LMR62014： Vin abnormal voltage drop

user6546719

Prodigy 40 points

Part Number: LMR62014

I use LMR62014XMF/NOPB.

Schematic and Layout as below:

Schematic:

Layout:

1.Vin=5V Vout=9.65V

2.Vin use Power Supply

3.Iout=300mA

4.When the load starts,the IC starts working after about 400us,is this normal?

5.When Iout only 300mA. Vin use Power Supply but still 0.7V voltage drop,is this normal?

over 3 years ago

0 user6546719 over 3 years ago

Prodigy 40 points

Sorry,Picture loss.

0 Zack Liu over 3 years ago

TI__Mastermind 34201 points

Hi Sir,

1. What do you mean IC starts working after about 400us?

2. Vin use Power supply but still 0,7V voltage drop? What do you mean hear a 0.7V voltage drop? At Vout? There is no label on your share waveform. Maybe you can tell me each channel name to help me understand your question.

0 user6546719 over 3 years ago in reply to Zack Liu

Prodigy 40 points

1. What do you mean IC starts working after about 400us?

Ans:After Vout drop abuot 315us,IC start work.@Vout=9.42V

Can LMR62014 speed up the response time?

Ans:The 0.7V Voltage drop at Vin. When Iout=300mA ,the voltage drops rapidly even Vin use power supply.Is it normal?

Thanks,

0 Zack Liu over 3 years ago in reply to user6546719

TI__Mastermind 34201 points

Hi,

1. 400us response time is slower than expectation. But in your application, 400uF aluminum electrolytic capacitor is put at output side so the loop cross over frequency maybe reduced to very low. And I recommend you put the C921 100nF cap across rectifying diode and IC GND pin to help improve IC performance.

2. During load transient, more energy needs to transfer from Vin side to Vout side. So input current also increases. Please use short, thick power cable for input side. You can also put a big bulk electrolytic capacitor at input side to store energy.