TSC2101_08 Datasheet, PDF (42/95 Pages) Texas Instruments – AUDIO CODEC WITH INTEGRATED HEADPHONE, SPEAKER AMPLIFIER AND TOUCH SCREEN CONTROLLER

TSC2101
SLAS392D− JUNE 2003 − REVISED MAY 2005
Battery
+
0.5 to 6 V −
R
LDO or DC-DC ^{3.0 V to 3.6 V}
Converter
V_DD
VBAT
8 kΩ
2 kΩ
ADC
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Figure 33. Battery Measurement Functional Block Diagram
Battery measurement can only be done in host−controlled mode.
See the section Conversion Time Calculation for the TSC2101 and subsection Non Touch Measurement
Operation in this data sheet for timing diagrams and conversion time calculations.
For increased protection and robustness, TI recommends a minimum 100−Ω resistor be added in series
between the system battery and the VBAT pin. The 100-Ω resistor will cause an approximately 1% gain change
in the battery voltage measurement, which can easily be corrected in software when the battery conversion data
is read by the operating system.
Auxiliary Measurement
The auxiliary voltage inputs (AUX1 and AUX2) can be measured in much the same way as the battery inputs
except the difference that input voltage is not divided. Applications might include external temperature sensing,
ambient light monitoring for controlling the backlight, or sensing the current drawn from the battery. The auxiliary
input can also be monitored continuously in scan mode.
The TSC2101 provides feature to measure resistance using auxiliary inputs. It has two modes of operation:
(1) External bias resistance measurement (2) Internal bias resistance measurement. Internal bias resistance
measurement mode does not need an external bias resistance of 50 kΩ, but provides less accuracy because
of on chip resistance variation, which is typically ±20%. Figure 34 shows connection diagram for resistance
measurement mode on AUX1.
VREF
VREF
AUX1
R
50 kΩ
SAR
Vsar
50 kΩ
AUX1
R
50 kΩ
SAR
Vsar
a. Internal bias, Resistance Measurement
b. External bias, Resistance Measurement
Figure 34. Connection DIagram for Resistance Measurement
Resistance can be calculated using following formula:
R + 50 KW
Vsar
VREF * Vsar
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