PS-SAU-1900E
Mar. 8
th
,1999 (Rev. 0.0)
--- CONFIDENTIAL AND PROPRIETARY ---
32
•
the housing’s internal temperature falls below -15(+/-5)
°
C.
•
the housing’s internal temperature rises above 50(+/-5)
°
C.
The Battery Management module has three outputs, as shown below.
Output Signal
Type
Function
AC_POWER
Analog
Indicates whether AC power is present.
MSM ADC levels as follows:
•
ADC <= 0x4D: No AC.
•
ADC > 0x4D: AC present.
BATT_TEMP
Analog
Battery Temperature monitor. Set-points
are placed for both the low and high
temperature limits.
V_BATT Analog
Indicates battery voltage level. The
following conditions are tested:
•
V_BATT <= 0x86: Battery is low.
Values in
italics
are the settings at power-up.
The Battery Management circuit has three analog outputs, shown above, which are fed into the MSM
ADC through the MSM pin BATT_THERM. The control of which output is connected to the MSM input
pin is through an analog MUX.
AC_POWER is monitored to determine if AC_POWER is present or not. If AC power is not present, then
the unit is running on battery power. If this is the case then the software will go to the battery voltage
monitoring state.
The software monitors the battery voltage through the output V_BATT. If the V_BATT reading from the
ADC drops below the minimum set point for more than one second, the battery is shut off.
If AC_POWER is present, the software shall go into the Temperature Monitoring state. In this state the
software monitors the battery temperature through the output BATT_TEMP. If a Temperature Out Of
Range condition is detected the charger is shut off. Otherwise, the charger remains on.
3.2.4.
GPIO Expansion Bus.
The purpose of the GPIO Expansion Bus is to serially expand the available four MSM GPIO control lines
into 16 outputs. These four control lines, and their functions, are defined below:
GPIO Pin
Signal Name
Function
GPIO_2
GPIO_EXPAND_CS
Strobes data to outputs of shift registers.
GPIO_3
GPIO_EXPAND_CLK
Clocks data into the registers serially.
GPIO_4
GPIO_EXPAND_DATA
Data to be clocked in.
GPIO_19
GPIO_EXPAND_ENAB
Chip enable. Outputs of shift registers are
enabled when this bit is set to “1”.
Values in
italics
are the settings at power-up.
The bus is initialized by clocking 16 zeroes with the GPIO_EXPAND_ENAB set low. After the data is
clocked in it is strobed to the output of the registers by a low to high transition on the
