Control System
The CPU (IC1203) sends and receives data to/from the FPGA (IC1) and the image processing IC (IC2) through serial
communication. This CPU also sets parameters for the LPF and the A/D converter through I²C communication.
Brightness, contrast, peaking potentiometer level signal lines are connected to CPU's A/D input ports to control them.
The D/A output ports are connected to the analog dimming control pins of the LED driver ICs (IC1401, IC1502) to
control backlight and UP TALLY brightness.
The FPGA (IC1) performs PWM dimming control for TALLY/INDICATOR, backlight ON/OFF control through the
LED driver IC (IC1401), and brightness control using the PWM dimming control in conjunction with the contrast
potentiometer. Furthermore, this FPGA performs I²C communication or serial communication with the connected
camera.
ROM
The onboard EEPROM (IC1208) retains setup data, operating hours of the unit, and other data. The EEPROM (IC105)
also retains model information of the unit such as serial number.
The FPGA can be upgraded through CN400. (Refer to
“1-9-3. Writing and Rewriting PLD Internal Data”
)
Power Supply Block
This block has 16 outputs that operate within the proper input power voltage range.
• Power input switching circuit
This unit is provided with other three power input methods: power supply from the CAM (camera) connectors (20p
and 26p) and power supply from the DC IN connector. Each power input is connected to the FET switch (Q1631,
Q1632, Q1635, Q1636, Q1639, and Q1640). When power is input to the DC IN connector, the DC IN connector
is preferentially selected.
• Input voltage monitoring circuit
The input voltage monitoring circuit (IC1601) supplies power to the DC/DC controller IC (IC1603) when the input
voltage is within the proper range.
Power supply operates when the input voltage is within the proper range (+9.5 to +17.5 V). Once power is supplied,
the power supply block works within an input voltage range of +8.3 to +18.5 V. If the input voltage lowers below
+8.3 V or rises above +18.5 V, Q1605 is turned off to shut off supply of UNREG power. The UNREG power
voltage is not restored until it enters the proper range.
• Protective circuit
The DC-DC converter (IC1700, IC1701, IC1702, and IC1800) incorporates an output error detection circuit. When
an error is detected in any output, the POWERGOOD pin is turned low. The POWERGOOD pin output signal is
input to IC1003. When an error is detected, the SHUTDOWN signal is output. This SHUT DOWN signal turns off
Q1605 to shut off the UNREG power supply.
HDVF-L750/HDVF-L770
1-6
