Dear
I have a problem with MPM3690-50D.
I tested it with EVB of MPM3690-50D.
External Vout is set to 1.2V => OK
But The internal Vout is output 0.25V higher than the set value.
What causes “internal Vout” to be 0.25V higher?
Even if we remove R2 (60.4kohm) from the EVB circuit, the problem remains the same.
Thank you
Hello Henry,
What do you mean by External Vout and Internal Vout? I see that there is Vout and VoutSense.
Best,
Krishan
Dear. KRISHAN RAM
The “Internal” output is controlled via PMBus, while the “External” output is set to the desired voltage by adjusting the FB resistor value.
In the case of the “External” setting, the output is exactly matched to the voltage, but in the case of the “Internal” setting, the output is about 0.25V higher than the voltage.
Test conditions
a. Using Bench Pro 4.0.
b. Internal divider 2:1(0.4V ~ 1.344V) : 0.5V //Scale Loop
c. Vout Command(V) : 0.9V
d. R2, R5: Not installed(Based on EVB circuit diagram)
A phenomenon in which the actual output voltage increases by 0.25 V compared to the “Vout Command”.
0.9V → 1.15V
R2, R5: Not installed(Based on EVB circuit diagram)
Thank you
Hello Henry,
Thanks for providing these added details and clarification. This helps provide insight on what you are dealing with and the discrepancies between the external and internal divider settings.
I’ll discuss this with my team and get back to you soon. However, I am sure if you are using the internal dividers, you will want R2 populated. R5 is only used as an external resistor so it is fine to leave this unpopulated when using the internal dividers.
Another thought, this is the structure of the internal divider where Vout is changed by the variation of Vref as shown:
I’ll try and get back to you on specifics with this module soon.
Dear Krishan
I am waiting for your reply.
Thank you
To use the internal FB resistor network, a resistor is needed between FB1 and VS1N. This means you will absolutely need R2.
Dear Krishan
Thank you for your support
When using “Internal Setting”, should I use 10Ω as the R-up value among the FB resistance values? Or is there another value?
Thank you
Hello again,
10 Ohms is the standard value that is shown when using the internal feedback resistor network when prompted to do so on the GUI. This is not stated anywhere on the datasheets specifically, but perhaps this should be the case.
Just to confirm, you got that from this message, correct?
In any case, please try adding this in place of R2 in reference to your schematic. Does the voltage output change as you would expect?
Let me know.
Best,
Krishan
Deqr Krishan
When setting internally, apply R-up as 10Ω among the FB resistance values.
I assembled 10Ω to R2 in the circuit and tested it on EVM.
Test conditions: VIN=12 V, no settings change
Overcurrent and short circuit symptoms occur immediately upon 12 V input.
The message you provided is the same as the one I received. (This message was confirmed in the past when R2 was not installed.)
I assembled a 10 ohm resistor in R2 in the circuit, and the test results show that the R2 value is affected.
Please provide guidance on how to achieve normal output.
Thank you
Hello Henry,
For more in depth and timely support, please fill out the following form and a ticket will be created for your case. Please let me know if there are delays in a response on this issue through this avenue. Here is the following link:
Contact MPS - Troubleshooting and Debug Support
I only do this because it seems that this issue warrants more in-depth support.
Best,
Krishan
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