ADS7951-Q1: ADS7951-Q1Inaccurate acquisition accuracy

Hi user6251042,

welcome to our forum.

When applying an exact 0V input signal to an ADC, you rarely read a conversion code of exactly 0x0000. This is because of the inherent offset of any ADC.
However the code you are reading is much larger than the offset error specified in the ADS7951-Q1 datasheet. Means there is something off.

Could you share more details about the settings of the ADC and potentially a schematic to see if we can identify any problems there?

Regards,

Hi,thank you for your reply!

My MCU is Frescale MC9S12G128 and the Communication mode is SPI.CPOL=0,CPHA=0;

this is my code :

void ADS1(void)
{
ADS1_CS = 0;
SPI0_send(0x1980);
temp1 = SPI0_receive();
temp11=temp1>>12;
temp1 = temp1<<4;
temp1 = temp1>>4; 
delay1us(20);
ADS1_CS = 1;
delay1us(20);

ADS1_CS = 0;
SPI0_send(0x1200);
temp2 = SPI0_receive();
temp12=temp2>>12;
temp2 = temp2<<4;
temp2 = temp2>>4; //采集电池总电压,单位mV
delay1us(20);
ADS1_CS = 1;
delay1us(20);

ADS1_CS = 0;
SPI0_send(0x1280);
temp3 = SPI0_receive();
temp13=temp3>>12;
temp3 = temp3<<4;
temp3 = temp3>>4;
ADS1_CH3 = (unsigned long int)(((unsigned long int)(temp3)*2500/4095)*255); 
delay1us(20);
ADS1_CS = 1;
delay1us(20);


ADS1_CS = 0;
SPI0_send(0x1300);
temp4 = SPI0_receive();
temp14=temp4>>12;
temp4 = temp4<<4;
temp4 = temp4>>4;
ADS1_CH4 = (unsigned long int)(((unsigned long int)(temp4)*2500/4095)*255); 
delay1us(20);
ADS1_CS = 1;
delay1us(20);}

Hi user6251042,

thanks a lot for providing those details. One of my colleagues who is an expert on this ADC will get back to you.

Regards,

Hi，can you give me the solution for this problem?thanks