Analog-to-Digital Converter (ADC)
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
26-26 Freescale Semiconductor

26.5.2.1 Single-Ended Samples

The ADC module performs a ratio metric conversion. For single ended measurements, the digital result is
proportional to the ratio of the analog input to the reference voltage in the following formula:
Single-ended measurements return the max value 32760 when the input is at VREFH, return 0 when the
input is at VREFL, and scale linearly between based on the amount by which the input exceeds VREFL.

26.5.2.2 Differential Samples

For differential measurements, the digital result is proportional to the ratio of the difference in the inputs
to the difference in the reference voltages (V REFH and VREFL). Figure 26-22 shows typical configurations
for differential inputs.
When converting differential measurements, the following formula is useful:
Diff erential measurements return the max value 32760 (= 4095 × 8) when the plus (+) input is VREFH and
the minus (−) input is VREFL, return 0 when the plus (+) input is at VREFL and the minus (−) input is at
VREFL, and scale linearly between based on the voltage difference between the two signals.
SingleEndedValue round VIN VREFL
VREFH VREFL
----------------------------------------- 4095×()8×=
VIN = Applied voltage at the input pin
VREFH and VREFL = Voltage at the external reference pins on the device (typically VREFH = VSSA and
VREFL = VDDA)
Note: The 12-bit result is rounded to the nearest LSB.
Note: The ADC is a 12-bit function with 4096 possible states. However, the 12 bits have been left
shifted three bits on the 16-bit data bus so its magnitude, as read from the data bus, is now
32760.
DifferentialValue round VIN1VIN2
VREFH VREFLO
-------------------------------------------4095×()8×=
VIN = Applied voltage at the input pin
VREFH and VREFL = Voltage at the external reference pins on the device (typically VREFH = VSSA and VREFL =
VDDA)
Note: The 12-bit result is rounded to the nearest LSB.
Note: The ADC is a 12-bit function with 4096 possible states. However, the 12 bits have been left
shifted three bits on the 16-bit data bus so its magnitude, as read from the data bus, is now
32760.