East-West Horizontal Convergence Canceling Function; Usb Circuit; Outline; Usb Downstream Power Supply - NEC DPro2070SB Service Manual

1.4.7 East-west horizontal convergence canceling function

It is the function which rectifies automatically change of YHJT, YHJB and XVL, and XVR (between Red
and Blue) by east-west magnetic field change, detects the detection voltage change from IC2S0
(geomagnetism sensor unit), and is carrying out automatic compensation.

1.5 USB circuit

1.5.1 Outline

This monitor loads the standard USB SELF POWERED HUB with 1 upstream and 4 downstreams.
(1) Serial data bus
Data bus is connected from upstream connector CN1A0 to upstream port of HUB controller IC1A0, and
downstream connectors CN1A1 to CN1A4 are connected from HUB controller.
HUB controller relays data communication between the upstream side (PC) and the downstream side
(device).
Port on circuit diagram
(2) Power supply to downstream
USB HUB of this monitor is SELF POWERED HUB, and it can supply the power of +5V 500mA (max)
to each downstream from transformer T902 on PWB-MAIN. Further, HUB controller IC1A0 has the
function of detecting overcurrent, and stops supplying the power to each downstream port when
overcurrent (500mA or more) is detected at each port.

1.5.2 USB downstream power supply

(1) Supply of Vpp power
When HUB controller IC1A0 is recognized from the direction of upstream, the signal which functions
as a switch of power output for a downstream port is output (IC1A0 pins 2, 16, 17 and 32).
When IC1A0 pins 2, 16, 17 and 32 become LOW, FET gates are turned ON (LOW), and EFT
transistors Q1A1, Q1A2, Q1A3 and Q1A4 supply the power to the downstream ports (CN1A1 to
CN1A4) respectively.
(2) Detection of overcurrent
HUB controller IC1A0 has the function of detecting overcurrent. If the current output at each port
exceeds 550mA (min), gates of FET transistors Q1A1, Q1A2, Q1A3 and Q1A4 turn OFF (HIGH),
automatically output of current stops only to the port that overcurrent is detected.
In order to re-operate the port that overcurrent is detected, either of the followings should be carried
out:
1.OFF/ON of monitor power supply
2.Pulling-out and pulling-in of upstream cable
3.Restart of PC

1.5.3 HUB controller power output

HUB controller IC1A0 has a built-in 3.3V regulator, and outputs from IC1A0 pin 1.

1.5.4 USB power on reset

At the time of a power ON and spark detection circuit operation, the reset pulse to USB is output to pin 21
of IC1A0 from pin 2 of IC102. At pin 21 of IC1A0, it is reset by LOW and is reset release by HIGH.
Downstream connection of HUB controller
Port 1
Port 2
Port 3
Port 4
Connector
CN1A1
CN1A2
CN1A3
CN1A4
1- 19
Silk indication
1
4
3
2