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general description the max13362 is a 24-channel automotive contact mon- itor designed as an interface between mechanical switches and low-voltage processors or other logic cir- cuits. the ic operates over a voltage range of 5.5v to 28v, and withstands voltages up to 40v. it protects low- voltage circuitry from high voltages and reverse battery conditions. the max13362? low-current operation under all operating conditions makes it suitable for use in elec- tronic control units (ecus) that are connected directly to the automotive battery. it has an adjustable scan mode that significantly reduces the current drawn in key-off. the max13362 features an spi interface to monitor the switch status and set the device configuration. multiple max13362s can be cascaded to support any multiple of 24 switches. the max13362 is available in a 6mm x 6mm, 40-pin thin qfn package and operates over the -40? to +125? temperature range. applications automotive body controllers automotive door modules automotive smart junction boxes features ? 9v to 18v operating voltage range with full performance ? fully functional range of 5.5v to 28v ? switch inputs withstand 27v ? switch inputs withstand reverse battery ? ultra-low operating current 100? (typ) in scan mode ? built-in switching hysteresis ? built-in switch deglitching ? cmos-compatible logic outputs down to 3.0v ? interrupt output to processor ? configurable wetting current (0ma, 5ma, 10ma, or 15ma) for each switch input ? aec-q100 qualified max13362 24-channel automotive switch monitor ________________________________________________________________ maxim integrated products 1 19-4464; rev 0; 2/09 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available ordering information part temp range pin-package m ax 13362atl/v + -40? to +125? 40 thin qfn-ep* (6mm x 6mm) * ep = exposed pad. + denotes a lead(pb)-free/rohs-compliant package. /v denotes an automotive qualified part. typical application circuit microcontroller /logic circuit sdo cs v dd vs in23 in6 in0 in7 int ecu connector 24 switches, 1 battery-connected sdi in21 in20 in18 in10 in9 in8 in5 in4 in3 in2 in1 gnd sd 0.047 f 0.047 f clk regulator in out battery 9v to 18v in11 in12 in13 in14 in15 in16 in17 in19 in22 100 max13362 pin configuration max13362 thin qfn (6mm x 6mm) + 31 in7 32 in8 33 in9 34 in10 35 in11 36 in12 37 in13 38 in14 39 in15 40 top view in16 20 vs 19 vs 18 gnd 17 v dd 16 gnd 15 sdi 14 cs 13 sdo 12 clk 11 n.c. 1 n.c. 2 n.c. 3 in17 4 in18 5 in19 6 in20 7 in21 8 in22 9 in23 10 int 30 n.c. 29 n.c. 28 in6 27 in5 26 in4 25 in3 24 in2 23 in1 22 in0 21 sd spi is a trademark of motorola, inc.
max13362 24-channel automotive switch monitor 2 _______________________________________________________________________________________ absolute maximum rating electrical characteristics (v dd = 5v, v vs = 14v, t a = -40? to +125?, unless otherwise noted. typical values are at t a =+25?.) 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. v dd , clk, sdi, cs to gnd ......................................-0.3v to +6v vs, sd , int to gnd................................................-0.3v to +40v in0?n23 to gnd.....................................................-15v to +27v sdo to gnd ...............................................-0.3v to (v dd + 0.3v) esd protection, all pins (hbm)............................................?kv esd protection on pins in0?n23 to iec 61000-4-2 specification (with added 0.047? capacitor, and/or 100 resistor)....?kv current into any pin..........................................................?0ma continuous power dissipation (t a = +70?) (derate 37mw/? above +70?)(multilayer board)....2963mw operating temperature range .........................-40? to +125? junction temperature........................................-40? to +150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units power supply v dd operating supply range v dd 3 5.5 v v dd supply current i dd 0.1 10 ? vs supply range v vs (note 1) 5.5 28 v vs undervoltage lockout v uvlo 3 5.5 v t poll = 64ms, t poll_act = 1ms; lp bit in internal register = 0, 24 channels active, all switches open, t a = +25? 