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19-6440; rev 3; 7/14 ordering information appears at end of data sheet. general description the MAX31910 industrial interface serializer translates, conditions, and serializes the 24v digital output of sen - sors and switches used in industrial, process, and build- ing automation to 5v cmos-compatible signals required by microcontrollers. it provides the front-end interface circuit of a programmable logic controller (plc) digital input module. the device features integrated current limiting, lowpass filtering, and channel serialization. input current limiting allows a significant reduction in power consumed from the field voltage supply as compared to traditional discrete resistor-divider implementations. in addition, to achieve the lowest in-class power dissipa - tion, the device uses patent-pending circuit techniques to achieve further reduction of power beyond what is possible by input current limiting alone. selectable on- chip lowpass filters allow flexible debouncing and filter - ing of sensor outputs based on the application. on-chip serialization allows a drastic reduction in the number of optocouplers used for isolation. the device serializer is stackable so that any number of input channels can be serialized and output through only one spi-compatible port. this reduces the number of optocouplers needed to only three, regardless of the number of input channels. for enhanced robustness with respect to high-frequency noise and fast electrical transients, a multibit crc code is generated and transmitted through the spi port for each 8 bits of data. the on-chip 5v voltage regulator can be used to power external optocouplers, digital isolators, or other external 5v circuitry. for low-cost applications, maxim integrated offers a pin-compatible version of this device, the max31911. the max31911 does not include the patent-pending cur - rent clamp-switching circuitry that is included with the MAX31910. the future generation version of the MAX31910 and max31911 will include energy-less led drivers while maintaining pin compatibility. features s eight high-voltage input channels (36v max) s configurable for iec 61131-2 input types 1, 2, 3 s wide operating supply range of 7v to 36v s optional configuration allows 5v supply s selectable input filtering and debouncing from 0ms to 3ms s configurable input current limiting from 0.5ma to 6ma s high hbm esd immunity on all field input pins s on-chip 8-to-1 serialization with spi interface s on-chip 5v regulator s overtemperature indicator s on-chip 24v field supply voltage monitor s achieves lowest in-class system power dissipation from 24v field supply s multibit crc code generation and transmission for error detection and more reliable data transmission to an external micro applications digital input modules for plcs industrial, building, and process automation motor control block diagram sout cs modesel sin db1 db0 faultb 5vout v cc24v riref gnd rt1 in1 rt8 in8 vref input channel 0 vref sensors 24v or crc gen. controller or isolation 5v 5v regulator input channel 7 supply monitor temp monitor switched current limiter lp filter clk voltage comparator serializer MAX31910 MAX31910 industrial, octal, digital input translator/serializer evaluation kit available for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.
2 (voltages relative to gnd.) voltage range on v cc24v ............................. -0.3v to +45v voltage range on in1Cin8 ............................ -0.3v to +45v voltage range on in1Cin8 (through 2.2k resistors) ............................ -45v to +45v voltage range on db0/db1, clk, sin, cs , modesel ............................... -0.3v to (v dd + 0.3v) continuous power dissipation (t a = +70 n c) tssop (derate 27mw/ n c above +70 n c) .......... 2162.2mw operating temperature range ambient temperature ............................. -40 n c to +125 n c junction temperature ............................ -40 n c to +150 n c storage temperature range ...................... -55 n c to +125 n c lead temperature (soldering, 10s) ......................... +300 n c soldering temperature (reflow) ............................... +260 n c tssop junction-to-ambient thermal resistance ( q ja ) .......... 37c/w junction-to-case thermal resistance ( q jc ) .................. 2c/w absolute maximum ratings 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 . stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional opera - tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. package thermal characteristics (note 1) recommended operating conditions (note 2) parameter symbol conditions min typ max units field supply voltage v cc24v 7 36 v field inputs voltage v inn (note 3) -0.3 36 v logic inputs voltage v logic 0 5.5 v current-limit setting resistor r ref 15 k i field input data rate f in (note 4) 200 khz MAX31910 industrial, octal, digital input translator/serializer maxim integrated
3 dc electrical characteristics (v cc24v = 7v to 36v, t j = -40 n c to +150 n c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units field-supply current i cc24v in1Cin8 = 24v, 5vout = open, rt1Crt8 = gnd, all logic inputs open 1.4 2.2 ma field-supply uvlo off/on v onuvlo 9 10 v field-supply uvlo on/off v offuvlo 7 8 v field input threshold high- to-low v in-(inf) 2.2k i external series resistor 6 7.5 v field input threshold low-to- high v in+(inf) 2.2k i external series resistor (note 11) 8.5 10 v field input hysteresis v hys(inf) 2.2k i external series resistor (note 11) 1 v input threshold high-to-low (at ic pin) v th-(inp) 2 2.5 v input threshold low-to-high (at ic pin) v th+(inp) (note 11) 3.5 4 v input threshold hysteresis (at ic pin) v hys(inp) (note 11) 1 v field input pin resistance r inp 0.8 k i field input current limit i inlim r ref = 15k i , v cc24v = 18v to 30v (note 5) 2.2 2.4 2.6 ma filter time constant t filter db1/db0 = 0/0: no filtering 0 ms db1/db0 = 0/1 0.008 0.025 0.038 db1/db0 = 1/0 0.25 0.75 1.1 db1/db0 = 1/1 1.0 3 4.5 linear regulator output v 5vout max i load = 50ma 4.75 5.0 5.25 v regulator line regulation dvreg line i load = 50ma 10 20 mv regulator load regulation dvreg load i load = 1ma to 50ma 20 50 mv logic-low output voltage v ol i ol = 4ma 0.4 1.0 v logic-high output voltage v oh i oh = -4ma 4.0 v logic-input trip point v ih-il 0.3 x v 5vout 0.5 x v 5vout 0.7 x v 5vout v logic-input leakage current i il -50 -30 -15 f a overtemperature alarm t alrm 135 n c MAX31910 industrial, octal, digital input translator/serializer maxim integrated
4 note 2: limits are 100% production tested at t a = +25c and/or t a = +125c. limits over the operating temperature range and relevant supply voltage range are guaranteed by design and characterization. typical values are not guaranteed. note 3: when using suggested external 2.2k series resistors, limits of -3v to +36v apply. note 4: f in refers to the maximum pulse frequency (1/f in = shortest pulse width) that can be detected from the field sensors and switches. note 5: external resistor r ref can be adjusted to set any desired current limit between 0.5ma and 6ma. note 6: see figure 9 . note 7: see figure 6 . note 8: see figure 8 . note 9: see figure 7 . note 10: this is the maximum bit transfer rate through the serializer interface. note 11: when input current switching is enabled (db0/db1 = 0), there is no input threshold hysteresis. in this case, the input threshold for both falling and rising signals is the high-to-low threshold. ac electrical characteristics: spi interface (v cc24v = 7v to 36v, t j = -40 n c to +150 n c, unless otherwise noted.) (note 2) ac electrical characteristics (v cc24v = 7v to 36v, t j = -40 n c to +150 n c, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units clk pulse duration t clkpw (note 6) 20 ns cs pulse duration t cspw (note 7) 20 ns sin to clk setup time t su1 (note 8) 5 ns sin to clk hold time t h1 (note 8) 8 ns cs to clk setup time t su2 (note 9) 8 ns cs to clk recovery time t rec (note 9) 12 ns clock pulse frequency f clk (notes 6, 10) dc 25 mhz propagation delay, clk to sout t p1 (note 6) 20 ns propagation delay, cs to sout t p2 (note 7) 20 ns rise/fall time sout/ fault t r/f (note 6) 40 ns parameter symbol conditions min typ max units field input pulse width t pw no external capacitors on pins in1 - in8 1 s esd hbm, all pins 2 kv hbm, in1 - in8 with respect to gnd 15 MAX31910 industrial, octal, digital input translator/serializer maxim integrated
