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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 indi- vidually user configurable to either a logic input, logic output, or common-anode (ca) led constant-current segment driver. each port configured as an led seg- ment 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 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 max6957 is controlled through an spi-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. applications set-top boxes panel meters white goods automotive bar graph displays industrial controllers system monitoring features high-speed 26mhz spi-/qspi-/microwire- compatible serial interface 2.5v to 5.5v operation -40? to +125? 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 11? (max) shutdown current 16-step individually programmable current control for each led logic transition detection for seven i/o ports max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ________________________________________________________________ maxim integrated products 1 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 v+ cs sclk din p31 p30 p22 p29 p28 p27 p26 p25 p24 p23 p21 p20 p19 p18 p17 p16 p15 p14 p13 p12 dout gnd gnd iset ssop/dip top view max6957 pin configurations 19-2429; rev 0; 4/02 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. typical operating circuit appears at end of data sheet. ordering information part temp range pin-package max6957ani -40 c to +125 c 28 dip MAX6957AAI -40 c to +125 c 28 ssop max6957aax -40 c to +125 c 36 ssop max6957agl* -40 c to +125 c 40 qfn spi and qspi are trademarks of motorola, inc. microwire is a trademark of national semiconductor corp. * future product?ontact factory for availability. pin configurations continued at end of data sheet.
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. 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 (t a = +70 c) 28-pin pdip (derate 20.8mw/ c above +70 c)........1667mw 28-pin ssop (derate 9.5mw/ c above +70 c) ..........762mw 36-pin ssop (derate 11.8mw/ c above +70 c) ........941mw operating temperature range (t min , t max ) ....-40 c to +125 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c electrical characteristics (typical operating circuit, v+ = 2.5v to 5.5v, t a = t min to t max , unless otherwise noted.) (note 1) parameter symbol conditions min typ max units operating supply voltage v+ 2.5 5.5 v t a = +25 c 5.5 8 ta = - 40 c to + 85 c 10 shutdown supply current i shdn al l d i g i tal i np uts at v + or g n d t a = t min to t max 11 a t a = +25 c 180 230 ta = - 40 c to + 85 c 250 operating supply current i gpoh al l p or ts p r og r am m ed as outp uts hi g h, no l oad , al l other i np uts at v + or g n d t a = t min to t max 270 a t a = +25 c 170 210 ta = - 40 c to + 85 c 230 operating supply current i gpol al l p or ts p r og r am m ed as outp uts l ow , no l oad , al l other i np uts at v + or g n d t a = t min to t max 240 a t a = +25 c 110 135 t a = - 40 c to + 85 c 140 operating supply current i led al l p or ts p r og r am m ed as le d outp uts, al l le d s off, no l oad , al l other i np uts at v + or g n d t a = t min to t max 145 a inputs and outputs logic-high input voltage port inputs v ih 0.7 ? v+ v logic-low input voltage port inputs v il 0.3 ? v+ v v+ = 2.5v 12 19 30 gpio input internal pullup to v+ i pu v+ = 5.5v 80 120 180 a hysteresis voltage gpio inputs ? v i 0.3 v gpio outputs, i source = 2ma, t a = -40 c to +85 c v+ - 0.7 v output high voltage v oh gpio outputs, i source = 1ma, t a = t min to t max (note 2) v+ - 0.7 v