100 170 t poll = 64ms, t poll_act = 1ms; lp bit in internal register = 0, 24 channels active, all switches open 100 200 total supply current (flowing into vs and v dd ) i sup continuous polling mode, wetting current set to 5ma 1000 ? vs supply current in shutdown mode i sdvs v sd = 0, v vs = 14v, all switches open, t a = +25? 610a v dd supply current in shutdown mode i sdvdd v sd = 0, v vs = 14v, t a = +25? 0.1 5 a switch inputs input voltage threshold v th v vs = 5.5v to 28v, measured with 100 series resistor for high-side switches 2.5 3.7 v input hysteresis v h v vs = 5.5v to 28v, measured with 100 series resistor for high-side switches 0.2 v wetting current rise/fall time t iwett 5s wetting current set to 15ma, 9v < v vs < 18v 12.7 15 17.25 wetting current i wett wetting current set to 15ma, (5.5v < v vs < 9v) or (18v < v vs < 28v) 10.5 15 19.5 ma v in_ = 0, t a = +25? 2 in0?n23 input current i in_ v in_ = 14v, t a = +25? (note 2) 16 30 ? in0?n23 input leakage current in shutdown i leaksd v vs = 0 or 14v, v sd = 0, t a = +25? ? ? in4?n23 dropout voltage v do15 i wett = 15ma (note 3) 2.8 4.0 v
max13362 24-channel automotive switch monitor _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units logic levels int output-voltage low v olint sinking 1ma 0.4 v sdo output-voltage low v olsdo sinking 1ma 0.2 x v dd v sdo output-voltage high v ohsdo sourcing 1ma 0.8 x v dd v sdo leakage current in high- impedance mode i lsdo v cs = 5v -1 +1 ? sdi, clk, cs input-voltage low v il 0.33 x v d d v sdi, clk, cs input-voltage high v ih 0.66 x v d d v sd input low voltage v ilsd 0.8 v sd input high voltage v ihsd 2.4 v sdi internal pulldown resistor r pd 30 50 120 k clk pin leakage i leakclk v clk = 5v, t a = +25? 1 a cs pin leakage i leakcs v cs = 5v, t a = +25? 1 a sd pin leakage i leaksd v sd = 5v, t a = +25? 1 a int pin leakage i leakint v int = high impedance, t a = +25? 1 a thermal shutdown thermal shutdown threshold t shdn temperature rising (note 4) +150 +165 ? thermal shutdown hysteresis t hyst 15 ? timing switch inputs deglitching time t gt 37 50 63 ? clk frequency range f clk (note 4) 0.01 4 mhz falling edge of cs to rising edge of clk setup time t lead polling mode, input rise/fall time < 10ns (note 4) 100 ns falling edge of clk to rising edge of cs setup time t lag input rise/fall time < 10ns (note 4) 100 ns sdi-to-clk falling edge setup time t si(su) (note 4) 30 ns sdi hold time after falling edge of clk t si ( hold ) (note 4) 20 ns time from rising edge of clk to sdo data valid t valid c sdo = 50pf (note 3) 70 ns time from falling edge of cs to sdo low impedance t so(en) (note 4) 55 ns time from rising edge of cs to sdo high impedance t sdo ( dis ) (note 4) 55 ns electrical characteristics (continued) (v dd = 5v, v vs = 14v, t a = -40? to +125?, unless otherwise noted. typical values are at t a =+25?.)
max13362 24-channel automotive switch monitor 4 _______________________________________________________________________________________ cs clk sdi msb in msb out lsb out t sdo(dis) t valid t so(en) t lead sdo t lag t si(su) t si(hold) figure 1. spi timing characteristics parameter symbol conditions min typ max units polling active time accuracy t poll_act -20 +20 % polling time accuracy t poll -20 +20 % time from shutdown to normal operation t start 0.1 1 ms electrical characteristics (continued) (v dd = 5v, v vs = 14v, t a = -40? to +125?, unless otherwise noted. typical values are at t a =+25?.) note 1: when v vs is above 28v, the wetting current is disabled to limit power dissipation, and the switch inputs are not monitored. when v vs returns, there is a 1ms blanking time before the external switches are polled. note 2: this current only flows during the polling active time thus the average value is much lower. for example with a polling time of 64ms and a polling active time of 1ms the average current on an input when connected to 14v is typically 16? x 1/64 = 0.25?. note 3: difference between vs and in_ voltage when wetting current has dropped to 90% of its nominal value. note 4: guaranteed by design.
