Power Supply Circuits - Icom IC-2GA Service Manual

(4) VCO CIRCUIT (RF UNIT)
D701 changes the inductive reactance of the oscillator
(Q702), shifting the receive and transmit frequencies.
Varactor diode D702 provides frequency control. Q703
buffer amplifies the VCO output signal; Q701 buffer ampli-
fies the PLL feedback signal.
(5) UNLOCK SENSOR CIRCUIT
When the PLL circuit is unlocked, pin 7 of IC2 is "LOW" and
a "LOW" signal is applied to the unlock sensor (Q23). The
unlock sensor outputs a current amplified "LOW" signal to
the CPU, ІС503 (ріп 60).
r ки!
| M VCO UNIT |
| |
| |
| 0703 |
from | Buffer |
МЕЗЕ
=.
|
> +
> T/R switching
|
|
circuit
RF bandpass filter -
4
disp | ола
| Buffer | шег
|
| CHARGE PUMP | > |
\ CONTROL
|
|
Q21, Q22
LC сылын
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лш 4
F RANGE
14| 8
ІС? | |
ТЕЛЕ
COUNTER AND LATCH
ZN
CHARGE PUMP
Q6, Q8
12
L | | PHASE DETECTOR
5
DATA
CK
| SHIFT REGISTER
4-4 POWER SUPPLY CIRCUITS
(1) VOLTAGE LINES
Battery pack output that passes through the
power switch. Vcc is applied to the power
module (!С3), the AF power amp regulator, and
the following 5 V lines.
Common 5 V current-amplified at (Q207, Q208)
using IC output as a reference voltage. The
heat factor of the voltage at 0207 (Vac) equals
that of the junction voltage at Q208. The
output is stable even with regard to tempera-
ture changes.
Common 5 V controlled by the power save
function. Current-amplified at Q213, Q214.
5 V controlled by the power save function.
Current-amplified at Q211, Q212. Used by the
receiver circuits.
5 V current-amplified at Q209, Q210. Used by
the transmitter circuits.
PLL STLB
COUNTER AND LATCH
(2) VOLTAGE REGULATOR CIRCUIT
(MAIN UNIT)
When the battery voltage is 5.5—16 V, the regulator (ІС204)
outputs a reference voltage of 5 V. The noise components
are removed by the noise filter (C220, R213). This output is
applied to the current amplifier (Q207, Q208).
(3) CPU POWER SUPPLY CIRCUIT (LOGIC UNIT)
When the power is turned off, voltage from the lithium
battery is applied to the CPU, ІС501 (pin 52) via D502.