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander _______________________________________________________________________________________ 3 note 1: all parameters tested at t a = +25 c. specifications over temperature are guaranteed by design. note 2: guaranteed by design. electrical characteristics (continued) (typical operating circuit, v+ = 2.5v to 5.5v, t a = t min to t max , unless otherwise noted.) (note 1) parameter symbol conditions min typ max units port sink current i ol v port = 0.6v 2 10 18 ma output short-circuit current i olsc port configured output low, shorted to v+ 2.75 11 20 ma v+ = 2.5v, v led = 2.3v at maximum led current 9.5 13.5 18 v+ = 3.3v, v led = 2.4v at maximum led current (note 2) 18.5 24 27.5 port drive led sink current, port configured as led driver i digit v+ = 5.5v, v led = 2.4v at maximum led current 19 25 30 ma v+ = 2.5v, v out = 0.6v at maximum led current 18.5 23 28.0 port drive logic sink current, port configured as led driver i digit_sc v+ = 5.5v, v out = 0.6v at maximum led current 19 24 28 ma v+ 3.3v 1.6 input high-voltage sclk, din, cs v ih v+ > 3.3v 2 v input low-voltage sclk, din, cs cs timing characteristics (figure 3) (v+ = 2.5v to 5.5v, t a = t min to t max , unless otherwise noted.) (note 1) parameter symbol conditions min typ max units clk clock period t cp 38.4 ns clk pulse width high t ch 19 ns clk pulse width low t cl 19 ns cs fall to sclk rise setup time t css 9.5 ns clk rise to cs rise hold time t csh 0ns din setup time t ds 9.5 ns din hold time t dh 0ns output data propagation delay t do c load = 25pf 21 ns minimum cs pulse high t csw 19 ns
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 4 _______________________________________________________________________________________ operating supply current vs. temperature max6957 toc01 temperature ( c) supply current (ma) 97.5 70.0 42.5 15.0 -12.5 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 0 -40.0 125.0 v+ = 2.5v to 5.5v no load all ports output (1) all ports output (0) all ports led (off) shutdown supply current vs. temperature max6957 toc02 temperature ( c) supply current ( a) 97.5 70.0 42.5 15.0 -12.5 4 5 6 7 8 3 -40.0 125.0 v+ = 5.5v v+ = 3.3v v+ = 2.5v operating supply current vs. v+ (no loads) max6957 toc03 v+ (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 2.5 0.1 1 10 100 0.01 2.0 5.5 all ports led (on) all ports led (off) all ports output (1) all ports output (0) led driver sink current vs. v+ max6957 toc04 v+ (v) port sink current (ma) 5.0 4.5 3.5 4.0 3.0 2.5 8 10 12 14 16 18 20 22 24 26 6 2.0 5.5 led drop = 2.4v led drop = 1.8v gpo source current vs. temperature (output = 1) max6957 toc07 temperature ( c) port source current (ma) 97.5 70.0 42.5 15.0 -12.5 3 4 5 6 7 8 9 2 -40.0 125.0 v port = 1.4v v+ = 5.5v v+ = 3.3v v+ = 2.5v led driver sink current vs. temperature max6957 toc05 temperature ( c) port sink current (ma) 97.5 70.0 42.5 15.0 -12.5 21 22 23 24 25 26 27 20 -40.0 125.0 v led = 2.4v v+ = 5.5v v+ = 3.3v gpo sink current vs. temperature (output = 0) max6957 toc06 temperature ( c) port sink current (ma) 97.5 70.0 -12.5 15.0 42.5 4 6 8 10 12 14 16 18 2 -40.0 125.0 v+ = 2.5v to 5.5v, v port = 0.6v gpi pullup current vs. temperature max6957 toc08 temperature ( c) pullup current ( a) 97.5 70.0 42.5 15.0 -12.5 100 1000 10 -40.0 125.0 v+ = 5.5v v+ = 3.3v v+ = 2.5v gpo short-circuit current vs. temperature max6957 toc09 temperature ( c) port current (ma) 97.5 70.0 42.5 15.0 -12.5 10 100 1 -40.0 125.0 gpo = 0, port shorted to v+ gpo = 1, port shorted to gnd __________________________________________typical operating characteristics (r iset = 39k ? , t a = +25 c, unless otherwise noted.)
