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MPC5744PFK1AMLQ9 VREF's current issue

Question asked by on Dec 26, 2018


   One question about the VREF and ADC sampling issue for MPC5744PFK1AMLQ9.

Currently, I am using TI LM4050-5V as the reference voltage for MPC5744PFK1AMLQ9 and the output current limits to 7.5mA. The issue is when I startup the ADC samping, the voltage of VREF drops to around 4.8V. the voltage will drop slowly with the time goes out.

And now, one thing I can clarify is that PIN 50 and PIN 56 are sinking much current than SPEC, I evaluate is about 10mA.

Now, I don's know where is the root cause, SCH has checked with NXP's demo.

Would you like provide some suggestions to me? including the ADC configuration.

PS: currently the ADC frequency is 16MHz.