max13362 24-channel automotive switch monitor _______________________________________________________________________________________ 5 wetting current vs. vs voltage max13362 toc01 vs voltage (v) wetting current (ma) 13 16 15 14 17 5 10 15 20 0 518 710 9 811 612 i wett = 15ma i wett = 10ma i wett = 5ma wetting current vs. temperature max13362 toc02 temperature ( c) wetting current (ma) 40 0 5 10 15 20 0 -40 80 20 -20 120 140 100 60 i wett = 15ma i wett = 10ma i wett = 5ma switch status change (continuous mode) max13362 toc03 10ms/div 10v/div 5ma/div v in0 i wett v int 2v/div 2v/div v cs 0v 5ma 10v 0ma wetting current (polling mode) max13362 toc04 5ma 4.096ms polling time 512 s polling active time 1ms/div wetting current (5ma/div) vs supply current vs. temperature (continuous mode) max13362 toc05 temperature ( c) supply current ( a) 1000 1400 2200 600 1800 2600 200 i wett = 15ma for all channels i wett = 10ma for all channels i wett = 5ma for all channels all channels open i wett = 0ma for all channels 40 0 -40 80 20 -20 120 140 100 60 vs supply current vs. temperature (polling mode) max13362 toc06 temperature ( c) supply current ( a) 20 120 40 100 60 -20 100 110 120 130 90 -40 140 080 polling time = 65.536ms polling active time = 1.024ms all channels open i wett = 5ma vs supply current vs. temperature (shutdown mode) max13362 toc07 temperature ( c) supply current ( a) 60 0 5.6 5.3 5.9 6.2 6.5 5.0 -40 -20 20 80 40 140 100 120 switch threshold vs. temperature (high side switch) max13362 toc08 temperature ( c) switch threshold (v) 20 120 40 100 60 -20 3.1 3.2 3.3 3.4 3.0 -40 140 080 high side switch 15ma wetting current 100 included switch open to close switch close to open switch threshold vs. temperature (low-side switch) max13362 toc09 temperature ( c) switch threshold (v) 20 120 40 100 60 -20 3.1 3.2 3.3 3.4 3.0 -40 140 080 low-side switch 15ma wetting current switch open to close switch close to open typical operating characteristics (v dd = v sd = 5v, v vs = 14v, t a = +25?, unless otherwise noted.)
