MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
19-114
Freescale Semiconductor
shows, for this particular case, examples of how the result values change according to GCC
and OCC when result calibration is executed (CAL=1) and when it is not (CAL=0).
19.5.6.3
Quantization Error Reduction During Calibration
shows how the ADC transfer curve changes due to the addition of two to the MAC output
during the calibration - see MAC output equation in
Section 19.4.5.4, “ADC Calibration Feature
. The
maximum absolute quantization error is reduced by half leading to an increase in accuracy.
Figure 19-68. Quantization Error Reduction During Calibration
19.5.7
eQADC versus QADC
This section describes how the eQADC upgrades the QADC functionality. The section also provides a
comparison between the eQADC and QADC in terms of their functionality. This section targets users
familiar with terminology in QADC.
is an overview of a QADC.
of the eQADC system.
Table 19-58. Calibration Example
Input Voltage
Raw result (CAL=0)
Calibrated result (CAL=1)
Hexadecimal
Decimal
Hexadecimal
Decimal
25% VREF
0x0ED6
3798
0x1000
4095.794
75% VREF
0x2D48
11592
0x3000
12287.486
4
Ideal Transfer Curve
0
Shifted Transfer Curve
ADC Transfer Curve
Input Voltage
(12-bit A/D Resolution)
Digital Value
(14-bit Result)
1/2
lsb
lsb
0
–4
Error for Shifted Transfer Curve
Input Voltage
(12-bit A/D Resolution)
Quantization Error
1/2
lsb
lsb
Error for ADC Transfer Curve
2
–2
Summary of Contents for MPC5553
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