TPS61088: Dynamically changing output voltage - better to use a DAC or digital pot?

Derek

Part Number: TPS61088
Other Parts Discussed in Thread: PMP9774,

Hello,

I have an application where we're using the TPS61088 to drive a motor. Input is 3 'C' cells, nominal voltage from 4.6V down to 3.6V. Motor voltage is 6V. I'd like to be able to vary the motor voltage from 4.5V to 6V. Is it better to use a digital potentiometer on the high side resistor of the FB pin, or would be be better to inject a DC voltage like the PMP9774 reference design? Rate of change is slow, like changing the value once per second.

Thanks,

Derek

over 5 years ago

0 Helen chen over 5 years ago

TI__Mastermind 40080 points

Hi Derek,

Both use a digital potentiometer on the high side resistor of the FB pin, or inject a DC voltage like the PMP9774 are good method. You can use either one of them.

0 Derek over 5 years ago in reply to Helen chen

Mastermind 9721 points

Hello, what voltage should I input to the FB pin to change the TPS61088 output voltage from 4.5V to 6V? For the feedback resistors, I currently am using Rtop=224k and Rbottom=56k, for a computed output voltage of 6V. Or should I set these for 4.5V and then use the DAC to increase it?

Thanks

0 Helen chen over 5 years ago in reply to Derek

TI__Mastermind 40080 points

Hi Derek,

If you reuse the PMP9774 circuit: when external add DC voltage Vdd=0V, Vo=4.5V; when Vadd=1V, Vomax=6V. Please check the parameter in the below circuit.

0 Helen chen over 5 years ago in reply to Derek

TI__Mastermind 40080 points

By the way, for the TPS61088, the output voltage should be always about 0.5V higher than the input voltage. Please take care about this during the design. Suggest you increase the output voltage to 5V-6.5V since your Vin-max=4.6V.

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TPS61088: Dynamically changing output voltage - better to use a DAC or digital pot?