LTC6991

1

Rev. D

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TYPICAL APPLICATION

FEATURES

DESCRIPTION

TimerBlox: Resettable, Low

Frequency Oscillator

The LTC®6991 is a silicon oscillator with a program-

mable period range of 1.024ms to 9.54 hours (29.1µHz

to 977Hz), specifically intended for long duration timing

events. The LTC6991 is part of the TimerBlox® family of

versatile silicon timing devices.

A single resistor, RSET, programs the LTC6991’s inter-

nal master oscillator frequency. The output clock period

is determined by this master oscillator and an internal

frequency divider, NDIV, programmable to eight settings

from 1 to 221.

tOUT =

NDIV •RSET

50kΩ

• 1.024ms, NDIV = 1,8,64,...,221

In normal operation, the LTC6991 oscillates with a 50%

duty cycle. A reset function is provided to truncate the

pulse (reducing the duty cycle). The reset pin can also be

used to prevent the output from oscillating.

The RST and OUT pins can be configured for active-low

or active-high operation using a polarity function.

POL BIT

RST PIN

OUTPUT STATE

0

0

Oscillating

0

1

0 (reset)

1

0

1 (reset)

1

1

Oscillating

For easy configuration of the LTC6991, use the LTC6991:

Low Frequency Oscillator Web-Based Design Tool.

APPLICATIONS

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Period Range: 1ms to 9.5 Hours

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Configured with 1 to 3 Resistors

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<1.5% Maximum Frequency Error

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Output Reset Function

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2.25V to 5.5V Single Supply Operation

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55µA to 80µA Supply Current

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(2ms to 9.5hr Clock Period)

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500µs Start-Up Time

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CMOS Output Driver Sources/Sinks 20mA

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–55°C to 125°C Operating Temperature Range

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Available in Low Profile (1mm) SOT-23 (ThinSOT™)

and 2mm × 3mm DFN Packages

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AEC-Q100 Qualified for Automotive Applications

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“Heartbeat” Timers

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Watchdog Timers

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Intervalometers

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Periodic “Wake-Up” Call

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High Vibration, High Acceleration Environments

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Portable and Battery-Powered Equipment

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Low Frequency Pulse Generator

Clock Period Range over Eight Divider Settings

DIV PIN VOLTAGE, VDIV (V)

0

10Sec

10Min

2.5

6991 TA01b

100ms

1ms

0.625

1.25

1.875

10Hr

1Sec

1Min

10ms

1Hr

LTC6991

5V

0.1µF

OUT

R1

1M

R2

392k

RSET

715k

RST

GND

SET

OUT

V+

DIV

CPW

470pF

RPW

2.26k

6991 TA01a

60 SECONDS

1µs PULSE WIDTH

tPULSE ≈ RPW • CPW ≈ 1µs