SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
The ADC supports two signal modes: single-ended and differential.
Each ADC has 6 selectable single-ended or 3 selectable differential inputs.
ADC input sampling has a scaling of 32/18 providing a full-scale range of 3.2V with a 1.8V reference.
In single-ended mode, the input voltage to the converter is sampled through a single pin (ADCINx), referenced to VREFLO.
In differential signaling mode, the input voltage to the converter is sampled through a pair of input pins, one of which is the positive input (ADCINxP) and the other is the negative input (ADCINxN). The actual input voltage is the difference between the two (ADCINxP – ADCINxN).
Note: The above condition is not met by connecting the negative input to VSSA or VREFLO.
In differential mode ADC output code can be estimated using the following equation:
Note: The addition factor is 2112 as the ADC generates a full-scale code in raw o/p mode as 4223.
Based on a given analog input voltage, the expected digital conversion is given in Table 7-143. Fractional values are truncated.
Mode | Digital Value | Analog Equivalent |
---|---|---|
Single-Ended | when | ADCRESULTy = 0 |
when < ADCINx < | ||
when | ADCRESULTy = 4095 |
Based on a given ADC conversion result, the corresponding analog input is given in Table 7-144. This corresponds to the center of the possible range of analog voltages that can produce this conversion result.
Mode | Digital Value | Analog Equivalent |
---|---|---|
Single-Ended | when ADCRESULTy = 0 | |
when 0 < ADCRESULTy < 4095 | ||
when ADCRESULTy = 4095 |
The ADC can be operated in either single-ended or differential mode; the input modes are configured according to Table 7-145.
Chsel<2:0> | Differential Mode | Single Ended Mode |
---|---|---|
000 | inp0-inm0 | inp0 |
001 | inm0-inp0 | inm0 |
010 | inp1-inm1 | inp1 |
011 | inm1-inp1 | inm1 |
100 | inp2-inm2 | inp2 |
101 | inm2-inp2 | inm2 |
110 | inp3-inm3 | inp3 |
111 | inm3-inp3 | inm3 |
The ADC output code is a 12-bit value, but internally the converter can generate slightly more than 12 effective data bits. Single-ended mode clips the output within 0 and 4095 to maintain a 12-bit value; this effectively limits the maximum input of the ADC to 3.2V. Furthermore while each bit of the ADC result is 1/4096 of the full-scale range, an output of 4096 is not possible which means the 4096th output bit gets saturated. This is demonstrated in Table 7-146.
Input | Output Code | |
---|---|---|
Input Voltage | Raw O/P | ADC Result |
0 | 0 | 0 |
0.00078125 | 1 | 1 |
0.0015625 | 2 | 2 |
0.09921875 | 127 | 127 |
0.1 | 128 | 128 |
0.10078125 | 129 | 129 |
3.1984375 | 4094 | 4094 |
3.19921875 | 4095 | 4095 |
3.2 | 4096 | 4095 |
3.29765625 | 4221 | 4095 |
3.2984375 | 4222 | 4095 |
3.29921875 | 4223 | 4095 |