Motorola Internal Use
6
V2288 – Circuit Description
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)
a power source via the test adapter, to allow power to be
applied to the unit whilst there is no battery present.
2)
T2288 charger will only work with NiCd and NiMH, Lithium Ion and Alkaline
batteries are not supported.
3)
Battery Power Source: The unit will contain 3 X 1.2V Nickel Metal Hydride (NiMH)
cells each 700mAH, type AAAL (theses are different to AAA regular batteries) part
number SNN5518A. They are connected to the unit by
battery contacts J605
and
produce
B+
through
Q691
4)
Charger Power Source: When the charger is connected (
IRQ4
goes low),
V2
(GCAP)
will provide a supply onto the sense resistor within the charger, the resultant voltage
drop over the resistor is sensed by the signal
MAN_TEST_AD
(approximately 2.4V),
CHGR_SW
must be high. This is sent to the GCAP II
Pin A1
, this decides the
charging current that the charger is capable of delivering. The GCAP II then checks
the MOBPORTB line (
PWR_ON
from
COVIC U960
). If the batteries are present
and in usable range,
PWR_ON
is pulled to 6.7V and the unit will power on. The
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
