Icom IC-T90A Power Supply Circuits, Port Allocations, Voltage Line, 2 R3V Switch IC AF Unit IC51

4-4 POWER SUPPLY CIRCUITS

VOLTAGE LINE

LINE	DESCRIPTION
HV	The voltage from the external power supply or
	attached battery pack.
VCC	The same voltage as the “HV” line (external
	power supply or battery pack).
	Common 3 V converted from the “VCC” line by
CPU3	CPU3 regulator IC (LOGIC unit; IC141). The out-
	put voltage is supplied to the +3C regulator cir-
	cuits, etc.
	Common 3 V converted from the “VCC” line by
+3C	the +3C regulator circuit (LOGIC unit; Q142 and
	Q145) using the +3CPU regulator (LOGIC unit;
	IC141.)
	Common 3 V converted from the “VCC” line by
+3	the +3 regulator circuit (LOGIC unit; Q8 and Q9)
	using the +3C regulator (LOGIC unit; Q142 and
	Q145).
	Common 10 V converted from the “+3” line by
+10V	the +10 regulator circuit(LOGIC unit; IC91, IC92,
	Q91, D91, D300–D302). The output voltage is
	applied to the RF and VCO units.
	6 V for receiver circuit converted from the “VCC”
AFV	line by the “AF” regulator circuit (LOGIC unit;
	Q201, Q202). The output voltage is applied to
	the AF amplifier (AF unit; IC252, pin 2).
R3	3 V for receiver circuit converted from the “+3”
	line by the “R3” regulator circuit (RF unit; O353).
	3 V for the receiver circuit converted from the
R3V	“VCC” line by the “R3V’ regulator circuit (AF unit;
	Q208 and Q209).
	3 V for transmitter circuit converted from the “+3”
T3	line by the “T3” regulator circuit (RF unit; Q56
	and D20). The output voltage is applied to the
	buffer amplifier (RF unit; IC51, pin 6).

4-5 PORT ALLOCATIONS

4-5-1 D/A CONVERTOR IC (RF UNIT; IC251)

Pin	Port	Description
number	name
5	FSET	Outputs frequnecy setting D/A data to
		the reference oscillator (RF unit; X1).
		Outputs the power amplifier’s output
6	PSET	power setting data to the APC con-
		troller (RF unit; IC101).
11	TUNE	Outputs D/A data to the tuned band-
		pass filters (RF unit).
		Outputs the R3 regulator (RF unit;
12	RXC	Q353) control signal.
		High: While receiving.
13	ATT	Outputs attenuator control signal.
		Low: Attenuator is ON.
		Outputs the drive amplifier’s output
14	DSET	power setting data to the APC con-
		troller (RF unit; IC101).

4-5-2 R3V SWITCH IC (AF UNIT; IC51)

Pin	Port	Description
number	name
4	BSFT	Outputs frequency shift control signal
		to tuned bandpass filters (RF unit).
		Outputs 0.5–29.995 MHz band control
5	B1C	signal.
		Low: While 0.5–29.995 MHz band is
		receiving.
		Outputs 30–75.995 MHz band control
6	B2C	signal.
		Low: While 30–75.995 MHz band is
		receiving.
		Outputs 76–229.995 MHz band con-
7	B3	trol signal.
		Low: While 76–229.995 MHz band is
		receiving.
		Outputs 230–629.995 MHz band con-
14	B4C	trol signal.
		Low: While 230–629.995 MHz band
		is receiving.
		Outputs 630–999.995 MHz band con-
15	B5	trol signal.
		Low: While 630–999.995 MHz band
		is receiving.

4 - 7