LMR14020 can't start at -40 degree C

jun soo lee

Prodigy 140 points

Other Parts Discussed in Thread: LMR14020

I'm Jun and HW engineer, from South Korea.

I designed power part of LMR14020.

- Input Voltage Range: DC +10V ~ +30V

- Output Voltage: +6.2V

- Load current: 40mA @ Motor "OFF"

220mA @ Motor "ON"

After 2 hours at -40 degree C, I turned on the power @Input voltage: DC +10V.

LMR14020 can't start. So I increase the Input voltage until LMR14020 Start.

I could check DC +15V or more.

And I set the input voltage DC +10V(0.1V step). But LMR14020 operate still.

I don't know why LMR14020 can't start at -40 degree C.

LMR14020 can start at -40 degree C @Input voltage: DC +15V ~ +30V. I tested it.

over 8 years ago

0 Anston Lobo over 8 years ago

TI__Genius 16025 points

Hi Jun,

I've forwarded your question to the apps team working on this part. You'll receive a reply soon.

Thanks,
Anston

0 Luke Pan over 8 years ago

TI__Intellectual 2790 points

Hi Jun,

Could you capture the waveform of Vin under the condition you mentioned.

'After 2 hours at -40 degree C, I turned on the power @Input voltage: DC +10V.

LMR14020 can't start.'

Usually a 4.7uF~10uF ceramic cap is needed parallel with the 47uF e-cap (C9), and it should be close to VIN pin and GND.

For C7 and C13, X7R type cap is recommended.

Luke

0 jun soo lee over 8 years ago in reply to Luke Pan

Prodigy 140 points

Hi Luke Pan

I captured Vin +10V waveform as below.

The input voltage is +9.4 ~ +9.6V. Because I used rectifier diode(P/N: S310) on Input Voltage part.

C9 value is 4.7~10uF. I used more value because of Input Voltage Noise.

C7 is X7R and C13 is Y5V.

I'm waiting your reply.

0 Luke Pan over 7 years ago in reply to jun soo lee

TI__Intellectual 2790 points

Hi Jun,
Pls use X7R cap for C13, as the recomended operation temp for Y5V is -30~85C with +22%~-82% tolerance, it's really bad for -40C application.
BR
Luke

0 jun soo lee over 7 years ago in reply to Luke Pan

Prodigy 140 points

Hi Luke Pan

After replaceing C13, I will test at -40 degree C and then reply result.

Thank you for your reply.

0 jun soo lee over 7 years ago in reply to jun soo lee

Prodigy 140 points

Hi Luke Pan

I replaced C13 X7R and tested it. But LMR14020 still can't start at -40 C.

Hum... What can I do?

0 Luke Pan over 7 years ago in reply to jun soo lee

TI__Intellectual 2790 points

Hi Jun,
Can you share us with the layout and BOM?
BR
Luke

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LMR14020 can't start at -40 degree C