TPS61372: Forced PWM mode

Sojeth Adili Rajan

Part Number: TPS61372

The TPS61372 integrates a power-save mode with pulse frequency modulation (PFM) at the light load. The device skips the switching cycles and regulate the output voltage at a higher threshold (typically 101.6% × VOUT_NORM).The auto PFM mode reduces the switching losses and improves efficiency at light load condition by reducing the average switching frequency

Whereas In the forced PWM mode, the TPS61372 keeps the switching frequency being constant across the whole load range. When the load current decreases, the output of the internal error amplifier decreases as well to lower the inductor peak current and delivers less power. The high-side FET is not turned off even if the current through the FET goes negative to keep the switching frequency be the same as that of the heavy load.

can you please elaborate this section? i found this in your data sheet

will the IC change ist mode to forced PWM mode for load current of 6.5mA

also let me know is their way to know how the IC changes its mode internally by changing the load conditions

over 3 years ago

0 Zack Liu over 3 years ago

TI__Mastermind 34201 points

Hi Sojeth,

Thanks for reaching out.

TPS61372 has a MODE pin to select its working mode, either PFM mode or PWM mode at light load condition. If you connect MODE pin to high logic (>1.2V), then TPS61372 works at forced PWM mode.

If you want to know which mode does the device work at 6.5mA, you can probe SW pin and check its switching frequency.

0 Abhishek Jadhav1 over 3 years ago in reply to Zack Liu

Prodigy 10 points

Thanks for replying

probing doesn't seems feasible for us.

so is their a way to check the switching frequency before actually implementing the board

is their any simulation tool to implement and check, if yes please let us know about the tool.

0 Zack Liu over 3 years ago in reply to Abhishek Jadhav1

TI__Mastermind 34201 points

Hi Abhishek,

Could you share the schematic? How do you connect MODE pin.

If MODE pin is logic high, this device works at forced PWM mode.

0 Sojeth Adili Rajan over 3 years ago in reply to Zack Liu

Prodigy 30 points

0 Zack Liu over 3 years ago in reply to Sojeth Adili Rajan

TI__Mastermind 34201 points

Hi Sojeth,

Is resistor R44 not populated?

If so, MODE pin is connected to GND. TPS61372 works at PFM mode at light load condition.

0 Sojeth Adili Rajan over 3 years ago in reply to Zack Liu

Prodigy 30 points

HI Zack Liu

We are keeping R44 DNP by default. We want to check that at what minimum current load the IC would switch to a switching frequency higher than 500KHz by keeping the MODE pin to GND. Right now the minimum load current in my circuit is 6.5mA.

When if we keep the MODE pin high what would be the switching frequency for 6.5mA load and will the efficiency gets significantly lower when MODE is pulled high?

Right now the efficiency when MODE pulled low is 92% and when pulled high the efficiency drops to 80%.

0 Zack Liu over 3 years ago in reply to Sojeth Adili Rajan

TI__Mastermind 34201 points

Hi Sojeth,

1. Please check SW pin waveform to know this thread.

2. If MODE in is kept high, the switching frequency is 1.5MHz at 6.5mA load. Efficiency is lower compared to when MODE is pulled low.

0 Zack Liu over 3 years ago in reply to Zack Liu

TI__Mastermind 34201 points

Hi Sojeth,

Please let me know if you still have questions. Otherwise I'll close this thread.

Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

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TPS61372: Forced PWM mode