SN74AHC16244: A

Sri Krishna Govind A

Part Number: SN74AHC16244
Other Parts Discussed in Thread: SN74LVC1G125, SN74AHCT1G125, SN74AHC1G125

Hello, I would like to add a PWM Buffer between my MCU and a PWM Port to be connected to a cooling fan ( From Noctua). I would like to add a buffer between the output of the MCU, and the PWM input to the BLDC Fan, to prevent any accidental short between the 12V Supply of the fan and its PWM port from affecting my MCU. Would like part recommendations to do this, along with any typical application circuit. The switching frequency of the PWM would be anywhere from 21-29kHz. Thanks and Regards.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 281620 points

There are no buffers that tolerate 12 V at their output. If the buffer gets damaged and creates a short from the output to VCC, then all other devices connected to VCC might see 12 V.

Anyway, you can use any 5 V buffer, such as the SN74AHC1G125 or SN74LVC1G125. When using a 3.3 V MCU, you can use the SN74AHCT1G125 to convert to 5 V.

0 Sri Krishna Govind A over 2 years ago in reply to Clemens Ladisch

Prodigy 10 points

Thanks for the reply. My concern is if there is a 12V short b/w VCC and the PWM port of the Fan, is there any chance that upon the buffer's damage, can it can introduce the 12V to the MCU? I mean, can the buffer's damage potentially cause any short between the 12V VCC of the fan and the MCU via the buffer. And if so, would there be any isolated buffers that can be utilized. Thanks and regards

+1 Clemens Ladisch over 2 years ago in reply to Sri Krishna Govind A

Guru 281620 points

There are no guarantees; a short to its VCC is possible.

You could isolate the signal with a discrete transistor. But such a short would also damage the PWM input of the fan.

Logic

Logic forum

SN74AHC16244: A