LTC2913 Linear Technology, LTC2913 Datasheet - Page 7

• Manufacturer Part Number: LTC2913
• Description: Dual UV/OV Voltage Monitor
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
Voltage Monitoring
The LTC2913 is a low power dual voltage monitoring
circuit with two undervoltage and two overvoltage inputs.
A timeout period that holds OV and UV asserted after all
faults have cleared is adjustable using an external capacitor
and is externally disabled.
Each voltage monitor has two inputs (VHn and VLn) for
detecting undervoltage and overvoltage conditions. When
configured to monitor a positive voltage V
3-resistor circuit configuration shown in Figure 1, VHn
is connected to the high side tap of the resistive divider
and VLn is connected to the low side tap of the resistive
divider.
3-Step Design Procedure
The following 3-step design procedure determines ap-
propriate resistances to obtain the desired UV and OV trip
points for the voltage monitor circuit in Figure 1.
For supply monitoring, V
ing voltage, I
resistive divider, V
and V
1. Choose R
overvoltage monitor.
Figure 1. 3-Resistor Positive UV/OV Monitoring Configuration
R
R
A
A
UV
is chosen to set the desired trip point for the
= 0 5 . •
is the desired undervoltage trip point.
V
n
R
R
R
I
n
C
B
A
A
V
n
is the desired nominal current through the
to obtain the desired OV trip point
V
V
LTC2913
VHn
VLn
OV
OV
n
+
–
is the desired overvoltage trip point
0.5V
n
is the desired nominal operat-
–
+
–
+
UV
OV
n
2913 F01
n
n
using the
(1)
2. Choose R
Once R
point for the undervoltage monitor.
3. Choose R
Once, R
If any of the variables V
step must be recalculated.
Voltage Monitor Example
A typical voltage monitor application is shown in Figure 2.
The monitored voltage is a 5V ±10% supply. Nominal cur-
rent in the resistive divider is 10µA.
1. Find R
2. Find R
3. Determine R
R
R
R
R
R
B
C
B
C
A
= 0 5 . •
=
=
=
=
A
A
10
10
V
A
10
B
0 5
I
is known, R
0 5
and R
n
n
5
I
.
.
to set the OV trip point of the monitor.
to set the UV trip point of the monitor.
n
µ A
V
µ A
µ A
B
V
C
–
V
V
to complete the design
Figure 2. Typical Supply Monitor
to obtain the desired UV trip point
R
•
C
B
•
–
5V ±10%
A
V
4 5
5 5
to complete the design.
V
are known, R
45 3
UV
5
–
V1
5
n
.
.
V
V
R
R
442k
R
10.2k
R
45.3k
.
V
V
C
B
A
–
B
B
k
n
–
R
≈
is chosen to set the desired trip
, I
−
A
45 3
45 3
n
10 2
, V
VH1
VL1
.
.
.
UV
k
LTC2913
k
k
C
GND
V
V
≅
or V
5V
CC
CC
is determined by:
≈
10 2
2913 F02
442
OV
UV
OV
.
k
k
change, then each
LTC2913
2913fa
7
(2)
(3)