5 typical operating characteristics (t a = +25c, r ref = 15k, unless otherwise noted.) power-supply current vs. v cc24v field supply MAX31910 toc01 supply voltage (v) supply current (ma) 1.35 1.40 1.45 1.50 1.55 1.60 1.30 51 52 53 5 supply current vs. temperature MAX31910 toc02 temperature (c) supply current (ma) 60 10 1.45 1.50 1.55 1.60 1.40 -40 current limit vs. r ref MAX31910 toc03 r ref (k i ) current limit (ma) 40 30 20 10 5.5 0.5 1.5 2.5 3.5 4.5 0 input current limit vs. temperature MAX31910 toc04 ambient temperature (c) current limit (ma) 110 60 10 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 2.0 -40 v inn = 24v input current limit vs. field input voltage MAX31910 toc05 field input voltage (v) current limit (ma) 35 25 15 0.5 1.0 1.5 2.0 2.5 3.0 0 5 v cc24v = 24v input voltage hysteresis vs. temperature MAX31910 toc06 temperature (c) threshold voltage (v) 110 60 10 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 2.0 -40 off-on threshold on-off threshold r in = 0i input voltage hysteresis vs. temperature MAX31910 toc07 temperature (c) threshold voltage (v) 110 60 10 7.2 7.4 7.6 7.8 7.0 8.2 8.4 8.6 8.8 9.0 7.0 -40 off-on threshold on-off threshold r in = 2.2i ldo load regulation MAX31910 toc08 5vout output current (ma) 5vout voltage (v) 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 4.90 0 40 50 30 20 10 ldo line regulation MAX31910 toc09 supply voltage (v) 5vout voltage (v) 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 4.90 6 36 31 26 21 16 11 i 5vout = 5ma MAX31910 industrial, octal, digital input translator/serializer maxim integrated
6 typical operating characteristics (continued) (t a = +25c, r ref = 15k, unless otherwise noted.) ldo line regulation MAX31910 toc10 supply voltage (v) 5vout voltage (v) 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 4.90 6 36 31 26 21 16 11 i 5vout = 50ma ldo output voltage vs. temperature MAX31910 toc12 ambient temperature (c) 5vout voltage (v) 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 4.90 -40 110 60 10 i 5vout = 0ma ldo output vs. v cc24v field supply MAX31910 toc11 supply voltage (v) 5vout otput voltage (v) 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 4.5 4 34 24 14 i 5vout = 50ma ldo output voltage vs. temperature MAX31910 toc13 ambient temperature (c) 5vout voltage (v) 4.92 4.94 4.96 4.98 5.00 5.02 5.04 5.06 5.08 5.10 4.90 -40 110 60 10 i 5vout = 5ma MAX31910 industrial, octal, digital input translator/serializer maxim integrated
7 pin description pin configuration pin name function 1, 2 db0, db1 debounce (filtering) time select inputs 3, 5, 7, 9, 11, 18, 20, 22 in1Cin8 field inputs 4, 6, 8, 10, 12, 17, 19, 21 rt1Crt8 connect directly to gnd. these pins are reserved for energy-less led drivers in future versions of the device. 13 riref current-limiter reference resistor 14 v cc24v field-supply voltage 15 5vout 5v regulator output 16 fault active-low overtemperature or undervoltage alarm 23 sout serial-data out 24 cs active-low chip-select input 25 clk serial-clock input 26 modesel mode-select input modesel = 1: selects 8-bit shift register modesel = 0: selects 16-bit shift register 27 sin serial-data input 28 gnd field ground ep exposed pad. must be connected to the pcb ground plane. top view MAX31910 25 4c lk rt1 26 3 modesel in1 27 2 sin db1 28 1 + gnd db0 22 7 in8 in3 23 6 sout rt2 21 8 rt8 rt3 20 9 in7 in4 19 10 rt7 rt4 18 11 in6 in5 17 12 rt6 rt5 16 ep 13 fault riref 24 5 cs in2 15 14 5vout v cc24v MAX31910 industrial, octal, digital input translator/serializer maxim integrated
