Data Sheet ADM1191
Rev. C | Page 15 of 16
APPLICATIONS INFORMATION
ALERTB OUTPUT
The ALERTB output is an open-drain pin with 30 V tolerance.
This output can be used as an overcurrent flag by connecting it
to the general-purpose logic input of a controller. During normal
operation, this output is pulled high (an external pull-up resistor
should be used because this is an open-drain pin). When an
overcurrent condition occurs, the ADM1191 pulls this output low.
The ALERTB pin is disabled by default on power up. See the
ALERT_EN register to enable.
R
SENSE
P = VI
CONTROLLER
ADM1191
SENSEVCC
SDA
SCL
SDA
SCL
GND
ALERTB
CONV
CONV
A0
A1
3.15V TO 26V
SETV
INTERRUPT
05804-013
Figure 25. Using the ALERTB Output as an Interrupt
SETV PIN
The SETV pin allows the user to adjust the current level that
trips the ALERTB 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 ADM1191 detects an overcurrent
condition at a different current level, with a gain of 18. See
Figure 12 for an illustration of this relationship.
ADM1191
SETV
ALERT
CURRENT
SENSE
AMPLIFIER
A
ALERTB
R
SENSE
I
LOAD
APPLIED
VOLTAGE
SENSEVCC
COMPARATOR
05804-014
Figure 26. SETV Operation
KELVIN SENSE RESISTOR CONNECTION
When using a low value sense resistor for high current
measurement, the problem of parasitic series resistance can
arise. The pad and solder resistance can be a substantial fraction
of the rated resistance, making the total resistance larger than
expected. This error problem can be largely avoided by using a
Kelvin sense connection. This type of connection separates the
high current path through the resistor and the voltage drop
across the resistor. A 4-pad resistor may be used or a split pad
layout can be used with a 2-pad sense resistor to achieve Kelvin
sensing.
