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general description the MAX20091 is a 35-channel automotive contact moni - tor for automotive applications. ten contact monitor inputs can be used with either ground- or battery-connected switches; the other 25 inputs are for use with ground- connected switches. the ic operates over a 5.5v to 28v voltage range and withstands voltages up to 42v. it protects low- voltage circuitry from high voltages and reverse-battery conditions. the ics low-current operation under all oper - ating conditions makes it suitable for use in electronic control units (ecus) that are connected directly to the automotive battery. the ic has an adjustable scan mode that reduces the current drawn in key-off while maintain - ing polling capability. the ic features an spi interface to monitor the switch status and set the device configuration. an interrupt out - put allows the device to wake a local microcontroller when a switch status change is detected. in addition, a switch status change turns on the internal regulator. the MAX20091 is available in a compact 48-pin tqfn package and operates over the -40c to +125c temperature range. benefts and features 5.5v to 28v operating voltage range switch inputs withstand 42v and reverse battery ultra-low 88a (typ) operating current in polling mode in0-34 esd performance to iso10605 (in-circuit): 10kv contact configurable wetting current spi interface for control/readback built-in hysteresis and deglitching interrupt output to processor compact 48-pin tqfn package applications automotive body computers smart junction boxes door modules ordering information and typical operating circuit appears at end of data sheet. for related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX20091.related . 19-6935; rev 0; 6/14 evaluation kit available MAX20091 35-channel contact monitor
batt to gnd ........................................................ -0.3v to +42v in0Cin34 to gnd ................................................... -18v to +42v current into any pin ......................................................... +20ma v io , pvl, sck, sdi, int to gnd ........................ -0.3v to +6.0v cs to gnd ........................................................... -0.3v to +6.0v sdo to gnd ................................................. -0.3v to v io + 0.3v esd protection, all pins (hbm) .......................................... 2kv esd protection on pins in0Cin35 to iso 10605 specification (with added 0.047f capacitor and/or 100 resistor) ..... 10kv continuous power dissipation (t a = +70c) 4877+6c on slb (derate 27.8mw/c above +70 c) ...... 2222mw 4877+6c on mlb (derate 40mw/c above +70 c) ......... 3200mw operating temperature range ......................... -40c to +125 c maximum junction temperature ..................................... +150 c storage temperature range ............................ -65 c to +150 c lead temperature (soldering, 10s) ................................. +300 c soldering temperature (reflow) ....................................... +260 c tqfn (four-layer board) junction-to-ambient thermal resistance ( ja ) ........... 25 c/w junction-to-case thermal resistance ( jc ) .................. 1 c/w tqfn (single-layer board) junction-to-ambient thermal resistance ( ja ) ........... 36 c/w junction-to-case thermal resistance ( jc ) .................. 1 c/w (note 1) (v batt = 14v, v io = 5v, t a = t j = t min to t max , unless otherwise noted. typical values are at t a = +25c.) (note 2) parameter symbol conditions min typ max units supply voltage range v batt (note 3) 7.5 28 v battery ovp threshold v battov polling disabled above v batt rising v batt rising 28.4 29.5 30.9 v v batt falling 28.1 29 30.4 v io voltage range v vio 3 5.5 v batt undervoltage lockout v uvlo rising 4 4.5 4.8 v falling 3.5 4 4.5 supply current i batt t poll = 64ms, t poll_act = 128s, 35 channels active, all switches open, i wett set to 2ma, v batt = 7.5v to 28v 88 130 a t poll = 64ms, t poll_act = 128s, 35 channels active, all switches open, i wett set to 2ma, v batt = 7.5v to 28v 88 110 continuous mode, i wett set to 10ma, all switches open, v batt = 7.5v to 28v 3.3 5.5 ma v io supply current i vio continuous mode, i wett set to 10ma, all switches open, v batt = 7.5v to 28v 10 55 200 na pvl voltage v pvl +7.5v v batt +28v 4.75 5 5.25 v maxim integrated 2 note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-layer board. for detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial . absolute maximum ratings 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 ab solute maximum rating conditions for extended periods may affect device reliability. package thermal characteristics electrical characteristics MAX20091 35-channel contact monitor www.maximintegrated.com
