Light load operation of TPS54335A

takahiko yokota

Mastermind 7135 points

Other Parts Discussed in Thread: TPS54335A, UC3825

I have two questions about light load operation of TPS54335A.

1.I think TPS54335A stops switching when switch current is lower than 0.5A.

Is this pulse skip operation? Please teach me detailed operation.

2.As long as I watch Fig31 of datasheet, I think this device is oscillating,

is this factor resonance?

Best regards,

Yokota

over 9 years ago

0 takahiko yokota over 9 years ago

Mastermind 7135 points

Let me ask you a additional question.
If TPS54335A operates DCM during pulse skip mode, are there methods to avoid this operation?
I will use it under Vin=5V(max=24V), Vout=3.3V, Iout=0.5A ~ 1A.

0 JohnTucker over 9 years ago in reply to takahiko yokota

TI__Guru**** 191445 points

TPS54335A is a synchronous buck converter with Forced Discontinuous Conduction Mode (FDCM). So the low side FET cannot sink any current. When switch current reaches 0 A, the low side FT turns off and the switch waveform will be just like DCM for a non synchronous converter. That is the waveform you observe in Fig 31. It is normal operation.

Eco-mode pulse skipping is not necessarily related to FDCM. Skip mode is enetered when the COMP pin voltage falls to its minimum clamp value. Typically, it will be lower than the CCM/FDCM threshold. It is difficult to predict the actual load current level.

0 takahiko yokota over 8 years ago in reply to JohnTucker

Mastermind 7135 points

Hi-Colin-san

Thank you for the reply.

The attached document is the customer's consideration circuit.

I think they can not use UC3825 with that design.

Can I use the circuits of ① or ②?

UC3825.pdf

Best regards,

Yokota

0 JohnTucker over 8 years ago in reply to takahiko yokota

TI__Guru**** 191445 points

I think you may have posted this to the wrong thread...

0 takahiko yokota over 8 years ago in reply to JohnTucker

Mastermind 7135 points

I'm sorry I made a mistake in the posting content.
Could you tell me the minimum clamp value when this device enter the Eco-mode?

Best regards,
Yokota

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Light load operation of TPS54335A