TPS61085: Switching Frequency

Srinivas Jahagirdar1

Part Number: TPS61085

Hello ,

We are using IC TPS61085A in a boost converter module. In one of the validation or evaluation tests related to Switching behavior & Frequency we have observed the switching frequency around 1700 kHz.

The datasheet spec. shows the range 900 kHz to 1.5 MHz. I wanted to know the reason behind the out of specification range.

The test procedure is as follows:

The load is is varied between 10 mA to 90 mA using FET switching circuitry. Switching frequency of circuitry is set for 20 Hz (50% duty), Rise time < 5 us (Image attached for reference)

over 5 years ago

0 Zack Liu over 5 years ago

TI__Mastermind 34201 points

Hi Srinivas,

Can you show me the schematic, loyout and tell me the working conditions?

It's be very helpful for me to analyze the reason if you can share the SW pin waveform?

0 Srinivas Jahagirdar1 over 5 years ago in reply to Zack Liu

Prodigy 20 points

Hello Zack,

Thanks for your quick feedback. I do not have the layout details as this is under development project.

I have the attached details (Sch & waveform) of our verification.

Thanks in advance.

TI Support.7z

0 Zack Liu over 5 years ago in reply to Srinivas Jahagirdar1

TI__Mastermind 34201 points

Hi Srinivas,

Thanks for sharing the schematic and waveform.

The switching frequency spec in EC table is the range under specific load condition so that the converter is working at CCM. However, the waveform you upload shows the converter is working at DCM. This device operates in a current mode scheme with quasi-constant frequency, the switching frequency varies with different temp, VIN/VOUT and load current.

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TPS61085: Switching Frequency