drain current sink, with sink current (up to 24mA) determined by the appropriate current register Active-low logic output Active-high logic output Schmitt logic input Schmitt logic input with pullup 0x09 to 0x0F 0 0 LOWER
Output Input Input
GPIO Output GPIO Input Without Pullup GPIO Input with Pullup
Written Low Written High Reading Port Reading Port
0x09 to 0x0F 0x09 to 0x0F 0x09 to 0x0F
0 1 1
1 0 1
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.
ond 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 14segment digit with DP can be updated in two byte-writes, 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 MAX6957 is in shutdown mode, all ports are forced to inputs, 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 MAX6957 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 6). Shutdown mode is temporarily overridden by the display test function.
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
INTENSITY TEST CONFIGURATION P4 TO P31 LED DRIVERS OR GPIO INTENSITY REGISTERS TEST REGISTER PORT REGISTERS MASK REGISTER LED DRIVERS AND GPIO PORT CHANGE DETECTOR CONFIGURATION REGISTERS DATA 8 SEGMENT OR GPIO DATA 8 COMMAND REGISTER DECODE R/W CE R/W
8
8
DATA BYTE
COMMAND BYTE
CS
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
DIN
D0
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
DOUT
SCLK
Figure 1. MAX6957 Functional Diagram
Serial Interface
The MAX6957 communicates through an SPI-compatible 4-wire serial interface. The interface has three inputs, Clock (SCLK), Chip Select (CS), and Data In (DIN), and one output, Data Out (DOUT). CS must be low to clock data into or out of the device, and DIN must be stable when sampled on the rising edge of SCLK. DOUT provides a copy of the bit that was input 15.5 clocks earlier, or upon a query it outputs internal register data, and is stable on the rising edge of SCLK. Note that the SPI protocol expects DOUT to be high impedance when the MAX6957 is not being accessed; DOUT on the MAX6957 is never high impedance. SCLK and DIN may be used to transmit data to other peripherals, so the MAX6957 ignores all activity on
SCLK and DIN except between the fall and subsequent rise of CS.
Control and Operation Using the 4-Wire Interface
Controlling the MAX6957 requires sending a 16-bit word. The first byte, D15 through D8, is the command address (Table 3), and the second byte, D7 through D0, is the data byte (Table 4). Connecting Multiple MAX6957s to the 4-Wire Bus Multiple MAX6957s may be daisy-chained by connecting the DOUT of one device to the DIN of the next, and driving SCLK and CS lines in parallel (Figure 4). Data at DIN propagates through the internal shift registers and appears at DOUT 15.5 clock cycles later, clocked out on the falling edge of SCLK. When sending commands
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
7-SEGMENT DIGIT 1 7-SEGMENT DIGIT 2 7-SEGMENT DIGIT 3 7-SEGMENT DIGIT 4 V+
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
7-SEGMENT DIGIT 7
V+
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 2. Two MAX6957s Controlling Seven 7-Segment Displays
CS
tCSS tCSH SCLK tCL
tCH
tCSH
tDS tDH DIN
tDV
tDO
DOUT
Figure 3. 4-Wire Interface Timing 8 _______________________________________________________________________________________
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
MICROCONTROLLER SERIAL DATA INPUT
SERIAL CS OUTPUT SERIAL CLOCK OUTPUT SERIAL DATA OUTPUT
CS
CS
CS
MAX6957
SCLK DIN DOUT SCLK DIN
MAX6957
SCLK DOUT DIN
MAX6957
DOUT
Figure 4. Daisy-Chain Arrangement for Controlling Multiple MAX6957s
CS
SCLK
D15 =0
DIN
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
DOUT
.
D15 = 0
Figure 5. 16-Bit Write Transmission to the MAX6957
to multiple MAX6957s, all devices are accessed at the same time. An access requires (16 n) clock cycles, where n is the number of MAX6957s connected together. To update just one device in a daisy-chain, the user can send the No-Op command (0x00) to the others.
4) Take CS high (either while SCLK is still high after clocking in the last data bit, or after taking SCLK low). 5) Take SCLK low (if not already low). Figure 5 shows a write operation when 16 bits are transmitted. It is acceptable to clock more than 16 bits into the MAX6957 between taking CS low and taking CS high again. In this case, only the last 16 bits clocked into the MAX6957 are retained.
