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19-1084; Rev 0; 11/07
Automotive Contact Monitor and Level Shifters with LDO Regulator
General Description
The MAX13037/MAX13038 automotive contact monitor and level shifters monitor and debounce eight remote mechanical switches and assert an interrupt (INT) if a switch changes state. The state of each switch is sampled through an SPITM interface by reading the status register. Any switch can be prohibited from asserting an interrupt by writing to the command register. Four of the switch inputs are intended for ground-connected switches (IN0-IN3) and the other four inputs (IN4-IN7) are programmable in groups of two for either groundconnected or battery-connected switches. Two switch inputs (IN0, IN1) have direct level-shifted outputs (DO0, DO1) to be used for PWM or other timing-based signals. Switch input thresholds are set to 50% of the voltage applied to BATREF. The threshold hysteresis is set by connecting an external resistor from HYST to ground. The MAX13037/MAX13038 supply an adjustable wetting current to each closed switch to clean mechanical switch contacts that are exposed to adverse conditions. The MAX13037/MAX13038 feature a low dropout (LDO) linear regulator capable of supplying up to 150mA of current. The MAX13037 LDO has an output voltage of +5V, whereas the MAX13038 has an output voltage of +3.3V. The MAX13037/MAX13038 also feature a watchdog timer and an open-drain reset output with adjustable timing. The MAX13037/MAX13038 operate with a +6V to +26V battery voltage applied to BAT. The MAX13037/ MAX13038 are available in a 6mm x 6mm, 36-pin TQFN package and operate over the automotive -40C to +125C temperature range. o +42V Compatibility on BAT o Switch Inputs Withstand Reverse Battery o 150mA LDO, +5V (MAX13037) or +3.3V (MAX13038) o Ultra-Low Operating Current 28A (typ) in 64ms Scan Mode with LDO ON o Resistor Adjustable Switching Hysteresis o Watchdog and Reset o Built-In Switch Debouncing o Interrupt Output o Immunity to Transients o High Modularity o Thermal Protection o 8kV HBM ESD Protection on IN0-IN7 Without External Components o Two Inputs (IN0, IN1) Programmable as Direct Outputs o Four Inputs (IN4-IN7) Programmable for BAT or GND Related Switches
Features
o +6V to +26V Operating Voltage Range
MAX13037/MAX13038
Applications
Body Computers Window Lifters Seat Movers Electric Sunroofs Other Control ECUs
MAX13038ATX+ MAX13037ATX+ PART
Ordering Information
LDO TEMP OUTPUT RANGE VOLTAGE +5V -40C to +125C -40C to +125C PINPACKAGE PKG CODE
36 TQFN-EP* (6mm x T3666-3 6mm) 36 TQFN-EP* (6mm x T3666-3 6mm)
+3.3V
SPI is a trademark of Motorola, Inc.
+Denotes a lead-free package. *EP = Exposed paddle.
Pin Configuration and Typical Application Circuit at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.) VLO ........................................................................-0.3V to +6.0V BAT.........................................................................-0.3V to +42V IN_ , BATREF...........................................................-45V to +45V IN_ to BAT ...............................................................-45V to +45V SD, REGON. ...........................................................-0.3V to +45V HYST, WET, TD, TDEB, THRESH, OT, INT, RST......-0.3V to 6.0V CS, CLK, SDI, SDO, WDI, DO0, DO1, REGOFF.......................................-0.3V to (VLO + 0.3V) Continuous Current (CS, CLK, SDI, SDO, WDI, DO0, DO1, REGOFF) .............................................................20mA Continuous Power Dissipation (TA = +70C) 36-Pin TQFN (derate 35.7mW/C above +70C) .......2857mW Junction-to-Case Thermal Resistance (JC) (Note 1) 36-Pin TQFN .............................................................. 1.4C/W Junction-to-Ambient Thermal Resistance (JA) (Note 1) 36-Pin TQFN ............................................................... 28C/W Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a 4-layer board. For detailed information on package thermal considerations see www.maxim-ic.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 operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(BAT = +6V to +26V, TA = -40C to +125C, unless otherwise noted. Typical values are at BAT = +14V, TA = +25C.) (Note 2)
PARAMETER POWER SUPPLY BAT Supply Range VBAT VBAT = +14V, continuous scan (SC2 = 1, SC1 = 1, SC0 = 0), programmable hysteresis off (M0 = M1 = 1), IN0-IN7 = unconnected, regulator on (REGON = REGOFF = GND). VBAT = +14V, continuous scan (SC2 = 1, SC1 = 1, SC0 = 0), programmable hysteresis off (M0 = M1 = 1), IN0-IN7 = unconnected, regulator off (REGON = BAT, REGOFF = GND). 6 26 V SYMBOL CONDITIONS MIN TYP MAX UNITS
BAT Supply Current with Regulator On
ISUP_REG
57
110
A
BAT Supply Current with Regulator Off
ISUP
46
80
A
BAT Supply Current in Scan Mode with Regulator On BAT Supply Current in Scan Mode with Regulator Off BAT Supply Current in Shutdown Mode BATREF Input Resistance BATREF Input Leakage Current in Shutdown
VBAT = +14V, scan mode (SC0 = 0, ISCAN_REG SC1 = 0, SC2 = 0), regulator on (REGON = REGOFF = GND). ISCAN VBAT = +14V, scan mode (SC0 = 0, SC1 = 0, SC2 = 0), regulator off (REGON = BAT, REGOFF = GND). VSD = 0V, VBAT = +14V, REGON = BAT VBATREF = +14V VSD = 0V, VBATREF = +14V TA = +25C TA = +125C 1
28
48
A
17 3 4 2.7
35 5 7
A
ISHDN RBATREF IL_BATREF
A M
1
A
2
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Automotive Contact Monitor and Level Shifters with LDO Regulator
ELECTRICAL CHARACTERISTICS (continued)
(BAT = +6V to +26V, TA = -40C to +125C, unless otherwise noted. Typical values are at BAT = +14V, TA = +25C.) (Note 2)
