ADS1015-Q1: Pull up requirement for ADS1015-Q1 multi device access using I2C

sundararao yanamala

Part Number: ADS1015-Q1

Hello,

I am conducting analysis on below circuit. Having doubt to use 10K pull up for this circuit. Please suggest appropriate pull up resistors.

over 8 years ago

0 Krunal Maniar over 8 years ago

TI__Intellectual 1610 points

Hello,

Thank you for your query. The I2C pull-up resistor values depend on the total bus capacitance as well as the I2C operating frequency. The rise and fall time are directly affected by the pull-ups and the bus capacitance.

What is your I2C operating frequency? We can provide a general recommendation here. For 100 kHz, a 10k ohms pull-up is a good starting point.

Thanks,
Krunal

0 Joseph Wu over 8 years ago

TI__Guru* 95205 points

Hi,

This wasn't written in our group, but it's a good reference for calculating pullup resistances:

www.ti.com/.../slva689.pdf

Joseph Wu

0 sundararao yanamala over 8 years ago in reply to Krunal Maniar

Intellectual 260 points

Hello Krunal,

Frequency of operation is about 400KHz, fast mode.

Connection flow as follows, Master to Level shifter which is having 4.7K pull up. Level shifter to 4ADC's here pull ups need to confirm.

Thanks

0 Krunal Maniar over 8 years ago in reply to sundararao yanamala

TI__Intellectual 1610 points

Hello,

You should be able to use the formula in the application report: http://www.ti.com/lit/an/slva689/slva689.pdf to calculate the pull-up value. You might have to estimate the parasitic capacitance though.

Assuming the parasitic capacitance ~100 pF and the supply = 3.3 V, you might want to start with a 2.2k ohm pull-up and tweak it if required.

May I know the end-application here?

Thanks,

Krunal

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ADS1015-Q1: Pull up requirement for ADS1015-Q1 multi device access using I2C