Audio Interference And Suspension Of Pulse Charging; Mmi; Display - Siemens SXG 75 Service Repair Documentation

Hide thumbs Also See for SXG 75:

Table of Contents

10 Audio interference and suspension of pulse charging

The low frequency pulsing of the charge current which takes place in TOPOFF charge mode makes

audible interference when the phone is in a state where audio circuits are active. Hence in all such

modes TOPOFF is suspended and constant current (FAST) charging becomes the only available

charging mode.

In this mode if the battery voltage falls below 4.0V FAST charging will be started and will terminate

when the voltage reaches 4.2V in both cases the voltage is read from the fuel gauge.

Consequently assuming that the charger can supply sufficient current to run phone activity and

supply charge current, the battery voltage will be maintained to always be 4.0V or greater. If the

phone is removed from the charger just before FAST charging is about to recommence then the

battery will not be fully charged. However a high percentage of charge will remain at a battery

voltage of 4.0V and satisfactory performance should be achieved for the user.

11.1.1 Overview

The SXG75 display is a 2.2" QVGA (240x320) TFT display with 262 k (18 bit) color depth. The

supplier for the TFT display is Epson - there is no second source. The controller is integrated with

the display module.

The display interface is connected to the 16-bit wide external bus interface (EBI2) of the MSM6250,

which is also shared with the NAND Flash. The display I/O supply voltage (VIO) is 1.85 V

(VREG_MSME) while the main display power supply (VDD) is 2.9 V (generated by regulator

N2201).

The display backlight is generated by 4 white LEDs connected in series inside the display module.

The LED chain is powered from a supply voltage of 18.75 V generated by a step-up converter. The

brightness is controlled by a current sink circuit driven by the MSM6250 (more details below). The

display is blanked at power-up and after a hardware reset.

Technical Documentation

TD_Repair_L3_SXG75_R1.0.pdf

Company Confidential

2006©BenQ

Release 1.0

01/2006

Page 50 of 73

Table of Contents