PARAMETER SWITCH INPUTS (IN0-IN7) Input Voltage Threshold Center (Note 3) RHYST = or programmable hysteresis disabled RHYST = 90k RHYST = or programmable hysteresis disabled Input Voltage Threshold Hysteresis (Note 4) VTH_HYS RHYST = 90k RHYST = 0 Switch-State Sense Resistor Wetting Current Rise/Fall Time (Note 5) Wetting Current IN0-IN7 Input Impedance in Shutdown ESD Protection IN0-IN7 SDO, DO1, DO2 Output Voltage High SDO, DO1, DO2 Output Voltage Low INT, OT, RST Output Voltage Low SD Input Leakage Current SD, REGON Input Voltage Low SD, REGON Input Voltage High REGON Pullup Current CS, CLK, SDI, REGOFF, WDI Input Voltage Low CS, CLK, SDI, REGOFF, WDI Input Voltage High CS, CLK, WDI, REGOFF Input Leakage Current INT, OT, RST Leakage Current SDI Pulldown Resistor RSENSE IWET_RISE_
FALL
MAX13037/MAX13038
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
VTH_C
0.425 x 0.5 x 0.575 x VBATREF VBATREF VBATREF 0.5 x 0.63 x VBATREF VBATREF VBATREF 0.133 x 0.166 x 0.22 x VBATREF VBATREF VBATREF 0. 26 x 0.361 x 0. 48 x VBATREF VBATREF VBATREF 0.5 x VBATREF 11 16 6 1 22 28 40 7.5 5.5 8.5 8 51 22 0.4 x
V
V
k s
RWET = 61k RWET = 61k
Rise Fall
IWET
RWET = 30k RWET = 330k VSD = 0V, VIN_ = +14V Human Body Model (HBM)
mA
M kV
LOGIC-LEVELS (CS, CLK, SDI , SDI, DO0, DO1, INT, OT, RST, SD, REGON, REGOFF) VOH VOL VINTL IL_SD VIL_SD VIH_SD IREGON VIL VIH IIL IOL RSDI 0.66 x VLO -1 -1 65 100 +1 +1 145 REGON = 0 2.4 0.4 1 3.0 0.33 x VLO Source current = 2mA Sink current = 4mA Sink current = 4mA VSD = VBAT = +14V 0.8 x VLO 0.2 x VLO 0.4 1 0.8 V V V A V V A V V A A k
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
ELECTRICAL CHARACTERISTICS (continued)
(BAT = +6V to +26V, TA = -40C to +125C, unless otherwise noted. Typical values are at BAT = +14V, TA = +25C.) (Note 2)
PARAMETER LINEAR REGULATOR Output Voltage VLO MAX13037, VBAT = +14V, ILOAD = 1mA MAX13038, VBAT = +14V, ILOAD = 1mA ILOAD = 1mA to 50mA, VBAT = +14V Load Regulation LOAD_REG ILOAD = 1mA to 150mA, VBAT = +14V Line Regulation Dropout Voltage Output Current Limit Power-Supply Rejection Ratio Start-Up Time RESET, WATCHDOG Reset Reference Voltage THERMAL SHUTDOWN Thermal Shutdown Temperature Thermal Shutdown Temperature for Wetting Currents Only Thermal Shutdown Hysteresis TSHDN TWARN THYST (Note 6) (Note 7) 165 135 15 C C C VRST THRESH from high to low 1.20 1.24 1.28 V LINE_REG VBAT = +6V to +26V VLO = +5V, ILO = 50mA (MAX13037) VDROP ILIM PSRR tSTART VLO = +5V, ILO = 150mA (MAX13037) VLO = +3.3V, ILO = 150mA (MAX13038) VBAT = +14V ILO = 10mA, f = 100Hz, 500mVP-P, AC-coupled into VBAT 150 68 1 VLO = +5V (MAX13037) VLO = +3.3V (MAX13038) VLO = +5V (MAX13037) VLO = +3.3V (MAX13038) -0.9 4.92 3.234 5.00 3.300 0.53 0.53 1 1 5.08 3.366 1 1 % 1.85 1.85 +0.9 330 1000 1300 mA dB ms mV mV/V V SYMBOL CONDITIONS MIN TYP MAX UNITS
TIMING CHARACTERISTICS
(BAT = +6V to +26V, TA = -40C to +125C, unless otherwise noted. Typical values are at BAT = +14V, TA = +25C.) (Note 2)
PARAMETER IN0 to DO0 Propagation Delay, IN1 to DO1 Propagation Delay CLK Frequency Falling Edge of CS to Rising Edge of CLK Required Setup Time Falling Edge of CLK to Rising Edge of CS Required Setup Time SYMBOL tPROP fCLK tLEAD VBAT = +6V VBAT = +14V Input rise/fall time < 2ns Input rise/fall time < 2ns, Figure 1 110 CONDITIONS MIN TYP 22 22 5 MAX 35 UNITS s MHz ns
tLAG
Input rise/fall time < 2ns, Figure 1
50
ns
4
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Automotive Contact Monitor and Level Shifters with LDO Regulator
TIMING CHARACTERISTICS (continued)
(BAT = +6V to +26V, TA = -40C to +125C, unless otherwise noted. Typical values are at BAT = +14V, TA = +25C.) (Note 2)
PARAMETER SDI to Falling Edge of CLK Required Setup Time Falling Edge of CLK to SDI Required Hold Time Time from Falling Edge of CS to SDO Low Impedance Time from Rising Edge of CS to SDO High Impedance Time from Rising Edge of CLK to SDO Data Valid Debounce Time Scanning Time Pulse Scanning Time Period Wetting Time Pulse Time from Shutdown to Normal Operation Time from SCAN Mode to Normal Operation Reset Output Pulse Width Watchdog Timeout Period 1 Watchdog Timeout Period 2 Minimum Watchdog Timeout Reset on WDI SYMBOL tSI(SU) tSI(HOLD) tSO(EN) tSO(DIS) tVALID tDEB tSCAN tSCAN-P tWETT tSD tSM tRST tWD1 tWD2 tWDI SC0 = 0, SC1 = 1, SC2 = 1 WTOFF = 0 SD low-to-high transition to input monitoring enabled (Note 8) CTD = 10nF (Figure 3) CTD = 10nF, time before INT goes low (Figure 3) CTD = 10nF, time before RST goes low (Figure 3) 300 10 40 CONDITIONS Input rise/fall time < 2ns, Figure 1 Input rise/fall time < 2ns, Figure 1 Input rise/fall time < 2ns, Figure 1 Figures 1 and 2 CSDO =15pF, Figure 1 CTDEB = 500pF CTDEB = 10nF 3.18 63 130 4 10 5.9 120 250 8 21 200 500 21 84 2 x tWD1 36 144 MIN 30 20 55 55 70 9.42 188 400 14 35 TYP MAX UNITS ns ns ns ns ms ms ms s ms ms s s ms ms ms ns
MAX13037/MAX13038
5
Note 2: All units are 100% production tested at TA = 125C. Limits over the operating temperature range are guaranteed by design and not production tested. Note 3: VTH_C = (VTH_HIGH + VTH_LOW) / 2. Note 4: VTH_HYS = (VTH_HIGH - VTH_LOW). Note 5: Wetting current rise/fall time is measured as the time it takes to go from 20% to 80% of the maximum wetting current. Note 6: TSHDN is the temperature at which the wetting currents and LDO are disabled. Note 7: TWARN is the temperature at which only the wetting currents are disabled. Note 8: When exiting SCAN mode to enter Normal Mode (through SPI) any input change is ignored for 500s (typ) to allow correct wake-up of input comparators. After this time elapses, the inputs are monitored in continuous mode.
