TCA9535: PWM capability of the IO expander

Jishnu E

Part Number: TCA9535
Other Parts Discussed in Thread: TCA6507, TCA9539-Q1, TCAL9539-Q1

Tool/software:

Hi Team,

I need to replace some signals from my controller with an IO expander. This includes PWM signals also. Could you please help me to understand what will be the minimum and maximum frequency supported by this IO expander for PWM signal.

Thanks

Jishnu

11 months ago

0 Clemens Ladisch 11 months ago

Guru 317310 points

This device does not have PWM capability. You would need to set the output high and low with explicit I²C commands, which is very slow, and requires a high processing overhead on the I²C master.

How many PWM signals are there? What are their characteristics? Do they have different values?

0 Tyler Townsend 11 months ago

TI__Mastermind 48228 points

Hi Jishnu,

Clemens' answer is accurate if using the TCA9535 for PWM.

Consider looking into the TCA6507 which has a built in oscillator and can generate PWM which can be configured through the I2C bus.

Regards,

Tyler

0 Jishnu E 10 months ago

Prodigy 10 points

Hello Clemens,

Thanks for your response.

Could you please what will be the maximum frequency of the signal that can be generated this way?

Hello Tyler,

I am looking for an automotive part, the part you suggested seems not an automotive grade.

Best regards

Jishnu

0 Clemens Ladisch 10 months ago in reply to Jishnu E

Guru 317310 points

At 400 kHz, the length of a write command is about 73 µs. I do not know how well your I²C master can control the timing of when a command begins.

0 Tyler Townsend 10 months ago in reply to Jishnu E

TI__Mastermind 48228 points

Hi Jishnu,

There is no automotive grade of the TCA6507.

Consider TCA9539-Q1, TCA6408-Q1, TCAL9539-Q1.

Regards,

Tyler

0 Jishnu E 10 months ago in reply to Tyler Townsend

Prodigy 10 points

Hi Tyler,

Thanks for the suggestion. But these parts are also do not support PWM feature right. Is there any other alternative available with PWM feature?

Thanks

Jishnu

0 Tyler Townsend 10 months ago in reply to Jishnu E

TI__Mastermind 48228 points

Hi Jishnu,

We do not have an IO expander that is automotive grade and supports PWM capability.

Only device currently is the TCA6507 for PWM capability.

You would have to do what Clemens was stating in earlier threads about making PWM with constant I2C writes. It is technically possible but would take up a large portion of the I2C bus bandwidth.

Regards,

Tyler

0 Jishnu E 10 months ago in reply to Tyler Townsend

Prodigy 10 points

Thanks Tyler and Clemens

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TCA9535: PWM capability of the IO expander