KX-UT670RU - Panasonic Telephone Service Manual (repair manual). Page 13

13

The circuit of the LCD backlight is composed of the step-up convertor circuit of the fixed current type.
The connector for backlight of LCD module is connected with CN303. 
Output current flows in order of L332,LCD module,L340 and R324/R325.
Output current is fixed by pin 3(200mV) of IC302.
If LCD backlight connector is not connected,IC302 operates so that may step up the voltage at pin3(FB) of IC302 to 200mV.
But, the output voltage is limited with the terminal of pin5 of IC302 as for the output voltage.  
The brightness of the LCD backlight is controlled in the ratio of ON/OFF of the voltage supplied from IC1(CPU) to pin4 of IC302

To recognize coordinates of the pushed point
When X coordinates are detected
After the voltage is impressed between the plus and the minus of X coordinates, the voltage value of the pushed part is read with
the terminal on Y coordinates side.

 When Y coordinates are detected
After the voltage is impressed between the plus and the minus of Y coordinates, the voltage value of the pushed part is read with
the terminal on X coordinates side.

This operation is repeated, and detection and the movement of coordinates are recognized.

XPLUS

XMINUS

YPLUS

YMINUS

IC1

AD14 TSC_XPLUS_UL

AE13 TSC_YPLUS_UR

AC14 TSC_XMINUS_LR

AD13 TSC_YMINUS_LL

AE14 TSC_WIPER

AC13 TSC_AUXIN

AB13 TSC_NEGIN

AA13 TSC_VTSCOUT

E22 CLD0

C23 CLD1

AC7

MIC0_A_BIAS

F22 CLD2

B24 CLD3

G22 CLD4

J21 CLD5

H22 CLD6

J22 CLD7

K21 CLD8

D23 CLD9

C24

AD6

MIC0_AP

AE6

MIC0_AN

AD10

SPK0_AP

AE10

SPK0_AN

AB7

MIC0_B_BIAS

AC6

MIC0_BP

AB6

MIC0_BN

AB10

SPK0_BP

AC10

SPK0_BN

AD7

MIC1_A_BIAS

AC8

MIC1_AP

AB8

MIC1_AN

AC12

SPK1_AP

AB12

SPK1_AN

XPLUS

YMINUS
XMINUS

YPLUS

CN302

1

2

3

4

D308

2

1

3

D309

2

1

3

D310

2

1

3

D311

2

1

3

3.3V

DG

C385 22p 1 2 3 45

6

7

8

DG

L339

1
2
3
4

5

6

7

8

YPLUS

XMINUS

YMINUS

XPLUS

To CN302

Resistive Type of Transparent Touch-panel