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
CS tLEAD CLK tSI(SU) tSI(HOLD) tLAG
SDI tSO(EN)
MSB IN tVALID tSO(DIS)
SDO
MSB OUT
LSB OUT
Figure 1. SPI Timing Characteristics
VL CS 1k CS
MAX13037/ MAX13038
tSO(EN) SDO 15pF SDO 1/3VL
tSO(DIS)
VOL + 0.1VL
Figure 2. SDO Enable/Disable Test Circuit and Timing Diagram
WDI tWD1 tWD1
INT
RST
NORMAL OPERATION (NO SWITCHES ACTIVE)
tWD2
tRST
Figure 3. Watchdog Interrupt/Reset Timing Diagram
6
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Automotive Contact Monitor and Level Shifters with LDO Regulator
Typical Operating Characteristics
(BAT = +14V, SD = VBAT, RWET = 61k, RHYST = 90k, CTDEB = 4700pF, CTD = 4700pF, TA = +25C, unless otherwise noted.)
MAX13037/MAX13038
WETTING CURRENT vs. VBAT
MAX13037/8toc01
WETTING CURRENT vs. RWET
MAX13037/8toc02
WETTING CURRENT PULSE (NORMAL MODE, WTOFF = 0, WEN = WEND = 1)
MAX13037/8toc03
30 20 WETTING CURRENT (mA) 10 0 -10 -20 -30 6 10 14 18 22 BAT-CONNECTED SWITCH GND-CONNECTED SWITCH
50 40 WETTING CURRENT (mA) 30 20 10 0 -10 -20 -30 -40 -50 BAT-CONNECTED SWITCH GND-CONNECTED SWITCH
VIN_ 10V/div
INT 2V/div
IIN_ 20mA/div
26
30
80
130
180 RWET (k)
230
280
330
20ms/div
VBAT (V)
BAT CURRENT vs. TEMPERATURE (NORMAL MODE)
MAX13037/8toc04
BAT CURRENT vs. TEMPERATURE (NORMAL MODE)
MAX13037/8toc05
BAT CURRENT vs. TEMPERATURE (SCANNING MODE)
LDO = ON SCANNING PERIOD = 2ms
MAX13037/8toc06
110 100 90 80 70 IBAT (A) ADJUSTABLE HYSTERESIS ON
8 SD = LOW 7 6 IBAT (A) 5 4 3 2
45
40
60 50 40 30 20 10 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) ADJUSTABLE HYSTERESIS OFF
IBAT (A)
35 SCANNING PERIOD = 64ms
30 25
1 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 20 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
TYPICAL IN0 DRIVING (NORMAL MODE, WTOFF = WEN = WEND = 0)
MAX13037/8toc07
TYPICAL IN0 DRIVING (NORMAL MODE, WTOFF = WEN = WEND = 0)
MAX13037/8 toc08
HYSTERESIS vs. RHYST
ADJUSTABLE HYSTERESIS ON 7 6 HYSTERESIS (V) 5 4 3 2 1
MAX13037/8toc09
f = 5kHz
f = 100Hz ADJUSTABLE HYSTERESIS OFF VIN0 5V/div
8
VIN0 5V/div
VDO0 2V/div
VDO0 2V/div
40s/div
2ms/div
0 0 200 400 600 800 1000 RHYST (k)
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
Typical Operating Characteristics (continued)
(BAT = +14V, SD = VBAT, RWET = 61k, RHYST = 90k, CTDEB = 4700pF, CTD = 4700pF, TA = +25C, unless otherwise noted.)
SWITCHING THRESHOLD vs. TEMPERATURE
MAX13037/8toc10
SWITCHING THRESHOLD vs. VBAT
MAX13037/8toc11
INPUT WAVEFORM IN SCAN MODE (SCAN MODE, WTOFF = WEN = 0, WEND = 1)
SCANNING PERIOD = 2ms INPUT SWITCH OPEN
MAX13037/8toc12
10 ADJUSTABLE HYSTERESIS OFF SWITCHING THRESHOLD (V) 9
20 ADJUSTABLE HYSTERESIS OFF SWITCHING THRESHOLD (V) 15 VIN_ RISING 10
8 VIN_ RISING 7 VIN_ FALLING 6
VIN_ 5V/div
5 VIN_ FALLING 0
5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6
10
14
18
22
26
400s/div
VBAT (V)
DEBOUNCE TIME vs. TEMPERATURE
MAX13037/8toc13
DEBOUNCE TIME vs. BAT VOLTAGE
MAX13037/8toc14
DEBOUNCE TIME vs. CTDEB
MAX13037/8toc15
60 58 56 DEBOUNCE TIME (ms) 54 52 50 48 46 44 42 40
51
120 100 DEBOUNCE TIME (ms) 80 60 40 20
DEBOUNCE TIME (ms)
50
49
48
47 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 6 10 14 18 22 26 VBAT (V)
0 0 2000 4000 6000 8000 10,000 CTDEB (pF)
VLO OUTPUT VOLTAGE vs. TEMPERATURE
MAX13037/8toc16
VLO OUTPUT VOLTAGE vs. LOAD CURRENT
5.0 VLO OUTPUT VOLTAGE (V) 4.5 4.0 3.5 3.0 MAX13038 2.5 MAX13037
MAX13037/8toc17
5.5
5.5
VLO OUTPUT VOLTAGE (V)
5.0
4.5
4.0 3.5
3.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
2.0 0 50 100 150 200 LOAD CURRENT (mA)
8
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
Typical Operating Characteristics (continued)
(BAT = +14V, SD = VBAT, RWET = 61k, RHYST = 90k, CTDEB = 4700pF, CTD = 4700pF, TA = +25C, unless otherwise noted.)
