Low-power 60-minute timer with operating current of 1MA - News - Global IC Trade Starts Here.

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Circuit Function

It is common practice to use a rechargeable CR timer that can last for a few minutes. However, as the required timing duration increases, the values of the resistor and capacitor must also increase, which presents practical limitations. A more effective solution for achieving longer durations is to incorporate an internal frequency divider. By dividing the output of the clock oscillator through a multi-stage frequency divider, long-term timing can be achieved. Additionally, using CMOS devices ensures minimal power consumption.

Circuit Working Principle

The TC9160 consists of an oscillating circuit and a 20-bit ground counter. The maximum timing capability is one hour, with the oscillator's oscillation frequency approximately at 1 kHz. The oscillation frequency FOSC of the 60-minute timer can be calculated using the following formula:

The value of the timing resistor should be above 200K. Based on the condition C2 ≤ 1/(2.2 × FOSC × RT), if C2 is 1800pF, then RT would need to be 216.76 ohms. To achieve this resistance value, a 180K resistor and a 50K variable resistor can be connected in series. The output is of an open-drain type, where OUT1~4 provides a division ratio of 1/4 of 60 minutes. Once the timing period ends, the oscillation stops, and the circuit consumes only about 1 microampere of current.