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PCF8575 output drive capability

Igal Kronshtein
Prodigy 120 points
Other Parts Discussed in Thread: PCF8575, PCA9555, PCA9539, PCA9535

Dear TI Support,

We are using the PCF8575 IO expander (Vcc = 5.0V)

Toggling output ports works ok when there is no load, but when connecting output load of (0.6mA - 0.8mA) the "high" output level reaches ~1.5V instead of 5V.

Unfortunately, in the datasheet the IOL is specified for VOL of 0.4V and 1.0V only.

We expect this part to operate as push-pull output 0V to 5.0V, directly connected to the described load, without additional external devices.

Please advice.

Thanks,

Igal

  • 0
    TI__Guru 62240 points

    Hi Igal ,

    Thank you for your query . Please give some time for a response from AE .

    It looks like the device cannot handle 0.6 to 0.8mA load on the output and hence it dips down to 1.5v . The datasheet mentions 300uA max IOH current .

  • 0 in reply to ShreyasRao
    Prodigy 120 points

    Hi Shreyas,

    Thank you for the support.

    In the PCF8575 datasheet - section 7.3 - Recommended Operating conditions, it is mentioned that IOH max is -1mA. Please advise as it is very confusing.

    300uA max IOH is very small and very disappointing, especially when all the alternative parts driving 10mA and above.

    If eventually, the PCF8575 can't drive more than 300uA, can you please recommend alternative footprint compatible part (SOIC24 to fit the SparkFun I2C Expander Breakout - PCF8575). I saw the PCA9535, PCA9539, PCA9555 that seems similar. What is difference between the parts? Which part is the bets fit?

    Thanks,

    Igal