Motorola T200 Service Manual page 63

Topaz T2688/T200, T2988/T205 L3 Circuit Description
VEGA IC and has a range of approximately 1.2V – 1.5V. The Oscillator supply is
generated from the
13Mhz is buffered by IC402 before being O/P as 13MHz to
system clock.
68. At the same time it is input to the Synthesiser IC on Pin 1 OSCin, from here the IF
tuning voltage IF_TUNE
(TRANSMIT) to drive the 540 / 135MHz Varactor diode.
69. All the controlling signals for the IC are generated from
DATA, the signals are clocked in (Pin 15 CLK) and the IC is enabled using the
control logic SYNPRG
70. The IF Support voltage for the IC is SYN2V8, a 2.8V support, generated in the
Voltage Regulator IC301
the synthesiser IC is switched off during idle time. This sample is fed into Pins 6 and
7.
71. The Feedback from the 540 / 135MHz Varactor diode is returned to the IC as the
signal LO2 and is fed in on Pin 3 (finif). To complete the phase lock loop.
72. On the RF side, the supporting voltage is again
(vccrf). The charge pump output for the TXVCO is fed out on Pin 8 (Dorf) to the
RXVCO U401 Pin 3.
73. The band select signal
to either GSM or DCS on Pin 1. The output will then be fed out to the
LO1 to create the 1
provide Phase Lock Loop feedback.
Power up Sequence
74. The main core of the power up sequence next to the operating software is the
Management IC U27.
?
DVCC – 2.765V @ 100mA and provides the Base-band logic supplies. Pin 2
?
AVCC – 2.765V @ 130mA and provides for analogue voltage supplies. Pin
27
?
VTCXO
?
VRTC – To charge to the Real Time Clock battery U32 (when battery voltage
falls below 1.2V). Pin 8
75. The battery voltage
76. Once power is supplied to the unit, there are a number of ways that the unit can be
powered up. The input pulse is a 40mS +ve going pulse through
onto U27 inputs Pins 4&5,
12
Base-band Voltage Regulator U27
as spoken about in points 12 (RECEIVE) and 46
on Pin 13(LE)
Pin 2 (OUTC). A sample of this voltage is taken to ensure
U401 is supported by SYN2V8.
BS enters U401
st
IF, and also a sample will be fed back into the
U27 contains 4 Voltage regulators.
– 2.765V @ 5mA – for use to drive the system 13Mhz clock. Pin 24
VBAT on Pin 1 supplies U27.
Motorola Proprietary Information
Pin 24 (VTCXO 2.8V). The
Gemini
SYN2V8 and enters on Pin 11
on Pin 4 and will select the appropriate output
VEGA for use as the
and enter on Pin 14
RF
TX / RX IC
Synthesiser IC
Power
U53 and U54 and
as
to