Datasheet

ADM1178 Data Sheet
Rev. D | Page 22 of 24
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 over-
current condition occurs, the ADM1178 pulls this output low.
If any of the enabled latched alerts in the status byte (ADC_ALERT,
HS_ALERT, and OFF_ALERT) are triggered, the ALERTB output
asserts. For a programmable ADC-based overcurrent limit level
point, the ADC_ALERT latch must be enabled. The overcurrent
threshold that triggers an alert is then programmed via the
ALERT_TH register. This pin is disabled by default at power up.
See the ALERT_EN register to enable.
R
SENSE
N-CHANNEL FET
P = VI
CONTROLLER
ADM1178
SENSEVCC
SDA
SCL
SDA
SCL
GND
GATE
INTERRUPT
ALERTB
ADR
TIMER
3.15V TO 16.5V
ON
06048-100
Figure 49. Using the ALERTB Output as an Interrupt
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 four pad resistor can be used or a split pad layout
can be used with a two pad sense resistor to achieve Kelvin sensing.