max13362 24-channel automotive switch monitor 6 _______________________________________________________________________________________ switch threshold vs. vs voltage (low-side switch) max13362 toc10 vs voltage (v) switch threshold (v) 12 17 13 16 14 10 3.1 3.2 3.3 3.4 3.5 3.0 918 11 15 switch open to close switch close to open switch status change (polling mode) max13362 toc11 2ms/div v in v int 5v/div 2v/div 0v 0v 10v pin description typical operating characteristics (continued) (v dd = v sd = 5v, v vs = 14v, t a = +25?, unless otherwise noted.) pin name function 1, 2, 11, 29, 30 n.c. no connection. not internally connected. 3 in17 switch monitor input channel 17. connect in17 to a ground-connected switch. 4 in18 switch monitor input channel 18. connect in18 to a ground-connected switch. 5 in19 switch monitor input channel 19. connect in19 to a ground-connected switch. 6 in20 switch monitor input channel 20. connect in20 to a ground-connected switch. 7 in21 switch monitor input channel 21. connect in21 to a ground-connected switch. 8 in22 switch monitor input channel 22. connect in22 to a ground-connected switch. 9 in23 switch monitor input channel 23. connect in23 to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. 10 int inter r up t outp ut. int i s an op en- d r ai n outp ut that asser ts l ow w hen one or m or e of the i np uts ( in 0in 23) chang e state and ar e enab l ed for i nter r up ts, or w hen the over tem p er atur e thr eshol d i s exceed ed . 12 clk spi serial clock input 13 sdo spi serial data output. spi data is output on sdo on the rising edges of clk while cs is held low. sdo is high impedance when cs is high. connect sdo to a microcontroller data input or to a succeeding device in a daisy chain. 14 cs spi chip-select input. drive cs low to enable clocking of data into and out of the ic. spi data is latched into the device on the rising edge of cs . 15 sdi spi serial data input. spi data is latched into the internal shift register on the falling edges of clk while cs is held low. sdi has an internal 50k pulldown resistor. connect sdi to the sdo of a preceding device in a daisy chain or to the microcontroller data output. 16, 18 gnd ground. pins 16 and 18 must be connected to ground. 17 v dd logic supply voltage. connect v dd to a 3.3v or 5v logic supply. bypass v dd to gnd with at least a 0.1? capacitor placed as close as possible to v dd .
max13362 24-channel automotive switch monitor _______________________________________________________________________________________ 7 pin description (continued) pin name function 19, 20 vs supply voltage input. vs should be protected from reverse battery using a series diode. bypass vs to gnd with a 0.1? ceramic capacitor placed as close as possible to vs. in addition, bypass vs with a 47? or greater capacitor. 21 sd shutdown input. drive sd low to place the ic into shutdown mode. drive sd high for normal operation. sd is battery-voltage compatible. 22 in0 switch monitor input channel 0. connect in0 to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. 23 in1 switch monitor input channel 1. connect in1 to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. 24 in2 switch monitor input channel 2. connect in2 to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. 25 in3 switch monitor input channel 3. connect in3 to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. 26 in4 switch monitor input channel 4. connect in4 to a ground-connected switch. 27 in5 switch monitor input channel 5. connect in5 to a ground-connected switch. 28 in6 switch monitor input channel 6. connect in6 to a ground-connected switch. 31 in7 switch monitor input channel 7. connect in7 to a ground-connected switch. 32 in8 switch monitor input channel 8. connect in8 to a ground-connected switch. 33 in9 switch monitor input channel 9. connect in9 to a ground-connected switch. 34 in10 switch monitor input channel 10. connect in10 to a ground-connected switch. 35 in11 switch monitor input channel 11. connect in11 to a ground-connected switch. 36 in12 switch monitor input channel 12. connect in12 to a ground-connected switch. 37 in13 switch monitor input channel 13. connect in13 to a ground-connected switch. 38 in14 switch monitor input channel 14. connect in14 to a ground-connected switch. 39 in15 switch monitor input channel 15. connect in15 to a ground-connected switch. 40 in16 switch monitor input channel 16. connect in16 to a ground-connected switch. ep exposed pad. connect ep to gnd for enhanced thermal performance.
