Table of Contents
Advertisement
9-3-3. Bias voltage generator IC (IC708) for LCD
LCD is driven by steps shaped AC voltage as shown to the right.
The number of steps shown to the right is three. This is called 1/3 bias.
Generally, if the quantity of pixels in a LCD common line is N dots, the
quantity of bias is 1/ N . At this time, contrast of LCD display becomes
maximum. The quantity of pixels in a LCD common line is 160 dots. There-
fore, the quantity of bias is set to 1/13 by this bias voltage generator circuit.
9-3-4. Countermeasure against EMI (Electro Magnetic Interference) with BN Unit
The copper films for shield and wires connecting between grounds on PC board are used for counter-
measure against EMI. If these parts doesn't exist, data transfer between BN Unit and MODOEM /PC
will not be performed.
9-3-5. EL (Electroluminescence) driver IC (IC701) (BN-20 only)
This IC is a DC/AC inverter for EL.
V5SYS terminal voltage (DC 5 V) is converted to AC output terminal voltage (AC 180 V
, 100 Hz,
P-P
triangle wave form) loading EL. When V5SYS terminal voltage becomes less than about 4.5 V or EL
button on the keyboard is pressed twice and so on , ENA terminal voltage becomes to be about 0 V,
and blue light from EL disappears.
— 47 —
Hide quick links:
Advertisement
Table of Contents
