LTC1536CS8 データシートの表示（PDF） - Linear Technology

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LTC1536CS8

Precision Triple Supply Monitor for PCI Applications

Linear Technology 

WU

W

TI I G DIAGRA S

VCC Monitor Timing

VCCX

VRTX

tRST

RST

LTC1536

1536 TD01

Pushbutton Reset Function Timing

PBR

t < tPB

tPB

tRST

tDB

RST

tSRST

SRST

1536 TD02

tFAIL Fast Undervoltage Detect

VCC3 OR

VCC5

VRTX

SLEW RATE ≤0.1V/µs

500mV

tFAIL

RST

1536 TD03

Power-Fail Detect

FALL TIME ≤ 10ns, VCC3 = 3.3V

3.3V

VCC5

300mV

tPF

RST

1536 TD04

APPLICATIONS INFORMATION

Operation

The LTC1536 is a low power, high accuracy triple supply

monitoring circuit. This reset generator has two basic

functions: generation of a reset when power supplies are

out of range, and generation of a reset or “soft” reset when

the reset button is pushed. The LTC1536 has the added

feature that when the reset supplies are grossly undervolt-

age there is a very short delay from undervoltage detect to

assertion of RST.

Supply Monitoring

All three VCC inputs must be above predetermined thresh-

olds for 200ms before the reset output is released. The

LTC1536 will assert reset during power-up, power-down

and brownout conditions on any one or more of the VCC

inputs.

On power-up, either the VCC5 or VCC3 pin can power the

drive circuits for the RST pin. This ensures that RST will

be low when either VCC5 or VCC3 reaches 1V. As long as

any one of the VCC inputs is below its predetermined

threshold, RST will stay a logic low. Once all of the VCC

inputs rise above their thresholds, an internal timer is

started and RST is released after 200ms. RST outputs the

inverted state of what is seen on RST.

RST is reasserted whenever any one of the VCC inputs

drops below its predetermined threshold and remains

asserted until 200ms after all of the VCC inputs are above

their thresholds.

On power-down, once any of the VCC inputs drops below

its threshold, RST is held at a logic low. A logic low of 0.4V

is guaranteed until VCC3 and VCC5 drops below 1V.

Pushbutton Reset

The LTC1536 provides a pushbutton reset input pin. The

PBR input has an internal pull-up current source to VCC3.

If the PBR pin is not used it can be left floating.

1536fa

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