MAX13037 Datasheet, PDF (18/22 Pages) Maxim Integrated Products – Automotive Contact Monitor and Level Shifters with LDO Regulator

Automotive Contact Monitor and
Level Shifters with LDO Regulator
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 compati-
ble with both logic and BAT voltage levels. Having SD
compatible to V_BAT allows the MAX13037/MAX13038 to
retain the settings in the command register as well as
input monitoring even when V_LO is disabled, provided
that SD = V_BAT.
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 pro-
tected against reverse battery in the application.
Power Dissipation
Wetting currents and the LDO output current can result in
overheating the MAX13037/MAX13038. At the early ther-
mal warning threshold of +135°C (typ), wetting currents
are disabled. This allows the LDO output to remain
enabled if overheating is caused by the wetting currents.
At temperatures above +170°C, 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 switch-
es have an on-resistance of 1Ω 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 1Ω)) x 25mA x 8 = 3.12W, which
is higher than the absolute maximum power dissipation
of 2857mW at +70°C.
The LDO is a second source of power dissipation. For
example, if V_LO = +3.3V, I_LO = 100mA and V_BAT =
+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.
ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static 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.
Human Body Model
The MAX13037/MAX13038 IN7–IN0 pins are charac-
terized for ±8kV ESD protection using the Human
Body Model. Figure 7a shows the Human Body Model,
and Figure 7b shows the current waveform it gener-
ates 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 1.5kΩ resistor.
R_C 1MΩ
CHARGE-CURRENT-
LIMIT RESISTOR
R_D 1500Ω
DISCHARGE
RESISTANCE
HIGH-
VOLTAGE
DC
SOURCE
Cs
100pF
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 7a. Human Body ESD Test Model
I_P 100%
90%
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
AMPERES
36.8%
10%
0
0 _tRL
TIME
t_DL
CURRENT WAVEFORM
Figure 7b. Human Body Model Current Waveform
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