User Guide

PAMS
UIF Module DU8
NHB–3
Technical Documentation
Original 26/97
Page 5–10
transistors are all wired together and supplied by emitter follower V40. The led
current is fixed by the values of R44 and R45 and the ratio of R51 to R52. The
current is about 5 mA/ each LED. Note that on DU9 flexis, the 17
th
led is driven
from an additional transistor.
The display illumination operates in a similar way to the keyboard drivers, two
transistors are used to drive eight leds. The current in this case is defined by
the value of R46, R47 and the ratio of R51 to R52. It is about 10 mA / each
LED.
The Call LED is fed from a simple emitter follower.
Audio Circuitry
The earpiece is routed directly via series resistors to connector X4. The ear-
piece is dynamic type. The impedance is 32 ohm and sensitivity 118 dB / 1 V.
Microphone is of the electret type and needs a voltage supply for operation.
When MIC_ENA is low bias voltage is connected to the microphone via transis-
tor V8. V2 is wired as a switch for VA1, controlled by the microphone enable
line [MICENA]. VA1 is an analogue rail supplied by the PSL+ chip on the sys-
tem board. It is 4.65V in magnitude. The sensitivity of the microphone is –62
dB (0 dB = 1V/ubar). C26 and C27 in the MIC nodes act as high pass filter with
pulldown resistors on the baseband side.–3dB point is about 100Hz.
The buzzer is dynamic one and the impedance is 25 ohm. Buzzer is driven
from a two transistor switch which acts as a buffer for a CMOS output signal
applied at BUZZER. The ringing volume is controlled by pulse width modula-
tion.The diode V37 prevents damage to the transistor when switched off, ab-
sorbing the stored energy in the buzzer inductance and suppressing large posi-
tive going spikes on the transistor collectors.
Small value capacitors are fitted at critical points in the circuit to avoid problems
with RF interference. One is placed directly across the microphone (C15). V9
has a cap to ground from each of its three terminals (C14, C17 and C21).
There is also capasitors in earphone nodes.
LCD Module Interface
The LCD module includes the LCD and the display driver. The driver TAB is
connected with heat seal connection to the LCD. The LCD is FSTN type. The
duty ratio is 1/32 and the bias ratio 1/6.7. Viewing direction is 6 o‘clock.
The display driver is NJU6406–02 from JRC. It has internal clock oscillator and
negative voltage generator. It has 9600 bit character generator ROM and 64 * 8
bits character generator RAM. The dispaly module is connected to the UIF
module with 24 pin soldered connection.
The display module contains an oscillator to generate a negative voltage re-
quired for operation. The oscillator frequency is fixed on the UIF module by the
resistance from pins 2 to 3 of X1, with the values of R6 and R16 shown, the fre-
quency is within 180 kHz to 370 kHz. The negative going pulses appear at pin 9
of X1 where they are smoothed by C1 to give a voltage which is nominally
equal but opposite to VL1.