MMC2107 Datasheet, PDF (487/618 Pages) –

Freescale Semiconductor, Inc.
Queued Analog-to-Digital Converter (QADC)
Pin Connection Considerations
V_DDA
V_RH
16 CHANNELS TOTAL
SAMPLE
AMP
S/H
RC DAC
COMPARATOR
CP
V _SSA
VRL
Figure 18-45. Equivalent Analog Input Circuitry
defined by V_RL and V_RH. If V_RH is greater than V_DDA, the sample
amplifier can never transfer a full-scale value. If V_RL is less than V_SSA,
the sample amplifier can never transfer a 0 value.
In addition, V_RH and V_RL must be within the range defined by V_DDA and
V_SSA. As long as V_RH is less than or equal to V_DDA and V_RL is greater
than or equal to V_SSA and the sample amplifier has accurately
transferred the input signal, resolution is ratiometric within the limits
defined by V_RL and V_RH. If V_RH is greater than V_DDA, the sample
amplifier can never transfer a full-scale value. If V_RL is less than V_SSA,
the sample amplifier can never transfer a 0 value.
Figure 18-46 shows the results of reference voltages outside the range
defined by V_DDA and V_SSA. At the top of the input signal range, V_DDA is
10 mV lower than V_RH. This results in a maximum obtainable 10-bit
conversion value of $3FE. At the bottom of the signal range, V_SSA is
15 mV higher than V_RL, resulting in a minimum obtainable 10-bit
conversion value of three.
MMC2107 – Rev. 2.0
MOTOROLA
Queued Analog-to-Digital Converter (QADC)
For More Information On This Product,
Go to: www.freescale.com
Technical Data
487