User's Manual

XFIN-BLADE-SM

TECHNICAL DESCRIPTION PAGE 47

The 2 groups of analogue switches are independently controlled by FPGA binary signals

MUX A0 and A1 and enable line MUXEN to output the required tuning voltages as a series

of pulses. These pulses are converted to steady state voltages by integration capacitors

C904 to 911 and C921 to 925.

4.3.7 RF Sub-Assembly Internal Power Supplies

4.3.7.1 Power On Function

This set of functionality is designed for normal use in a vehicle environment; hence much

of it is unused in this product.

The unregulated 13.8V DC input is routed directly to high current devices and is also

switched via FET Q350. The output from Q350 feeds three, low drop out series regulators

and associated switched and auxiliary supplies that along with a negative voltage

generator provide all the switched power requirements of the transceiver.

Q315/316/317 and U313 form a power on/off latch circuit that is activated by a pulse from

the control unit or microphone/handset via PWR ON or PWR OFF and controls the FET

power switch Q350. A PWR OFF operation requires the button to be held down for more

than 2 seconds. This is then sensed by the FPGA via the PWR SENSE line that turns the

radio off by placing a positive pulse on the PWR OFF line thereby resetting U313B.

4.3.7.2 Power Lines

The following is a list of the internal RF Sub-Assembly’s power supplies and some of the

devices and circuits they supply.

+8V Regulator U310

Regulated +8.0V supply (8V0 and +8V)

• TX buffer Q612

• VCOs and VCO buffers via active filter Q615

• RX second local oscillator via Q403

Regulated +8.0V switched supply (RX PSU)

• RX front-end

• IF Amplifier

• Various switching functions

+5V Regulator U311

Regulated +5.0V supply (5V0 and +5V)

• RX front-end varactor positive bias

• Synth. buffer Q607

• VCO varactor negative supply Q700 to Q703

• TCXO U700

• RX audio amplifiers U803A/B

• RX mute switch Q810/813

• Multiplexer U902

• FE TUNE level translator and buffer U901A, Q900/901

Regulated +5.0V switched supply (TX PSU and TX PSU+)

• TX power control U3