LMR62014: Vout is gradually decreasing at <3.5Vin

Jun Ishida

Part Number: LMR62014

Hi team,

The customer is using LMR62014 in the condition of 12Vin/15Vout as normal operation, but they observed that the output voltage is also gradually decreasing at <3.5Vin if the input voltage is gradually decreased as below.

12Vin --> 15Vout

10Vin --> 15Vout

5.0Vin --> 15Vout

3.3Vin --> 13.3Vout

3.0Vin --> 10.2Vout

2.7Vin --> 7.1Vout

The peripheral parameters are

- C1: 4.7uF

- L1: 10uH

- D1: MBR0520LT1G

- R1: 180kohm

- R2: 13.3k,ohm

- CF: 1000pF

- C2: 4.7uF

Could you tell us the reason the Vout is gradually decreasing at <3.5Vin along with the decrease of Vin?

Regards,

Jun

over 6 years ago

0 Zack Liu over 6 years ago

TI__Mastermind 34231 points

Hi Jun,

What's the load current of this EE?

0 Jun Ishida over 6 years ago in reply to Zack Liu

TI__Expert 5640 points

Hi Zack-san,

Sorry for my lack of load current information. The load is around 80mA.

Regards,
Jun

0 Zack Liu over 6 years ago in reply to Jun Ishida

TI__Mastermind 34231 points

Hi Jun,

I'll check it on EVM today and tell you the results later.

0 Zack Liu over 6 years ago in reply to Jun Ishida

TI__Mastermind 34231 points

Hi Jun,

Please see below graph on page 13 of datasheet. It shows the current limit will change dependent on duty cycle of the application. When Vin is down to 3V, the device current limit is 700mA. On EVM the device could generate 15V even Vin decrease to 3V.

If customer really cares about the Vout line regulation performance during the range of 2.7-3.5V, we may need to find another device.

Another thing, R1 should be 150kohm.

0 Jun Ishida over 6 years ago in reply to Zack Liu

TI__Expert 5640 points

Hi Zack-san,

Thank you for your comments. I will get back to you if we have additional questions.

Regards,
Jun

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LMR62014: Vout is gradually decreasing at <3.5Vin