LTC2913

7

2913fa

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

faultshaveclearedisadjustableusinganexternalcapacitor

and is externally disabled.

Each voltage monitor has two inputs (VHn and VLn) for

detecting undervoltage and overvoltage conditions. When

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.

overvoltage monitor.

R

V

I

V

V

A

n

n

OV

= 0 5

.

•

(1)

point for the undervoltage monitor.

R

V

I

V

V

R

B

n

n

UV

A

= 0 5

.

•

–

(2)

R

V

I

R

R

C

n

n

A

B

=

–

–

(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

≈

0 5

10

5

5 5

45 3

.

•

.

.

R

V

µA

V

V

k

k

≅

0 5

10

5

4 5

45 3

10 2

.

•

.

–

.

.

R

V

µA

k

k

k

−

≈

5

10

45 3

10 2

442

–

.

.

LTC2913

VHn

2913 F01

VLn

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

VH1

442k

10.2k

45.3k

GND

LTC2913

VL1

2913 F02

OV

UV

5V

V1

5V

±10%

Figure 2. Typical Supply Monitor