MC68HC705JP7 Datasheet, PDF (118/242 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Analog Subsystem
NOTE:
Voltage comparators power up slower than digital logic and their outputs
may go through indeterminate states which might set their respective
flags (CPF1, CPF2). It is therefore recommended to power up the
charge current source first (ISEN), then to power up any comparators,
and finally clear the flag bits by writing a logic 1 to the respective CPFR1
or CPFR2 bits in the ACR.
CP1EN
The CP1EN enable bit will power down the voltage comparator 1 in
the analog subsystem. Powering down a comparator will drop the
supply current. This bit is cleared by a reset of the device.
1 = Writing a logic 1 powers up voltage comparator 1
0 = Writing a logic 0 powers down voltage comparator 1
ISEN
The ISEN enable bit will power down the charge current source and
disable the discharge device in the analog subsystem. Powering
down the current source will drop the supply current by about 200 µA.
This bit is cleared by a reset of the device.
1 = Writing a logic 1 powers up the ramping current source and
enables the discharge device on the PB0/AN0 pin.
0 = Writing a logic 0 powers down the ramping current source and
disables the discharge device on the PB0/AN0 pin.
NOTE:
The analog subsystem has support circuitry which draws current. This
current will be powered down if both comparators and the charge current
source are powered down (ISEN, CP1EN, and CP2EN all cleared).
Powering up either comparator or the charge current source will activate
the support circuitry.
Advance Information
118
MC68HC705JJ7 • MC68HC705JP7 — REV 4
Analog Subsystem
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