Tool/software:
I created a small PCB using the TLV320ADC3120.
The inputs are set as single ended Input, INX-M tied to GND.
SIGNALS:
VREF: 2.50V
AREF: 1.80V
AVDD: 3.37V
VDD: 3.41V
All seem pretty stable, hence why i did not attach a screenshot of my scope.
What am I trying to measure:
Currently a 18.9 kHz Signal, 90mV PP (0V to 90mV), no DC offset.
The signal is coupled directly to IN2 with a 1kOhm Resistor.
IN1 is floating at the Moment.
Configuration:
I am using a STM32L533 for communication with the ADC. It is configured using I2C and Data is transferred using SAI.
data[0]=(SW_RESET_RESET); HAL_I2C_Mem_Write(&hi2c1,0x9c,SW_RESET_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(SLEEP_CFG_AREG_SELECT_INTERNAL | SLEEP_CFG_SLEEP_ENZ_ACTIVE|SLEEP_CFG_VREF_QCHG_100_MS); HAL_I2C_Mem_Write(&hi2c1,0x9c,0x02,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(ASI_CFG0_WLEN_32_BITS); HAL_I2C_Mem_Write(&hi2c1,0x9c,ASI_CFG0_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(BIAS_CFG_MBIAS_VAL_VREF); HAL_I2C_Mem_Write(&hi2c1,0x9c, BIAS_CFG_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(IN_CH_EN_CH1_ENABLED | IN_CH_EN_CH2_ENABLED); HAL_I2C_Mem_Write(&hi2c1,0x9c,IN_CH_EN_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(ASI_OUT_CH_EN_CH1_ENABLED | ASI_OUT_CH_EN_CH2_ENABLED); HAL_I2C_Mem_Write(&hi2c1,0x9c,ASI_OUT_CH_EN_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(CH1_CFG0_INTYP_LINE | CH1_CFG0_INSRC_SINGLE |CH1_CFG0_DC_DC ); HAL_I2C_Mem_Write(&hi2c1,0x9c,CH1_CFG0_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(CM_TOL_CFG_CH2_INP_FULL |CM_TOL_CFG_CH1_INP_FULL); HAL_I2C_Mem_Write(&hi2c1,0x9c,CM_TOL_CFG_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(CH1_CFG2_DVOL_MUTE); HAL_I2C_Mem_Write(&hi2c1,0x9c, CH1_CFG2_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(CH2_CFG2_DVOL_0dB); HAL_I2C_Mem_Write(&hi2c1,0x9c, CH2_CFG2_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(CH2_CFG0_INTYP_LINE | CH2_CFG0_INSRC_SINGLE |CH2_CFG0_DC_DC ); HAL_I2C_Mem_Write(&hi2c1,0x9c,CH2_CFG0_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100); data[0]=(PWR_CFG_ADC_PDZ_ON | PWR_CFG_PLL_PDZ_ON | PWR_CFG_MICBIAS_PDZ_OFF ); HAL_I2C_Mem_Write(&hi2c1,0x9c,PWR_CFG_ADDRESS,I2C_MEMADD_SIZE_8BIT,data,1,100);
Channel 1 is Muted, since I wanted to verify that my SAIconfiguration is working and correct.
SAI is configured to 96kHz Master Receive on the STM32 side.
The data I receive is this:
The 0 are correct since channel 1 is muted. But on Channel 2 I am not measureing my signal. As you can see, thavalues are jumping between a positive and a negative value.
In the data you see, I tied the IN2_P directly to GND so i should measure a somehow stable value. If i connect my signal the values look really similar.
If i am measureing the Open Circuit IN1-P i read a DC offset on that pin of 1.47V. On Pin 2 it is 0.45V when my signal is connected (or 0V if IN2 is grounded).
I am sure i misconfigured something. Does anybody have a hint for me?
