
Analog Integrated Circuit Device Data
Freescale Semiconductor
94
PC34708
Functional Block Requirements and Behaviors
10 Bit ADC Core Block Description and Application Information
7.6.2.3.4
Channel 3 Die Temperature
The relation between the read out code and temperature is given in
Table 95.
The Actual Die Temperature is obtained as follows: Die Temp = 25 + 0.426 * (ADC Code - 680)
7.6.2.3.5
Channel 4 AUX Charger Voltage
The aux charger voltage is measured at the VAUX pin on channel 4. The aux charger voltage is first scaled in order to fit the input
range of the ADC by multiplying by 0.24.
7.6.2.3.6
Channel 5 VBUS Voltage
The VBUS voltage is measured at the VBUS pin on channel 5. The VBUS voltage is first scaled in order to fit the input range of
the ADC by multiplying by 0.4.
7.6.2.3.7
Channel 6 Reserved
Channel 6 is reserved.
7.6.2.3.8
Channel 7 Battery Thermistor
Channel 7 is used to read out the battery pack thermistor. The thermistor is biased to NTCREF (1.5 V) with an external pull-up.
The THERM SPI bit must be set high to enable the NTCREF voltage. To save current when the thermistor reading is not required,
the bias can be disabled by setting the THERM SPI bit low. A resistor divider network should assure the resulting voltage falls
When an application is on and supplied by the charger, a battery removal can be detected by a battery thermistor presence check.
When the thermistor terminal becomes high-impedance, the battery is considered removed. This detection function is available
at the BPTHERM input and can be enabled by setting the BATTDETEN bit. The voltage at BPTHERM is compared to the
NTCREF voltage, and when the voltage exceeds the battery removal detect threshold, the sense bit BATTDETBS is set high,
and after a debounce period the BATTDETBI interrupt is generated.
7.6.2.3.9
Channel 8 Coin Cell Voltage
The voltage of the coin cell connected to the LICELL pin can be read on channel 8. Since the voltage range of the coin cell
Table 95. Die Temperature Voltage Reading
Parameter
Min
Typ
Max
Unit
Die Temperature Read Out Code at 25 °C
680
Decimal
Slope temperature change per LSB
+0.426
°C/LSB
Slope error
5.0
%
Table 96. Battery Removal Detect Specification
Parameter
Condition
Min
Typ
Max
Units
Battery Removal
Detect Threshold
31/32 *
NTCREF
V