LTC2912

7

2912fa

APPLICATIONS INFORMATION

Voltage Monitoring

The LTC2912 is a low power voltage monitoring circuit

with an undervoltage and an overvoltage input. A timeout

period that holds OV and UV asserted after a fault has

cleared is adjustable using an external capacitor and may

be externally disabled. When configured to monitor a posi-

shown in Figure 1, VH will be connected to the high side

tap of the resistive divider and VL will be connected to the

low side tap of the resistive divider.

3-Step Design Procedure

The following 3-step design procedure allows selecting

appropriate resistances to obtain the desired UV and OV

trip points for the voltage monitor circuit in Figure 1.

overvoltage monitor.

R

V

I

V

V

A

n

n

OV

=

05

.

•

(1)

point for the undervoltage monitor.

R

V

I

V

V

R

B

n

n

UV

A

=

05

.

•–

(2)

R

V

I

RR

C

n

n

AB

=

––

(3)

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.

R

V

µA

V

V

k

≈

05

10

5

55

45 3

.

•

.

.

R

V

µA

V

V

kk

≅

05

10

5

45

45 3

10 2

.

•

.

–.

.

R

V

µA

kk

k

−≈

5

10

45 3

10 2

442

–.

.

Figure 1. 3-Resistor Positive UV/OV Monitoring Configuration

Figure 2. Typical Supply Monitor

+

LTC2912

UV

VH

2912 F01

VL

OV

VH1

442k

10.2k

45.3k

GND

LTC2912-1

VL1

2912 F02

OV

UV

5V

V1

5V ±10%