Tait Orca 5000, Руководство по обслуживанию

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June 2003 IPN: M5000-00-105
Tait Orca vehicle kit F - 21
D4 and R46 create a virtual ground (VGND)
and protect the MAX1627 from over voltages.
Conducted noise is filtered by C42, C43 and
L5. The blocking diode, D6, stops the radio
battery from powering the vehicle kit when the
current source is off.
The radio is protected from over voltages at the
battery terminal by IC5:C, IC5:D and their
associated circuity. If the voltage at the output
(BAT1) reaches approximately 10.3 V, then Q3
is turned on by the Schmitt trigger IC5:D. This
changes the feedback from current controlled
(via IC5:B) to voltage controlled (via IC5:C).
The non inverting amplifier of IC5:C is config-
ured such that it overrides the output of IC5:B
and sets the output voltage to approximately
10.6 V.
The current source is normally controlled by
the micro controller (IC3). When pin 20 goes
low, the current source is turned on.
Fast charger micro controller
IC3 is a 68HC05 based micro controller, which
runs custom charger software to control the
current source and intelligently monitor the
charge state of the battery. Note that this
software behaves differently from the desktop
fast charger software. When working correctly
the microcontroller will always make the LED
glow orange for 3 seconds whenever power is
reapplied.
The line into IC3 pin 1 (RESET) is used by the
5 V regulator (IC1) to control the startup of
IC3. RESET is only released by IC1, once power
has stabilised and the circuits are powered up.
The RESET line is also controlled by the power
save circuity, so that the fast charger can be
turned off.
The control line for the current source is IC3
pin 20, with low being on and high impedance
being off. This line controls the current source,
via Q7.
The coarse voltage input used for general
voltage measurements is IC3 pin 16. The
expanded voltage input used for fine voltage
measurements is IC3 pin 17. Battery tempera-
ture is measured via IC3 pin 18. This pin is
pulled to ground via a 10 k
Ω
(nominal)
thermistor inside the battery case. The battery
capacity input used to tell the charger whether
the battery is NiCd or NiMH is IC3 pin 19.
The line to IC3 pin 7 is an input which tells the
micro controller when the vehicle kit PTT is
activated. The line to IC3 pin 9 is an input
which tells the micro controller when the radio
is on.
Vehicle kit power supply input protection
Power to the circuit (13.8 V nominal) is provid-
ed through a Mini Fit Molex connector.
Protection circuitry consists of a 22 V transient
suppressor (D1) and a 2.5 A PolySwitch™
(PS1). C11 and C12 provide some filtering of
the input power.
Over voltage protection is also provided by D1.
Short transient over voltage (>22 V) pulses will
be clamped by D1, preventing harm to the
circuit. Longer sustained over voltage condi-
tions, such as incorrect connection to a 24 V
vehicle supply, will cause D1 to conduct and
eventually fail to a short circuit state. This will
result in a power lead fuse blowing or PS1
tripping, if the fuses are of the incorrect rating
(> 3A) or not fitted (i.e. the line is shorted).
Vehicle kit power supply 5 volt regulator
IC1, an L4949, is the 5 V regulator for the
vehicle kit and produces the +5 V rail. It also
controls the RESET line of the micro controller
under startup and will reset the micro control-
ler if there are any voltage dips. C13 is fitted to
improve output noise and transient response.
C14 sets the reset delay time. The tantalum
capacitor C15 maintains the stability of the
output voltage. The maximum current availa-
ble from the +5 V rail is 100mA.
Vehicle kit power supply power save
The low voltage shut down (LVSD) circuitry on
the charger PCB is used to power down
sections of the vehicle kit under various condi-