XC68HC705JJ7 Motorola, XC68HC705JJ7 Datasheet - Page 138

• Manufacturer Part Number: XC68HC705JJ7
• Description: MICROCONTROLLER
• Manufacturer: Motorola

Analog Subsystem
8.9 Current Source Features
8.10 Internal Temperature Sensing Diode Features
8.11 Sample and Hold
Advance Information
138
NOTE:
The internal current source connected to the PB0/AN0 pin supplies
about 100 A of current when the discharge device is disabled and the
current source is active. Therefore, this current source can be used in an
application if the ISEN enable bit is set to power up the current source
and by setting the A/D conversion method to manual mode 0 (ATD1 and
ATD2 cleared) and the charge current enabled (CHG set).
An internal diode is forward biased to V
change, V
device. This temperature sensing diode is powered up from a current
source only during the time that the diode is selected. When on, this
current source typically adds about 30 A to the I
The temperature sensing diode can be selected by setting both the
HOLD and DHOLD bits in the AMUX register (see
Register).
When using the internal sample capacitor to capture a voltage for later
conversion, the HOLD or DHOLD bit must be cleared first before
changing any channel selection. If both the HOLD (or DHOLD) bit and
the channel selection are changed on the same write cycle, the sample
may be corrupted during the switching transitions.
The sample capacitor can be affected by excessive noise created with
respect to the device’s V
charge up depending on the voltage level stored on the sample
capacitor. It is recommended to avoid switching large currents through
the port pins while a voltage is to remain stored on the sample capacitor.
The additional option of adding an offset voltage to the bottom of the
sample capacitor allows unknown voltages near V
then shifted up past the comparator offset and the device offset caused
D
, for each degree centigrade rise in the temperature of the
Analog Subsystem
SS
pin such that it may appear to leak down or
MC68HC705JJ7 • MC68HC705JP7 — REV 4
SS
and will have its voltage
DD
8.3 Analog Multiplex
SS
current.
to be sampled and
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