LPC 54606 Simulated open-drain

ceso — Thu, 28 Oct 2021 20:53:22 GMT

Hello,

Could someone please explain the difference between true open-drain like those on the i2c and serial busses on the LPC54606 compared to the Simulated open-drain found on the GPIO pins?

Trying to use the GPIO0_0 through GPIO0_2 to change the voltage before a sensor using sequential resistors with a GPIO output line in between them to toggle resistances. I want to make sure that the simulated open drain will not cause too much draw that will affect the reading when the output is turned off.

Thank you

Re: LPC 54606 Simulated open-drain

xiangjun_rong — Fri, 29 Oct 2021 04:47:29 GMT

Hi, Chris,

Regarding your question, I think the dedicated I2C pin are true open drain pins, which can be configured as I2C different mode.

For the non-I2C dedicated pin, you can configure them as open drain pin by setting the OD bit in IOCON register of each pin. In open drain mode, the top mosfet is disabled as the Fig, I copied from UM10912.pdf. So you can drive the PIN to only low, of course, the pin can be high with external pull-up resistor.

Regarding the pin sink current, the sink current is 6mA with the VOH is 0.4V at most. Pls refer to the Fig copied from data sheet.

Hope it can help you

XiangJun Rong

topic Re: LPC 54606 Simulated open-drain in LPC Microcontrollers

LPC 54606 Simulated open-drain

Re: LPC 54606 Simulated open-drain