MAX9921 Ver la hoja de datos (PDF) - Maxim Integrated
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MAX9921 Datasheet PDF : 16 Pages
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Dual, 2-Wire Hall-Effect Sensor Interface
with Diagnostics
Table 2. Diagnostic Truth Table (Diagnostic Mode)
INPUT
DIAG
1
1
1
1
1
1
1
1
ERR
0
0
0
0
1
1
1
1
OUTPUT
OUT1
0
0
1
1
0
0
1
1
OUT2
0
1
0
1
0
1
0
1
DIAGNOSIS
No fault
IN1 open circuit, or IN1 open circuit and fault on IN2
IN1 shorted to battery, or IN1 shorted to battery and fault on IN2
IN1 shorted to ground, or IN1 shorted to ground and fault on IN2
VBAT out of range, or power-up or restart and blanking cycle (dominant
fault masks all other faults)
IN2 open circuit
IN2 shorted to battery
IN2 shorted to ground
Hall Sensor Protection from Supply Transients
If the VBAT voltage is lower than 6V or exceeds 18V,
IN1 and IN2 shut off current to both Hall sensors and
ERR, OUT1, and OUT2 go low. When VBAT returns to
the proper range, both IN1 and IN2 restart, following a
blanking cycle.
Hall Inputs Open Condition
If either IN1 or IN2 is open (IIN < 2mA), the correspond-
ing input shuts off current to the Hall sensor. If IN1 or
IN2 is loaded, it exits the open input fault condition and
restarts the corresponding Hall input, following a blank-
ing cycle.
Hall Input Shorted to Battery
If either IN1 or IN2 is shorted to the battery (VIN > VBAT
+ 100mV), the MAX9921 shuts off current to the corre-
sponding Hall sensor. In this case, if IN1 or IN2 is more
than 1V above VBAT, it may back-drive current into
BAT. In such a condition, the current level in the Hall
input should not exceed 100mA. Therefore, all the
MAX9921s together can share a separate reverse-
polarity protection diode to avoid powering up other cir-
cuitry sharing a common diode (Figure 3).
BATTERY
REVERSE-POLARITY DIODE
FOR MAX9921s
RISET
RISET
REVERSE-POLARITY DIODE
FOR OTHER CIRCUITRY
MAX9921
BAT
DIAG
ISET
OE
IN1
ERR
IN2
OUT1
GND
OUT2
MAX9921
BAT
DIAG
ISET
OE
IN1
ERR
IN2
OUT1
GND
OUT2
BAT
OTHER
CIRCUITRY
GND
Figure 3. Several MAX9921s Connected to a Common Reverse-Polarity Diode
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