SPRZ423K October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
Analog Trim of Some TMX Devices
B
Some TMX samples may not have analog trims programmed. This could degrade the performance of the ADC, buffered DAC, and internal oscillators. A value of all zeros in these trim registers due to lack of trim will have the following impact.
| TRIM | REGISTER | IMPACT OF UNTRIMMED REGISTER |
|---|---|---|
| ADC reference | AnalogSubsysRegs.ANAREFTRIMA | Degraded performance of the ADC for all specifications. |
| AnalogSubsysRegs.ANAREFTRIMB | ||
| AnalogSubsysRegs.ANAREFTRIMD | ||
| ADC linearity | AdcaRegs.ADCINLTRIM1-6 | Degraded INL and DNL specifications of the ADC in 16-bit mode. No workaround available. |
| AdcbRegs.ADCINLTRIM1-6 | ||
| AdcdRegs.ADCINLTRIM1-6 | ||
| ADC offset | AdcaRegs.ADCOFFTRIM | Degraded performance of the ADC offset error specification. |
| AdcbRegs.ADCOFFTRIM | ||
| AdcdRegs.ADCOFFTRIM | ||
| Internal oscillator | AnalogSubsysRegs.INTOSC1TRIM | Degraded frequency accuracy and temperature drift of the internal oscillators. |
| AnalogSubsysRegs.INTOSC2TRIM | ||
| Buffered DAC offset | DacaRegs.DACTRIM | Degraded offset error specification of the buffered DAC. No workaround available. |
| DacbRegs.DACTRIM | ||
| DaccRegs.DACTRIM |
The following workarounds can be used for improved performance, though it still may not meet data sheet specifications.
To determine if a device is TMX in software, check the status of the PARTIDL[QUAL]. If this field is 0, the device is TMX. PARTIDL[QUAL] can be read via the function call SysCtl_getDeviceParametric(SYSCTL_DEVICE_QUAL). This check is implemented in the Device_init() function, which will then call the Device_configureTMXAnalogTrim() function if needed. The user can place any additional self-calibration or static calibration code in the Device_configureTMXAnalogTrim() function.
If the ADC reference trim registers contain all zeros, write the static reference trim value of 0x7BDD to the reference trim register for all ADCs.
Missing ADC offset trim can be generated by following the instructions in the “ADC Zero Offset Calibration” section of the TMS320F2807x Real-Time Microcontrollers Technical Reference Manual.
If the internal oscillator trim contains all zeros, the user can adjust the lowest 10 bits of the oscillator trim register between 1 (minimum) and 1023 (maximum) while observing the system clock on the XCLOCKOUT pin.