TPS23751 VFO

Munin Lin

Prodigy 230 points

Other Parts Discussed in Thread: TPS23751, TPS23751EVM-104

Hello,

I have project use TPS23751 but my system always work on heave load,

can you provide without VFO function the reference design?

Thank you.

over 11 years ago

0 Eric Wright over 11 years ago

TI__Mastermind 42795 points

To disable VFO, simply connect SRT to RTN.

0 Phong Nguyen over 10 years ago in reply to Eric Wright

Prodigy 20 points

How is about the case to disable PWM?

0 Eric Wright over 10 years ago in reply to Phong Nguyen

TI__Mastermind 42795 points

Do you mean to turn off the DC/DC completely so VOUT=0?

0 Phong Nguyen over 10 years ago in reply to Eric Wright

Prodigy 20 points

PWM is for heavy load. VFO is for light load. I just want it provides power for light load only.

0 Lonsn over 10 years ago in reply to Phong Nguyen

Prodigy 180 points

I have the same requirements. Can I remove the R30 in TPS23751EVM-104 for always in VFO mode? is there any power limitations for VFO mode(my power consumption is about 7W(5V 1.4A))?

Since I meet a strange situation, the TPS23751 switch VFO/PWM mode frequently(about 125KHz). I check it in the pin U3.2, there is a square waveform.

Then the 5V output is not stable(drop 0.3V) when TPS23751 switch mode.

0 Eric Wright over 10 years ago in reply to Lonsn

TI__Mastermind 42795 points

The recommended usable maximum for the PWM-VFO threshold (set at the SRT pin) is 1.5V. This correlates to a CTL pin threshold voltage of 2.5V (see EQ 2 in the datasheet). If your feedback loop demands current from the output less than 2.5V (programmed by CTL pin) then the circuit should remain in VFO mode if SRT is set at 1.5V.

For non-synchronous operation (using only D20 as the output rectifier) remove not only R3 but U3, Q7, Q4 (and associated gate drive circuitry).

Power management

Power management forum

TPS23751 VFO