When the power supply ramp itself is slow, the RC network tends to get charged up along with the power-supply ramp up. When the power supply ramp is rapid, the R and C values can be calculated so that the time to reach the switching threshold of the schmitt trigger is enough to apply a long enough reset pulse. One of the issues with using RC network to generate PoR pulse is the sensitivity of the R and C values to the power-supply ramp characteristics. The resistor and capacitor values should be determined so that the charging of the RC network takes long enough that the supply voltage will have stabilised by the time the threshold is reached. A Schmitt trigger may be used to deassert the reset signal cleanly, once the rising voltage of the RC network passes the threshold voltage of the Schmitt trigger.
In VLSI devices, the power-on reset ( PoR) is an electronic device incorporated into the integrated circuit that detects the power applied to the chip and generates a reset impulse that goes to the entire circuit placing it into a known state.Ī simple PoR uses the charging of a capacitor, in series with a resistor, to measure a time period during which the rest of the circuit is held in a reset state. It ensures that the device starts operating in a known state.
POWER ON TIME GENERATOR
JSTOR ( December 2009) ( Learn how and when to remove this template message)Ī power-on reset ( PoR, POR) generator is a microcontroller or microprocessor peripheral that generates a reset signal when power is applied to the device.
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