detailed description the max6957 led driver/gpio peripheral provides up to 28 i/o ports, p4 to p31, controlled through an spi- compatible serial interface. the ports can be config- ured 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 seg- ments with individual 16-step adjustment of the con- stant current through each led segment. a single resistor sets the maximum segment current for all seg- ments, 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 regis- ter bit, as well as an interrupt pin (port p31), if desired. the typical operating circuit shows two max6957s working together controlling three monocolor 16-seg- ment-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 only use 20 out- puts, 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 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 sec- max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander _______________________________________________________________________________________ 5 pin ssop dip ssop name function 1 1 iset segment current setting. connect iset to gnd through a resistor (r iset ) to set the maximum segment current. 2, 3 2, 3 gnd ground 4 4 dout 4-wire serial data output port 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 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. 25 33 sclk 4-wire serial clock input port 26 34 din 4-wire serial data input port 27 35 cs 4-wire chip-select input, active low 28 36 v+ positive supply voltage. bypass v+ to gnd with a minimum 0.047f capacitor. pin description
max6957 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 nonexis- tent, so the instructions to these bits are ignored). using 8-bit control, a seven-segment digit with a deci- mal point can be updated in a single byte-write, a 14- segment 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, dis- crete 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 shut- down 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. 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 6 _______________________________________________________________________________________ table 1. port configuration map register data register address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 port configuration for p7, p6, p5, p4 0x09 p7 p6 p5 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 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. port configuration bit pair mode function port register pin behavior address code ( hex ) upper lower written low high impedance output led segment driver written high open-drain current sink, with sink current (up to 24ma) determined by the appropriate current register 0x09 to 0x0f 00 written low active-low logic output output gpio output written high active-high logic output 0x09 to 0x0f 01 input gpio input without pullup reading port schmitt logic input 0x09 to 0x0f 10 input gpio input with pullup reading port schmitt logic input with pullup 0x09 to 0x0f 11
serial interface the max6957 communicates through an spi-compati- ble 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 connect- ing 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 max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander _______________________________________________________________________________________ 7 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d11 d12 d13 d14 d15 d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d11 d12 d13 d14 d15 r/w 8 ce data 8 test register intensity registers port registers led drivers and gpio intensity configuration test p4 to p31 led drivers or gpio segment or gpio data r/w configuration registers port change detector mask register command register decode 8 8 data byte command byte cs din sclk dout figure 1. max6957 functional diagram
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander figure 2. two max6957s controlling seven 7-segment displays 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 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 1 virtual segments virtual segments 7-segment digit 5 7-segment digit 6 7-segment digit 7 7-segment digit 2 7-segment digit 3 7-segment digit 4 v+ v+ figure 3. 4-wire interface timing t csh t cl t css t ch t csh cs sclk din dout t ds t dh t dv t do 8 _______________________________________________________________________________________
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 togeth- er. to update just one device in a daisy-chain, the user can send the no-op command (0x00) to the others. 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). 4) take cs high (while sclk is still high after clocking in the last data bit). 5) take sclk 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. 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 reg- ister to be read. bits d7 d0 contain dummy data, which is discarded. max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander _______________________________________________________________________________________ 9 microcontroller serial data output serial clock output serial data input din sclk cs dout din sclk cs dout din sclk cs dout serial cs output max6957 max6957 max6957 figure 4. daisy-chain arrangement for controlling multiple max6957s . d15 = 0 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 d15 = 0 cs sclk din dout figure 5. 16-bit write transmission to the max6957