Writing Device Registers
The MAX6957 contains a 16-bit shift register into which DIN data are clocked on the rising edge of SCLK, when CS is low. When CS is high, transitions on SCLK have no effect. When CS goes high, the 16 bits in the Shift register are parallel loaded into a 16-bit latch. The 16 bits in the latch are then decoded and executed. The MAX6957 is written to using the following sequence: 1) Take SCLK low. 2) Take CS low. This enables the internal 16-bit shift register. 3) Clock 16 bits of data into DIN--D15 first, D0 last-- observing the setup and hold times (bit D15 is low, indicating a write command).
Reading Device Registers
Any register data within the MAX6957 may be read by sending a logic high to bit D15. The sequence is: 1) Take SCLK low. 2) Take CS low (this enables the internal 16-bit shift register). 3) Clock 16 bits of data into DIN--D15 first to D0 last. D15 is high, indicating a read command and bits D14 through D8 containing the address of the register to be read. Bits D7-D0 contain dummy data,
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
which is discarded. 4) Take CS high (while SCLK is still high after clocking in the last data bit), positions D7 through D0 in the Shift register are now loaded with the register data addressed by bits D1 through D8. 5) Take SCLK low. 6) Issue another read or write command (which can be a No-Op), and examine the bit stream at DOUT; the second 8 bits are the contents of the register addressed by bits D1 through D8 in step 3. ed with the condition of P24 through P31 whenever the configuration register is written with the M bit set. 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 data change detection bit is set, the MAX6957 continuously compares the snapshot register against the changing states of P24 through P31. When a difference occurs, IRQ port P31 goes high if it is configured as an output. The IRQ output remains set until the mask register is next read or written. The IRQ status may be read back through the serial interface by externally connecting P31 (IRQ status pin) to any port pin configured as an input.
Initial Power-Up
On initial power-up, all control registers are reset, current registers are set to minimum value, and the MAX6957 enters shutdown mode (Table 4).
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 one register, the Global Current register, sets the current for all ports configured as LED segment drivers. It is also possible to individually control the current drive of each LED segment driver. Individual/global brightness control is selected by setting the configuration register I bit (Table7). The global current register (0x02) data are then ignored, and segment currents are set using register addresses 0x12 through 0x1F (Tables 10, 11, and 12). Each segment is controlled by a nibble of one of the 16 current registers.
Display Test Register
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 14). 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.
Selecting External Component RISET to Set Maximum Segment Current
The MAX6957 uses an external resistor RISET to set the maximum segment current. The recommended value, 39k, 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 = 936k / ISEG where ISEG is the desired maximum segment current in mA. The recommended value of RISET is 39k. 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 9) or individual segment current registers (Tables 10, 11, and 12), according to the setting of the current control bit of the configuration register (Table 7).
Transition (Port Data Change) Detection
Port transition detection allows seven maskable ports P24 through P30 to be continuously monitored for changes in their logic status (Figure 6). Enable transition detection by setting the M bit in the configuration register (Table 8) after setting the mask register. If port 31 is configured as an output (Tables 1 and 2), then P31 automatically becomes an interrupt request (IRQ) output to flag detected transitions. Port 31 can be configured and used as a general-purpose input port instead if not required as the IRQ output. The mask register determines which of the seven ports P24 through P30 are monitored (Table 13). 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 by the transition detection logic. Ports are monitored regardless of their I/O configuration, both input and output. The MAX6957 maintains an internal 7-bit snapshot register to hold the comparison copy of the logic states of ports P24 through P30. The snapshot register is updat10
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 3. Register Address Map