(v batt = 14v, v io = 5v, t a = t j = t min to t max , unless otherwise noted. typical values are at t a = +25c.) (note 2) parameter symbol conditions min typ max units switch inputs input voltage threshold (open to closed) v thr v batt = 7.5v to 28v, spi setting 00 3.7 4.3 v v batt = 7.5v to 28v, spi setting 01 3.5 3.8 4.1 v batt = 7.5v to 28v, spi setting 10 2.75 3 3.25 v batt = 7.5v to 28v, spi setting 11 1.8 2 2.2 input hysteresis v hyst v batt = 7.5v to 28v 0.2 v wetting current accuracy i wett 2ma setting, 5.5v < v batt < 28v 1.7 2 2.3 ma in0Cin34 input current i in_ v batt = 14v, wetting current set to zero, t a = +25c -2 1 +2 a dropout voltage with gnd-connected switch v dropout v batt - v in_ , w etting c urrent at 90% of set value (90% of actual value when set to 10ma) 2.9 v v batt - v in_ , w etting c urrent at 90% of set value (90% of actual value when set to of 2ma) 1.5 polling active time accuracy t pollact -10 +10 % polling time accuracy t poll -10 +10 % logic levels int output voltage low v outl sinking 2ma 0.4 v sdo output voltage low v sdol sinking 2ma 0.2 x v io v sdo output voltage high v sdoh sourcing 1ma 0.8 x v io v sdo leakage current in high-impedance mode i lksdo cs = v io -1 +1 a sdi, clk, cs input voltage low v inl 0.8 v sdi, clk, cs input voltage high v inh 2.2 v int output leakage current -5 +5 a sdi internal pulldown resistor r sdi 50 k thermal protection thermal warning t warn int asserted low and t bit set in spi word 145 oc thermal shutdown t shdn 165 oc thermal-shutdown hysteresis t shdn.hys 15 oc maxim integrated 3 electrical characteristics (continued) MAX20091 35-channel contact monitor www.maximintegrated.com
(v batt = 14v, v io = 5v, t a = t j = t min to t max , unless otherwise noted. typical values are at t a = +25c.) (note 2) note 2: all devices 100% production tested at t a = +25c. limits over temperature are guaranteed by design. note 3: when batt is above 28v, the wetting current is disabled to limit power dissipation, and the switch inputs are not monitored. when batt returns below 28v, there is a 1ms blanking time before the external switches are polled. parameter symbol conditions min typ max units timing sck frequency range 0.1 4 mhz falling edge of cs to rising edge of sck setup time 15 ns falling edge of sck to rising edge of cs setup time 60 ns minimum sck low after rising edge of cs hold time t hs 15 ns minimum data valid to sck rising-edge setup time t ds 30 ns minimum data valid to sck rising-edge hold time t dh 15 ns minimum sck high pulse width t ch 120 ns minimum sck low pulse width t cl 120 ns minimum cs high pulse width t csh 120 ns maximum transition time from falling edge of cs to valid sdo t csg c l = 10pf load capacitance from sdo to ground 40 ns maximum transition time from falling edge of sck to valid sdo t cg c l = 10pf load capacitance from sdo to ground 40 ns maxim integrated 4 electrical characteristics (continued) MAX20091 35-channel contact monitor www.maximintegrated.com
(v batt = 14v, t a = +25c, unless otherwise noted.) t csh t sc cs sck sdi sdo t csg t cg t hs t hcs t css t ds t dh t cl t ch 0 2 4 6 8 10 4 12 20 28 wetting current (ma) supply voltage (v) wetting current vs. supply voltage MAX20091 toc01 2ma 10ma 5ma 0 1 2 3 4 5 6 7 8 9 10 -40 -20 0 20 40 60 80 100 120 wetting current (ma) temperature ( c) wetting current vs. temperature MAX20091 toc02 maxim integrated 5 spi timing diagram typical operating characteristics MAX20091 35-channel contact monitor www.maximintegrated.com
(v batt = 14v, t a = +25c, unless otherwise noted.) wetting current rise/fall time 10ma MAX20091 toc03 20 s/div 0 10ma switch status change (continuous mode) 10v/div 5v/div MAX20091 toc04 500 s/div v in_ int 5v/div cs 0v switch status change (polling mode) 10v/div 5v/div MAX20091 toc05 1ms/div v in_ int 0v 0v wetting current (polling mode) MAX20091 toc06 2ms/div 512 s polling active time 8ms polling time 10ma 0.0 1.0 2.0 3.0 4.0 -40 10 60 110 current (ua) temperature ( c) quiescent current in continuous mode MAX20091 toc07 maxim integrated 6 7slfdo2shudwlqjkdudfwhulvwlfvfrqwlqxhg MAX20091 35-channel contact monitor www.maximintegrated.com