max6957 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. initial power-up on initial power-up, all control registers are reset, cur- rent 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 regis- ter, sets the current for all ports configured as led seg- ment drivers. it is also possible to individually control the current drive of each led segment driver. individual/global brightness control is selected by set- ting the configuration register i bit (table7). the global current register (0x02) data are then ignored, and seg- ment 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. 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 transi- tion 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 con- figured 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 reg- ister to hold the comparison copy of the logic states of ports p24 through p30. the snapshot register is updat- 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, the irq bit (mask register bit d7) is set and irq port p31 goes high if it is configured as an output. the irq bit and irq output remain set until the mask register is next read or written, so if the irq is set, then the mask register reads with bit d7 set. writing the mask register clears the irq output and resets the irq bit, regardless of the value of bit d7 written. 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 r iset . selecting external component r iset to set maximum segment current the max6957 uses an external resistor r iset 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: r iset = 936k ? / i seg where i seg is the desired maximum segment current in ma. the recommended value of r iset 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. r iset can be a higher value to set the segment current to a lower maxi- mum 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). 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 10 ______________________________________________________________________________________
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ______________________________________________________________________________________ 11 table 3. register address map command address register d15 d14 d13 d12 d11 d10 d9 d8 hex code no-op r/ w 00 0 0 0 00 0x00 global current r/ w 00000 10 0x02 configuration r/ w 00001 00 0x04 transition detect mask r/ w 00001 10 0x06 display test r/ w 00001 11 0x07 port configuration p7, p6, p5, p4 r/ w 00010 01 0x09 port configuration p11, p10, p9, p8 r/ w 00010 10 0x0a port configuration p15, p14, p13, p12 r/ w 00010 11 0x0b port configuration p19, p18, p17, p16 r/ w 00011 00 0x0c port configuration p23, p22, p21, p20 r/ w 00011 01 0x0d port configuration p27, p26, p25, p24 r/ w 00011 10 0x0e port configuration p31, p30, p29, p28 r/ w 00011 11 0x0f current054 r/ w 00100 10 0x12 current076 r/ w 00100 11 0x13 current098 r/ w 00101 00 0x14 current0ba r/ w 00101 01 0x15 current0dc r/ w 00101 10 0x16 current0fe r/ w 00101 11 0x17 current110 r/ w 00110 00 0x18 current132 r/ w 00110 01 0x19 current154 r/ w 00110 10 0x1a current176 r/ w 00110 11 0x1b current198 r/ w 00111 00 0x1c current1ba r/ w 00111 01 0x1d current1dc r/ w 00111 10 0x1e current1fe r/ w 00111 11 0x1f port 0 only (virtual port, no action) r/ w 01000 00 0x20 port 1 only (virtual port, no action) r/ w 01000 01 0x21 port 2 only (virtual port, no action) r/ w 01000 10 0x22 port 3 only (virtual port, no action) r/ w 01000 11 0x23 port 4 only r/ w 01001 00 0x24 port 5 only r/ w 01001 01 0x25 port 6 only r/ w 01001 10 0x26 port 7 only r/ w 01001 11 0x27 port 8 only r/ w 01010 00 0x28 port 9 only r/ w 01010 01 0x29 port 10 only r/ w 01010 10 0x2a
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 12 ______________________________________________________________________________________ command address register d15 d14 d13 d12 d11 d10 d9 d8 hex code port 11 only r/ w 0101011 0x2b port 12 only r/ w 0101100 0x2c port 13 only r/ w 0101101 0x2d port 14 only r/ w 0101110 0x2e port 15 only r/ w 0101111 0x2f port 16 only r/ w 0110000 0x30 port 17 only r/ w 0110001 0x31 port 18 only r/ w 0110010 0x32 port 19 only r/ w 0110011 0x33 port 20 only r/ w 0110100 0x34 port 21 only r/ w 0110101 0x35 port 22 only r/ w 0110110 0x36 port 23 only r/ w 0110111 0x37 port 24 only r/ w 0111000 0x38 port 25 only r/ w 0111001 0x39 port 26 only r/ w 0111010 0x3a port 27 only r/ w 0111011 0x3b port 28 only r/ w 0111100 0x3c port 29 only r/ w 0111101 0x3d port 30 only r/ w 0111110 0x3e port 31 only r/ w 0111111 0x3f 8 ports 0 7 (ports 0 3 are virtual) r/ w 1000000 0x40 8 ports 1 8 (ports 1, 2, 3 are virtual) r/ w 1000001 0x41 8 ports 2 9 (ports 2, 3 are virtual) r/ w 1000010 0x42 8 ports 3 10 (port 3 is virtual) r/ w 1000011 0x43 8 ports 4 11 r/ w 1000100 0x44 8 ports 5 12 r/ w 1000101 0x45 8 ports 6 13 r/ w 1000110 0x46 8 ports 7 14 r/ w 1000111 0x47 8 ports 8 15 r/ w 1001000 0x48 8 ports 9 16 r/ w 1001001 0x49 8 ports 10 17 r/ w 1001010 0x4a 8 ports 11 18 r/ w 1001011 0x4b 8 ports 12 19 r/ w 1001100 0x4c 8 ports 13 20 r/ w 1001101 0x4d 8 ports 14 21 r/ w 1001110 0x4e 8 ports 15 22 r/ w 1001111 0x4f table 3. register address map (continued)