WATCHDOG INTERRUPT AND RESET PERIOD vs. TEMPERATURE
MAX13037/8toc19 MAX13037/8toc18
VLO TRANSIENT LOAD REGULATION
100
WATCHDOG INTERRUPT AND RESET PERIOD vs. CTD
MAX13037/8toc20
150 125 100 75 50
ILO 50mA/div
90 PERIOD (ms)
80
VLO (AC-COUPLED) 50mV/div
70
60
PERIOD (ms) -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
25 0 0 2000 4000 6000 8000 10,000 CTD (pF)
50 1ms/div
Pin Description
PIN 1, 15, 31 2 3 4 5 6 7 8 9 10, 11, 34 12 13 14 16 17 18 NAME GND IN0 IN1 IN2 IN3 IN4 IN5 IN6 IN7 N.C. HYST WET TDEB OT INT TD Ground Switch Input Channel 0. Connect IN0 to a switch connected to GND. IN0 can be programmed as a direct input with a level-shifted output on DO0 (see the Mechanical Switch Inputs (IN0-IN7) section). Switch Input Channel 1. Connect IN1 to a switch connected to GND. IN1 can be programmed as a direct input with a level-shifted output on DO1 (see the Mechanical Switch Inputs (IN0-IN7) section). Switch Input Channel 2. Connect IN2 to a switch connected to GND. Switch Input Channel 3. Connect IN3 to a switch connected to GND. Switch Input Channel 4. Connect IN4 to a switch connected to GND or BAT. Switch Input Channel 5. Connect IN5 to a switch connected to GND or BAT. Switch Input Channel 6. Connect IN6 to a switch connected to GND or BAT. Switch Input Channel 7. Connect IN7 to a switch connected to GND or BAT. No Connection. Not internally connected. Hysteresis Input. Connect HYST to GND with a 0 to 900k resistor to set the input voltage hysteresis on IN0-IN7. Wetting Current Input. Connect a 30k to 330k resistor from WET to GND to set the wetting current on IN0-IN7. Switch Debounce Time Input. Connect a 500pF to 10nF capacitor from TDEB to GND to set the switch debounce time. Overtemperature Warning Output. OT is an open-drain output that asserts low when the thermal warning threshold is exceeded. Interrupt Output. INT is an open-drain output that asserts low when one or more of the IN0-IN7 inputs change state and are enabled for interrupts or when the watchdog times out. Reset and Watchdog Timeout Input. Connect TD to GND with a 500pF to 10nF capacitor to set the timeout period for the reset and watchdog. FUNCTION
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
Pin Description (continued)
PIN 19 NAME SD REGON REGOFF CS SDO SDI CLK RST DO1 DO0 THRESH WDI BATREF FUNCTION Shutdown Input. Drive SD low to place the MAX13037/MAX13038 into shutdown mode and disable the linear regulator. Drive SD high for normal operation. SD is compatible with voltages up to VBAT. Linear Regulator Enable Input (Active Low). Connect REGON to INT to enable a wake-up when a switch status change is detected. Drive REGON using an open-drain logic output to control the regulator directly. REGON is internally pulled up to an internal bias voltage of approximately +4.8V. Linear Regulator Disable Input (Active Low). REGOFF is used in conjunction with REGON when the internal regulator is enabled by an interrupt (see the Low-Dropout Linear Regulator (VLO) section). SPI Chip-Select Input. Drive CS low to enable the clocking of data into and out of the MAX13037/MAX13038. SPI data is latched into the MAX13037/MAX13038 on the rising edge of CS. SPI Serial-Data Output. SPI data is output on SDO on the rising edges of CLK while CS is held low. SDO is three-state when CS is high. 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 100k pulldown resistor. SPI Serial-Clock Input Reset Output. RST is an open-drain output that asserts low when VLO is below the threshold determined by the THRESH input. RST also asserts low when the watchdog times out. Data Output Channel 1. DO1 is the level-shifted output of IN1 when WEND = 0. Data Output Channel 0. DO0 is the level-shifted output of IN0 when WEND = 0. Reset Threshold Level Input. Connect THRESH to a resistor divider between VLO and GND to set the reset reference level. Watchdog Timer Input. The watchdog timer is reset at every transition on the WDI input. Battery Reference Input. Switch thresholds are set to 50% of the voltage applied to BATREF. Connect BATREF to the system's battery supply voltage. Linear Regulator Output. VLO is the output of an internal linear regulator and is the reference voltage for all digital I/O. Bypass VLO with a 2.2F or greater ceramic capacitor. Alternatively, a 10F electrolytic capacitor can be used in parallel with a 0.1F ceramic capacitor. Battery Supply Input. Connect BAT to a positive +6V to +26V battery supply voltage. Bypass BAT to ground with a 0.1F ceramic capacitor and a 10F electrolytic capacitor placed as close as possible to BAT. Exposed Paddle. Connect EP to GND.
20
21 22 23 24 25 26 27 28 29 30 32
33
VLO
35, 36 --
BAT EP
10
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Automotive Contact Monitor and Level Shifters with LDO Regulator
Functional Diagram
SD BAT
MAX13037/MAX13038
LINEAR REGULATOR
VLO WDI RESET + WATCHDOG THRESH TD
MAX13037 MAX13038
REGON REGOFF
WAKE-UP LOGIC
DO0 BATREF DIGITAL INTERFACE CS IN0 IN1 IN2 IN3 IN4 IN5 IN6 IN7 INTERRUPT LOGIC WETTING CURRENT CONTROL LEVEL TRANSLATORS SPI INTERFACE CLK SDI SDO SHIFT REGISTER INT RST OT DO1
WET
HYST
TDEB
GND
Detailed Description
The MAX13037/MAX13038 automotive contact monitor and level shifters monitor and debounce eight remote mechanical switches and assert an interrupt (INT) if a switch changes state. Any of the switch inputs can be prohibited from asserting an interrupt. The switch threshold levels are set to 50% of the voltage applied to BATREF and all switch inputs feature a common adjustable hysteresis, debounce time, and wetting current. Two switch inputs (IN0, IN1) are programmable to have direct outputs (DO0, DO1), useable for PWM or other timing-based signals. The MAX13037/MAX13038 feature an SPI interface to monitor individual switch inputs and to configure interrupt masking, hysteresis, and wetting current enable/disable, switch configuration (batteryconnected or ground-connected), and scanning period.
The MAX13037/MAX13038 provide an internal low dropout (LDO) linear regulator capable of supplying up to 150mA. The LDO can be enabled or disabled through two digital control inputs: REGON and REGOFF. A watchdog timer and power-on reset circuitry is provided on the MAX13037/MAX13038 to supervise external microcontrollers (C). The MAX13037/MAX13038 feature three modes of operation: normal mode, scanning mode, and shutdown mode. In normal mode, the part is fully functional and internal sensing resistors are connected to all switch inputs. In scanning mode, the sensing resistors are connected for a finite duration to reduce power consumption. In shutdown mode, all switch inputs are high impedance and the internal LDO is switched off to further reduce power consumption.
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11
Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
BAT
BAT is the main power-supply input. Bypass BAT to ground with a 0.1F ceramic capacitor placed as close as possible to BAT. In addition, bypass BAT with a 10F or greater capacitor. BAT can withstand DC voltages up to +42V.
