TSC2005
www.ti.com
SBAS379–DECEMBER 2006
AUXILIARY AND TEMPERATURE MEASUREMENT
The TSC2005 can measure the voltage from the auxiliary input (AUX) and from the internal temperature sensor.
Applications for the AUX can include external temperature sensing, ambient light monitoring for controlling
backlighting, or sensing the current drawn from batteries. There are two converter functions that can be used for
the measurement of the AUX:
1. Non-continuous AUX measurement shown in Figure 38 (converter function select bits C[3:0] = Control
Byte 1 D[6:3] = 0101); or
2. Continuous AUX Measurement shown in Figure 39 (converter function select bits C[3:0] = Control Byte 1
D[6:3] = 1000).
See Table 7 for more information on the converter function select bits.
There are also two converter functions for the measurement of the internal temperature sensor:
1. TEMP1 measurement (converter function select bits C[3:0] = Control Byte 1 D[6:3] = 0110); or
2. TEMP2 measurement (converter function select bits C[3:0] = Control Byte 1 D[6:3] = 0111).
See Table 7 for more information on the converter function select bits.
For the detailed calculation of the internal temperature sensor, please see the SubSec1 9.3 section. These two
converter functions have the same timing as the non-continuous AUX measurement operation as shown in
Figure 38; therefore, Equation 12 can also be used for internal temperature sensor measurement. The time
needed to make a non-continuous auxiliary measurement or an internal temperature sensor measurement is
given by:
f
LPPRO
fOSC
OH3
fOSC
1
fOSC
OSC )OHCONV
fADC
)ǒN @ B)2 @
(
)
Ǔ@ ǒ Ǔ)ǒ Ǔ
tCOORDINATE
+
(12)
Where:
OH3 = overhead time #3 = 3.5 internal clock cycles.
CS
Deactivated
CS
Deactivated
CS
Deactivated
Reading
AUX-Data
Register
Programmed for
Non-Continuous
AUX Measurement
tCOORDINATE
No Touch
Detected
Sample, Conversion, and
Averaging for AUX Measurement
Host Write to
Control Byte 1 D[6:3]
Waiting for Host to
Read AUX Data
As DAV
Figure 38. Non-Touch Screen, Non-Continuous AUX Measurement
The time needed to make continuous auxiliary measurement is given by:
f
LPPRO
fOSC
OH3
fOSC
1
fOSC
OSC )OHCONV
)ǒN @ B)2 @
(
)
Ǔ@ ǒ Ǔ)ǒ Ǔ
tCOORDINATE
+
fADC
(13)
CS
Deactivated
CS
Deactivated
CS
Deactivated
CS
Deactivated
Programmed for
Continuous
Reading
AUX-Data
Register
Reading
AUX-Data
Register
AUX Measurement
tCOORDINATE
tCOORDINATE
tCOORDINATE
Sample, Conversion,
and Averaging for
AUX Measurement
Sample, Conversion,
and Averaging for
AUX Measurement
Sample, Conversion,
and Averaging for
AUX Measurement
No Touch
Detected
Host to Write to
Control Byte 1 D[6:3]
As DAV
Figure 39. Non-Touch Screen, Continuous AUX Measurement
38
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