Tool/software: WEBENCH® Design Tools
Dear All,
I'm using the LMZM33606 to generate 12 V - 5A from a battery.
The battery voltage range is: 14 - 20 V.
Using WEBENCH software it says: "Design update failed. This design is not stable due phase margin either smaller than 35 or greater than 120"
On datasheet, the allowed voltage droput is 1.1xVout.
Why? Can you help me?
Thanks
Damiano
Hi Praveen,
i have bought the eavaluation board.
I have done some test with different Vin for 12Vout. The load is 50W.
In the following table you can find the measured voltage value.
| Vin | Vout | P Good |
| 15 | 12.1 | Good |
| 14 | 12.1 | Good |
| 13 | 12.1 | Good |
| 12.5 | 11.8 | Good |
| 11.7 | 11.1 | Not Good |
It seems work good until 12.5Vin without voltage drop on Vout.
Below 12.5Vin appears a voltage drop on Vout until 11.7Vin when the power good signal goes down.
Furthermore i have done another test to see the transient effects.
The test consists in activating/disactivating the 50W load (1 second on - 1 second off) 13Vin - 12Vout.
In the image you can see the Vout when the load is activated (12.06 V) and when the load is deactivated (12.2V).
It seems stable.
I have added a 470uF output capacitor to reduce the Vout voltage drop during transient load activation.
What do you think about that? can you recommend further tests to do?
Thanks
Regards
Damiano
