ADM1192 Analog Devices, ADM1192 Datasheet - Page 16

• Manufacturer Part Number: ADM1192
• Description: Digital Power Monitor with Clear Pin and ALERT Output
• Manufacturer: Analog Devices

Specifications of ADM1192

• Max Pos Supply (v): +26V
• Current Monitoring: 2
• Glitch Filter: Programmable Timer
• Clrb Pin: X
• Alert/alertb: ALERT
• Number Of I2c Addresses: 4
• Package: MSOP

ADM1192
APPLICATIONS INFORMATION
ALERT OUTPUT
The ALERT output is an open-drain pin with 30 V tolerance.
There are two uses for this output.
Overcurrent Flag
The ALERT pin can be connected to the general-purpose logic
input of a controller. During normal operation, the ADM1192
drives this output low. When an overcurrent condition occurs,
the output asserts high. An external pull-up resistor should
be used.
Implementing a Basic Hot Swap Circuit
A basic P-channel FET hot swap circuit can be created. The
ALERT output should be connected to the GATE pin of a P-
channel FET connected in series with the power path. A pull-up
from GATE to source ensures that the P-channel FET GATE is
pulled up and the device held off as soon as power is applied.
When the ADM1192 powers up, the GATE is pulled low by the
ALERT output. A capacitor on the TIMER pin determines the
slew rate of the GATE pin at startup. Note that if a current fault
occurs during the operation, the ALERT output asserts high,
turning off the P-channel FET.
3.15V TO 26V
3.15V TO 26V
Figure 28. P-Channel FET Hot Swap Implementation
Figure 27. Using the ALERT Output as an Interrupt
TIMER
SETV
VCC
ADM1192
TIMER
SETV
R
VCC
GND
SENSE
ADM1192
R
SENSE
GND
SENSE
ALERT
CLRB
ADR
SDA
SCL
SENSE
ALERT
P-CHANNEL FET
CLRB
ADR
SDA
SCL
SDA
SCL
CLRB
CONTROLLER
INTERRUPT
SDA
SCL
CLRB
CONTROLLER
P = VI
P = VI
Rev. B | Page 16 of 20
SETV PIN
The SETV pin allows the user to adjust the current level that
trips the ALERT output. The output of the current sense amplifier
is compared with the voltage driven onto the SETV pin. If the
current sense amplifier output is higher than the SETV voltage,
the output of the comparator asserts. By driving a different voltage
onto the SETV pin, the ADM1192 detects an overcurrent condition
at a different current level, with a gain of 18. See Figure 12 for
an illustration of this relationship.
When the output of the SETV comparator asserts, this tells the
ALERT block to begin charging the external TIMER capacitor
with a 60 μA charging current. When the voltage on the TIMER
capacitor reaches 1 V, the charging cycle is complete. The ALERT
output then asserts (goes high). Different values of TIMER
capacitor generate different time delays between current faults
occurring and the ALERT output asserting. When using the
ALERT output to implement a hot swap circuit, the TIMER
capacitor should be chosen to generate a large enough startup
delay to allow the maximum inrush current to completely
charge up the load without tripping an ALERT fault.
VOLTAGE
APPLIED
SETV
VCC
R
SENSE
COMPARATOR
A
Figure 29. SETV Operation
AMPLIFIER
CURRENT
SENSE
SENSE
I
LOAD
ALERT
1.3V
ADM1192
TIMER
60µA
ALERT