Power Supply For Leds - Nokia NPL-4 Series Manual

NPL-4/5/RM-104
System Module and User Interface
are first written high and then one column at the time is written down. All other col-
umns except one, which was written down, are set as inputs. Rows are read while col-
umn at the time is written down. If some row is down it indicates that key which is at
the cross point of selected column and row was pressed. After detecting pressed key all
register inside the UPP are reset and columns are written back to zero.
ROW0
ROW1
ROW2
ROW3
ROW4

Power supply for LEDs

DC/DC converter generates VLED supply voltage for white LEDs. There are two white LEDs
connected series in display and on keypad PWB in four branches. The flashlight has one
white LED. Feedback resistors R300, R302 and R310 set output voltage. The voltage ref-
erence is 0.515V inside the driver.
Driver is controlled by the UEMEK via CALLED1 output. This signal is connected to driver
EN-pin (on/off). R317 is used to increase converter output current.
CALLED
Copyright © 2005 Nokia Corporation. All rights reserved.
Page 68
Table 28: Key mapping
COL0 COL1
VOL+ LEFT
VOL- SOFT LEFT
1
SELECT 2
PTT 3
Figure 28: VLED Voltage Supply
Nokia Customer Care
COL2 COL3
SEND END
UP DOWN
4 7
5 8
6 9
COL4
RIGHT
SOFT RIGHT
*
0
#
Issue 2 05/05