K64 ADCs in differential mode are disabled

[jimmyli]

Hi，

      In 2020 and 2021, we designed two products by MK64FX512VLQ12, and sent them to our end cusomter to test, but some portotypes were returned to us for ADC failing.

      1>Prototypes worked well firstly, but the ADCs in differential mode work abnormally lately.

      2>The inputs of ADCs are still sin signals, but the results turn to ladder-shapped, showed as below.

      3>Reboot or power on again can't fix the problem;

      4>Customer used heat gun to warm K64(about 300℃), and K64 will work well again.

      5>ADCs used PDB to trigger the conversion. 

      How the problem happens and how fix it?

      Thanks.

[KalaimaniArumugamdev]

Hi,

•  Point1: It may happen in two ways 1. Vref input oscillation or 2. PDB sequences error also cause this kind of output.
•  Point2: Check ADC in single ended mode, if it's not working than the chip have some issue. Why because "Figure 35-1. ADC block diagram" mentioned that both single and differential ADC input process block is same 

[jimmyli]

Hi， 

     Thanks very much for your advises.

     We will check again.

[jimmyli]

Hi,

     The problem can't be fixed by rebooting and initializing the ADC model, so I guess the chip have some issue.

     But the phenomenon has been disappeared, we can't continue to verify and analyze.

     Thanks.

[vicentegomez]

Hi

I got a little bit confused 

After touching up (reworking) the board it starts working again?

If this is the case you have a solder problem and you need to check your solder profile

Regards

Vicente

[jimmyli]

Hi Vicente,

    Thanks for your reply.

    Touching up can't let K64 work again, but only warming the chip can when they were going to replace new K64 chip.

     Meanwhile, repairing welding for the pins of K64 without warming also can't let K64 rework yet.

     We suspect that K64 has internal failure that reset or power-on can't fix.

     Need you help to analyze.

     Thanks again.

[vicentegomez]

If you need an analysis of the part you need to contact your distributor where you bought the part to start the CQC

Where did you buy the parts?