REGISTER No-Op Global Current Configuration Transition Detect Mask Display Test Port Configuration P7, P6, P5, P4 Port Configuration P11, P10, P9, P8 Port Configuration P15, P14, P13, P12 Port Configuration P19, P18, P17, P16 Port Configuration P23, P22, P21, P20 Port Configuration P27, P26, P25, P24 Port Configuration P31, P30, P29, P28 Current054 Current076 Current098 Current0BA Current0DC Current0FE Current110 Current132 Current154 Current176 Current198 Current1BA Current1DC Current1FE Port 0 only (virtual port, no action) Port 1 only (virtual port, no action) Port 2 only (virtual port, no action) Port 3 only (virtual port, no action) Port 4 only Port 5 only Port 6 only Port 7 only Port 8 only Port 9 only Port 10 only COMMAND ADDRESS D15 R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W D14 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D13 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 D12 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 D11 0 0 0 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 D10 0 0 1 1 1 0 0 0 1 1 1 1 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 D9 0 1 0 1 1 0 1 1 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 D8 0 0 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 HEX CODE 0x00 0x02 0x04 0x06 0x07 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A
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11
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 3. Register Address Map (continued)
REGISTER Port 11 only Port 12 only Port 13 only Port 14 only Port 15 only Port 16 only Port 17 only Port 18 only Port 19 only Port 20 only Port 21 only Port 22 only Port 23 only Port 24 only Port 25 only Port 26 only Port 27 only Port 28 only Port 29 only Port 30 only Port 31 only 4 ports 4-7 (data bits D4-D7) 5 ports 4-8 (data bits D3-D7) 6 ports 4-9 (data bits D2-D7) 7 ports 4-10 (data bits D1-D7) 8 ports 4-11 8 ports 5-12 8 ports 6-13 8 ports 7-14 8 ports 8-15 8 ports 9-16 8 ports 10-17 8 ports 11-18 8 ports 12-19 8 ports 13-20 8 ports 14-21 8 ports 15-22 COMMAND ADDRESS D15 R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W D14 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D13 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D12 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D11 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D10 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D9 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D8 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 HEX CODE 0x2B 0x2C 0x2D 0x2E 0x2F 0x30 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3D 0x3E 0x3F 0x40 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4D 0x4E 0x4F
12
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 3. Register Address Map (continued)
REGISTER 8 ports 16-23 8 ports 17-24 8 ports 18-25 8 ports 19-26 8 ports 20-27 8 ports 21-28 8 ports 22-29 8 ports 23-30 8 ports 24-31 7 ports 25-31 6 ports 26-31 5 ports 27-31 4 ports 28-31 3 ports 29, 30, 31 2 ports 30, 31 1 port 31 only COMMAND ADDRESS D15 R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W R/ W D14 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D13 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D12 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D11 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D10 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 D9 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 D8 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 HEX CODE 0x50 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5A 0x5B 0x5C 0x5D 0x5E 0x5F
Note: Unused bits read as 0.
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, I STEP , is therefore determined by the formula: ISTEP = ISEG / 16 If ISEG = 24mA, then ISTEP = 24mA / 16 = 1.5mA.
Power Dissipation Issues
Each MAX6957 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 MAX6957 can sink 28 x 24mA = 672mA when all outputs are operating as LED segment drivers at full current. On a 3.3V supply, a MAX6957 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 +98C. If a higher supply voltage is used or the LEDs used have a lower forward-voltage drop than 2.4V, the MAX6957 absorbs a higher voltage, and the MAX6957'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 MAX6957 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
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 MAX6957 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.
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13
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
GPIO INPUT CONDITIONING GPIO/PORT OUTPUT LATCH
