EVAL-ADM1191EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADM1191EBZ' PDF : 16 Pages View PDF
ADM1191
Table 15. Status Byte Operations
Bit Name
Function
0 ADC_OC
An ADC-based overcurrent comparison has been detected on the last three conversions.
1 ADC_ALERT An ADC-based overcurrent trip has occurred, which has caused the alert. Cleared by writing to Bit 4 of the ALERT_EN
register.
2 OC
An overcurrent condition is present (that is, the output of the current sense amplifier is greater than the voltage on the
SETV input).
3 OC_ALERT An overcurrent condition has caused the ALERT block to latch a fault, and the ALERTB output has asserted. Cleared by
writing to Bit 4 of the ALERT_EN register.
4 OFF_STATUS Set to 1 by writing to the SWOFF bit of the CONTROL register.
5 OFF_ALERT An alert has been caused by the SWOFF bit. Cleared by writing to Bit 4 of the ALERT_EN register.
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. Under 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.
3.15V TO 26V
RSENSE
VCC SENSE
ALERTB
ADM1191
SETV
SDA
SCL
CLRB
TIMER
GND ADR
CONTROLLER
ALERTB
P = VI
SDA
SCL
CLRB
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, then 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 15 for an illustration of this
relationship.
RSENSE
ILOAD
VCC
SENSE
A CURRENT
SENSE
AMPLIFIER
ADM1191
APPLIED
VOLTAGE
SETV
COMPARATOR
ALERT
ALERT
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 lead resistance can be a substantial fraction of the
rated resistance, making the total resistance a function of lead
length. This problem can be avoided by using a Kelvin sense
connection. This type of connection separates the current path
through the resistor and the voltage drop across the resistor.
Figure 27 shows the correct way to connect the sense resistor
between the VCC pin and the SENSE pin of the ADM1191.
SENSE RESISTOR
CURRENT
FLOW FROM
SUPPLY
CURRENT
FLOW TO
LOAD
KELVIN SENSE TRACES
VCC
SENSE
ADM1191
Figure 27. Kelvin Sense Connections
Rev. 0 | Page 14 of 16
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