Linear Regulator Wake-Up
Regulator wake-up can be controlled with the INT output by connecting it to REGON. REGON is a TTL input with an internal pullup to a low-voltage internal reference of +4.8V (typ). With this control scheme, any change of the input switches (enabled for interrupt generation) causes the regulator to turn on, thus providing power to any external circuitry connected to VLO. If an external microcontroller is supplied from V LO , the microcontroller can keep the LDO on by forcing REGOFF high. Reading from the MAX13037/MAX13038 over the SPI interface causes the INT output to go into high-impedance so that both INT and REGON are pulled high. After this phase, the microcontroller can turn off the regulator again by driving REGOFF low. Note that it is also possible to tie multiple open-drain active-low outputs in an ORing configuration, allowing the wakeup of the regulator from other devices. If the INT output is not used to control the regulator, connect the REGOFF input to ground and use REGON to enable or disable the regulator as shown in Figure 4.
Low-Dropout Linear Regulator (VLO) The MAX13037/MAX13038 contain an internal LDO linear regulator supplied by the BAT input. The LDO output voltage is present on V LO and is capable of supplying up to 150mA of current. The MAX13037 output voltage is set to +5V and the MAX13038 output voltage is set to +3.3V.
The LDO regulator is controlled through the REGON and REGOFF inputs as shown in Figure 4. REGON is an input able to withstand voltages up to VBAT. The LDO startup time is 1ms (typ). There are two options for controlling the linear regulator: * Wake-Up on Interrupt: In this case, REGON is connected to INT and when the MAX13037/MAX13038 generate an interrupt, the linear regulator is turned on, thus providing power to the local Cs. The C pulls REGOFF high to keep the regulator on before making an SPI read (which causes INT and REGON to go high). The linear regulator can then be turned off by pulling REGOFF low. * Direct Control: In this case, the regulator is enabled/disabled by some other signal in the system which must be connected to REGON. If REGOFF is not used, it must be connected to GND to allow the turnoff of the LDO.
Watchdog Timer (WDI)
The MAX13037/MAX13038 feature a watchdog timer that is reset on every transition on the WDI input. If there is no transition on WDI before the first timeout period (tWD1) the INT output asserts low. If there is still no transition on WDI after the second timeout period (tWD2), the RST output is pulsed low for tRST and the INT output deasserts (see Figure 3). The watchdog timeout period can be adjusted by changing the capacitor value on the TD input. tRST (ms) = 2 x CTD (nF) tWD1 = 4 x tRST (ms) tWD2 = 8 x tRST (ms) Note that WDI can be tied to the CS input to allow a watchdog reset for every read/write operation over the SPI interface. To avoid any corruption of the internal command register, it is necessary to transmit the full programming word (16 bits) for every CS negative pulse.
LDO ON REGON = 0 REGOFF = 0
REGOFF = 1
LDO ON REGON = 0 REGOFF = 1
REGOFF = 0
REGON = 1
REGON = 0
REGON = 0
REGON = 1
Reset Output (RST)
LDO OFF REGON = 1 REGOFF = 0 REGOFF = 0 LDO ON REGON = 1 REGOFF = 1
REGOFF = 1 IS NOT ALLOWED BECAUSE VLO IS ABSENT.
The RST output asserts low when a watchdog timeout occurs or when the LDO output voltage drops below a certain threshold. The threshold voltage is set by connecting an external voltage divider on the THRESH input between VLO and GND. The voltage on THRESH is compared with an internal reference voltage of +1.24V and if it is lower, the RST output asserts low for tRST and remains low if VLO does not rise above the threshold.
Figure 4. Linear Regulator State Diagram
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Automotive Contact Monitor and Level Shifters with LDO Regulator
Mechanical Switch Inputs (IN0-IN7)
IN0-IN7 are the inputs for remote mechanical switches. The status of each switch input is indicated by the SW0 through SW7 bits in the status register, and each switch input can be programmed to not assert an interrupt (INT) by writing to the P0-P7 bits in the command register. All switch inputs are configured to assert an interrupt upon power-up. The first four inputs (IN0-IN3) are intended for groundconnected switches. The remaining four inputs (IN4-IN7) can be programmed in sets of two for either ground-connected or battery-connected switches by writing to the M0 and M1 bits (see Table 5). The default state after power-up is IN2-IN7 configured for ground-connected switches, and IN0/IN1 configured for direct inputs. All switch inputs have internal 16k sense resistors to detect switch transitions. Inputs configured for groundconnected switches are pulled up to BAT and inputs configured for battery-connected switches are pulled down to GND. Figure 5 shows the switch input structure for IN0 and IN1. IN0 and IN1 can be programmed as direct inputs with level-shifted outputs (DO0 and DO1) by clearing the WEND bit in the command register (normal mode only). When programmed as direct inputs, IN0 and IN1 can be used for PWM or other signaling. Clearing the WEND bit disables the sense resistors and wetting currents on IN0 and IN1. When programmed as direct inputs, the status of IN0 and IN1 is not reflected in the status register, and interrupts are not allowed on these inputs.
Switch Threshold Levels and Hysteresis (BATREF, HYST)
Input thresholds for the remote switches are 50% of the voltage applied to BATREF. The BATREF input is typically connected to the battery voltage before the reversebattery protection diode. The MAX13037/MAX13038 feature adjustable hysteresis on the switch inputs by connecting an external 0 to 900k resistor from HYST to ground (normal mode only). Short HYST to ground to obtain the maximum hysteresis of (0.5 x VBATREF). The approximate formula for hysteresis is given below: 43 VHYST = 0.166 + (VBATREF ) (123 + (RHYST(k) ) To reduce power consumption, the adjustable hysteresis can be disabled by setting [SC2:SC1:SC0 = 1:1:0] in the command register. When the adjustable hysteresis is disabled, the hysteresis is set to 0.166 x VBATREF.
MAX13037/MAX13038
Switch Debounce and Deglitch
The switch inputs IN0-IN7 share a common programmable debounce timer to increase the noise immunity of the system in normal and scan mode. The switch debounce time is set by connecting a capacitor between the t DEB input and ground. The minimum value of this capacitor is 500pF and the maximum value is 10nF, corresponding to a debounce time of 5ms to 100ms respectively. To calculate other debounce times the following formula should be used: C(nF) = tDEB(ms) / 10 All switch input glitches of less than 20s in duration are automatically rejected by the MAX13037/MAX13038.
