Motorola Internal Use
7
V2288 – Circuit Description
presence detection of the batteries is decided within the COVIC by comparing the
actual battery voltage with the
B+
created by the charger (
Q960
à
CR960
à
Q691
). If
B+
is higher than the normal operating voltage of the batteries,
PWR_ON
will go
low, powering the phone off. Battery voltage is sensed by
B+
Pin E10
GCAP II when
battery not present, or
BATTERY
Pin F7
GCAP II when batteries are present this is
then output to Whitecap as
BATT_SENSE
.
5)
Test Adapter Source:
B+
is sent directly from the external power source i.e. replaces
the battery power source entirely and therefore the unit has no requirement for the
batteries to be present.
6)
The GCAP II is programmed to Boost mode (5.6V) by
PGB0
Pin G7
and
PGM1
Pin
G8
both being tied to Ground. Once
B+
is applied to GCAP II
Pin K5
, all the
appropriate voltages to supply the circuit are provided. These are:
•
V1
– Programmed to 5.0V.
V1
is at 2.775V at immediate power on, but is ‘boosted’
to 5.0V through the switch mode power supply
L901 / C901 / CR902
and
C913
. See
Fig 6.1 for basic operation.
V1
supplies the DSC bus drivers, negative voltage
regulators and MAGIC.
V1
is created from GCAP II
Pin A6
and can be measured on
C906
.
The basic circuit operation for the Boost circuit is as follows the
LX
signal (GCAP II
Pin B10
) allows a path for
B+
to charge the capacitor, when the switch is on, the
capacitor then discharges through the inductor (switch off), setting up an electric
field. The field then collapses setting up a back EMF to charge the capacitor, and so
on and so on. The back EMF created by the inductor is greater than
B+
with the +ve
half of the cycle passing through the diode to charge a capacitor from where the
V_BOOST
voltage is taken. The frequency of the switching signal
LX
decides the
duty cycle of the output wave and therefore the resultant voltage.
V_BOOST
is fed
back into the GCAP.
•
V2
– Programmed to 2.775V, available whenever the radio is on and supplies most of
the logic side of the board.
V2
is supplied out of GCAP II
Pin J2
and can be
measured on either
C939
or
C941
.
•
V3
– Programmed to 2.003V to support the Whitecap, but does support the normal
2.75V logic output from the Whitecap, it originates from GCAP II
Pin B5
and can be
measured on
C909
or
C910
.
•
VSIM1
– Used to support either 3V or 5V SIM cards. Will dynamically be set to 3V
upon power up, but if the card cannot be read then the SIM card is powered down and
an attempt to read the card at 5V is tried. VSIM1 can be measured on C905 and is
distributed from GCAP II
Pin
C6
(For further information, see SIM Card Operation).
LX
Output
B+
Fig 6.1
