Only For Training And Service Purposes - LG KS10 Service Manual

3.5.4 Thermistor (R527)
This thermistor senses temperature variations around UMTS PA to adjust PA gain deviation for
assure compliance with the applicable transmit power control standards. Negative temperature
compensation thermistor is used in the KS10.
3.5.5. UMTS transmit power detector (U504)
This detector couples PA output power level to calibrate the transmitter characteristic over the channel
variation and temperature. Its detector coupling range and converted voltage is based on diode
sensitivity and transmitter power level.
The KS10 uses National Semiconductor ADL5500 power detector IC. In Figure 1.5.5-1, C580 is set to
47ohm&Coupler resulting in an attenuation of 31.4dB. The output voltage is proportional to the
logarithm of the input power. Figure1.5.5-2 shows the output voltage versus PA output power of the
ADL5500 setup as depicted in Figure1.5.5-1
Figure 1.5.5-1 Block diagram of ADL5500 with resistive tap
Figure 1.5.5-2 Power detector response, Vout vs PA output power
Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

3. TECHNICAL BRIEF
- 31 -
LGE Internal Use Only