TCA9803: TCA9803 Pull Up Resistance Calculation

Tanveer Ahmed

Part Number: TCA9803

Hi,

I am using TCA9803 in my PCB for converting 1.8V I2C (at Side A) to 3.3V Level (at Side B)
For the calculation of the pull up resistors at the input of the TCA9803 IC, what should I consider:

VCCA = 1.8V or VCCB = 3.3V should be considered for Rp(min) calculation?
VOL should be 0.4V or some other values?
IOL should be 3mA or 3.3mA?

Kindly suggest me the correct value to be considered?

28 days ago

0 Clemens Ladisch 27 days ago

Guru 320490 points

1. There must not be any pull-up resistors on side B.

2. Yes; the I²C specification requires 0.4 V. (Side B uses a current source and has not specific V_OL.)

3. On the A side, the current is determined by the pull-up resistor. Use 3 mA, as required by the I²C specification.

0 Tyler Townsend 27 days ago

TI__Guru 55968 points

Hi Tanveer,

For the B-side, Clemens is correct.

For the A-side, you can utilize the VOLA and IOLA specs of the buffer to determine a pull-up resistor combined with the rise-time limitation of I2C spec and the bus capacitance on A-side.

please see this application note for more details: https://www.ti.com/lit/an/slva689/slva689.pdf?ts=1720204726016&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards,

Tyler

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TCA9803: TCA9803 Pull Up Resistance Calculation