max13362 24-channel automotive switch monitor 8 _______________________________________________________________________________________ functional diagram in4 in5 in6 in7 in0 in3 in2 in1 shift register + control cs clk sdi sdo vs v dd int gnd sd in8 in9 in10 in11 in12 in13 in14 in15 1 of 24 wetting current control ref generator 24 of 24 in16 in17 in18 in19 in20 in21 in22 in23 max13362
detailed description the max13362 is a 24-channel automotive contact monitor designed as an interface between mechanical switches and low-voltage microcontrollers or other logic circuits. it features an spi interface to monitor individual switch inputs and to configure interrupt capability, wet- ting current, switch configuration (battery-connected or ground-connected), polling time and polling active time. any switch status change will cause an interrupt signal if the switch is interrupt enabled. the max13362 has three modes of operation: continuous mode, polling mode, and shutdown mode. v dd and vs v dd is the power-supply input for the logic input/ output circuitry. connect v dd to a 3v to 5.5v logic-level supply. bypass v dd to gnd with at least a 0.1? capacitor placed as close as possible to v dd . vs is the main power-supply input. bypass vs to gnd with a 0.1? ceramic capacitor placed as close as pos- sible to vs. in addition, bypass vs with a 47? or greater capacitor. mechanical switch inputs (in0?n23) in0?n23 are the inputs for remote mechanical switch- es. the switch status is indicated by the s0?23 bits in the status register, and each switch input can be pro- grammed to assert an interrupt ( int ) by writing to the ie0?e23 bits in the command register. all switch inputs are interrupt disabled upon power-up. the in4?n22 inputs are intended for ground-connect- ed switches. the in0?n3 and in23 inputs can be pro- grammed for either ground-connected switches or battery-connected switches by writing to the lh0?h3 and lh23 bits (see table 2). the default configuration of the in0?n3 and in23 inputs after power-up is for ground-connected switches. wetting current the max13362 applies a programmable wetting current to any closed switch to clean switch contacts that are exposed to adverse conditions. the wetting current for each switch can be set to 0ma, 5ma, 10ma, or 15ma by the w_.0 and w_.1 data bits in the command regis- ters (see table 5) by means of an spi data transaction. when using wetting current, special care must be taken to avoid exceeding the maximum power dissipa- tion of the max13362 (see the applications information section). disabling the wetting current or limiting the active-wetting current time reduces power consump- tion. the default state upon power-up is with wetting current disabled. interrupt output ( int ) int is an active-low, open-drain output that asserts low when any of the switch inputs change state and is enabled for interrupts, or when the overtemperature threshold is exceeded. an external pullup resistor to v dd is needed on int . int is cleared when cs is driven low for a read/write operation. however, in polling mode, any switch state change or overtemperature change which occurs during an spi transaction is stored and causes an additional interrupt after the spi transaction is over and cs goes high (shown in figure 2). if v dd is absent, the int output is functional provided that it is pulled up to a different supply voltage. max13362 24-channel automotive switch monitor _______________________________________________________________________________________ 9 cs clk int switch status change new interrupt figure 2. switch state change during the spi transaction
max13362 serial peripheral interface ( cs , sdo, sdi, clk) the max13362 operates as a serial peripheral interface (spi) slave device. an spi master accesses and pro- grams the max13362 by reading/writing the control registers. the control registers are 32 bits wide, have 2 command bits (or register addresses) and 30 data bits (see table 1). figure 3 shows the read/write sequence through spi. the spi logic counts the number of bits clocked into the ic (using a modulo-32 counter so that daisy chaining is possible) and enables data latching only if exactly 32 bits (or an integer multiple thereof) have been clocked in. status register the status register contains the status of the switches connected to in0?n23. the status register also con- tains an overtemperature warning bit, a power-on-reset bit and a device type bit (see table 1). the status reg- ister is accessed by the spi-compatible interface. 