LTC2904 データシートの表示（PDF） - Linear Technology

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LTC2904

Precision Dual Supply Monitors with Pin-Selectable Thresholds

Linear Technology 

TIMING DIAGRAM

VX Monitor Timing

VRTX

VX

tUV

tRST

RST

LTC2904/LTC2905

1V

RST

1V

29045 TD

APPLICATIONS INFORMATION

Supply Monitoring

The LTC2904/LTC2905 are low power, high accuracy dual

supply monitors with a common reset output and selectable

thresholds. Reset delay is set to a nominal of 200ms for

the LTC2904 and is adjustable using an external capacitor

for the LTC2905.

The two 3-state input pins (S1 and S2) select one of nine

possible threshold voltage combinations. Another three-

state input pin sets the supply tolerance (5%, 7.5% or

10%). Both input voltages (V1 and V2) must be above

predetermined thresholds for the reset not to be invoked.

The LTC2904/LTC2905 assert the reset outputs during

power-up, power-down and brownout conditions on either

of the voltage inputs.

Power-Up

The greater of V1, V2 is the internal supply voltage (VCC).

VCC powers the drive circuits for the RST pin. Therefore as

soon as V1 or V2 reaches 1V during power-up, the RST

output asserts low.

VCC also powers the drive circuits for the RST pin in the

LTC2904. Therefore, RST weakly pulls high when V1 or

V2 reaches at least 1V.

Threshold programming is complete when V1 reaches

at least 2.17V. After programming, if either V1 or V2 falls

below its programmed threshold, RST asserts low (RST

weakly pulls high) as long as VCC is at least 1V.

Once V1 and V2 rise above their thresholds, an internal

timer is started. After the programmed delay time, RST

weakly pulls high (RST asserts low).

29045fd

9

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