LG KG290 - Page 43

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3. TECHNICAL BRIEF
♦ Temperature Sensing System
The AD6852 includes voltage reference buffers and Auxiliary ADC inputs for measuring the
temperature of the system oscillator crystal (to compensate for temperature variations) and the
battery temperature (for charging applications). Each of these external temperatures may be
measured using an external thermistor in series with an external resistor. The temperature ranges
are based on the requirements of 3GPP TS 51.010-1 version 5.2.1 Release 5 (2003-02), Annex 1
(normative): Reference test methods, A1.2: Normal and extreme Test Conditions (TC). The more
narrow temperature span, + 15 ˚C to + 80 ˚C, provides for a difference between operating
temperature and ambient temperature under normal test conditions of up to 45 ˚C. There are two
temperature measurement channels available, TEMP1 and TEMP2. TEMP1 is chosen if the
BatTempCh bit in the AuxControl2 register (0x14) is set low. TEMP2 is chosen if the bit is high.
♦ Auxiliary Section Control Registers
The AD6852 Auxiliary ADC digital interface provides a method for making a single Auxiliary ADC
measurement and a method for updating the battery condition. If a single Auxiliary ADC
measurement is desired, the Auxiliary ADC channel can be selected and the Auxiliary ADC
enabled. After the conversion is complete the interrupt is asserted. The result can be read from the
AuxADCM (0x18 ) and AuxADCL (0x19 ) registers. If the battery condition update is desired, the
BatCondition bit in the AuxControl2 register should be set. The battery condition is determined by
reading the BatCondM (0x1A ) and BatCondL (0x1B ) registers four times.
♦ Light Controllers
The AD6852 Auxiliary Section provides three independent PWM light controllers. The PWM output
controllers regulate the average current through active lights.
Minimum Output Frequency fMCLK / 262144 Hz
Maximum Output Frequency fMCLK / 256 Hz
The output frequencies of the LIGHTx PWM output controllers are set by the
Light12Period (0x2F ) and Light3Period (0x31 ) control registers.
With fMCLK = 13 MHz, frequencies ranging from 50.781 kHz to 49.591 Hz may be specified.
fLIGHT1 = ( fMCLK / 256 ) / ( Light12Period[9:0] + 1 )
fLIGHT2 = ( fMCLK / 256 ) / ( Light12Period[9:0] + 1 )
fLIGHT3 = ( fMCLK / 256 ) / ( Light3Period[9:0] + 1 )
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