ADCMP671 AD [Analog Devices], ADCMP671 Datasheet - Page 14

• Manufacturer Part Number: ADCMP671
• Description: Low Power, Adjustable UV and OV Monitor
• Manufacturer: AD [Analog Devices]

ADCMP671
APPLICATIONS INFORMATION
The
reference that operates from 1.7 V to 5.5 V. The comparator is
0.275% accurate with a built-in hysteresis of 9.2 mV. The outputs
are open-drain, capable of sinking 40 mA.
COMPARATORS AND INTERNAL REFERENCE
There are two comparators inside the ADCMP671. The
comparator with its noninverting input connected to the INH
pin (and its inverting input connected internally to the 400 mV
reference) is for undervoltage detection, and the comparator
with its inverting input available through the INL pin (and its
noninverting input connected internally to the 400 mV reference)
is for overvoltage detection. The rising input threshold voltage of
the comparators is designed to be equal to that of the reference.
POWER SUPPLY
The
A 0.1 μF decoupling capacitor is recommended between V
and GND.
INPUTS
The comparator inputs are limited to the maximum V
range. The voltage on these inputs can be more than V
more than the maximum allowed V
resistor string to the input, choose resistor values carefully because
the input bias current is in parallel with the bottom resistor of
the string. Therefore, choose the bottom resistor first to control
the error introduced by the bias current.
To minimize the number of external components use three
resistor dividers to program the UV and OV thresholds.
HYSTERESIS
To prevent oscillations at the output caused by noise or slowly
moving signals passing the switching threshold, each comparator
has a built-in hysteresis of approximately 8.9 mV.
VOLTAGE MONITORING SCHEME
When monitoring a supply rail, the desired nominal operating
voltage for monitoring is denoted by V
through the resistor divider, V
and V
Figure 34 illustrates the voltage monitoring input connection.
Three external resistors, R
for monitoring (V
side voltage (V
pin, and the low-side voltage is connected to the INL pin.
ADCMP671
ADCMP671
UV
is the undervoltage trip point.
L
). The high-side voltage is connected to the INH
is a UV and OV monitor with a built-in 400 mV
is designed to operate from 1.7 V to 5.5 V.
M
) into the high-side voltage (V
X
, R
Y
, and R
OV
is the overvoltage trip point,
DD
Z
, divide the positive voltage
M
, I
voltage. When adding a
M
is the nominal current
H
) and low-
DD
DD
but never
voltage
DD
Rev. 0 | Page 14 of 16
To trigger an overvoltage condition, the low-side voltage (in this
case, V
low-side voltage, V
Also,
Therefore, R
monitor, is calculated using the following equation:
To trigger the undervoltage condition, the high-side voltage, V
must fall below the 0.4 V threshold on the INH pin. The high-
side voltage, V
Because R
When R
equation:
If V
R
R
R
X
Y
Z
12V
M
V
V
R
R
R
R
, I
Figure 34. Undervoltage/Overvoltage Monitoring Configuration
Y
L
Z
H
X
X
L
M
) must exceed the 0.4 V threshold on the INL pin. The
=
Y
, V
+
=
=
INH
=
=
INL
and R
V
Z
R
V
(
(
. 0 (
. 0 (
( )
( )
V
V
OV
OV
is already known, R
V
Y
Z
I
UV
, which sets the desired trip point for the overvoltage
OV
UV
M
M
) 4
, or V
) 4
+
⎛
⎜
⎜
⎝
H
⎛
⎜
⎜
⎝
( )
) ( )
R
( )
) ( )
, is given by the following equation:
Z
R
V
V
R
−
I
I
are known, R
X
Z
UV
OV
M
X
M
M
M
R
400mV
L
R
+
=
UV
, is given by the following equation:
+
Z
Y
R
R
V
−
I
−
R
changes each step must be recalculated.
+
Z
Y
M
M
Y
R
R
R
+
Z
+
Y
Z
R
5V
R
Z
Z
GND
V
⎞
⎟
⎟
⎠
ADCMP671
DD
⎞
⎟
⎟
⎠
X
=
Y
=
is calculated using the following
0
can be expressed as follows:
0
4 .
4 .
V
V
OV
PWRGD
Data Sheet
H
,