TPS63070: Maximum Duty Ratio

Ryu Yamashita

Part Number: TPS63070

Tool/software:

Hi team,

The PS pin is dropped to Lo and the switching frequency fs is set to fixed (2.4MHz) to output 5V.
I thought it would always be 2.4MHz, but when the potential difference between input and output is less than 0.8V, it becomes 1.2MHz.
I assumed that this was due to a limit on the maximum duty ratio or potential difference, is this correct?
And if so, I would like to know the specific value.

Best Regards,
Ryu.

6 months ago

0 Mulin Yuan 6 months ago

TI__Mastermind 18220 points

Hi Ryu,

Thank you for reaching out. I am not sure about your working condition. Can you provide Vin, Vout, Iout information? Do you have a schematic? Can you provide waveform of SW1, SW2, Vin, Vout, inductor current?

Regards,

Mulin

0 Ryu Yamashita 6 months ago in reply to Mulin Yuan

Genius 4315 points

Hi Mulin,

The output voltage of the IC is set to 5V
VIN 346mA at 6V (switching frequency 2.5MHz)
VIN 356mA at 5.3V (switching frequency 1.25MHz)

The schematic is almost the same as the Simplified Schematic in the datasheet.
0.1μF is added to CIN and COUT.

Waveforms are attached.

Best Regards,
Ryu.

0 Mulin Yuan 6 months ago in reply to Ryu Yamashita

TI__Mastermind 18220 points

Hi Ryu,

I will look into this and reply to you later.

Regards,

Mulin

+1 Mulin Yuan 6 months ago in reply to Ryu Yamashita

TI__Mastermind 18220 points

Hi Ryu,

Thank you for your waiting.

Vin=6V, Vout=5V, TPS63070 works in buck mode, only buck side MOS switch, frequency is 2.5MHz。

Vin=5.3V, Vout-5V, TPS63070 works in buck-boost mode, which is one cycle buck and one cycle boost. So both LX1 and LX2 switch, the frequency will reduce to half for LX2 and LX2. But this is IC normal behavior.

Regards,

Mulin

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TPS63070: Maximum Duty Ratio