Sony DXC-S500, Service Manual

Page: 50 / 148

6-6
DXC-S500 (E)
6-6. SY-301 Board
The SY-301 board consists of the following blocks.
.
DC/DC converter for generating the power used in the whole CCU
.
DSP circuit that processes the camera image data input from camera head unit
.
ARMCPU circuit located in the same DSP as RISC-CPU that performs the system control of DXC-
S500
The SY-301 board is a system control board that mounts SDRAM of 256 MB that memorizes an image
around CPU, an interface circuit, CPU working SRAM, external timer function RTC, and EEPROM that
stores ARM program flash memory and adjustment values or initial value data. In other words, the SY-
301 board is designed to control all functions of CCU and CHU. However, an IEEE1394 circuit is
controlled jointly with the H8 microcomputer on the FM-84 board. (Refer to section 6-5.)
n
The schematic diagram of the SY-301 board is divided into five blocks and described in this manual. The
schematic diagram is here described in one-division units. Refer to “Section 10 Schematic Diagrams” for
the schematic diagram of the SY-301 board.
1. DC/DC converter power circuit (1/5 circuit)
This is a DC/DC converter circuit that generates the power supplied to the board in CCU.
The generated voltage becomes a 9 VLCD monitor voltage of 12 V used on the PD-106 board and the
voltage used on the SY-301 and FM-84 boards when a voltage of 12 V is input from the switching
regulator of CCU to the SY-301 board. The voltage used on the SY-301 board is a circuit power supply
of
+
2.5 V,
+
3.3 V (D),
+
5 V, and
+
5 V(D).
Actually, a 46-pin SQFP-type IC package of 12 V is used in Q302 so as to obtain the controller of a
switching regulator. Q302 has a four-channel internal controller and generates a voltage.
Switching regulator functions
Reference voltage circuit
The reference voltage circuit uses the temperature-compensated reference voltage (2.5 V), generated by
the power supplied from pin 18 (power pin) of IC201, as the operation power inside IC. This circuit can
also read the reference voltage from pin 19 of IC201 to the outside as a Vref signal.
Chopping wave generator circuit
The chopping wave generator circuit generates an arbitrary chopping wave oscillation waveform by
connecting a timing capacitor (C204) and resistor (R206) to pins 17 and 16 of IC201, respectively. The
amplitude of this waveform is 1.3 V to 1.9 V. The chopping wave is input to the PWM converter inside
IC201 to drive each channel.
Error amplifier
The error amplifier detects the output voltage of a switching regulator and outputs a PWM control signal.
It has a wide in-phase input range and can facilitate the voltage setting. The error amplifier also sets the
gain and voltage arbitrarily by connecting a feedback resistor and capacitor from the output pin of the
error amplifier to the inversion input pin.