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Analog Integrated Circuit Device Data
62
Freescale Semiconductor
13892
FUNCTIONAL DEVICE OPERATION
Because of an order from the United States International Trade Commission, BGA-packaged product lines and part numbers indicated here currently are not
available from Freescale for import or sale in the United States prior to September 2010: MC13892VK and MC13892VL in 139, 186 MAPBGA packages.
Figure 12. 13892 Coulomb Counter Block Diagram.
PROTECTIONS AGAINST FAULT CONDITIONS
Counter roll over: CCOUT[15:0]=8000HEX
This occurs when the contents of CCOUT[15:0] go from a
negative to a positive value or vice versa. Software may
interpret incorrectly the battery charge by this change in
polarity. When CCOUT[15:0] becomes equal to 8000HEX the
CCFAULT is set. The counter stays counting so its contents
can still be exploited.
Battery removal: ‘BP<UVDET’
When removing and replacing the battery, the contents of
the counter are no longer valid. A battery removal is
characterized by the input supply to the IC dropping below
the under-voltage detect threshold, so BP<UVDET. To avoid
false detection due to short power cuts, the CCFAULT is set
only after a long debounce of 1.0 second.
Battery removal when charging: BATTDETBS=1
The battery removal detection as described previously is
not applicable when charging, since in this case, the charger
will continue to supply the application and the BP will not drop
below UVDET. To still detect a battery removal, one can use
on page 61. When the sense bit BATTDETBS becomes a 1,
the CCFAULT is set only after a long debounce of 1.0
second.
Touch Screen Interface
The touch screen interface provides all circuitry required
for the readout of a 4-wire resistive touch screen. The touch
screen X plate is connected to TSX1 and TSX2, while the Y
plate is connected to TSY1 and TSY2. A local supply TSREF
will serve as a reference. Several readout possibilities are
offered.
To perform touch screen readings, the processor will have
to select the touch screen mode, program the delay between
the conversions via the ATO and ATOX settings, trigger the
ADC via one of the trigger sources, wait for an interrupt
indicating the conversion is done, and then read out the data.
In order to reduce the interrupt rate and to allow for easier
noise rejection, the touch screen readings are repeated in the
readout sequence.
The reference for the touch screen is
TSREF and is powered from VCORE. In touch screen
operation, TSREF is a dedicated regulator that is to
say, no other loads than the touch screen should be
connected here.
Table 17. 13892 Touch Screen ADC Readings
ADC CONVERSION
SIGNALS SAMPLED
0
X position
1
X position
2
Dummy
3
Y position
4
Y position
5
Dummy
6
Contact resistance
7
Contact resistance