VBAT
MAX13037 MAX13038
CONTROL LOGIC WETTING* CURRENT 16k*
Debounce in Normal Mode When a change of state occurs at the switch input the debounce timer starts. If the new state is stable for at least tDEB, the status register is updated and an interrupt is generated (if enabled). If the input returns to its previous state before the debounce time has elapsed, an interrupt is not generated and the status register is not updated. Debounce in Scan Mode A change of state at the switch input causes the device to automatically enter normal mode and the debounce timing to start. The device remains in normal mode as long as the input state differs from the previous state. As soon as the debounce time ends, the status register is updated, an interrupt is generated, and the device re-enters scan mode. If the input returns to its previous state before the end of the debounce time, the device re-enters scan mode, an interrupt is not generated, and the status register is not updated.
13
IN0, IN1
NOTES: *WETTING CURRENT AND PULLUP/DOWN RESISTORS ARE CONTROLLED BY THE WEN AND WEND BITS IN THE COMMAND REGISTER (SEE TABLE 4).
Figure 5. Input Structure of IN0 and IN1
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
Wetting Current (WET)
The MAX13037/MAX13038 feature adjustable wetting current to any closed switch to clean switch contacts that are exposed to adverse conditions. The wetting current is set by connecting a 30k to 330k resistor from WET to ground. A 30k resistor corresponds to a wetting current of 40mA (typ) and a 330k resistor corresponds to a 4mA (typ) wetting current. See the Typical Operating Characteristics section for the relationship between the wetting current and RWET. The WEN and WEND bits in the command register enable and disable the wetting currents and the WTOFF bit allows the wetting current to be activated for a duration of 20ms (typ) (see the Command Register section). Disabling wetting currents, or limiting the active wetting current time reduces power consumption. The default state upon power-up is all wetting currents disabled. Wetting current is activated on closed switches just after the debounce time. The wetting current pulse starts after the debounce time. A wetting current pulse is provided to all closed switches when a valid input change is detected. Wetting current rise and fall times are controlled to enhance EMC performance. There is one wetting current timer for all switch inputs. Therefore, it is possible to observe wetting pulses longer than expected whenever two switches turn on in sequence and are spaced out less than tWET. In scan mode, the wetting current is enabled during the polling pulse only. When using wetting currents, special care must be taken to avoid exceeding the maximum power dissipation of the MAX13037/MAX13038 (see the Applications Information section). asserts when the first watchdog timeout period elapses (tWD1). A pullup resistor to VLO is needed on INT. INT is cleared when CS is driven low for a read/write operation. The INT output still asserts when VLO is disabled provided that it is pulled up to a different supply voltage.
Thermal Protection (OT)
The MAX13037/MAX13038 feature a two-level thermal protection strategy that prevents the device from being damaged by overheating. At the initial warning temperature of +135C (typ), only wetting currents are disabled. The MAX13037/MAX13038 return to normal operation after the internal temperature decreases below +120C (typ). This protection feature is disabled when WEN = 0 or when all inputs are open. At the second thermal warning temperature of +170C (typ), the LDO is shut down. Because a C is often supplied by the LDO, an overheating event caused by excessive power dissipation related to I/O wetting currents is normally resolved without affecting the C status. An open-drain, active-low output (OT) asserts low when the internal temperature of the device rises above the thermal warning threshold. OT is immediately cleared when the CS input is driven low for read/write operations, regardless of whether the temperature is above the threshold, or not. The overtemperature status of the MAX13037/MAX13038 can also be monitored by reading the OT bit in the status register. The OT bit is set when the internal temperature rises above the temperature threshold, and it is cleared when the temperature falls below the temperature hysteresis level. This allows a C to monitor the overtemperature status, even if the OT output has been cleared. See Figure 6 for an example timing diagram of the overtemperature alerts. If desired, the OT and INT outputs can be connected to the same C GPIO in a wired-OR configuration to save a C pin. The OT output still asserts when VL is absent provided that it is pulled up to a different supply voltage.
Switch Outputs (DO0, DO1)
DO0 and DO1 are direct level-shifted outputs of the switch inputs IN0 and IN1 when the WEND bit of the command register is cleared and when operating in normal mode. When configured as direct inputs, the wetting currents and sensing resistors are disabled on IN0 and IN1. DO0 and DO1 are three-stated when the WEND bit is set or when operating in scan mode. When programmed as direct inputs, the status of IN0 and IN1 are not reflected in the status register and interrupts are not allowed on these inputs.
TEMPERATURE
OT
Interrupt Output (INT)
INT is an active-low, open-drain output that asserts when any of the switch inputs change state, as long as the particular input is enabled for interrupts (set by clearing P7-P0 in the command register). INT also
14
CS
OT BIT
Figure 6. Example Timing Diagram of the Overtemperature Alerts
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
STATUS REGISTER IS COPIED TO SHIFT REGISTER CS CLK SDI SDO * = UNUSED. 15 14 13 SC1 SW5 12 SC0 SW4 11 10 9 M1 SW1 8 M0 SW0 7 P7 OT 6 P6 * 5 P5 * 4 P4 * 3 P3 * 2 P2 * 1 P1 * 0 P0 * SHIFT REGISTER IS COPIED TO COMMAND REGISTER
WTOFF SC2 SW7 SW6
WEN WEND SW3 SW2
Figure 7. SPI Read/Write Example
Serial Peripheral Interface (CS, SD0, SDI, CLK)
The MAX13037/MAX13038 operate as a Serial Peripheral Interface (SPI) slave devices. An SPI master accesses the MAX13037/MAX13038 by reading from a status register and writing to a command register. Both registers are 16 bits long and are accessed most significant bit (MSB) first. On the falling edge of CS, the status register is immediately loaded to an internal shift register and the contents are transferred out of the SDO output on the rising edge of CLK. Serial data on the SDI input is latched into the shift register on the falling edge of CLK. On the rising edge of CS, the contents of the shift register are copied to the command register (see Figure 7). The status and command registers are 16 bits wide, so it is essential to clock a total of 16 bits while CS is low for the input and output data to be valid. When CS is high, the SDO output is high-impedance and any transitions on CLK and SDI are ignored. The INT and OT flags are cleared on the CS falling edge. Input status changes occurring during the CS reading/writing operation are allowed. If a switch status changes when CS is low, the interrupt is asserted as usual. This allows the part to be used even if VLO is disabled provided that the INT output is pulled up to another supply voltage.
Status Register The status register contains the status of the switches connected to IN7 through IN0 and it also contains an overtemperature warning bit (see Table 1). The status register is accessed through an SPI-compatible master.
Notes: Bits 15-8: Switch 7 Through 0 Status (SW7-SW0) SW7 through SW0 reflect the status of the switches connected to inputs IN7 through IN0, respectively. Open switches are returned as a [0] and closed switches are returned as a [1]. Bit 7: Overtemperature Warning (OT) The OT bit returns a [1] when the internal temperature of the MAX13037/MAX13038 is above the temperature warning threshold of +135C (typ). The OT bit returns a [0] when the MAX13037/MAX13038 is either below the temperature threshold, or it has fallen below the temperature hysteresis level following an overtemperature event. Bits 6-0: Unused Bits 6 through 0 are unused and should be ignored.
