TDMA T2290/T2297:
Reference Oscillator
B20
The reference oscill ator U150, operating at 19.44MHz, provides a "reference frequency" for the RF synthesize rs and various logic circuits.
The OSC_DIS line which is controlled by U1000 (CPU) is used to turn off U150 during sleep mode. The OSC_DIS line switches Q151 on or off, controllin g the supply
voltage to U150 and Q152.
U1800 (DCI) can "fine tune" U150 via the AFC line. Tuning of the reference oscillator is needed to synchroniz e frequencie s with the cellula r base station, therefore, the
signal re ceived from the base wil l be used to determine th e correct reference frequency.
The output of U150 is split into two sign als. RF_19 .44MHz is used for the RF frequency reference. Output 19.44MHz is amplified by Q152 and then sent to the logic
section for logic clock synchronization.
Q152
U150
OSC_DIS
RX_2.75
AFC
19.44MHZ
RF_19.44MHZ
Q151
Description
Summary of Contents for T2290
Page 1: ...DIGITAL WIRELESS TELEPHONE Service Manual Level 3 Release 1 TDMA T2290 T2297 ...
Page 26: ... 2000 Motorola Inc TDMA T2290 T2297 Cellular Overview 16 ...
Page 40: ...Motorola Confidential Proprietary TDMA T2290 T2297 TDMA Test Mode NAM Programming 30 ...
Page 68: ...Disassembly TDMA T2290 T2297 Keypad Removal Motorola Confidential Proprietary 58 ...