(v batt = 14v, t a = +25c, unless otherwise noted.) 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 -40 -20 0 20 40 60 80 100 120 input threshold (v) temperature ( c) input threshold vs. temperature (low - side switch, th_.1 = th_.0 = 0 ) MAX20091 toc10 open closed closed open 50 55 60 65 70 75 80 85 90 95 100 -40 10 60 110 current (ua) temperature ( c) quiescent current in polling mode (pt = 64ms, pat =128 s) MAX20091 toc08 3 4 5 5 10 15 20 25 threshold batt voltage (v) switch threshold vs. batt voltage (th_.1 = th_.0 = 0) MAX20091 toc11 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 -40 -20 0 20 40 60 80 100 120 input threshold (v) temperature ( c) input threshold vs. temperature (high - side switch, th_.1 = th_.0 = 0) MAX20091 toc09 open - >closed closed - >open maxim integrated g 7 7slfdo2shudwlqjkdudfwhulvwlfvfrqwlqxhg MAX20091 35-channel contact monitor www.maximintegrated.com
1 2 3 4 5 6 7 8 9 10 11 12 36 35 34 33 32 31 30 29 28 27 26 25 37 38 39 40 41 42 43 44 45 46 47 48 24 23 22 21 20 19 18 17 16 15 14 13 top view tqfn (7mm x 7mm, 0.5mm pitch) in20 + in21 in22 in23 in24 in25 in26 in27 in28 in29 in30 in31 in7 in6 in5 in4 in3 in2 in1 in0 batt gnd gnd gnd in19 in18 in17 in16 in15 in14 in13 in12 in11 in10 in9 in8 in32 in33 in34 sgnd v io sdo cs sck sdi int pvl pvl MAX20091 maxim integrated 8 pin confguration MAX20091 35-channel contact monitor www.maximintegrated.com
pin name function 1, 2 in8, in9 switch monitor input channels 8 and 9. connect to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. 3C27 in10, in34 switch monitor input channels 10C34. connect to a ground-connected switch. 28 gnd ground connection 29 v io logic supply for spi interface pins. connect to a supply between 3v and 5v. bypass vio to gnd with a 0.1f capacitor placed as close to vio as possible. 30 sdo spi data output. sdo is high impedance when cs is high. 31 cs spi active-low chip-select. 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 . 32 sck spi clock input 33 sdi spi data input. spi data is latched into the internal shift register on the rising edges of sck while cs is held low. sdi has an internal 75k pulldown resistor. connect sdi to the sdo of a preceding device in a daisy chain or to the microcontroller data output. 34 int open-drain interrupt output. int goes low when an input switch change has been detected in scan mode. 35, 36 pvl internal linear regulator output. pvl is the supply for the internal blocks. bypass pvl with a 2.2f capacitor to ground. 37C39 gnd ground 40 batt battery voltage connection. batt should be protected from reverse battery using a series diode. bypass batt to gnd with a 0.1f ceramic capacitor placed as close as possible to the pin. in addition, bypass batt with a 47f or greater capacitor. 41C48 in0Cin7 switch monitor input channels 0C7. connect to a battery-connected or ground-connected switch. when used for a battery-connected switch, add a 100 series protection resistor to the input. ep exposed pad. connect ep to a large-area contiguous copper ground plane for effective power dissipation. do not use as the only ic ground connection. ep must be connected to gnd. maxim integrated 9 pin description MAX20091 35-channel contact monitor www.maximintegrated.com
max 20091 gnd spi i weth ref 10 x ref temp sensor int i wetl in 0 in 9 scan logic + control i weth 25 x batt in 10 in 34 ref sdi mux ref mux sck cs sdo v io oscillator tbd 1 mhz bias circuitry batt pvl ref mxim ineed 10 functional diagram MAX20091 35-channel contact monitor www.maximintegrated.com
