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Modification of the PMIC command resolution -- Ultra96V2

jsobas

Hello,

 

I work on the Avnet96_V2 which manages the distribution of the power supply with the PMIC IRPS 5401 of Infineon (Datasheet in attachment).

I communicate (read/write) with the PMIC registers in IIC protocol (list of registers : see datasheet in PJ).

To have a better precision on vout_command (register 0x42), I want to modify the resolution. Vout_mode (register 0x40) allows to change the resolution.

The problem : If I change the resolution (for example : from 3.906mV to 1.953), automatically Vout is divided by 2 and I have an alarm that turns off the card for safety reasons (under voltage).

I thought of disabling the alarms by SMBALERT_MASK (register 0x036), but I still have alarms that turn on.

Does anyone have any idea how I can do this? The goal is to have the best command resolution (-12).

It's quite complicated to explain my problem by message, but I can give details without problem image

 

Thanks

Justin

 

Protocol to disable alarms :

image

Attachments:
imageInfineon-DC-DC_POL_IRPS5401_Register_Map-AdditionalTechnicalInformation-v01_03-EN.pdf
imageInfineon-IRPS5401M-DataSheet-v02_06-EN.pdf
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  • 0

    Hey Justin,

     

    Short answer is the output resolution is "fixed". You can't make it more precise without changing other multipliers (that's why changing that resolution by 50% changes the Vout divider) Both the set points and reporting resolutions are fixed. I'm not really sure why the datasheet describes them the way they do because it does sound somewhat ambiguous.
    Thanks
    Chris

  • 0 in reply to ctammann

    Thanks Chris!

     

    So, do you think that disabling the under/over voltage alarms will make it possible to change the resolution ?

    The protocol to do it:

         -I disable the alarms;

         -I change the resolution from 3.906mV to 1.953mV (so the output voltage is divided by 2, but the board still works because I disabled the alarms);

         -I write a new voltage (normal operating voltage);

         -I activate the alarms;

     

    I think the alarm (red led on the picture) comes from the ALERT# output (pin 17 IRPS 5401 component).

    But I don't understand how disable ALERT# output...

    Do you have another idea ?

     

    Thanks

    Justin

     

    imageimage

  • 0 in reply to jsobas

    Hey Justin,

     

    That LED is driven from the Zynq device and if I'm not mistaken indicates an error. We don't actively use the ALERT output from the PMICs. I fear that when you change that resolution you may be changing the reference voltage of the output from 1:1 to 2:1. Have you checked the supply output with a meter to see what happens when you change that resolution?

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  • 0 in reply to jsobas

    Hey Justin,

     

    That LED is driven from the Zynq device and if I'm not mistaken indicates an error. We don't actively use the ALERT output from the PMICs. I fear that when you change that resolution you may be changing the reference voltage of the output from 1:1 to 2:1. Have you checked the supply output with a meter to see what happens when you change that resolution?

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