MAX13036 Datasheet, PDF (14/18 Pages) Maxim Integrated Products – Automotive Contact Monitor and Level Shifter

Automotive Contact Monitor
and Level Shifter
Table 5. Switch Configuration Controlled by M1 and M0
M1
M0
0
0
0
1
1
0
1
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
Table 4). The DO0 and DO1 outputs are tri-stated 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 corre-
sponding 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 confi-
gured as direct inputs (WEND = 0).
Operating Modes
The MAX13036 features three modes of operation: nor-
mal mode, scan mode, and shutdown mode. Normal
mode is entered when the scanning period bits in the
command register are configured for continuous scan-
ning ([SC2:SC1:SC0] = [1:1:1] or [1:1:0]). Scan mode is
entered when the scanning period bits are set for a peri-
odic 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.
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 hys-
teresis 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
command register to ([SC2:SC1:SC0] = [1:1:0]). The
hysteresis is set to 0.166 x V_BATREF when adjustable
hysteresis is disabled.
Scan Mode
In scan mode, each sense resistor is connected for a
finite duration of 250µs (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. Scan mode reduces the current consumption from
BAT to 17µA (typ) when all external switches are open
and the scanning period is 64ms. Wetting currents (if
enabled) are applied to closed switches during the
polling time of 250µs (typ) and are pulsed at the pro-
grammed 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 quies-
cent current for a given scan mode can be calculated
by the following formula:
I_BAT(μA)
= 16
×
⎛
⎜^{1 +}
⎝
1
⎞
t_{SCAN_}
P(ms)
⎟
⎠
Where SD = 3.3V, I_BAT is the BAT current expressed in
microamps and t_{SCAN_P} is the scanning period
expressed in miliseconds.
Shutdown Mode
In shutdown mode, all switch inputs are high impedance
and the external switches are no longer monitored, reduc-
ing current consumption on BAT to 2µA (typ). The
MAX13036 resets 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
MAX13036 takes 200µs (typ) to exit shutdown, at which
point the command register is restored to its power-up
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