detailed description the MAX20091 is a 35-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 indi - vidual switch inputs and to configure interrupt capability, wetting current, switch configuration (battery-connected or ground-connected), polling time, and polling active time. any switch status change causes an interrupt signal if the switch is interrupt enabled. the ic has two modes of operation: continuous mode and polling mode. batt and v io v io is the power-supply input for the logic output circuitry. connect v io to a 3v to 5.5v logic-level supply. bypass v io to gnd with at least a 0.1f capacitor placed as close as possible to the v io pin. batt is the main power-supply input. bypass batt to gnd with a 0.1f ceramic capacitor placed as close as possible to the pin. in addition, bypass batt with a 47f or greater capacitor. when batt exceeds 28v (typ) wet - ting current is disabled, switch scanning is stopped and the ovp bit in spi register 0x04 is set. pvl is the output of an internal ultra-low current regulator that is always enabled when batt is above its undervolt - age lockout. bypass pvl with a 2.2f capacitor. operating modes the ic features two modes of operation: continuous mode and polling mode. in continuous mode, the wetting currents (if enabled) are continuously applied to closed switches. in polling mode, the wetting currents are applied to the closed switches for a preset duration to reduce the power consumption. continuous mode operation (p2:p0 = 0) in continuous mode, reading of the switch status is initiated by a falling edge on cs . the microcontroller initiates a low pulse on cs to update the ics switch status register. if int remains high, no action needs be taken by the microcontroller. if int goes low, the microcontroller 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 at least 4s before initiating a switch status read operation. polling-mode operation in polling mode, each switch input is sampled for a programmable polling active time set by the pa[2:0] bits between 96s and 4ms (see table 5 ). sampling is repeated at a period set by the p[3:0] bits (from 8ms to continuous, see table 4 ). 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. polling mode thus reduces the current consumption from the batt power supply to a value dependent on the polling time and polling active time chosen. mechanical switch inputs (in0Cin34) in0Cin34 are the inputs for remote mechanical switches. the switch status is indicated by the ss[34:0] bits in the switch status registers, and each switch input can be programmed to assert an interrupt ( int ) by writing to the ie[34:0] bits in registers 0x07 to 0x0b. all switch inputs are interrupt-disabled upon power-up. the in10Cin34 inputs are intended for ground-connected switches. the in0Cin9 inputs can be programmed for either ground-connected switches or battery-connected switches by writing to the lh[9:0] bits in registers 0x05 and 0x06. the default configuration of the in0Cin9 inputs after power-up is for ground-connected switches. all inputs have an internal glitch filter with a typical filter time of 50s. wetting current the ic 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, 2ma, 5ma, or 10ma by the w_.[1:0] data bits in the wetting current registers by means of spi. when using wetting current, special care must be taken to avoid exceeding the maximum power dissipation of the ic (see the applications information section). disabling the wetting current or limiting the active-wetting current time reduces power consumption. the default state upon power-up is with wetting current set to 2ma. 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 warning threshold is exceeded. an external pullup resistor to v io 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 that occurs during an spi transaction is stored and causes an addi - tional interrupt after the spi transaction is over and cs goes high. if v io is absent, the int output is functional provided that it is pulled up to a different supply voltage. maxim integrated 11 MAX20091 35-channel contact monitor www.maximintegrated.com
serial peripheral interface the ic is controlled by means of an spi interface with the local microcontroller. any number of 8-bit data bursts can be sent within one cycle of cs low to allow for burst-write of all or a subset of the registers. the spi logic counts the number of bits clocked into the ic and enables data latch - ing only after each 8 bits. the first 8-bit byte is the com - mand byte that is followed by an 8-bit address byte and then by n 8-bit data bytes (write) or n further addresses (read). spi commands the following four spi commands are implemented: write: within the same cs cycle, a write command is implemented as follows: sdi: <0x01> with this command, data 1 is written to the address given by , data 2 is written to , and so on. figure 1. write sequence figure 2. read sequence a7 a6 a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 d7 d0 sck sdi cs write command (0x01) initial address (a[7:0]) data 1 data n a7 sck sdi sdo cs read command (0x02) address 1 address 2 address n 0x00 a6 a5 a4 a3 a2 a1 a0 a7 a6 a5 a4 a3 a2 a1 a0 a7 a0 d7 d6 d5 d4 d3 d2 d1 d0 d7 d0 d0 d7 data 1 data 2 data n maxim integrated 12 MAX20091 35-channel contact monitor www.maximintegrated.com
