The TPS929240-Q1 implements a EEPROM CRC check after loading the EEPROM code to configuration register in NORMAL state.

The calculated CRC result is sent to register CALC_EEPCRC and compared to the data in register EEPCRC, which stores the CRC code for all EEPROM registers except for DIM-R reserved register. The reserved DIM-R register value is not included in the EEPCRC calculation. The TPS929240-Q1 EEPROM configuration tool are available on ti.com to help calculate the EEPCRC value. If the code in register CALC_EEPCRC is not matched to the code in register EEPCRC, the TPS929240-Q1 pulls the ERR pin down with pulsed current sink for 50 μs to report the fault and set the registers including FLAG_EEPCRC and FLAG_ERR to 1. The TPS929240-Q1 only loads EEPROM to corresponding registers one time during initialization state. Parity check is used to detect whether the internal configuration parameters are correctly loaded from trim EEPROM or not. When there is internal trim EEPROM error, the FLAG_EEPPAR is set to 1. The master controller can write 1 to REGDEFAULT to reset all the regiters to default value and reload the EEPROM to corresponding registers in NORMAL state. Reloading the EEPROM triggers the EEPROM CRC check.

The master controller must write CLRFAULT to 1 to clear the fault flags, and the CLRFAULT bit automatically returns to 0.

The CRC code for all the EEPROM registers must be burnt into EEPROM register of EEPCRC in the end of production line. The CRC code algorithm for multiple bytes of binary data is based on the polynomial, X⁸ + X⁵ + X⁴ + 1. The CRC code contain 8 bits binary code, and the initial value is FFh. As described in the below figure, all bits code shift to MSB direction for 1 bit with three exclusive-OR calculation. A new CRC code for one byte input canbe generated after repeating the 1 bit shift and three exclusive-OR calculation for eight times. Based on this logic, the CRC code can be calculated for all the EEPROM register byte. When the EEPROM design for production is finalized, the corresponding CRC code based on the calculation must be burnt to EEPROM register EEPCRC together with other EEPROM registers in the end of production line. If the DC current for each output channel must be calibrated in the end of production for different LED brightness bin, the CRC code for each production devices must be calculated independent and burnt during the calibration. The CRC algorithm must be implemented into the LED calibration system in the end of production line.

Figure 6-7 CRC Algorithm Diagram