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TMS320F28376S: Interal Temperature affect other ADC sample

Eyal Saban1
Intellectual 905 points

Part Number: TMS320F28376S

Dear Sir ,

We are under development of new producut (form motion control ) that is based TMS320F28376S  , and encouter some issue that affect ADC result

the setup is as follow (SYSCLK = 200Mhz  , ADC A,B,C,D CLK=50Mhz)

SOC 0,1,2,3    on all ADC are sample 

1.Motor Current Phase 1

2.Motor Phase Current 2

3,4 Encoder SIN/COS  output 

All of the Soc are trigger form ePWM1.SOCA   ath rate of 20Khz  with ACQ time of ~230ns ( according to datasheet recommendation considering the R,C components)

in addtion ADC -A   SOC15  is set to sample  the internal temperature Sensor  every  3 Seconds (trigger by Software , ACQ time = 700ns )

my issue is once in every 10-11minutes i get some offset or "noise"  in SOC0/SOC1  in ADC-A  , after disableing the measumernt of the internal temperature sensor

there is no such isse  (it is easly repredoucable on the setup i have )

my question is 

1.is the cause of it cant be due to interal temepratrue Sensor ?

2.is it relaedt to the fact that every 3 sec there is software trigger that may cause the ADC-A somtimes is not  Synchronous  with ADC-B,ADC-C,ADC-D  due to addtional sample ?

BR ,

  • 0
    TI__Guru 60865 points

    Hi Eyan,

    What package are you using and how much is the offset?  

    Is it possible the additional error is just because the readings get delayed by the temp sensor conversion? (is the input signal moving fast)

    You might try adding the temp sensor reading so it is always part of the SOC-A set of ePWM triggered conversions:

    SOC1, SOC2, SOC3, SOC4, SOC15

    Then in the software just read the most recent temp sensor result instead of software triggering a new reading to occur asynchronously.  

    To be extra safe, you could also add a dummy SOC15 conversion to all the other ADCs.