Command Register The command register is used to configure the MAX13037/MAX13038 for various modes of operation and is accessed by an SPI-compatible master (see Table 2). The power-on reset (POR) value of the command register is 0x00.
Table 1. Status Register
BIT NAME 15 SW7 14 SW6 13 SW5 12 SW4 11 SW3 10 SW2 9 SW1 8 SW0 7 OT 6 -- 5 -- 4 -- 3 -- 2 -- 1 -- 0 --
Table 2. Command Register
BIT NAME POR 15 WTOFF 0 14 SC2 0 13 SC1 0 12 SC0 0 11 WEN 0 10 WEND 0 9 M1 0 8 M0 0 7 P7 0 6 P6 0 5 P5 0 4 P4 0 3 P3 0 2 P2 0 1 P1 0 0 P0 0
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Automotive Contact Monitor and Level Shifters with LDO Regulator
Notes: Bit 15: Wetting Current Mode (WTOFF) Set the WTOFF bit to configure the wetting currents as continuous on closed switches. Clear the WTOFF bit to configure the wetting current as a pulse where the wetting current is turned on for a set duration of 20ms after a switch closes (and the debounce is timed out). After 20ms elapses, the wetting current is turned off. Either wetting current mode is only applicable to switches that have wetting currents enabled (see WEN and WEND bits). In scan mode, the wetting currents are on for the polling time of 250s (typ) and are pulsed at the programmed scanning period. When WTOFF is set, the wetting current continuously pulses at the programmed scanning period. When WTOFF is cleared, the wetting current pulses at the programmed scanning period, but turns off after 20ms elapses. Bits 14, 13, 12: Scanning Period (SC2, SC1, SC0) The SC2, SC1, and SC0 bits are used to program the scanning period as depicted in Table 3. Switch inputs are simultaneously polled for a finite duration of 250s (typ), and polling occurs at a period selected through the SC2, SC1, and SC0 inputs. Figure 8 shows a timing diagram of switch scanning and sampling. When the inputs are not being polled, the sense resistors are disconnected, reducing the current consumption caused from polling closed switches. For a continuous scanning
MAX13037/MAX13038
period ([SC2:SC1:SC0] = [1:1:1] or [1:1:0]), the switch inputs are constantly being monitored and the sense resistors are always connected. The state [SC2:SC1:SC0] = [1:1:0] also disables adjustable hysteresis (normally set by RHYST) and fixes hysteresis at 0.166 x VBATREF. When adjustable hysteresis is not needed, it is recommended to disable this feature to reduce power consumption. Bit 11: Global Wetting Current Enable (WEN) The WEN bit is a global enable for the wetting currents on all the channels. Set the WEN bit to enable wetting currents on all channels and clear the WEN bit to disable wetting currents. Even with wetting currents globally enabled, the wetting currents and sense resistors on IN0 and IN1 can still be turned off with the WEND bit (see Table 4). Bit 10: IN0 and IN1 Wetting Current Enable (WEND) The WEND bit is used to turn on wetting currents and sense resistors on inputs IN0 and IN1. Set the WEND bit to enable wetting currents on IN0 and IN1 and clear the WEND bit to turn off the wetting current and sense resistors on IN0 and IN1. When the wetting currents and sense resistors are disabled (WEND = 0), IN0 and IN1 are configured as direct inputs with level-shifted outputs on DO0 and D01. DO0 and DO1 can only be used as level-shifted outputs in normal mode and are three-stated in scan mode (see the Scan Mode section). Note that both the WEN and WEND bits need to be set for wetting currents to be enabled on IN0 and
Table 3. Programmable Scanning Period
SC2 0 0 0 0 1 1 1 1 SC1 0 0 1 1 0 0 1 1 SC0 0 1 0 1 0 1 0 1 SCANNING PERIOD (ms) 64 32 16 8 4 2 Continuous/adjustable hysteresis off Continuous
SWITCH CLOSES STATUS REGISTERS AND INT ARE UPDATED AFTER tDEB INT GND-CONNECTED SWITCH INPUT tSCAN-P tSCAN SWITCHES ARE POLLED FOR 250s SWITCH DEBOUNCE STARTS
tDEB
Figure 8. Switch Sampling in Scan Mode
Table 4. Truth Table for WEN and WEND
WEN 0 0 1 1 WEND 0 1 0 1 WETTING CURRENT (IN0, IN1) Off Off Off On 16k SENSE RESISTOR (IN0, IN1) Off On Off On WETTING CURRENT (IN2-IN7) Off Off On On 16k SENSE RESISTOR (IN2-IN7) On On On On
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Automotive Contact Monitor and Level Shifters with LDO Regulator
Table 5. Switch Configuration Controlled by M1 and M0
M1 0 0 1 1 M0 0 1 0 1 IN7 AND IN6 SWITCH CONFIGURATION Ground Ground Battery Battery IN5 AND IN4 SWITCH CONFIGURATION Ground Battery Ground Battery IN3-IN0 SWITCH CONFIGURATION Ground Ground Ground Ground
MAX13037/MAX13038
IN1 (see Table 4). The DO0 and DO1 outputs are threestated when WEND = 1. When programmed as direct inputs (WEND = 0), any input changes on IN0 and IN1 are not reflected by the status register. Bits 9 and 8: Switch Configuration for IN7-IN4 (M1, M0) The M1 and M0 bits set the switch configuration in groups of two for IN7 through IN4 (see Table 5). Set M1 to configure IN7 and IN6 for battery-connected switches and clear M1 for ground-connected switches. Set M0 to configure IN5 and IN4 for battery-connected switches and clear M0 for ground-connected switches. Bits 7-0: Interrupt Enable for IN7-IN0 (P7-P0) The P7 through P0 bits allow independent control of whether inputs IN7 through IN0 generate an interrupt (INT). Set any bit to disable interrupts on the corresponding input and clear the bit to enable interrupts on the corresponding channel. An interrupt is asserted when any input configured for interrupts changes state. IN0 and IN1 do not generate an interrupt when configured as direct inputs (WEND = 0).
command register to ([SC2:SC1:SC0] = [1:1:0]). The hysteresis is set to 0.166 x VBATREF when adjustable hysteresis is disabled.
