LM25122-Q1: LM25122-Q1 ISSUE & Schematic review

Hello CHO,

I cannot observe anything obviously wrong in the schematic. Could you please share your inductor specifiction and please measure the inductor current shortly before the system turns off.

Hi Brigitte

Sorry for the late reply.

The customer checked late because he was on vacation.

1.Attached is the inductor specification. 

2. The inductor current measurement is not confirmed.

However, the customer tested the inductor change, and the problem was not solved..

Inductor Part : EMA13050S-330M --> EMA13050S-100M 

EMA13050S Series-Datasheet.pdf

Hello CHO,

Changing the inductor from 33uF to 10uF will not really help to increase the current, as this increases the ripple current by a factor of 3.

What is the minimum and maximum input voltage? Could you please ask the customer to check the input voltage on the input capacitor at 1.8A output current?

Hello CHO,

The current rating of the inductor seems not to be sufficient for the application. Please exchange the inductor with at least 11A current rating and check the maximum output current again. (this is only for testing)

Hi Brigitte

1. What is the minimum and maximum input voltage?

• Min : 10.6V
• Typ : 14.4V
• Max : 20V

1. Could you please ask the customer to check the input voltage on the input capacitor at 1.8A output current?

• Input cap : 330uF(AL)*2ea, 10uF(ceramic) * 2ea, 0.1uF(ceramic) * 2ea, 0.01uF(ceramic) *2ea

1. Please exchange the inductor with at least 11A current rating and check the maximum output current again. (this is only for testing)

• 33uH(rated 6.8A) and 10uH(rated 12.5A) are same the symptom.
• But 10uH generate heat.

Hello CHO,

Please test with a 33uH inductor with 11A current rating not a 10uH with 12.5A rating.

Please measure the voltage on the input pin while the output current is at the maximum achievable.

Hi Brigitte

Please test with a 33uH inductor with 11A current rating not a 10uH with 12.5A rating.

--> To be updated after purchase of inductor. ( ~ Aug 21 )

Please measure the voltage on the input pin while the output current is at the maximum achievable.

LM25122-Q1_Data.zip

1. LM25122 Loadless EN pin input and output waveform.

2. Start after connecting load.(1.9A)

3. Shutdown after load connection. (1.95A)

4. After the shutdown.

5. No-load CSP & CSN

6. CSP & CSN After Load Connection

7. CSP & CSN during shutdown

8. Update the schematic to a pdf file.