these registers select the led s constant-current drive from 16 equal fractions of the maximum segment cur- rent. the current difference between successive cur- rent steps, i step , is therefore determined by the formula: i step = i seg / 16 if i seg = 24ma, then i step = 24ma / 16 = 1.5ma. 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 cur- rent 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 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 there- fore (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 tempera- ture 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 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 forward- voltage 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 max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ______________________________________________________________________________________ 13 command address register d15 d14 d13 d12 d11 d10 d9 d8 hex code 8 ports 16 23 r/ w 1010000 0x50 8 ports 17 24 r/ w 1010001 0x51 8 ports 18 25 r/ w 1010010 0x52 8 ports 19 26 r/ w 1010011 0x53 8 ports 20 27 r/ w 1010100 0x54 8 ports 21 28 r/ w 1010101 0x55 8 ports 22 29 r/ w 1010110 0x56 8 ports 23 30 r/ w 1010111 0x57 8 ports 24 31 r/ w 1011000 0x58 7 ports 25 31 r/ w 1011001 0x59 6 ports 26 31 r/ w 1011010 0x5a 5 ports 27 31 r/ w 1011011 0x5b 4 ports 28 31 r/ w 1011100 0x5c 3 ports 29, 30, 31 r/ w 1011101 0x5d 2 ports 30, 31 r/ w 1011110 0x5e 1 port 31 only r/ w 1011111 0x5f table 3. register address map (continued) note: unused bits read as 0.
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander gpio input conditioning p31 p30 p29 p28 p27 p26 p25 p24 gpio/port output latch gpio input conditioning gpio/port output latch gpio input conditioning gpio/port output latch gpio input conditioning gpio/port output latch gpio input conditioning gpio/port output latch gpio input conditioning gpio/port output latch gpio input conditioning gpio/port output latch d q d q d q d q d q d q d q clock pulse when writing configuration register with m bit set or control register m bit = 1 r s gpio in gpio/port out clock pulse after each read access to mask register irq status stored as msb of mask register mask register bit 6 mask register bit 5 mask register bit 4 mask register bit 3 mask register bit 2 mask register bit 1 mask register lsb gpio in gpio/port out gpio in gpio/port out gpio in gpio/port out gpio in gpio/port out gpio in gpio/port out gpio in gpio/port out gpio in gpio/port out gpio input conditioning gpio/port output latch irq output latch figure 6. maskable gpio ports p24 through p31 14 ______________________________________________________________________________________
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ______________________________________________________________________________________ 15 table 4. power-up configuration register data register function power-up condition address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 port register bits 4 to 31 led off; gpio output low 0x24 to 0x3f xxxxxxx 0 global current 1/16 (minimum on) 0x02 xxxx000 0 configuration register shutdown enabled current control = global transition detection disabled 0x04 00xxxxx 0 input mask register all clear (masked off) 0x06 x000000 0 display test normal operation 0x07 xxxxxxx 0 port configuration p7, p6, p5, p4: gpio inputs without pullup 0x09 1010101 0 port configuration p11, p10, p9, p8: gpio inputs without pullup 0x0a 1010101 0 port configuration p15, p14, p13, p12: gpio inputs without pullup 0x0b 1010101 0 port configuration p19, p18, p17, p16: gpio inputs without pullup 0x0c 1010101 0 port configuration p23, p22, p21, p20: gpio inputs without pullup 0x0d 1010101 0 port configuration p27, p26, p25, p24: gpio inputs without pullup 0x0e 1010101 0 port configuration p31, p30, p29, p28: gpio inputs without pullup 0x0f 1010101 0 current054 1/16 (minimum on) 0x12 0000000 0 current076 1/16 (minimum on) 0x13 0000000 0 current098 1/16 (minimum on) 0x14 0000000 0 current0ba 1/16 (minimum on) 0x15 0000000 0 current0dc 1/16 (minimum on) 0x16 0000000 0 current0fe 1/16 (minimum on) 0x17 0000000 0 current110 1/16 (minimum on) 0x18 0000000 0 current132 1/16 (minimum on) 0x19 0000000 0 current154 1/16 (minimum on) 0x1a 0000000 0 current176 1/16 (minimum on) 0x1b 0000000 0 current198 1/16 (minimum on) 0x1c 0000000 0 current1ba 1/16 (minimum on) 0x1d 0000000 0 current1dc 1/16 (minimum on) 0x1e 0000000 0 current1fe 1/16 (minimum on) 0x1f 0000000 0 x = unused bits; if read, zero results.
