LP87524Q1EVM: LP87524B-Q1 Incorrect output of four voltage levels

Hi,

Since I do not have schematics so I cannot comment what could be the issue. As per your problem description, it seems that PMIC is losing input power and as result it couldn't supply power at outputs. You better check the schematic from input side and if you followed our reference design check that as well. 

If the PMIC communication interface does not have power (VIO) then PMIC won't be able to talk to the I2C. I can help if get more detailed information regarding your system design. Thanks!

Regards,

Ishtiaque 

Hello, from your reply, it seems you suspect there is a problem with the power input part. I rechecked the circuit and found that the PMIC part and the design of AWR1642BOOST are the same. However, my 5V_UNREG does not directly use 5V_IN for power supply like AWR1642BOOST. Instead, it uses a 12V-5V DC-DC buck circuit to input 5V_IN.

Another issue is that I want to determine whether LP87524BRNFRQ1 requires software programming to output voltage normally. If it does, what should be the slave address of this chip? I attempted to use IIC to read the value of the chip's registers from the IIC interface reserved on AWR1642BOOST (which is providing normal power supply) using this method, but I did not receive a response from the chip.

Hi,

From your first description, yes, it sounded like that. Can you check that your 5V from the pre-regulator is stable?

I2C address is 0x60. You can refer to TRM for other OTP settings. https://www.ti.com/lit/pdf/snvu663 

This device has default output voltages. This is how it needs to be used. 

Regards,

Ishtiaque 

Hi, I would like to ask if unstable voltage could damage this chip? After I detected no output voltage, I checked the four voltage input pins and found that all four pins were short-circuited and grounded. What could be the reason for this? The strangest thing was that when I removed the chip, I found that the four input voltage pins on the chip were not grounded, and the solder pads on the board were also not grounded. But when I re-soldered the chip and tested it again, it was grounded.

Hi Mandy,

I cannot say what could be reason. You need to carefully investigate what is causing the short? 

Also do you any other board which works fine. Then you can do a ABA swap test to just confirm whether it is device related issue or coming from board.

Regards,

Ishtiaque

Hello, I can currently measure four output voltages. However, only two of them (BUCK0 and BUCK1) have the correct output voltage. While BUCK2 and BUCK3 are supposed to output 1.8V and 2.3V respectively, both BUCK2 and BUCK3 are actually outputting 2.0V. What could be the reason for this? The manual indicates that in the PWM mode, each channel of BUCK has a load current of 19mA. So, the no-load current measured at my 5V input terminal is around 65mA. Is this considered a normal no-load current?

Hello,

These current values are per phase. So you need to disable all other regulators except one and then measure it. Also make sure that there isn't any external leakage current outside the PMIC. 

Regarding different output. I am not sure why there is different voltages. Could be related to soldering if you tried to resoldered or soldered on with new PMIC. 

Regards,

Ishtiaque 

The problem has been solved. Thank you for your reply.

Hi Mandy,

That's good to know. What is the reason? would like to hear incase some other may see the same issue. 

Regards,

Ishtiaque 

During the testing process, we encountered some errors. Initially, it was because the output of our adjustable voltage power supply was unstable and had interference, which prevented us from driving the PMIC. We then replaced it with a more stable adjustable voltage power supply and found that there was a deviation in the output voltages of BUCK2 and BUCK3. Later, upon further inspection, we discovered that it was due to the fact that the capacitors were not properly attached.