8 basic application circuit detailed description input current clamp the MAX31910 industrial interface serializer inputs (in1C in8) sense the state (on vs. off) of field sensors by moni - toring both voltage and current flowing through the sen - sor output. the current sinking through these input pins rises linearly with input voltage until the limit set by the current clamp is reached. any voltage increase beyond this point does not increase the input current any further. the value of the current clamp is adjustable through an external resistor connected between the riref pin and gnd. pins rt1Crt8 must be connected directly to gnd to provide a return path for the input current. the volt - age and current at the in1Cin8 input pins are compared against internally set references to determine whether the sensor is on (logic 1) or off (logic 0). the trip points deter - mining the on/off status of the sensor satisfy the require - ments of iec 61131-2 type 1 and 3 switches. the device can also be configured to work as a type 2 switch. glitch filter a digital glitch filter provides debouncing and filtering of noisy sensor signals. the time constant of this filter is programmable from 0ms to 3ms through the db0 and db1 pins. see table 1 for debounce settings. to provide the digital glitch filter, the device checks that an input is stable for at least three clock cycles. the dura - tion of a clock cycle is 1/3 of the selected debounce time. if the input is not stable for at least three clock cycles, the input change is not sent to the internal shift register. low-power current clamp switching the MAX31910 uses a patent-pending switched cur - rent limiter to reduce power consumption below what is achievable by current limiting alone ( figure 1 ). the inter - nal filter clock is used to switch input current between 100% and 20% of the chosen current limit. for example, if the current limit is set to 2.4ma, the input current switches between 2.4ma and 0.48ma. the switching is done at a controlled ramp rate of t delay (0.5 s typ). the filter clock switches input current at a 50% duty cycle. the clock period for current switching is automatically selected by the db1 and db0 glitch filter settings. see table 1 for current switching settings. gnd modesel db1 db0 5vout sin clk cs sout fault clk cs sout fault isolation jumpers to 5vout and gnd c4 vdd_logic r ref r inx r1 24v f in1?8 riref c1 in1?8 rt1?8 v cc24v MAX31910 note: see figure 1 for additional components needed for emc. MAX31910 industrial, octal, digital input translator/serializer maxim integrated
9 table 1. debounce settings reading serial data the filtered outputs of the input comparators are latched into a shift register at the falling edge of cs . clocking the clk pin, while cs is held low, shifts the latched data out of sout 1 bit at a time. the internal data serializer comprises a 16-bit shift regis - ter, containing 8 bits of data corresponding to the eight field inputs, as well as an 8-bit status byte containing sup - plementary status and crc information. the status byte contains 1 bit representing the status of the field-supply voltage (uv), 1 bit representing the status of the internal temperature monitor (ot), a 5-bit crc code internally calculated and generated, and a trailing 1 as a stop bit. the undervoltage (uv) bit is normally 0. if the supply voltage falls below v offuvlo , the uv becomes a 1. the uv bit returns to 0 once the supply voltage has returned above v onuvlo . the overtemperature (ot) bit is also normally 0. if the junction temperature increases to above t alrm , the ot bit becomes a 1. the bit returns to 0 once the junction temperature has returned below t alrm . the crc code can be used to check data integrity during transfer from the device to an external microcontroller. in applications where the integrity of data transferred is not of concern, the crc bits can be ignored. the crc uses the following polynomial: p(x) = x 5 + x 4 + x 2 + x 0 figure 1. operation of patent-pending switched current limiter db1 db0 binary value debounce time current switching period 0 0 0 0 dc (disabled) 0 1 1 25 f s 8 f s 1 0 2 0.75ms 0.25ms 1 1 3 3ms 1ms 24v 0v t delay t delay 100% i limit 20% i limit time internal filter clock comparator output is latched into filter on rising edge of clock input current limi t sensor output voltag e MAX31910 industrial, octal, digital input translator/serializer maxim integrated
