LTC2931HF 查看數據表（PDF） - Linear Technology

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LTC2931HF

Confi gurable Six Supply Monitor with Adjustable Reset and Watchdog Timers

Linear Technology 

LTC2931

PIN FUNCTIONS

COMP5 (Pin 1): Comparator Output 5. Real-time logic

output with weak 6μA pull-up to V2. Pulls high when V5

is above reset threshold. May be pulled greater than V2

using external pull-up. Leave open if unused.

V5 (Pin 2): Adjustable Voltage Input 5. High impedance

comparator input with 0.5V typical threshold. See

Applications Information for details. Tie to V1 if unused.

COMP3 (Pin 3): Comparator Output 3. Real-time logic

output with weak 6μA pull-up to V2. Pulls high when V3

is above its reset threshold. May be pulled greater than

V2 using external pull-up. Leave open if unused.

COMP1 (Pin 4): Comparator Output 1. Real-time logic

output with weak 6μA pull-up to V2. Pulls high when V1

is above its reset threshold. May be pulled greater than

V2 using external pull-up. Leave open if unused.

V3 (Pin 5): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V,

or ADJ. See Applications Information for details. Tie to

V1 if unused.

V1 (Pin 6): Voltage Input 1. Select from 5V or 3.3V. See

Applications Information for details. The greater of V1 or

V2 is also VCC for the device. Bypass this pin to ground

with a 0.1μF (or greater) capacitor.

CRT (Pin 7): Reset Timeout Capacitor. Attach an external

capacitor (CRT) to GND to set a reset timeout of 2ms/nF.

Leaving the pin open generates a minimum delay of

approximately 25μs. A 47nF capacitor generates a 94ms

reset delay time.

RST (Pin 8): Reset Output. Logic output with weak 6μA

pull-up to V2. Pulls low when any voltage input is below

the reset threshold and held low for the configured delay

time after all voltage inputs are above threshold. May be

pulled greater than V2 using external pull-up. Leave open

if unused.

WDO (Pin 9): Watchdog Output. Logic output with weak

6μA pull-up to V2. May be pulled greater than V2 using

external pull-up. The watchdog timer is enabled when RST

is high. The watchdog output pulls low if the watchdog timer

times out and remains low for one reset timeout period.

The watchdog output is cleared with a WDI transition or

anytime RST is low.The output will toggle between high

and low as long as the watchdog and reset timers are

allowed to time out. Leave open if unused.

WDI (Pin 10): Watchdog Input. A logic input whose rising

or falling edge must occur on this pin (while RST is high)

within the selected watchdog time-out period, prohibiting

a high-to-low transition on the WDO pin. The capacitor

attached to the CWT pin sets the watchdog time-out period.

A rising or falling edge on the WDI pin clears the voltage

on the CWT capacitor, preventing WDO from going low. Tie

WDI to V1 or GND if unused. Tie CWT to GND to disable

the watchdog function.

CWT (Pin 11): Watchdog Timeout Capacitor. Attach

a capacitor (CWT) between CWT and GND to set a

watchdog time-out period of 20ms/nF. Leaving the pin open

generates a minimum timeout of approximately 200μs.

A 47nF capacitor generates a 940ms watchdog time-out

period. Tie CWT to GND to disable the watchdog function.

GND (Pin 12): Ground.

VPG (Pin 13): Threshold Select Input. Connect to an

external 1% resistive divider between VREF and GND to

select 1 of 16 combinations and/or ±adjustable voltage

thresholds (See Table 1). Do not add capacitance on the

VPG pin.

VREF (Pin 14): Buffered Reference Voltage Output. A

1.210V nominal reference used for the mode selection

voltage (VPG) and for the offset of negative adjustable

applications. The buffered reference can source and sink

up to 1mA. The reference can drive a bypass capacitor of

up to 1000pF without oscillation.

V4 (Pin 15): Voltage Input 4. Select from 1.8V, 1.5V, ADJ

or –ADJ. See Applications Information for details. Tie to

V1 if unused and configured for positive voltage.

V2 (Pin 16): Voltage Input 2. Select from 3.3V, 3V or 2.5V.

See Applications Information for details. The greater of V1,

V2 is also VCC for the device. Bypass this pin to ground

with a 0.1μF (or greater) capacitor. All status outputs are

weakly pulled up to V2.

COMP4 (Pin 17): Comparator Output 4. Real-time logic

output with weak 6μA pull-up to V2. Pulls high when V4

is above its reset threshold. May be pulled greater than

V2 using external pull-up. Leave open if unused.

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