table 1. register summary address description 0x00 switch state register 1 0x01 switch state register 2 0x02 switch state register 3 0x03 switch state register 4 0x04 switch state/status register 5 0x05 confguration register 1 0x06 confguration register 2 0x07 interrupt enable register 1 0x08 interrupt enable register 2 0x09 interrupt enable register 3 0x0a interrupt enable register 4 0x0b interrupt enable register 5 0x0c wetting current register 1 0x0d wetting current register 2 0x0e wetting current register 3 0x0f wetting current register 4 0x10 wetting current register 5 0x11 wetting current register 6 0x12 wetting current register 7 0x13 wetting current register 8 0x14 wetting current register 9 0x15 threshold select register 1 0x16 threshold select register 2 0x17 threshold select register 3 0x18 threshold select register 4 0x19 threshold select register 5 0x1a threshold select register 6 0x1b threshold select register 7 0x1c threshold select register 8 0x1d threshold select register 9 maxim integrated 13 MAX20091 35-channel contact monitor www.maximintegrated.com
read: within the same cs cycle, a read command is implemented as follows: sdi: <0x02>

<0x00> sdo: <0xxx> <0xxx> with this command, all the registers can be read within the same cycle of cs . the addresses can be given in any order. read all: within two cs cycles, the read-all command is implemented as follows: cs _dev cycle 1 cs_dev cycle 2 sdi_pwr1: <0x03>

<0x00> <0x00> <0x00> ... <0x00> sdo: ... reset: an spi reset command is implemented as follows: sdi_pwr1: <0x04> an internal master reset pulse is generated from the fall - ing edge of the last sck signal to the falling edge of the following cs signal. the command bits indicate the registers to be addressed according to table 2 . switch state bits the ss[34:0] bits indicate the state of the switches connected to inputs in0Cin34, respectively. ss_ is 0 when the switch is open and 1 when the switch is closed. table 2. register map address data mode bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 0x00 ss34 ss33 ss32 ss31 ss30 ss29 ss28 ss27 r 0x01 ss26 ss25 ss24 ss23 ss22 ss21 ss20 ss19 r 0x02 ss18 ss17 ss16 ss15 ss14 ss13 ss12 ss11 r 0x03 ss10 ss9 ss8 ss7 ss6 ss5 ss4 ss3 r 0x04 ss2 ss1 ss0 ovp otw ot r 0x05 p2 p1 p0 pa2 pa1 pa0 lh9 lh8 r/w 0x06 lh7 lh6 lh5 lh4 lh3 lh2 lh1 lh0 r/w 0x07 ie34 ie33 ie32 ie31 ie30 ie29 ie28 ie27 r/w 0x08 ie26 ie25 ie24 ie23 ie22 ie21 ie20 ie19 r/w 0x09 ie18 ie17 ie16 ie15 ie14 ie13 ie12 ie11 r/w 0x0a ie10 ie9 ie8 ie7 ie6 ie5 ie4 ie3 r/w 0x0b ie2 ie1 ie0 r/w 0x0c w34.1 w34.0 w33.1 w33.0 w32.1 w32.0 r/w 0x0d w31.1 w31.0 w30.1 w30.0 w29.1 w29.0 w28.1 w28.0 r/w maxim integrated 14 MAX20091 35-channel contact monitor www.maximintegrated.com
ovp bit when 1, the ovp bit indicates that the ic is in overvoltage shutdown due to batt being over 29.5v (typ). otw/ot bits the otw bit indicates an overtemperature warning, while the ot bit indicates overtemperature shutdown when 1. interrupt enable bits the ie[34:0] bits program 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. switch confguration for in0Cin9 the lh[9:0] bits set the switch configuration for in0C in9, respectively. set lh[9:0] to 0 to configure the input channel for a ground-connected switch. set lh[9:0] to 1 to configure the input channel to battery connected. the default value after power-on is 0. wetting current-setting bits the w_.