Features and Benefits

  • Period Range: 1ms to 9.5 Hours
  • Configured with 1 to 3 Resistors
  • <1.5% Maximum Frequency Error
  • Output Reset Function
  • 2.25V to 5.5V Single Supply Operation
  • 55µA to 80µA Supply Current
  • (2ms to 9.5hr Clock Period)
  • 500µs Start-Up Time
  • CMOS Output Driver Sources/Sinks 20mA
  • –55°C to 125°C Operating Temperature Range
  • Available in Low Profile (1mm) SOT-23 (ThinSOT) and 2mm × 3mm DFN Packages
  • AEC-Q100 Qualified for Automotive Applications

Product Details

The LTC6991 is a silicon oscillator with a programmable 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 internal 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.

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


  • “Heartbeat” Timers
  • Watchdog Timers
  • Intervalometers
  • Periodic “Wake-Up” Call
  • High Vibration, High Acceleration Environments
  • Portable and Battery-Powered Equipment

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (1)

Tools & Simulations


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Models for the following parts are available in LTspice:


Reference Designs (2)

Product Recommendations

LTC6991 Companion Parts

Recommended Related Parts

Design Resources

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PCN-PDN Information

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Evaluation Boards

Pricing displayed is based on 1-piece.

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.