TCA9803: Internal Pull-up at VCCB pin

Kaushal C

Intellectual 440 points

Part Number: TCA9803

Please provide the internal pull-up value at VCCB pin of TCA9803DGKR

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 316690 points

V_CCB is a power-supply pin and has no pull-up.

The SDAB and SCLB pins have internal current sources; the datasheet specifies them as 3.3 mA ±25 %.

0 Kaushal C over 2 years ago

Intellectual 440 points

Yes what is the pull-up at SDAB and SCLB

0 Clemens Ladisch over 2 years ago in reply to Kaushal C

Guru 316690 points

SDAB and SCLB are pulled up by their current sources.

What is the actual problem you're trying to solve?

0 Kaushal C over 2 years ago in reply to Clemens Ladisch

Intellectual 440 points

So this is my connection and SDA/SCL of temperature sensor recommends 10K pull-up. Since this TCS9803 has internal pull-up at SDAB/SCLB, can you please say the value of internal pull-up

+1 Clemens Ladisch over 2 years ago in reply to Kaushal C

Guru 316690 points

The pull-ups to be used on an I²C bus depend on the frequency and on the total bus capacitance. That recommendation is either useless or wrong.

The TCA903 does not have internal pull-up resistors. It does have internal pull-up current sources, and you must not add pull-up resistors on the B side.

For how to choose the TCA90x device with the correct pull-up current, see section 12.2.1.2 of the datasheet.

0 Jack Guan over 2 years ago in reply to Clemens Ladisch

TI__Mastermind 40136 points

Hey Kaushal,

If B side is attempting to drive the line low but there are pull up resistors used on the B-side, then A-side will not be able to pull low since the current is not coming from the internal current source (you may also see lots of oscillations as well).

In short- its just best practice to not use external pull up resistors on B side of TCA980x devices as Clemens mentioned as well.

Regards,

Jack

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TCA9803: Internal Pull-up at VCCB pin