TPS61040: On-load voltage drawdown problem of TPS61040DBVR

WEI MA

Prodigy 80 points

Part Number: TPS61040

problem description

The output load capacity is insufficient

experimental apparatus

electronic load（IT8510）

design objective

Input：5V

Output: 8V 0.3A

experimental data

1. testing environment

Output voltage（V）	load current（A）	Chip temperature（℃）	temperature rise（℃）
8.03	0.002
7.99	0.050
7.98	0.100	25	3
7.83	0.200
7.03	0.250	30	8
6.08	0.301
5.38	0.350	32.4	10.4
4.97	0.4

Load depressurization question

Principle diagram:

PCB placement：

Why is V (FB) less than 1.208V?

over 1 year ago

0 Lei Zhong over 1 year ago

TI__Expert 8270 points

Hi Wei,

Your attached picture is not clear. I think the less than 1.208V was measured when the Iout was big and Vout could not be regulated at 8V.

The reason is that the inductor current has been clamped at the limit, which means the loop can't regulate the Vfb = Vref now. And the Vfb is less that Vref.

Regards

Lei

0 WEI MA over 1 year ago

Prodigy 80 points

Hi Lei Zhong,

This is a pretty clear picture。

file:///C:/Users/MAWEI.CRPROBOT/Desktop/oscillogram.png

0 Lei Zhong over 1 year ago in reply to WEI MA

TI__Expert 8270 points

Hi Wei,

The picture is not uploaded, it's just a path in you computer I think.

Well, with you description, I think the reason is clear.

Regards

Lei

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TPS61040: On-load voltage drawdown problem of TPS61040DBVR