Operating Modes
The MAX13037/MAX13038 feature three modes of operation: normal mode, scan mode, and shutdown mode. Normal mode is entered when the scanning period bits in the command register are configured for continuous scanning ([SC2:SC1:SC0] = [1:1:1] or [1:1:0]). Scan mode is entered when the scanning period bits are set for a periodic scanning time as shown in Table 3. Shutdown mode is entered by driving the shutdown input (SD) low. The default mode after power-up is scan mode (when SD = high) with a scan period of 64ms.
Scan Mode In scan mode, each sense resistor is connected for a finite duration of 250s (typ) and is repeated at a period according to the scanning period bits SC2, SC1, and SC0 (see Table 3). All input resistors are connected simultaneously and the inputs are polled at the same time. When all external switches are open and the scanning period is set to 64ms the scanning mode reduces current consumption to typically 28A (LDO on) and 17A (LDO off). Wetting currents (if enabled) are applied to closed switches during the polling time of 250s (typ) and are pulsed at the programmed scanning period. When WTOFF is set, the wetting current continuously pulses at the programmed scanning period. When WTOFF is cleared, the wetting current pulses at the programmed scanning period, but turns off after 20ms elapses. Inputs IN0 and IN1 cannot be used as direct inputs (WEND = 0) in scan mode. When configured as direct inputs in scan mode, the outputs DO0 and DO1 are high impedance. The quiescent current for a given scan mode can be calculated by the following formula (LDO off):
1 IBAT(A) = 16 x 1 + t SCAN _ P(ms) Where V BAT = SD = +14V, I BAT is the BAT current expressed in microamps and tSCAN_P is the scanning period expressed in milliseconds.
Normal Mode (Continuous Scanning) In normal mode, the input sense resistors are always connected to the switch inputs to detect any input status change (except IN0 and IN1 when WEND = [0]). Wetting currents are enabled according to the WEN, WEND, and WTOFF bits in the command register. If adjustable hysteresis is not required, this feature can be disabled to reduce power consumption (see the Typical Operating Characteristics) by setting the scanning period bits in the
Shutdown Mode In shutdown mode, the LDO is disabled, all switch inputs are high impedance and the external switches are no longer monitored, reducing current consumption on BAT to 2.85A (typ). The MAX13037/MAX13038 reset upon entering shutdown mode and the contents of the command register are lost. Exit shutdown mode by bringing the voltage on SD above +2.4V. The SD input is compatible with voltages up to V BAT . The MAX13037/MAX13038 take 200s (typ) to exit shutdown
17
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Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
at which point the command register is restored to its power-up default (0x00) and the MAX13037/ MAX13038 enter scan mode. Note that SD is compatible with both logic and BAT voltage levels. Having SD compatible to VBAT allows the MAX13037/MAX13038 to retain the settings in the command register as well as input monitoring even when VLO is disabled, provided that SD = VBAT.
ESD Protection
As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. The IN7-IN0 inputs have extra protection against static electricity. Maxim's engineers have developed state-of-the-art structures to protect these pins against ESD of 8kV without damage.
Applications Information
Automotive Considerations
Reverse-Battery Tolerance The BATREF and IN0-IN7 inputs can withstand voltages down to -45V without damage so that reverse battery is not an issue. The BAT input should be protected with a reverse-battery diode as shown in the Typical Application Circuit. The shutdown (SD) and REGON inputs can be controlled from a battery-level source, but should be protected against reverse battery in the application.
Human Body Model The MAX13037/MAX13038 IN7-IN0 pins are characterized for 8kV ESD protection using the Human Body Model. Figure 7a shows the Human Body Model, and Figure 7b shows the current waveform it generates when discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the device through a 1.5k resistor.
RC 1M RD 1500 DISCHARGE RESISTANCE DEVICE UNDER TEST
Power Dissipation
Wetting currents and the LDO output current can result in overheating the MAX13037/MAX13038. At the early thermal warning threshold of +135C (typ), wetting currents are disabled. This allows the LDO output to remain enabled if overheating is caused by the wetting currents. At temperatures above +170C, the LDO is also turned off to avoid damage to the device. It is important to consider the effects of wetting currents on the power dissipated by the MAX13037/MAX13038. For example, assume all inputs are configured for a continuous wetting current of 25mA, all external switches have an on-resistance of 1 and the battery voltage is +16V. If all switches are simultaneously closed, the corresponding power dissipated due to wetting currents only is (16V - (25mA x 1)) x 25mA x 8 = 3.12W, which is higher than the absolute maximum power dissipation of 2857mW at +70C. The LDO is a second source of power dissipation. For example, if VLO = +3.3V, ILO = 100mA and VBAT = +16V, the power dissipated by the LDO is (16V - 3.3V) + (0.1) = 1.27W. Both the LDO and wetting currents should be taken into account for correct use of the MAX13037/MAX13038.
CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE
Cs 100pF
STORAGE CAPACITOR
Figure 7a. Human Body ESD Test Model
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
tDL CURRENT WAVEFORM
Figure 7b. Human Body Model Current Waveform
18
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Automotive Contact Monitor and Level Shifters with LDO Regulator
Pin Configuration
MAX13037/MAX13038
REGOFF
DO1
CLK
SD0
RST
SDI
TOP VIEW
REGON
CS
27
26
25
24
23
22
21
20
19
SD
DO0 THRESH WDI GND BATREF VLO N.C. BAT BAT
28
*EP
18 17 16 15
TD INT OT GND TDEB WET HYST N.C. N.C.
29 30 31 32 33 34 35 36
+
MAX13037/MAX13038
14 13 12 11 10
1
2
3
4
5
6
7
8
IN6
IN0
IN1
IN2
IN5
GND
TQFN (6mm x 6mm)
*CONNECT EXPOSED PADDLE TO GROUND
______________________________________________________________________________________
IN3
IN4
IN7
9
19
Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
Typical Operating Circuit
BATTERY +6V TO +26V, +42V LOAD DUMP ECU CONNECTOR 0.01F 0.01F
IN0
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN0
IN1
IN2
IN3
IN4
IN5
IN6
DO0 DO1
BATREF
BATREF
DO0 DO1 THRESH 4700pF TDEB
BAT 4700pF TDEB 47F 0.1F 0.1F
BAT
MAX13036
WET 90k HYST 30k SDI SDO CLK CS GND INT SD OT VL 0.1F SDO SDI CLK CS WDI
MAX13037 MAX13038
IN7
VLO
4700pF TD WET 61k HYST 30k REGOFF
REGON
4.7F
C
Chip Information
PROCESS: BiCMOS
20
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GND
RST
VLO
INT
SD
OT
Automotive Contact Monitor and Level Shifters with LDO Regulator
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX13037/MAX13038
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QFN THIN.EPS
21
Automotive Contact Monitor and Level Shifters with LDO Regulator MAX13037/MAX13038
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
22 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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