SN74LVC1G04: Slow Clock

Julian Chen

Expert 2550 points

Part Number: SN74LVC1G04
Other Parts Discussed in Thread: SN74LVC1G14

Dear E2E member,

we use SN74LVC1G04 to design the low clock ,

But the the 4 of U20 (Output) signal keep 1.5V at all, the waveform as below,

Ch.1 VCC

Ch.2 pin2 of U20

Ch.3 Pin4 of U20

If we use 74LVC14A (NXP) can work normally.

Did we use other part to design or need to modify the circuit?

over 6 years ago

0 Emrys Maier over 6 years ago

TI__Guru* 96591 points

I would recommend using the SN74LVC1G14 instead of the SN74LVC1G04 for U20. The 1G04 doesn't have any hysteresis on the input, so the device essentially latches once the input and output are at 1/2Vcc. I can't speak for NXP, but I would guess their device has some designed in hysteresis that is allowing it to oscillate.

Also, I would replace U19 with a schmitt-trigger inverter such as SN74LVC1G14 to reduce current consumption and clean up the clock output.

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SN74LVC1G04: Slow Clock