Read Panasonic KX-DT321UA Service Manual online
7
KX-DT321UA/KX-DT321UA-B
4.2.2.
LCD Control Circuit
KX-DT321 uses a 16 characters by 1 line LCD.
Power is supplied to LCD from +5V rail, formed as follows:
Pin 24 of IC6 is made to switch, forming a square waveform which is input to IC8 pin 2. The output of IC8 pin 4 switches between
+3.3V and 0V. When the output is low, C603 charges via D61. When output is high, anode of D62 rises to 6V and C601 is charged
via D62. D63 limits the voltage across C601 to +5V. D5V powers the LCD and also IC10.
Pin 24 of IC6 is made to switch, forming a square waveform which is input to IC8 pin 2. The output of IC8 pin 4 switches between
+3.3V and 0V. When the output is low, C603 charges via D61. When output is high, anode of D62 rises to 6V and C601 is charged
via D62. D63 limits the voltage across C601 to +5V. D5V powers the LCD and also IC10.
IC10 is a converter circuit to allow the 3V output of IC6 to drive the LCD, which uses 5V inputs.
LCD contrast is adjusted by means of voltage level supplied at pin 3 of LCD module.
It is adjusted to one of 3 settings by means of a bias circuit (R600, R622) and IC6 pins 19 and 59, according to the following table:
It is adjusted to one of 3 settings by means of a bias circuit (R600, R622) and IC6 pins 19 and 59, according to the following table:
Data is sent to the LCD module via IC10 from the processor using a 3-wire interface (IC6 pins 13, 14, 15).
Contrast
IC6 pin 59
IC6 pin 19
High
L
L
Middle Z
L
Low
Z
L
Click on the first or last page to see other KX-DT321UA service manuals if exist.