24-channel automotive switch monitor 10 ______________________________________________________________________________________ figure 3. spi read/write sequence cs clk sdi sdo d12 cb0 cb1 d0 rst dt z d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d11 t s0 s8 s7 s6 s5 s4 s3 s2 s1 s9 s10 d24 d13 d14 d15 d16 d17 d18 d19 d20 d21 d22 d23 d29 d25 d26 d27 d28 z s11 s12 s13 s14 s15 s16 s17 s18 s19 s20 s21 s22 s23 x x x x x note: x = unused, z = high impedance. bit name bit description cb0, cb1 command bits. select the internal register to which data bits d0?29 are to be written. d0?29 data bits. s0?23 switch state bit. 0 = switch open, 1 = switch closed. t overtemperature bit. when overtemperature occurs, this bit is set to 1. it is reset on the rising edge of cs . rst power-on-reset bit. it indicates whether the ic has had a power-on-reset since the last spi read. 0 = device has been reset. rst is set to 1 on the rising edge of cs . dt device type. 0 = reserved for future use, 1 = max13362. table 1. bit description
command register three 32-bit command registers are used to configure the max13362 for various modes of operation and are accessed by the spi-compatible interface (see table 2). lh_: switch configuration for in0?n3 and in23 the lh0?h3 and lh23 bits set the switch configuration for in0?n3 and in23, respectively. set lh_ to 0 to con- figure the input channel to ground connected. set lh_ to1 to configure the input channel to battery connected. the default configuration after power-on is lh_ = 0, ground connected. p0?3: polling time p0?3 are used to set the polling time as shown in table 3. pa0?a2: polling active time pa0?a2 are used to set the polling active time as shown in table 4. max13362 24-channel automotive switch monitor ______________________________________________________________________________________ 11 p3 p2 p1 p0 polling time (ms) 0 0 0 0 continuous* 0 0 0 1 4.096 0 0 1 0 4.096 0 0 1 1 4.096 0 1 0 0 4.096 0 1 0 1 4.096 0 1 1 0 8.192 0 1 1 1 16.384 1 0 0 0 32.768 1 0 0 1 65.536 1010 131 1 0 1 1 262.1 1 1 0 0 524.3 1 1 0 1 1049 1 1 1 0 2097 1 1 1 1 4194 table 3. polling time setting d29 d28 d27 d26 d25 d24 d23 d22 d21 d20 d19 d18 d17 d16 d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 cb1 cb0 x lp pa2 pa1 pa0 w23. 0 w22. 0 w21 .0 w20 .0 w19 .0 w18 .0 w17 .0 w16. 0 w15 .0 w14 .0 w13 .0 w12 .0 w11 .0 w10 .0 w9. 0 w8. 0 w7. 0 w6. 0 w5. 0 w4. 0 w3. 0 w2. 0 w1. 0 w0. 0 x00 xp3p2p1p0 w23. 1 w22. 1 w21 .1 w20 .1 w19 .1 w18 .1 w17 .1 w16. 1 w15 .1 w14 .1 w13 .1 w12 .1 w11 .1 w10 .1 w9. 1 w8. 1 w7. 1 w6. 1 w5. 1 w4. 1 w3. 1 w2. 1 w1. 1 w0. 1 x01 lh2 3 lh3 lh2 lh1 lh0 ie23 ie22 ie21 ie20 ie19 ie18 ie17 ie16 ie15 ie14 ie13 ie12 ie11 ie10 ie9 ie8 ie7 ie6 ie5 ie4 ie3 ie2 ie1 ie0 x 1 0 no operation (no data written) 11 table 2. command register map * default por value. * default por value. table 4. polling-active time setting pa2 pa1 pa0 polling active time (?) 000 64 001 128 010 256 0 1 1 512* 1 0 0 1024 1 0 1 2048 1 1 0 4096 1 1 1 4096
max13362 ie_: interrupt enable the ie_ bit programs the switch input channel, in_, to be interrupt-enabled or interrupt-disabled (0 = interrupt disabled, 1 = interrupt enabled). the default value after power-on is 0. w_.0 and w_.1: wetting current w_.0 and w_.1 bits set the corresponding switch channel-wetting current as shown in table 5. lp : low quiescent current bit in polling mode, when lp is set to 0, the ic is operating with the lowest quiescent current. the channels that are not enabled to interrupt have their wetting current dis- abled and are not monitored. the first pulse of wetting current after the switch is closed and sampled is 5ma unless the wetting current for that channel is set to 0ma. the default value of lp after power-on is 0. when lp is 1, all channels are monitored and the wetting cur- rent for each channel is set to the value determined by w_.0 and w_.1. if the max13362 is in continuous mode, lp is ignored. operating modes the max13362 features three modes of operation: con- tinuous mode, polling mode, and shutdown mode. in continuous mode, the wetting currents (if enabled) are continuously applied to the closed switches. in polling mode, the wetting currents are applied to the closed switches for a preset duration to reduce the power con- sumption. in shutdown mode, all switch inputs are high impedance and all circuitry is shutdown. continuous mode operation (p0?3 = 0) in continuous mode, reading of the switch status is initi- ated by a falling edge on cs . the microcontroller initi- ates a low pulse on cs to update the max13362 switch status register. if int remains high, no action needs be taken by the microcontroller. if