10 the number of bits in the internal serializer can be select - ed between 8 bits or 16 bits. the modesel pin is used to configure the serializer as an 8-bit (disabling the status byte) or 16-bit shift register. in 8-bit mode, only the eight field input states are transferred through the spi port and the status byte is ignored. therefore, in multiple ic appli - cations (input channels greater than 8), if desired, only a single status byte can be generated and transmitted for any number of input channels. the shift register contents are read only (no write capa - bility exists) through the spi-compatible interface. for higher input counts than 8, multiple devices can be cascaded. in this case, the sout pin of one device should be connected to the sin pin of the next device, effectively cascading the internal shift registers. the clk and cs pins of all the devices should be con - nected together in this configuration. see the serial-port operation section for more detailed information on oper - ating the spi interface. temperature monitoring the internal junction temperature of the device is con - stantly monitored. an alarm is raised, by asserting the fault pin, if the temperature rises above t alrm . in addition to asserting fault , the device sets the ot bit to a 1. supply voltage monitoring a supply voltage monitor circuit constantly monitors the field-supply voltage. if this voltage falls below a threshold (v offuvlo ), an alarm is raised by asserting the fault pin, indicating that the part is experiencing a fault condition and the data in the serializer is not to be trusted. in addition, the device sets the uv bit to a 1. once the field-supply voltage has recovered and goes above v onuvlo , the fault pin is released, indicating normal operation of the part. applications information emc standards compliance the external components shown in figure 2 allow the device to operate in harsh industrial environments. components were chosen to assist in suppression of voltage burst and surge transients, allowing the system to meet or exceed international emc requirements. table 2 lists an example device for each component in figure 2 . the system shown in figure 2 , using the components shown in table 2 , is designed to be robust against iec fast transient burst, surge, conducted rfi specifications, and esd specifications (iec 61000-4-2, -4, -5, and -6). serial-port operation serial output of the device functions in one of two modes, depending on the modesel setting ( table 3 ). with modesel = 0, the device output includes a 5-bit crc, an undervoltage alarm, and an overtemperature alarm. see the detailed description for crc, undervolt - age, and overtemperature functional descriptions. with modesel = 1, the device outputs only the state of the in1Cin8 inputs and omits the crc, undervoltage alarm, and overtemperature alarm. daisy-chain operation for systems with more than eight sensor inputs, multiple devices can be daisy-chained to allow access to all data inputs through a single serial port. when using a daisy- chain configuration, connect sout of one of the devices to the sin input of another upstream device. cs and sck of all devices in the chain should be connected together in parallel (see figure 3 ). in a daisy-chain configuration, external components used to enhance emc robustness do not need to be duplicated for each device of a circuit board. figure 4 illustrates a 16-input application. spi waveforms the serial output of the device adheres to the spi proto - col, running with cpha = 0 and cpol = 0. input states on in1Cin8 are latched in on the falling edge of cs . the transfer of data out of the slave output, sout, starts immediately when cs is asserted (i.e., msb is output onto sout independent of clk). the remaining data bits are shifted out on the falling edge of clk. the data bits are written to the output sout with msb first. when cs is high, sout is high impedance. the resultant timing is shown in figure 5 . note that all bits after in1 are invalid if 8-bit operation mode is selected with the modesel input. figure 6 , figure 7 , figure 8 , and figure 9 illustrate spi timing specifications. MAX31910 industrial, octal, digital input translator/serializer maxim integrated
