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Original question:

TCA9535: QFN package differences (VQFN vs WQFN), besides thermal performance?

TCA9535: Configuration setting

Shunsuke Nagata
Genius 12240 points
Part Number: TCA9535
Other Parts Discussed in Thread: TCA6416A

Hi, 

I've several question for initial setting for TCA9535. Could you please give me your help?

1. Is there recommend sequence for setting register? e.g. Polarity Inversion Port 0→Polarity Inversion Port 1→Configuration Port 0→Configuration Port 1

2. How should user set I2C Fast mode? Is there a specific bit to set Fast or Standard mode?

3. Power-on-reset time: How long will POR take in the case of VDD = 1.8V? e.g Master MCU should wait ?? us after power on. 

Regards,
Nagata.

  • 0
    TI__Guru 62910 points

    Hello Nagata-san,

    There isn't a required sequence for the register writes.  In most applications, though, it would be best to make sure any output ports are configured to a correct state before being being set as outputs (for example, so they do not briefly drive the output "low" when it is expected for it to be "high").

    The device supports either fast mode or standard mode I2C communication, and no special settings are required in order to enable one or the other.  The user should just make sure their I2C communication meets the level and timing requirements for these modes as defined in the I2C standard.  (These requirements are what show up in the I2C interface specifications of this datasheet.)

    The power-on-reset circuit works by holding the internal logic in a default state until the VPORR threshold is reached.  So, as soon as the VCC voltage reaches this threshold the device would be OK to use.

    Please let us know if this is not clear or if you have additional questions.

    Regards,
    Max

  • 0
    TI__Mastermind 49660 points

    "1. Is there recommend sequence for setting register?"

    If you are setting something to be an output for the first. I would recommend you set the output registers first then go set the configuration register. Otherwise if you set the configuration register first, then the pins will automatically be set to OUTPUT HIGH immediately. This may be unwanted if you didn't plan to have a certain pin go HIGH.

    "2. How should user set I2C Fast mode? Is there a specific bit to set Fast or Standard mode?"

    You don't have to set anything. Just toggle the SCL line between 100kHz and 400kHz for fast mode. Our device will sample the data a little bit after the rising clock.

    "3. Power-on-reset time: How long will POR take in the case of VDD = 1.8V? e.g Master MCU should wait ?? us after power on. "

    It should be instantaneous. TCA6416A uses the same internal PoR block as the TCA9535 but has a reset pin (for TCA9535you can assume Vcc is tied to the reset internally). In that datasheet the tREC is set to 0ns so there shouldn't be any waitting necessary.

    -Bobby

  • 0 in reply to BOBBY
    TI__Genius 12240 points

    Bobby, 

    For 1 : Are your recommend procedure Output / input register(COMMAND byte: 0x00~0x03) -> Configuration register (COMMAND byte : 0x06/0x07)-> Polarity register (COMMAND byte :0x04/0x05)?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Guru 62910 points

    Nagata-san,

    In general you may want to make sure the desired output logic state (high or low) is configured before the port is configured as an output.  To do this, you would write the output port registers (command bytes 0x02 and 0x03) and polarity inversion registers (command bytes 0x04 and 0x05) to the desired values, then configure the port as an output by writing to the configuration registers (command bytes 0x06 and 0x07).

    Regards,
    Max