SLASFM1A June 2025 – December 2025 AFE10004-EP
PRODUCTION DATA
In the following figure, the TEMP column represents the temperature value to the LUT. This value is produced by either the local temperature sensor, the remote temperature sensor, or provided directly by the user.
TEMP is truncated to a resolution of 4°C/LSB to index the LUT. The overall transfer function is stored in the LUT as a set of unsigned 4-bit increments from the BASE value; that is, LUT location (+1) stores the value of the increment Δ1. The baseline is set to 24°C and BASE is the numeric representation of the required output at the BASELINE temperature.
When TEMP exceeds the BASELINE temperature, the LUT is addressed greater than the BASELINE address, and all increments are added to the BASE value to produce DACIN, a numeric equivalent of the analog output. When TEMP is less than the BASELINE temperature, LUT is addressed less than the BASELINE, and all increments are subtracted from the BASE value.
The interpolation function is implemented in the ALU that follows the LUT. The truncated lower bits of the TEMP value, REM = TEMP[5:0], are used to interpolate between data points stored in the LUT. A portion of increment, αΔi, is added to form the final input data to the DAC. The factor α is a fraction of 4°C temperature span, or equivalently a fraction of the 64-code temperature span, that is α = REM/64.
Figure 6-10 depicts the process of calculating DACIN, including the interpolation. DACIN is the final 13-bit value produced by the ALU and the LUT, and forwarded to the DAC for conversion to analog domain.
Up to this point, the algorithm description referred only to the generation of a monotonically increasing transfer function. The device also produces a monotonically decreasing transfer function by setting the LUT polarity bit.
Figure 6-11 shows the effect of polarity reversal on the overall transfer function. The LUT content is unchanged from the original example in Figure 6-9. Notice that now, the LUT values stored at locations greater than the BASELINE address are subtracted from BASE value, and the LUT values stored at locations less than the BASELINE address are added to the BASE value.
Equation 6 and Equation 7 summarize the expressions used in the calculation of the transfer function:
LUT index > BASELINE:
LUT index < BASELINE: