Ampro Corporation 486E Selecting Vee Polarity, LCD Bias Supply Option, J4 Pin J3 Pin Description

Product Reference

LCD Bias Supply Option

The LCD Bias supply option is a small circuit board that supplies Vee power to an LCD display. The board converts the +5V from the Little Board/486e CPU to the Vee voltage (between 15V – 35V) required by many LCD panels. This voltage is available on flat panel connector J3.

LCD displays are sensitive to the sequence order and timing that power supply and control signals are applied to the display during power up and removed during power down cycles. LCD manufactures warn OEMs that violating the sequence and timing specifications of these signals can damage the display or reduce its service life. The LCD Bias supply option, in conjunction with control signals from the Little Board/486e video controller automatically sequences the appropriate signals to meet the requirements of virtually any LCD display

The Ampro LCD Bias Supply option mounts parallel to the Little Board/486e CPU connected to the board via a 12-pin connector, J4. Secure the board to the Little Board/486e CPU using a .6 inch standoff. Table 2–32 shows the connector pinout for J4, with a description of each signal. Some signals also appear on flat panel connector J3.

Table 2–32. LCD Bias Supply Option Connector (J4)

J4 Pin	J3 Pin	Description
1		Ground
2		+5V to the Vee Supply Option Board
4		Ground
6	38	Enable Vee
		TTL control signal driver by the VGA controller chip
8		Ground
11	46	Vee output, to panel
12	47	Contrast adjustment
		Analog control signal

Selecting Vee Polarity

Most LCD displays require a Vee supply of between 15v – 35V. Some panels need a negative supply, and some a positive supply. The LCD Bias Supply Option provides a jumper for selecting the Vee output polarity. To select the polarity for the panel being used, set the jumper on W1 on the LCD Bias Supply board, not on the Little Board/486e CPU, as shown in Figure 2–-9.

W1

Selects Negative Vee

Selects Positive Vee

Figure 2–9. Vee Polarity Selection Jumper

2–39