PCF8574: PCF8574 for reset pulse generation

Juan Journade

Prodigy 60 points

Part Number: PCF8574
Other Parts Discussed in Thread: TCAL6416, TCAL9539

Tool/software:

Hello I have a pcb design using a PCF8574 to generate a reset pulse for DRV8243 wake up.

Is it possible to get a 30 micro second with this io expander?

If not, is there some i2c alternative with same footprint SSOP?

Regards

over 1 year ago

0 Tyler Townsend over 1 year ago

TI__Guru 64738 points

Hi Juan,

Can you elaborate on the following statement?

Juan Journade said:
Is it possible to get a 30 micro second with this io expander?

What needs to be 30 us? Can you be more specific here?

Regards,

Tyler

0 Juan Journade over 1 year ago in reply to Tyler Townsend

Prodigy 60 points

Hello Tyler, below a figure from your TI DRV8243 mosfet.

To wake up a sequence is required at "SLEEP" pin. A 30 us reset pulse (pin low) is required put this device active.

As I don't have micro controller GPIOs available I tried with this io expander.

If you need some more detail let me know.

Regards,

Juan

0 Tyler Townsend over 1 year ago in reply to Juan Journade

TI__Guru 64738 points

Hi Juan,

You might need to write I2C FM+ in order to get a tRESET pulse < 30 us. The clocking period for 1 MHz i2c is 1 us. If you use 100kHz or 400kHz I2C bus, it will be too slow to change the output in time for a tRESET pulse.

A device like TCAL6416 or TCAL9539 might be better for this application.

Regards,

Tylerh

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PCF8574: PCF8574 for reset pulse generation