Datasheet
+
-
+
-
UV1
OV6
OV5
OV4
OV3
OV2
OV1
+IN1
-IN1
GND
AO
CO1
*
COPOL
UV6
UV5
UV4
UV3
UV2
UV1
* Open
Drain
AOSEL
*
OV1
RESERVED
+IN6
-IN6
CO6
REF
REF
LMV7231
COPOL
REF
UV6OV6
REF
V
IN
R1
R2
R3
V
OUT
10k
10k
*
Ch. 6
Ch. 1
V+
0.1 PF
LMV7231
SNOSB45E –FEBRUARY 2010–REVISED MARCH 2013
www.ti.com
APPLICATION INFORMATION
3 RESISTOR VOLTAGE DIVIDER SELECTION
The LMV7231 trip points can be set by external resistor dividers as shown in Figure 33
Figure 33. External Resistor Dividers
Each trip point, over-voltage, V
OV
, and under-voltage, V
UV
, can be optimized for a falling supply, V
THF
, or a rising
supply, V
THR
. Therefore there are 2
2
= 4 different optimization cases. Exiting the voltage detection window
(Figure 34), rising into and out of the window (Figure 35), entering the window (Figure 36), falling into and out of
the window (Figure 37). Note that for each case each trip point can be optimized for either a rising or falling
signal, not both. The governing equations make it such that if the same resistor, R3, and over/under-voltage
ratio, V
OV
/V
UV
, is used across the channels the same nominal current will travel through the resistor ladder. As a
result R2 will also be the same across channels and only R1 needs to change to set voltage detection window
maximizing reuse of resistor values and minimizing design complexity. Select the R3 resistor value to be below
100kΩ so the current through the divider ladder is much greater than the LMV7231 bias current. If the current
traveling through the resistor divider is on the same magnitude of the LMV7231 I
BIAS
, the I
BIAS
current will create
error in your circuit and cause trip voltage shifts. Keep in mind the greatest error due to I
BIAS
will be caused when
that current passes through the greatest equivalent resistance, REQ = R1‖(R2+R3), which will be seen by the
positive input of the window comparator, +IN.
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Product Folder Links: LMV7231