MC68HC11KA4TS Datasheet, PDF (48/68 Pages) Motorola, Inc – 8-Bit Microcontroller

9 Analog-to-Digital Converter
The analog-to-digital (A/D) converter system uses an all-capacitive charge-redistribution technique to
convert analog signals to digital values. The MC68HC11KA4/KA2 A/D converter system is an 8-channel
(four channels on 64-pin version), 8-bit, multiplexed-input, successive-approximation converter. It does
not require external sample and hold circuits. The sample and hold time is 12 clock cycles. Refer to Fig-
ure 15.
The clock source for the A/D converter's charge pump, like the clock source for the EEPROM charge
pump, is selected with the CSEL bit in the OPTION register. When the E clock is slower than 1 MHz,
the CSEL bit must be set to ensure that the successive approximation sequence for the A/D converter
will be completed before any charge loss occurs. In the case of the EEPROM, it is the efficiency of the
charge pump that is affected.
PE0
AN0
PE1
AN1
PE2
AN2
PE3
AN3
ANALOG
MUX
PE4
AN4
PE5
AN5
PE6
AN6
PE7
AN7
8-BIT CAPACITIVE DAC
WITH SAMPLE AND HOLD
SUCCESSIVE APPROXIMATION
REGISTER AND CONTROL
RESULT
ADCTL A/D CONTROL
V_RH
V_RL
INTERNAL
DATA BUS
RESULT REGISTER INTERFACE
ADR1 A/D RESULT 1
ADR2 A/D RESULT 2
ADR3 A/D RESULT 3
ADR4 A/D RESULT 4
Figure 14 A/D Converter Block Diagram
EA9 A/D BLOCK
The A/D converter can operate in single or multiple conversion modes. Multiple conversions are per-
formed in sequences of four. Sequences can be performed on a single channel or on a group of chan-
nels.
MOTOROLA
48
MC68HC11KA4
MC68HC11KA4TS/D