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Watchdog Timers: Introduction

Watchdog Timer (WDT)

Watchdog timer ICs (WDT) monitor whether or not the system operates normally by detecting periodical clock signals from an MCU.
They are also called supervisor IC, the same another name as voltage detectors (reset ICs) which detect supply voltage decrease.

If clock signals are not input within the timer period, the WDT judges that the system is under abnormal operation (or is going out of control), and outputs a reset signal.
There are two types of abnormality detection: the timeout type which detects abnormality by no signals within a certain period, and the window type which detects abnormality also by signals coming earlier than a certain cycle as well as no signals.

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  • *1 The MR pin is implemented only on the R5107.
  • *2 The function of the CD pin is integrated with CTW pin and named the CT pin on the R5106.
  • *3 CD is the capacitor for setting the VD output delay time.
  • *4 The function of the CTW pin is integrated with CD pin and named the CT pin on the R5106.
  • *5 CTW is the capacitor for setting the WDT monitoring time.
  • *6 The SENSE pin is implemented only on the R5108.

Various Types of WDTs Available

We have a wide lineup of WDTs featuring two types of clock input, a manual reset function (MR function), monitoring halt function by an INH pin, etc.
Besides, some of our products contain not only a WDT but also a voltage detector to monitor the supply voltage drop, and others incorporate an LDO regulator, a voltage detector, and a WDT in a single chip.