GPIO IN
GPIO/PORT OUT IRQ STATUS STORED AS MSB OF MASK REGISTER
P31 IRQ OUTPUT LATCH R S CLOCK PULSE AFTER EACH READ ACCESS TO MASK REGISTER
CONFIGURATION REGISTER M BIT = 1 GPIO INPUT CONDITIONING P30 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P29 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P28 GPIO/PORT OUTPUT LATCH GPIO IN GPIO IN D GPIO/PORT OUT Q MASK REGISTER BIT 4 GPIO IN GPIO IN D GPIO/PORT OUT Q MASK REGISTER BIT 6
D
Q MASK REGISTER BIT 5
GPIO/PORT OUT
GPIO INPUT CONDITIONING P27 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P26 GPIO/PORT OUTPUT LATCH GPIO INPUT CONDITIONING P25 GPIO/PORT OUTPUT LATCH
D
Q MASK REGISTER BIT 3
OR
GPIO/PORT OUT
GPIO IN D GPIO/PORT OUT Q MASK REGISTER BIT 2
GPIO IN
D
Q MASK REGISTER BIT 1
GPIO/PORT OUT
GPIO INPUT CONDITIONING P24 GPIO/PORT OUTPUT LATCH
GPIO IN D GPIO/PORT OUT Q MASK REGISTER LSB CLOCK PULSE WHEN WRITING CONFIGURATION REGISTER WITH M BIT SET
Figure 6. Maskable GPIO Ports P24 Through P31
14
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 4. Power-Up Configuration
REGISTER FUNCTION Port Register Bits 4 to 31 Global Current Configuration Register Input Mask Register Display Test Port Configuration Port Configuration Port Configuration Port Configuration Port Configuration Port Configuration Port Configuration Current054 Current076 Current098 Current0BA Current0DC Current0FE Current110 Current132 Current154 Current176 Current198 Current1BA Current1DC Current1FE POWER-UP CONDITION ADDRESS CODE (HEX) 0x24 to 0x3F 0x02 REGISTER DATA D7 X X D6 X X D5 X X D4 X X D3 X 0 D2 X 0 D1 X 0 D0 0 0
LED Off; GPIO Output Low 1/16 (minimum on) Shutdown Enabled Current Control = Global Transition Detection Disabled All Clear (Masked Off) Normal Operation P7, P6, P5, P4: GPIO Inputs Without Pullup P11, P10, P9, P8: GPIO Inputs Without Pullup P15, P14, P13, P12: GPIO Inputs Without Pullup P19, P18, P17, P16: GPIO Inputs Without Pullup P23, P22, P21, P20: GPIO Inputs Without Pullup P27, P26, P25, P24: GPIO Inputs Without Pullup P31, P30, P29, P28: GPIO Inputs Without Pullup 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on) 1/16 (minimum on)
0x04
0
0
X
X
X
X
X
0
0x06 0x07 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F
X X 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 X 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 X 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 X 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X = unused bits; if read, zero results. ______________________________________________________________________________________ 15
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 5. Configuration Register Format
FUNCTION Configuration Register ADDRESS CODE (HEX) 0x04 REGISTER DATA D7 M D6 I D5 X D4 X D3 X D2 X D1 X D0 S
X = Don't care bit.
Table 6. Shutdown Control (S Data Bit D0) Format
FUNCTION Shutdown Normal Operation ADDRESS CODE (HEX) 0x04 0x04 REGISTER DATA D7 M M D6 I I D5 X X D4 X X D3 X X D2 X X D1 X X D0 0 1
X = Don't care bit.
Table 7. Global Current Control (I Data Bit D6) Format
FUNCTION Global Constant-current limits for all digits are controlled by one setting in the Global Current register, 0x02 Individual Segment Constant-current limit for each digit is individually controlled by the settings in the Current054 through Current1FE registers ADDRESS CODE (HEX) REGISTER DATA D7 D6 D5 D4 D3 D2 D1 D0
0x04
M
0
X
X
X
X
X
S
0x04
M
1
X
X
X
X
X
S
X = Don't care bit.
Table 8. Transition Detection Control (M-Data Bit D7) Format
FUNCTION Disabled Enabled X = Don't care bit. ADDRESS CODE (HEX) 0x04 0x04 REGISTER DATA D7 0 1 D6 I I D5 X X D4 X X D3 X X D2 X X D1 X X D0 S S
Table 9. Global Segment Current Register Format
LED DRIVE FRACTION 1/16 2/16 3/16 4/16 5/16 TYPICAL SEGMENT CURRENT (mA) 1.5 3 4.5 6 7.5 ADDRESS CODE (HEX) 0x02 0x02 0x02 0x02 0x02 D7 X X X X X D6 X X X X X D5 X X X X X D4 X X X X X D3 0 0 0 0 0 D2 0 0 0 0 1 D1 0 0 1 1 0 D0 0 1 0 1 0 HEX CODE 0xX0 0xX1 0xX2 0xX3 0xX4
X = Don't care bit.
16
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 9. Global Segment Current Register Format (continued)
LED DRIVE FRACTION 6/16 7/16 8/16 9/16 10/16 11/16 12/16 13/16 14/16 15/16 16/16 TYPICAL SEGMENT CURRENT (mA) 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 ADDRESS CODE (HEX) 0x02 0x02 0x02 0x02 0x02 0x02 0x02 0x02 0x02 0x02 0x02 D7 X X X X X X X X X X X D6 X X X X X X X X X X X D5 X X X X X X X X X X X D4 X X X X X X X X X X X D3 0 0 0 1 1 1 1 1 1 1 1 D2 1 1 1 0 0 0 0 1 1 1 1 D1 0 1 1 0 0 1 1 0 0 1 1 D0 1 0 1 0 1 0 1 0 1 0 1 HEX CODE 0xX5 0xX6 0xX7 0xX8 0xX9 0xXA 0xXB 0xXC 0xXD 0xXE 0xXF
X = Don't care bit.