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 16 ______________________________________________________________________________________ table 5. configuration register format register data function address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 configuration register 0x04 m i xxxxxs table 6. 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 xxxxx0 normal operation 0x04 m i xxxxx1 register data function address code (hex) 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 xxxxxs individual segment constant-current limit for each digit is individually controlled by the settings in the current054 through current1fe registers 0x04 m 1 xxxxxs table 7. global current control (i data bit d6) format table 8. 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 xxxxxs enabled 0x04 1 i xxxxxs table 9. global segment current register format 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 xxxx0000 0xx0 2/16 3 0x02 xxxx0001 0xx1 3/16 4.5 0x02 xxxx0010 0xx2 4/16 6 0x02 xxxx0011 0xx3 5/16 7.5 0x02 xxxx0100 0xx4 x = don? care bit. x = don? care bit. x = don? care bit. x = don? care bit. x = don? care bit.
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ______________________________________________________________________________________ 17 table 9. global segment current register format (continued) led drive fraction typical segment current (ma) address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 hex code 6/16 9 0x02 xxxx0101 0xx5 7/16 10.5 0x02 xxxx0110 0xx6 8/16 12 0x02 xxxx0111 0xx7 9/16 13.5 0x02 xxxx1000 0xx8 10/16 15 0x02 xxxx1001 0xx9 11/16 16.5 0x02 xxxx1010 0xxa 12/16 18 0x02 xxxx1011 0xxb 13/16 19.5 0x02 xxxx1100 0xxc 14/16 21 0x02 xxxx1101 0xxd 15/16 22.5 0x02 xxxx1110 0xxe 16/16 24 0x02 xxxx1111 0xxf x = don? care bit. table 10. individual segment current registers register function address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 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 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
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 18 ______________________________________________________________________________________ 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 for- ward-voltage drop, i.e., 0.020 x (5.25v - 2.0v - (0.020a ? 82 ? x 0.98)) = 32.86mw. worst-case max6957 dissi- pation is 920mw, driving all 28 leds at 20ma full cur- rent at once, which meets the 941mw dissipation ratings of the 36-pin ssop package. 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. 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. table 11. even individual segment current format led drive fraction segment constant current with r iset = 39k ? (ma) address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 hex code 1/16 1.5 0x12 to 0x1f 0000 0xx0 2/16 3 0x12 to 0x1f 0001 0xx1 3/16 4.5 0x12 to 0x1f 0010 0xx2 4/16 6 0x12 to 0x1f 0011 0xx3 5/16 7.5 0x12 to 0x1f 0100 0xx4 6/16 9 0x12 to 0x1f 0101 0xx5 7/16 10.5 0x12 to 0x1f 0110 0xx6 8/16 12 0x12 to 0x1f see table 12. 0111 0xx7 9/16 13.5 0x12 to 0x1f 1000 0xx8 10/16 15 0x12 to 0x1f 1001 0xx9 11/16 16.5 0x12 to 0x1f 1010 0xxa 12/16 18 0x12 to 0x1f 1011 0xxb 13/16 19.5 0x12 to 0x1f 1100 0xxc 14/16 21 0x12 to 0x1f 1101 0xxd 15/16 22.5 0x12 to 0x1f 1110 0xxe 16/16 24 0x12 to 0x1f 1111 0xxf
