TCA9535: Schematic review

U2501 - TCA9535RTWR

Check

Status?

Comments

Within Supply Voltage Range?

 Yes - 1.8V

PCA Devices - 2.3 V - 5.5 V

TCA Devices - 1.65 V - 5.5 V

TCAL Devices - 1.08 V - 3.6 V

Local Decoupling Capacitors

Yes - C2506, C2507

Generally, a 0.1-uF capacitor is placed on VCC, as close to the device as possible

Verify the schematic pinout matches the data sheet pinout

Good

sometimes RTW is mixed up with PW package pinout

Check that the pullup resistors are present on the SDA and SCL net within the schematic.

 verify they exist on another schematic page

Unused GPIO pins configured as INPUT’s are biased to either VCC or GND via resistor

verify

Most of TI's IO expander portfolio do not include internal pull-up resistors on the p-port pins; the exceptions are PCF8575, PCF8574, PCF8574A, TCA9555|PCA9555, PCA9554|TCA9554, and TCA9554A|PCA9554A and therefore can be left floating.

An alternative approach is after powering up the device, any unused p-port pins can be set as an output (does not matter if set high or low).

TCAL agile IO expanders also have the ability to enable internal PU or PD resistors.

GPIO pins configured to OUTPUT must be current limited externally

 Verify

i.e. the push-pull output sources current from VCC or sinks current to GND. Ensure that the output is never tied directly to VCC, GND, or to another output that could contend with the push/pull output. Otherwise, IOH/IOL may not be limited and could exceed abs. max conditions of the device which could cause permanent damage.

Device address is unique on the bus unless using an I2C switch or I2C MUX to resolve conflicts

Good - only 1 IO expander in review

If the device has a /RESET pin, bias the pin high (preferably with a pull-up resistor) after powering up.

 n/a

If the device has a /INT pin and the /INT pin is used, tie this pin to a pull-up resistor.

verify PU resistor.