LTC2910IGN datasheet(9/16 Pages) LINER

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LTC2910

2910fb

APPLICATIONS INFORMATION

2. Choose RB to complete the design

Once RA is known, RB is determined by:

=−

(2)

If any of the variables Vm, Im, or VUV change, then both

steps must be recalculated.

Positive Voltage Monitor Example

A positive voltage monitor application is shown in Figure

3. The monitored voltage is a 5V ±10% supply. Nominal

current in the resistive divider is 10µA.

1. Find RA to set the UV trip point of the monitor.

µA

A =≈

56 2

•

2. Determine RB to complete the design.

µA

B =−

≈

56 2

499

Negative Voltage Monitor Example

A negative voltage monitor application is shown in Figure

4. The monitored voltage is a –5V ±10% supply. Nominal

current in the resistive divider is 10µA. For the negative

case, 1V is subtracted from Vm and VUV.

1. Find RA to set the UV trip point of the monitor.

µA

A =

−

≈

54 9

•

–

–.

2.Determine RB to complete the design.

µA

B =

−

−≈

–

57 6

549

Power-Up/Down

As soon as VCCreaches1Vduringpowerup,the⎯R⎯S⎯Toutput

asserts low and the RST output weakly pulls to VCC.

The LTC2910 is guaranteed to assert ⎯R⎯S⎯T low and RST

high under conditions of low VCC, down to VCC = 1V. Above

VCC = 2V (2.1V maximum) the Vn inputs take control.

Once all inputs and VCC become valid, an internal timer is

started. After an adjustable delay time, RST pulls low and

⎯R⎯S⎯T weakly pulls high.

Threshold Accuracy

Reset threshold accuracy is important in a supply sensitive

system. Ideally, such a system would reset only if supply

Figure 3. Positive Supply Monitor

2910 F02

449k

56.2k

± 10%

RST

SEL

VCC

GND

LTC2910

Figure 4. Negative Supply Monitor

2910 F04

54.9k

549k

–5V

± 10%

RST

SEL

REF

VCC

GND

LTC2910

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