int goes low, the micro- controller may perform a read operation to read the updated switch status. on the rising edge of cs , int is updated. to get correct data, the microcontroller must wait 10? before initiating a switch status read opera- tion. (see figure 4.) polling-mode operation in polling mode (see figure 5), each switch input is sampled for a programmable polling active time set by the pa0?a2 bits between 64? and 4ms (see table 4). sampling is repeated at a period set by the p0?3 bits (from 4ms to continuous, see table 3). all switch inputs are sampled simultaneously at the end of the polling active time. wetting currents (if enabled) are applied to closed switches during the polling active time. therefore, the polling mode reduces the current con- sumption from the vs power supply to some value dependent on the polling time chosen. 24-channel automotive switch monitor 12 ______________________________________________________________________________________ * default por value. table 5. wetting current setting w_.1 w_.0 wetting current (ma) 00 0* 01 5 10 10 11 15 cs int switch status change int updated, perform read operation figure 4. continuous mode operation ground-connected switch-input int switch open polling time switch position sampled switch position sampled polling active time polling active time figure 5. switch sampling in polling mode
any switch position change (if the switch is interrupt- enabled) is signaled through the active-low open-drain int output. the int output is cleared when cs goes low. shutdown mode in shutdown mode, all switch inputs are high imped- ance and the external switches are no longer moni- tored, reducing current consumption on vs to 6? (typ). the ic resets upon entering shutdown mode and the contents of the command registers are lost. therefore, any setting other than power-on-reset defaults needs to be reprogrammed after exiting from the shutdown mode. applications information overtemperature protection if the ic junction temperature exceeds +165?, an interrupt signal is generated and the wetting currents are disabled to reduce the on-chip power dissipation. during an overtemperature event, the last switch status is retained in internal memory and the switch status is not updated. the interrupt output is cleared when cs goes high, but the overtemperature bit t in the output word remains for as long as the overtemperature condi- tion persists. when the junction temperature drops by 15?, the wetting currents are re-enabled and there is a 1ms blanking time before the switches can be polled. reverse-battery tolerance the in0?n23 switch inputs withstand up to -15v dc voltage without damage. a reverse-battery diode is needed to protect vs as shown in the typical application circuit . sd can be controlled from a bat- tery-level source but should be protected against reverse battery in the application. wetting current and power dissipation the maximum power dissipation happens when all switch inputs configured with 15ma continuous wetting current are all closed. assuming the battery voltage is 14v, the corresponding power dissipated by the ic is 24 x 14v x 15ma = 5040mw. this exceeds the absolute maximum power dissipation of 2963mw. in polling mode, the wetting currents are pulsed at the programmed polling time to reduce the total power dis- sipated in the ic. iso 7637 pulse immunity vs, sd, and in0?n23 are potentially exposed to iso 7637 pulses. bypass vs with a 0.1? and a 47? capacitor. the vs and sd voltage must be limited below 40v during load dump. bypass in0?n23 with at least 0.047? capacitors at the ecu connector. when in0?n3 or in23 inputs are used with battery-connected switches, a 100 series resistor is needed. these external components allow vs, sd, and in0?n23 to withstand iso 7637 pulses in the application circuit. mechanical switch characteristics the max13362 is designed to operate with switches that have the following characteristics: 1) minimum resistance value with switch open (due to leakage): 10k . 2) maximum resistance value with switch closed: 100 . chip information process: bicmos max13362 24-channel automotive switch monitor ______________________________________________________________________________________ 13
max13362 24-channel automotive switch monitor 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. 14 ____________________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. package type package code document no. 40 tqfn-ep t4066+5 21-0141 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages .

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