Irda And Fuel Gauge; Irda Transceiver; Battery Fuel Gauge And Irda Multiplexing - Siemens SXG 75 Service Repair Documentation

15 IrDA and fuel gauge

The IrDA transceiver and battery fuel gauge communicate with the MSM6250 using the same UART
(a further spare UART is not available). So both functions are covered in this section.

15.1 IrDA transceiver

V2106 is a low power infrared data interface transceiver module. It is compatible to "IrDA - Infrared
Data Association; Serial Infrared Physical Layer Specification, Version 1.3".
It supports transmission rates up to 115.2kbps (Serial IrDA).
As a Low-Power-Device, the infrared data interface has a transmission range of at least:
• 20cm to other Low-Power-Devices and
• 30cm to Standard-Devices
The viewing angle is +/-15° (resulting in 30° viewing cone). The Infrared-Interface implies a Class 1
IRLED, according to IEC 60825-1:1993+A1:1997+A2:2000.
The transceiver module is connected to UART 3 on the MSM6250. The IrDA interfaces are:
• IRDA_RXD. Data from the transceiver, connected to UART3_DP_RX_DATA/GPIO85.
• IRDA_TXD. Data to the transceiver, connected to UART3_DP_TX_DATA/ GPIO84.
• IRDA_EN. This puts the transceiver into low-current shutdown mode when high. It also allows the
transmit power to be varied. See datasheet for more details. IRDA_EN is connected to MPP1 on the
PM6650. MPP1 is configured to use VREG_MSMP as a supply reference.
The IrDA transceiver digital interface is powered from VREG_MSMP. The transmit LED is powered
from VPH_PWR, with a current-limited LED driver.

15.2 Battery fuel gauge and IrDA multiplexing

The battery pack contains a fuel gauge monitor from Texas Instruments (BQ27000). The fuel gauge
signal is a 1-wire HDQ interface. It is multiplexed with the IrDA signal to the UART 3 port on the
MSM6250.
The multiplexing of the IrDA with the fuel gauge is illustrated below.
IrDA and fuel gauge multiplexing
Technical Documentation
TD_Repair_L3_SXG75_R1.0.pdf
Company Confidential
2006©BenQ
Release 1.0
01/2006
Page 63 of 73