Table 10. Individual Segment Current Registers
REGISTER FUNCTION Current054 register Current076 register Current098 register Current0BA register Current0DC register Current0FE register Current110 register Current132 register Current154 register Current176 register Current198 register Current1BA register Current1DC register Current1FE register ADDRESS CODE (HEX) 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F D7 D6 D5 D4 D3 D2 D1 D0
Segment 5 Segment 7 Segment 9 Segment 11 Segment 13 Segment 15 Segment 17 Segment 19 Segment 21 Segment 23 Segment 25 Segment 27 Segment 29 Segment 31
Segment 4 Segment 6 Segment 8 Segment 10 Segment 12 Segment 14 Segment 16 Segment 18 Segment 20 Segment 22 Segment 24 Segment 26 Segment 28 Segment 30
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17
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 11. Even Individual Segment Current Format
LED DRIVE FRACTION SEGMENT CONSTANT CURRENT WITH RISET = 39k (mA) 1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 ADDRESS CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE
1/16 2/16 3/16 4/16 5/16 6/16 7/16 8/16 9/16 10/16 11/16 12/16 13/16 14/16 15/16 16/16
0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F See Table 12.
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
0xX0 0xX1 0xX2 0xX3 0xX4 0xX5 0xX6 0xX7 0xX8 0xX9 0xXA 0xXB 0xXC 0xXD 0xXE 0xXF
value is (4.75V - 2.4V - 0.6V)/0.020A = 87.5. We choose 82 2%. Worst-case resistor dissipation is at maximum toleranced resistance, i.e., (0.020A)2 (82 1.02) = 34mW. The maximum MAX6957 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 82 x 0.98)) = 32.86mW. Worst-case MAX6957 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.
Power-Supply Considerations
The MAX6957 operates with power-supply voltages of 2.5V to 5.5V. Bypass the power supply to GND with a 0.047F capacitor as close to the device as possible. Add a 1F capacitor if the MAX6957 is far away from the board's input bulk decoupling capacitor.
Low-Voltage Operation
The MAX6957 operates down to 2V supply voltage (although the sourcing and sinking currents are not guaranteed), providing that the MAX6957 is powered up initially to at least 2.5V to trigger the device's internal reset, and also that the serial interface is constrained to 10Mbps.
18
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Table 12. Odd Individual Segment Current Format
LED DRIVE FRACTION 1/16 2/16 3/16 4/16 5/16 6/16 7/16 8/16 9/16 10/16 11/16 12/16 13/16 14/16 15/16 16/16 SEGMENT CONSTANT CURRENT WITH RISET = 39k (mA) 1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5 24 ADDRESS CODE (HEX) 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F 0x12 to 0x1F D7 D6 D5 D4 D3 D2 D1 D0 HEX CODE
0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 See Table 11.
0x0X 0x1X 0x2X 0x3X 0x4X 0x5X 0x6X 0x7X 0x8X 0x9X 0xAX 0xBX 0xCX 0xDX 0xEX 0xFX
X = Don't care bit.
Table 13. Transition Detection Mask Register
FUNCTION REGISTER ADDRESS (HEX) READ/ WRITE Read 0x06 Write Unchanged REGISTER DATA D7 0 D6 Port 30 mask D5 Port 29 mask D4 Port 28 mask D3 Port 27 mask D2 Port 26 mask D1 Port 25 mask D0 Port 24 mask
Mask Register
Table 14. Display Test Register
MODE Normal Operation Display Test Mode ADDRESS CODE (HEX) 0x07 0x07 REGISTER DATA D7 X X D6 X X D5 X X D4 X X D3 X X D2 X X D1 X X D0 0 1
X = Don't care bit.