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ______________________________________________________________________________________ 19 register data function register address (hex) read/ write d7 d6 d5 d4 d3 d2 d1 d0 read irq status* read mask register 0x06 write unchanged port 30 mask port 29 mask port 28 mask port 27 mask port 26 mask port 25 mask port 24 mask * irq is automatically cleared after it is read. register data mode address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 normal operation 0x07 xxxxxxx0 display test mode 0x07 xxxxxxx1 table 14. display test register x = don? care bit. x = don? care bit. table 12. odd individual segment current format led drive fraction segment constant current with r iset = 39k ? (ma) address code (hex) d7 d6 d5 d4 d3 d2 d1 d0 hex code 1/16 1.5 0x12 to 0x1f 0000 0x0x 2/16 3 0x12 to 0x1f 0001 0x1x 3/16 4.5 0x12 to 0x1f 0010 0x2x 4/16 6 0x12 to 0x1f 0011 0x3x 5/16 7.5 0x12 to 0x1f 0100 0x4x 6/16 9 0x12 to 0x1f 0101 0x5x 7/16 10.5 0x12 to 0x1f 0110 0x6x 8/16 12 0x12 to 0x1f 0111 see table 11. 0x7x 9/16 13.5 0x12 to 0x1f 1000 0x8x 10/16 15 0x12 to 0x1f 1001 0x9x 11/16 16.5 0x12 to 0x1f 1010 0xax 12/16 18 0x12 to 0x1f 1011 0xbx 13/16 19.5 0x12 to 0x1f 1100 0xcx 14/16 21 0x12 to 0x1f 1101 0xdx 15/16 22.5 0x12 to 0x1f 1110 0xex 16/16 24 0x12 to 0x1f 1111 0xfx table 13. transition detection mask register
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 20 ______________________________________________________________________________________ chip information transistor count: 30,316 process: cmos 36 35 34 33 32 31 30 29 28 27 26 25 24 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 v+ cs din sclk p4 p31 p26 p5 p30 p6 p29 p7 p28 p27 p17 p16 p15 p11 p14 p10 p13 p9 p12 p8 dout gnd gnd iset ssop top view max6957 22 21 20 19 15 16 17 18 p22 p25 p24 p23 p21 p20 p19 p18 pin configurations (continued)
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander ______________________________________________________________________________________ 21 p5 p4 p7 p8 p6 p10 p9 p12 p13 p11 p15 p14 p17 p18 p16 p20 p19 a2 a1 c d1 b e d2 g1 g2 f i h k l j dp m ca p22 p23 p21 36 2 1 3 33 35 34 4 29 27 31 24 25 22 21 23 v+ gnd iset gnd sclk din dout p30 p29 p31 p27 p28 p25 p24 p26 32 30 26 5 7 9 28 6 8 11 10 12 14 15 13 17 16 19 20 18 cs max6957aax 39k ? 3v 3v 4-wire data in 4-wire clock in chip select led1 p5 p4 p7 p8 p6 p10 p9 p12 p13 p11 p15 p14 p17 p18 p16 p20 p19 a2 a1 c d1 b e d2 g1 g2 f i h k l j dp m ca p22 p23 p21 36 2 1 3 33 35 34 4 29 27 31 24 25 22 21 23 v+ gnd iset gnd sclk din dout p30 p29 p31 p27 p28 p25 p24 p26 32 30 26 5 7 9 28 6 8 11 10 12 14 15 13 17 16 19 20 18 cs max6957aax 39k ? 3v 4-wire data out irq out led3 a2 a1 c d1 b e d2 g1 g2 f i h k l j dp m ca led2 u1 u2 2 12 sw3 sw2 sw1 47nf 47nf typical operating circuit
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander 22 ______________________________________________________________________________________ ssop.eps package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)
max6957 4-wire-interfaced, 2.5v to 5.5v, 20-port and 28-port led display driver and i/o expander maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it 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 ? 2002 maxim integrated products printed usa is a registered trademark of maxim integrated products. ssop.eps package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .)

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