43B
Service Manual
3-10
keep running, and the test tool is not operative: the test tool is in the Mask active state.
For test purposes the mask active mode can also be entered by pressing the ^ and > key
when the test tool is turned on.
If valid software is present, one of the three modes Operational, Operational &
Charge or Charge will become active. The Charger/Converter circuit is active in the
Operational & Charge and in the Charge mode. The Fly back converter is active in the
Operational and in the Operational & Charge mode.
Charger/Converter (See also Figure 3-3.)
The power adapter powers the Charge Control circuit in the P-ASIC via an internal linear
regulator. The power adapter voltage is applied to R501. The Charger/Converter circuit
controls the battery charge current. If a charged battery pack is installed VBAT is
approximately +4.8V. If no battery pack is installed VBAT is approximately +15V. The
voltage VBAT is supplied to the battery pack, to the P-ASIC, to the Fly Back Converter,
and to transistor V569. The FET control signal CHAGATE is a 100 kHz square wave
voltage with a variable duty cycle, supplied by the P-ASIC Control circuit. The duty
cycle determines the amount of energy loaded into L501/C503. By controlling the
voltage VBAT, the battery charge current can be controlled. The various test tool
circuits are supplied by the Fly Back Converter and/or V569.
Required power adapter voltage
The P-ASIC supplies a current to reference resistor R516 (VADALOW pin 8). It
compares the voltage on R516 to the power adapter voltage VADAPTER on pin 20
(supplied via R502, and attenuated in the P-ASIC). If the power adapter voltage is below
10V, the P-ASIC output pin 12, and the line MAINVAL, are low. This signal on pin 12
is also supplied to the P-ASIC internal control circuit, which then makes the CHAGATE
signal high. As a result FET V506 becomes non-conductive, and the Charger/Converter
is off.
Battery charge current control
The actual charge current is sensed via resistors R504-R506-507, and filter R509-C509,
on pin 9 of the P-ASIC (IBATP). The sense voltage is supplied to the control circuit.
The required charge current information is supplied by the D-ASIC via the CHARCUR
line and filter R534-C534 to pin 80. A control loop in the control circuit adjusts the
actual charge current to the required value.
The filtered CHARCUR voltage range on pin 80 is 0... 2.7V for a charge current from
0.5A to zero. A voltage of 0V complies to 0.5A (fast charge), 1.5V to 0.2A (top off
charge), 2.3V to 0.06A (trickle charge), and 2.7V to 0A (no charge). If the voltage is > 3
Volt, the charger converter is off (V506 permanently non-conductive).
The D-ASIC derives the required charge current value from the battery voltage VBAT.
The P-ASIC converts this voltage to an appropriate level and supplies it to output pin 78
(BATVOLT). The D-ASIC measures this voltage via the Slow ADC. The momentary
value, and the voltage change as a function of time (-dV/dt), are used as control
parameters.
Charging process
If the battery voltage drops below 5.2V, and the battery temperature is between 10 and
45°C, the charge current is set to 0.5A (fast charge). From the battery voltage change -
dV/dt the D-ASIC can see when the battery is fully charged, and stop fast charge.
Additionally a timer in the D-ASIC limits the fast charge time to 6 hours. After fast
charge, a 0.2A top off charge current is supplied for 2 hours. Then a 0.06A trickle
To Next Page
Loading...
Need help?
General
