I'm building a device around a cellular radio and the radio has a quirky power on sequence. It wants power (3.3V) for 30ms, then to have a power-on line (that is internally pulled up to 1.5V) pulled down for >500ms, then left to float back high.
I looked and couldn't find a reset controller that could be cajoled into working this way. So I debated for a bit and settled on solving it with a logic gate and a pair of R/Cs. My thought is to use a TI SN74LVC1G132 schmitt trigger NAND gate. For other parts of the board, I've already got an N channel mosfet and 1uF ceramic caps, so I figured I'd re-use those, add the resistors and only inflate by BOM by 3 parts. Any better suggestions, improvements or criticisms of this circuit?
I expect that I'll have to tinker with the resistor values to account for the input impedance of the nand gate.
I looked and couldn't find a reset controller that could be cajoled into working this way. So I debated for a bit and settled on solving it with a logic gate and a pair of R/Cs. My thought is to use a TI SN74LVC1G132 schmitt trigger NAND gate. For other parts of the board, I've already got an N channel mosfet and 1uF ceramic caps, so I figured I'd re-use those, add the resistors and only inflate by BOM by 3 parts. Any better suggestions, improvements or criticisms of this circuit?
I expect that I'll have to tinker with the resistor values to account for the input impedance of the nand gate.