MOTOROLA V100
Service Manual

Circuit Description

Product Family 38C

is amplified through tuned transistor amplifier Q252 before being used to mix with the received frequencies through the emitters of the dual mixer transistor Q450. The mixer produces sum and difference signals consisting of RX frequency plus RX VCO frequency and RX frequency minus RX VCO frequency. The difference signal is fed to SAW (surface acoustic wave) filter FL457. The purpose of the SAW filter is to provide comprehensive removal of harmonics created during the mixing process. The resulting 400 MHz IF signal is passed to isolation amplifier Q480. The isolation amplifier couples the analog IF signal to the following circuit which has a different ground and also protects the base-band signals from stray RF. The isolation amplifier is supported by Magic IC U200 Pin C7 SW_VCC.

Isolation Amp

MAGIC IC U200

Base-band Signal

101001010100

000714-O

000714-O

Figure 2. IF Isolation Amplifier Operation The IF signal is then passed to the Magic IC U200 Pin A7 PRE IN where it is demodulated using external 800 MHz varactor diode CR249 (RX local oscillator set up), which is driven by from Magic IC U200 Pin A9 LO2_CP. The demodulated signal is converted internally to base-band digital form and passed along the RX SPI bus to the Whitecap IC. The RX SPI signal is made up of BDR (base-band data receive), BFSR (Base-band Frame Synch Receive) and BCLKR (base-band clock receive), fed from Magic IC Pin G8, Pin G9, and Pin F7 respectively. The Whitecap IC U800 receives these signals on Pin A3, Pin D4, and Pin B4. Within the Whitecap IC the signal is digitally processed to reduce Baud rate and remove error correction bits. The resulting digital signal is fed down the DIG_AUD_SPI bus to the GCAP II U900, where it is converted to analog form and distributed to the correct outputs: The Alert is generated within the Whitecap IC, given the appropriate data from the incoming signal or SMS, and is fed to the alert pads LS1. This signal is supported by ALRT_VCC, which is generated from B+ through Q903. For the headset only, the SPKR signal is used from GCAP II Pin H6. The output is fed out to the headset jack J504 Pin 3.

Transmit
Analog voice is fed from the Aux Microphone attached to the headset and is routed from Pin 1 of the headset jack J504 to GCAP II, Pin H3. Within the GCAP II, the analog audio is converted to digital and clocked out onto the DIG_AUD SPI bus to the Whitecap IC U800.

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MOTOROLA CONFIDENTIAL - PROPRIETARY November 20, 2000

6881036B20