Hi team
Our customer is evaluating the LM5576 and find some difference between datasheet and experiment.
In the recent test, it was found that the undervoltage point calculated according to the undervoltage point calculation formula provided by your LM5576 chip is inaccurate with the actual measured value. I would like to ask whether it is because the undervoltage comparator of the chip is inaccurate. Caused? Or are there other reasons?
in datasheet, the Vuv_sb=Vsb*(1+Rup/Rdown)-Isource*Rup. The hysteresis of the benchmark is 0.1V.
Comparison of measured value and theoretical calculated value:
Rup=24.9kΩ*2 1%, Rdown=3.9kΩ 1%
|
Project1 |
Verify internal comparator reference voltage(Isource=5uA) |
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|
Vin_uvlo（test） |
Vin_uvlo（calculated） |
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|
Min 1.17 |
TYP 1.225 |
Max 1.28 |
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|
no load OFF |
15.247 |
15.422 |
16.618 |
17.866 |
|
fully loaded OFF |
15.255 |
|||
|
no load ON |
16.476 |
16.761 |
17.995 |
19.282 |
|
fully loaded ON |
16.477 |
|||
Rup=49.9.9kΩ 1%,Rdown=1.74kΩ 1%
|
project2 |
Verify internal comparator reference voltage(Isource=5uA) |
|||
|
Vin_uvlo（test） |
Vin_uvlo（calculated） |
|||
|
Min 1.17 |
TYP 1.225 |
Max 1.28 |
||
|
no load OFF |
33.347 |
33.812 |
36.106 |
38.478 |
|
fully loaded OFF |
33.437 |
|||
|
no load ON |
36.317 |
36.723 |
39.074 |
41.503 |
|
fully loaded ON |
36.314 |
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From the above test results, it can be found that the actual measured value is always 0.2V~0.4V lower than the theoretically calculated minimum value.
could you help to check which may lead to the difference? and what we should do to check the issue?
