
Motorola Internal Use
8
P7389i – Circuit Description
5)
EXC
Pin 7
.This output drives the power control port of the exciter. An increase of
this voltage will cause the exciter to increase its output power.
6)
SAT_DET
Pin 12
. If the feedback signal from the RF detector lags too far behind the
AOC signal then this output will go low, indicating that the loop in at or near
saturation. This signals the DSP to reduce the
AOC_DRIVE
signal until
SAT_DET
rises. See
Fig 6.1
7)
AOC_DRIVE
Pin 8
. The voltage on this pin will determine the output power of the
transmitter. Under normal conditions the control loop will adjust the voltage on EXC
so that the power level presented to the RF detector results in equality of the voltage
present at INT and AOC. The input level will be between 0 and 2.5V.
8)
ACT
Pin 9
. This pin will hold a high voltage when no RF is present. Once the RF
level increases enough to cause the detector to rise a few millivolts then this output
will go low. In the GSM radio a resistor is routed between this point and the AOC
input to cause the radio to ramp up the power until the detector goes active.
Logic: Power Up sequence
1)
Three power sources available, battery, External Power via Charger
(Battery must be
present to power up)
2)
Battery Power Source: The L7389i uses the slim 3.6V Lithium Ion battery
AANN4010A. The power from the batteries is taken from
BATT +
(
Battery contacts
J604
) and is routed through the
Battery FET Q901
. Once
B+
is available the unit
carries out the following checks.
•
The battery temperature is monitored to establish whether rapid charge is required,
(
J604
P
in 2
BATT_THERM_AD
to
GCAP II
Pin B3
)
-40 deg C – 2.75V
25 deg C – 1.39V
40 deg C – 0.96V
•
Charger sensed (
J600
Pin 5
MANTEST_AD
to
GCAP II
Pin A1
) This is achieved
using different sense resistors within the accessory.
DMCS
goes high
TX starts
TX_KEY
goes high
SAT_DET
goes low
Linear ramp
down begins
SAT_DET
goes high
Ramp down
ceases
TX_KEY
Goes low
DMCS
goes low
Fig 6.1