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AMC131M03EVM: Problem Activating "HLDO_OUT" with the Evaluation Module

Wilson Gonzalez
Prodigy 10 points
Part Number: AMC131M03EVM

Tool/software:

Hello, I am developing a project using the AMC131M03EVM evaluation module. Initially, I conducted preliminary tests using the "PHI" expansion board to understand the operation of both the chip and the evaluation module. I was able to do this without any issues. Later, I decided to configure it using a microcontroller with SPI communication, in my case, one from the STM32 family. After making the physical connections and configuring the SPI following the datasheet recommendations, I conducted initial tests. I am able to successfully read and write the different registers.

The specific problem I have is that, supposedly, when enabling the DC-DC converter using the write command and subsequently confirming it with the read command, it indicates that the converter is enabled. However, the voltage that should be present at HLDO_OUT relative to HGND never goes high (around 2.8 V), causing the SEC_FAIL bit in the status register to never go to (0b). This occurs regardless of how many times I execute the NULL command. However, by performing this same process using the evaluation module's (GUI), it can be observed that disabling the DC-DC converter automatically drops the voltage to 0 V. I would like to know what could be causing this error. Thank you in advance.

  • 0
    TI__Expert 5860 points

    Hi Wilson,

    A few questions:

    1. Are you testing your microcontroller setup with the AMC131M03EVM (i.e. just replacing the phi with your MCU)?
    2. What is supplying the power to the low side of the device? 
      1. Is power coming from the MCU? 
      2. Have you checked the low side voltage going to the device?

    Also, could you provide some information into your project and use case?

    Thanks.

  • 0 in reply to Saleh Ahmad
    Prodigy 10 points

    Thank you for your response, Saleh.

    1) Yes, I am testing the configuration of my microcontroller with the AMC131M03EVM in terms of SPI communication.

    2) The minimum necessary connections for SPI communication (DIN, DOUT, SCLK, and CS) are being made through the "J5" connector. At this initial stage, I am not using DRDY or SYNC/RESET. Regarding power supply, it is being provided through the "J1" terminal block with a regulated output of 3.3V and GND from the microcontroller. For CLKIN, I am still using the clock provided by the evaluation module in its high-resolution option (HR [8.192 MHz]).

    Finally, regarding the project, it is an integration of this chip using the configuration provided in the datasheet with a shunt resistor for current measurement. In this case, it is focused on measuring current from various functional devices in 4-20 mA loops that are sampled periodically.

    Initially, I had already managed to configure the evaluation module using channels 0 and 1. I sent 5-word frames with the microcontroller to configure the necessary registers and was able to obtain the reading after following the steps indicated in the guide. Subsequently, I executed the standby command, and when I needed to sample again, I executed wakeup.

    My question arises because after having it running continuously for around 3 weeks, all my readings suddenly went to zero. Initially, I thought a physical component on the board had failed. Then, I reviewed the command sequence and saw that after activating the DC-DC converter in the corresponding register, the voltage at HLDO-OUT never rose, so SEC_FAIL never clears, resulting in no valid readings in the channel registers.

    However, as I mentioned, it confuses me because using the board's own (GUI) this error does not occur. I appreciate any comments and/or recommendations.

  • 0 in reply to Wilson Gonzalez
    TI__Expert 5860 points

    Hi Wilson,

    Could you verify that the Oscillator for CLKIN is working.

    Wilson Gonzalez said:
    My question arises because after having it running continuously for around 3 weeks, all my readings suddenly went to zero. Initially, I thought a physical component on the board had failed. Then, I reviewed the command sequence and saw that after activating the DC-DC converter in the corresponding register, the voltage at HLDO-OUT never rose, so SEC_FAIL never clears, resulting in no valid readings in the channel registers.

    Was this 3 week run with the PHI or your MCU?  When did the readings go to 0,  was there valid data in the beginning?

    Thanks.

  • 0 in reply to Saleh Ahmad
    TI__Expert 5860 points

    Hi Wilson,

    Could you also monitor the DRDY pin to verify it goes high after you power up the low side of the device, before enabling the DCDC.

    Also, what do you do with the SYNC/RESET pin?  Is it floating? Could you tie it to VDD with a 10kOhm pullup?

    Thanks.

  • 0 in reply to Saleh Ahmad
    Prodigy 10 points

    I verified the signal from the local clock of the evaluation module using an oscilloscope; the frequency appears correct. On the other hand, when it started to fail, it was operating with the MCU. The MCU has a periodic interrupt that occurs every 5 minutes. So, every 5 minutes, the MCU sent the Wake-up command, turned on the DC-DC converter, executed a double NULL command, and then read the data. The MCU received the data and performed the conversion, and after reading, it executed STANDBY and waited for the next 5 minutes. The voltage I obtained after performing the conversion corresponded to the one applied to each of the channels using a variable DC power supply. I verified this through a virtual serial port that allowed me to view these values extracted from the AMC131 to the MCU.

  • 0 in reply to Saleh Ahmad
    Prodigy 10 points

    Hello Saleh, by default, the evaluation module has the SYNC/RESET pin in "Pull-Up" to DVDD with a 100 kΩ resistor. Additionally, when checking DRDY with an oscilloscope, what we observe is a rectangular signal with a frequency of 4kHz, but this is not affected by whether the DC-DC converter is active or not. Therefore, I wouldn't know if this is the verification we are looking for in DRDY. This behavior occurs with both the "PHI" board and the MCU.

  • 0 in reply to Wilson Gonzalez
    TI__Expert 5860 points

    Hi Wilson,

    Have you checked the low side voltage to verify it is at 3.3V once the DCDC is enabled?  

    What MCU are you using?  The Device when operating can consume >20mA on the primary side power supply.

    Thanks.

  • 0 in reply to Saleh Ahmad
    Prodigy 10 points

    Hi Saleh, the low-side voltage is at 3.3V, both before and after enabling the DC-DC converter. I am currently using a NUCLEO-WL55JC1. I also tried using an external power supply in case there was any current consumption issue, but I get the same result. The DC-DC converter bit can be read and appears to be enabled, but the voltage at HLDO_OUT never increases from 0V.

  • 0 in reply to Wilson Gonzalez
    TI__Expert 5860 points

    Hi Wilson,

    Could you send me the data read from the status register and rest of the register map after you enable the DCDC_Out?

    Thanks,
    Saleh

  • 0 in reply to Saleh Ahmad
    Prodigy 10 points

    Hi Saleh, I am sharing a file with the register map of the configuration bits both from the "GUI" and the MCU after turning on the DC-DC converter.

    REGISTER MAP.docx