11 figure 2. typical emc protection circuitry note: for higher emc performance, a 1nf, 1000v capacitor can be added from nodes f in1 Cf in8 to earth. component description required/recommended/optional c0 4.7nf, 2kv polypropylene capacitor recommended c1 10 f f, 60v ceramic capacitor required c3 100nf, 10v ceramic capacitor recommended c4 4.7f, 10v low esr ceramic capacitor required c5 100nf, 100v ceramic capacitor recommended d0 36v fast zener diode (zsmb36) recommended d1 general-purpose rectifier (in4007) optional: for reverse polarity protection. this diode can alternatively be placed in series with the field supply (24v). r1 150 i , 1/3w melf resistor recommended r inx 2.2k i , 1/4w melf resistor required r ref 15k i , 1/8w resistor required table 2. recommended circuit components gnd modesel db1 db0 5vout sin clk cs sout fault clk cs sout fault isolation jumpers to 5vout and gnd c4 c3 vdd_logic r ref 0v r inx f in1?8 riref in1?8 rt1?8 d1 v cc24v MAX31910 r1 24v d0 c1 c0 c0 c5 earth earth MAX31910 industrial, octal, digital input translator/serializer maxim integrated
12 table 3. modesel settings figure 3. daisy-chain operation modesel setting functionality 0 16-bit output; [in8Cin1][crc (5 bit)][uv][ot][x] 1 8-bit output; [in8Cin1] MAX31910 MAX31910m ax3191 0 sin sout sin sout sin sout to controller MAX31910 industrial, octal, digital input translator/serializer maxim integrated
13 figure 4. 16-input application circuit modesel db1 db0 5vout clk cs sout fault clk cs sout fault isolation sin jumpers to 5vout and gnd jumpers to 5vout and gnd c4 c3 c4 c3 vdd_logic r ref 0v d1 r inx f in1?8 riref gnd in1?8 rt1?8 v cc24v MAX31910 r1 24v d0 c1 c0 c0 earth earth gnd fault sout cs clk sin modesel db1 db0 5vout r ref r inx f in1?8 riref c1 in1?8 rt1?8 v cc24v MAX31910 MAX31910 industrial, octal, digital input translator/serializer maxim integrated
14 figure 5. spi communication example figure 6. spi timing diagram 1 figure 7. spi timing diagram 2 figure 8. spi timing diagram 3 figure 9. spi timing diagram 4 clk sout in8 ? in1 in8 in7 in6 in5 in4 in3 in2 in1 crc4 crc3 crc2 crc1 crc0 uv ot res valid cs sout t cspw t p2 cs clk sin t su1 t h1 sin valid clk t su2 t rec cs t cspw 1/ f clk t r/f t r/f t p1 sout cs MAX31910 industrial, octal, digital input translator/serializer maxim integrated
15 ordering information + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. chip information process: s45jrs 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. part temp range pin- package carrier MAX31910aui+ -40 n c to +125 n c 28 tssop bulk MAX31910aui+t -40 n c to +125 n c 28 tssop tape and reel package type package code outline no. land pattern no. 28 tssop-ep u28e+4 21-0108 90-0146 MAX31910 industrial, octal, digital input translator/serializer maxim integrated
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 specifications 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 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 16 ? 2014 maxim integrated products, inc. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. revision history revision number revision date description pages changed 0 8/12 initial release 1 9/12 changed the supply voltage minimum from 10v to 7v; changed the current limits in the ec table note 5; added a new figure 1 to show current-limit switching; added the crc polynomial to the reading serial data section 1 - 4, 9 2 11/13 updated block diagram , tocs 4, 5, 8C10, input current clamp , low-power current clamp switching , basic application circuit , and emc standards compliance sections, table 2, and figures 2, 4, and 5 1, 5, 6, 8, 10C13 3 7/14 added note 11 to dc electrical characteristics table, deleted portion of table 2 note. 3, 4, 11 MAX31910 industrial, octal, digital input translator/serializer

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