Led Power Supply For Display And Touchpad Module - Nokia RH-6 Series Baseband Description & Troubleshooting

CCS Technical Documentation
4 values (x-co-ordinate, y-co-ordinate) are required for every stylus position that is mea-
sured.
GenIO11
GenIO 17
GenIO 12
UPP8M
GenIO18
v2.x
GenIO25
GenIO15
Figure 13: Touchpad module digital and analog interface connections

LED power supply for display and touchpad module

In RH-6, white LED's are used for LCD and keypad lighting. Two LED are used for LCD
lighting and six LED for keyboard. A step up DC-DC converter TK11851 is used as a LED
driver.
The LCD LED's are driven in serial mode to achieve stable backlight quality. This means,
that constant current flow through LCD LED's. Serial resistance Rlcd is used to define the
proper current. The feedback signal, FB, is used to control the current. Driver will increase
or decrease the output voltage for LED's to keep the current stable.
Keyboard LED are driven in 2 serial/3 parallel modes. Serial resistance R is used to limit
the current through LED's. The feedback signal, FB, is not used to control the current.
Driver is controlled by the UEM via DLIGHT output. This signal is connected to driver EN-
pin (on/off). It is possible to control the LED brightness by PWM to achieve smooth on/off
operation.
RH-6 Flip backlighting is implemented with Dual transistor. Four Blue LED's (CL-191B1
are connected in parallel with shunt resistors in series. Constant current is set by exter-
Issue 1 10/2003
Company Confidential
Clk
DIN
Touchpad
Dout
controller
Busy
TSC2046
IRQ
_CS
4*1nF
© 2003 Nokia Corporation.
6 - BB Description & Troubleshooting
ESDA
RH-6
X-
X+
Touchpad
Y-
Module
Y+
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