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19
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Pin Configurations (continued)
TOP VIEW
ISET 1 GND 2 GND 3 DOUT 4 P8 5 P12 6 P9 7 P13 8 P10 9 P14 10 P11 11 P15 12 P16 13 P17 14 P18 15 P19 16 P20 17 P21 18 36 V+ 35 CS 34 DIN 33 SCLK 32 P4 31 P31 30 P5 29 P30
Chip Information
TRANSISTOR COUNT: 30,316 PROCESS: CMOS
MAX6957
28 P6 27 P29 26 P7 25 P28 24 P27 23 P26 22 P25 21 P24 20 P23 19 P22
SSOP
20
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4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
Typical Operating Circuit
3V 3V 36 V+ 47nF 3 GND 2 GND 1 ISET 39k 4-WIRE DATA IN 4-WIRE CLOCK IN CHIP SELECT 34 DIN 33 SCLK 35 CS 4 DOUT 31 P31 29 P30 27 P29 25 P28 24 P27 23 P26 22 P25 21 P24 P4 32 P5 30 P6 28 P7 26 P8 P9 P10 5 7 9 11 a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp ca
LED1
U1 MAX6957AAX
P11 P12 6 P13 8 P14 10 P15 12 P16 13 P17 14 P18 15 P19 16 P20 17 P21 18 P22 19 P23 20
a1 a2 b c d1 d2 e f g1 g2 h i 3V 36 V+ 47nF 3 GND 2 GND 1 ISET 39k 34 DIN 33 SCLK 35 CS 4-WIRE DATA OUT IRQ OUT 4 DOUT 31 P31 29 P30 27 P29 25 P28 24 P27 32 P4 30 P5 28 P6 26 P7 5 P8 7 P9 P10 9 P11 11 P12 6 P13 8 P14 10 P15 12 P16 13 P17 14 P18 15 P19 16 P20 17 P21 18 P22 19 P23 20 j k l m dp ca
LED2
U2 MAX6957AAX
a1 a2 b c d1 d2 e f g1 g2 h i j k l m dp ca
LED3
1
2
23 P26 22 P25 21 P24
SW1
SW2
SW3
______________________________________________________________________________________
21
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander MAX6957
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.)
2
1
INCHES DIM A A1 B C E H D E e H L MIN 0.068 0.002 0.010 MAX 0.078 0.008 0.015
MILLIMETERS MIN 1.73 0.05 0.25 MAX 1.99 0.21 0.38 D D D D D INCHES MIN 0.239 0.239 0.278 0.317 0.397 MAX 0.249 0.249 0.289 0.328 0.407 MILLIMETERS MIN 6.07 6.07 7.07 8.07 10.07 MAX 6.33 6.33 7.33 8.33 10.33 N 14L 16L 20L 24L 28L
0.20 0.09 0.004 0.008 SEE VARIATIONS 0.205 0.301 0.025 0 0.212 0.311 0.037 8 5.20 7.65 0.63 0 5.38 7.90 0.95 8 0.0256 BSC 0.65 BSC
N
A C e D B A1 L
NOTES: 1. D&E DO NOT INCLUDE MOLD FLASH. 2. MOLD FLASH OR PROTRUSIONS NOT TO EXCEED .15 MM (.006"). 3. CONTROLLING DIMENSION: MILLIMETERS. 4. MEETS JEDEC MO150. 5. LEADS TO BE COPLANAR WITHIN 0.10 MM.
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, SSOP, 5.3 MM
APPROVAL DOCUMENT CONTROL NO. REV.
21-0056
C
1 1
22
______________________________________________________________________________________
SSOP.EPS
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and 28-Port LED Display Driver and I/O Expander
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.)
SSOP.EPS
MAX6957
36
INCHES DIM A A1 B C e E H L D MAX MIN 0.104 0.096 0.004 0.011 0.017 0.012 0.013 0.009 0.0315 BSC 0.299 0.291 0.398 0.414 0.040 0.020 0.598 0.612
MILLIMETERS MAX MIN 2.65 2.44 0.29 0.10 0.44 0.30 0.23 0.32 0.80 BSC 7.40 7.60 10.11 10.51 0.51 15.20 1.02 15.55
E
H
1
TOP VIEW
D A1 e A C 0-8
B
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 36L SSOP, 0.80 MM PITCH
APPROVAL DOCUMENT CONTROL NO. REV.
21-0040
E
1 1
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 23 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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