[1:0] bits set the corresponding switch channel- wetting current as shown in table 3. table 2. register map (continued) table 3. wetting current setting *default por value. address data mode bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 0x0e w27.1 w27.0 w26.1 w26.0 w25.1 w25.0 w24.1 w24.0 r/w 0x0f w23.1 w23.0 w22.1 w22.0 w21.1 w21.0 w20.1 w20.0 r/w 0x10 w19.1 w19.0 w18.1 w18.0 w17.1 w17.0 w16.1 w16.0 r/w 0x11 w15.1 w15.0 w14.1 w14.0 w13.1 w13.0 w12.1 w12.0 r/w 0x12 w11.1 w11.0 w10.1 w10.0 w9.1 w9.0 w8.1 w8.0 r/w 0x13 w7.1 w7.0 w6.1 w6.0 w5.1 w5.0 w4.1 w4.0 r/w 0x14 w3.1 w3.0 w2.1 w2.0 w1.1 w1.0 w0.1 w0.0 r/w 0x15 th34.1 th34.0 th33.1 th33.0 th32.1 th32.0 r/w 0x16 th31.1 th31.0 th30.1 th30.0 th29.1 th29.0 th28.1 th28.0 r/w 0x17 th27.1 th27.0 th26.1 th26.0 th25.1 th25.0 th24.0 th24.0 r/w 0x18 th23.1 th23.0 th22.1 th22.0 th21.1 th21.0 th20.1 th20.0 r/w 0x19 th19.1 th19.0 th18.1 th18.0 th17.1 th17.0 th16.1 th16.0 r/w 0x1a th15.1 th15.0 th14.1 th14.0 th13.1 th13.0 th12.1 th12.0 r/w 0x1b th11.1 th11.0 th10.1 th10.0 th9.1 th9.0 th8.1 th8.0 r/w 0x1c th7.1 th7.0 th6.1 th6.0 th5.1 th5.0 th4.1 th4.0 r/w 0x1d th3.1 th3.0 th2.1 th2.0 th1.1 th1.0 th0.1 th0.0 r/w w_.1 w_.0 wetting current (ma) 0 0 0 0 1 2* 1 0 5 1 1 10 maxim integrated 15 MAX20091 35-channel contact monitor www.maximintegrated.com
table 4. polling time setting table 5. polling active time setting table 6. switch threshold setting *default por value. *default por value. *default por value. p2 p1 p0 polling time (ms) 0 0 0 continuous* 0 0 1 8 0 1 0 16 0 1 1 32 1 0 0 64 1 0 1 128 1 1 0 256 1 1 1 512 pa2 pa1 pa0 polling active time (fs) 0 0 0 96 0 0 1 128* 0 1 0 192 0 1 1 256 1 0 0 512 1 0 1 1024 1 1 0 2048 1 1 1 4096 th_.1 th_.0 switch threshold 0 0 4v* 0 1 3.8 1 0 3 1 1 2 maxim integrated 16 MAX20091 35-channel contact monitor www.maximintegrated.com
applications information power dissipation calculate the total power dissipation of the ic using the following formula: p = v batt x (i batt + i wett ) where i wett is the total wetting current flowing in all closed switches. the junction-to-ambient thermal resistance is pcb- dependent and is between 26c/w (jedec multilayer board) and 37c/w (jedec single-layer board) for this package. the junction temperature rise is somewhere between p x 26c/w and p x 37c/w. ensure that the junction temperature does not exceed 150c during normal operation. if the ic junction temperature exceeds +165c, 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 condition persists. when the junction temperature drops by 15c, the wetting currents are reenabled and there is a 1ms blanking time before the switches can be polled. reverse-battery tolerance the in0Cin23 switch inputs withstand up to -18v dc voltage without damage. a reverse-battery diode is need - ed to protect batt, as shown in the typical application circuit . iso 7637 pulse immunity the batt pin and the in0Cin35 pins are potentially exposed to iso 7637 pulses. bypass batt with a 0.1f and a 47f capacitor. the batt voltage must be limited below 42v during load dump. bypass in0Cin35 with at least 0.047f capacitors at the ecu connector. when in0Cin9 are used with battery-connected switches, a 100 series resistor is needed. these external compo - nents allow batt and in0Cin35 to withstand iso 7637 pulses in the application circuit. mechanical switch characteristics the ic 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. the above resistor value limits vary with the value of wetting current used and the maximum expected ground shift in the system. maxim integrated 17 MAX20091 35-channel contact monitor www.maximintegrated.com
/v denotes an automotive qualified part. +denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. * ep = exposed pad. part temp range pin-package pkg code MAX20091atm/v+t -40c to +125c 48 tqfn 4877+6c batt b attery , kl 30 remote switch int sdi sck cs sdo v io c v io v reg supply max 200 9 1 2 of 35 in 0 1 0 0 47 n f in 9 47 n f in 10 in 34 remote switch pvl gnd sgnd ecu connector 0 . 1 f 2 . 2 f 0 . 1 f typical operating circuit maxim integrated g 18 ordering information/selector guide MAX20091 35-channel contact monitor www.maximintegrated.com
package type package code outline no. land pattern no. 48 tqfn-ep 4877+6c 21-0144 90-0132 maxim integrated 19 chip information process: bicmos package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. MAX20091 35-channel contact monitor www.maximintegrated.com
revision number revision date description pages changed 0 6/14 initial release ? 2014 maxim integrated products, inc. 20 revision history maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifcations without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. MAX20091 35-channel contact monitor for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.

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