Datasheet
4
UCC2305
UCC3305
PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNITS
Timing Capacitor Section (cont.)
SLOPEC Discharge Current SLOPEC = 2.2V, VCC = 0V, BOOST = 0V,
BYPASS = 8V
40 100 200 nA
WARMUPC Charge Current WARMUPC = 0V –525 –375 –275 nA
WARMUPC = 2V –525 –375 –300 nA
WARMUPC = 6V –200 –120 –75 nA
WARMUPC Voltage, Charging I
WARMUPC = –250nA 3.39 3.8 4.1 V
WARMUPC Discharge Current WARMUPC = 5V, VCC = 0V, BOOST = 0V,
BYPASS = 8V
23 50 126 nA
WARMUPC = 1V, VCC = 0V, BOOST = 0V,
BYPASS = 8V
51034nA
WARMUPC Voltage, Discharging I
WARMUPC = 25nA, VCC = 0V, BOOST = 0V,
BYPASS = 8V
1.5 1.9 2.3 V
ADJ Bias Current V
ADJ = 0V
−38 −20 −12 µA
WARMUPV Voltage WARMUPC = 1V 0.05 0.125 0.25 V
WARMUPC = 2V 0.09 1.00 1.5 V
WARMUPC = 3V 2.3 2.48 2.66 V
WARMUPC = 5V 4.5 4.8 5.25 V
WARMUPC = 10V 4.5 4.8 5.25 V
BYPASS Voltage VCC = 0V 8.8 9.6 V
BYPASS Current VCC = 0V, BOOST = 0V, BYPASS = 8V 2.5 7
µA
ELECTRICAL CHARACTERISTICS (cont.) Unless otherwise stated, VCC = 6.6V, ISET = 100k
Ω
to GND, ADJ = 100k
Ω
to GND, OSC = 200pF to GND, BAT = 4V, LOADISENSE connected to LPOWER, VOUTSENSE = 0.666V, BOOST = 10.5V,
COMP connected to FB through a 100k
Ω
resistor, –40°C<T
A<+105°C for the UCC2305, 0°C<TA<+70°C for the UCC3305, and
T
A=TJ.
5VREF: Circuitry in the UCC3305 uses the internal 5V
reference to set currents and thresholds. This reference
can also be used for other functions if required.
ADJ: The ratio of cold lamp peak current to warmed-up
lamp peak current is controlled by the voltage on ADJ. To
select this voltage, connect a resistor from ADJ to GND.
BAT: This input is used to detect excessively high input
voltage and shut down the IC if the input exceeds a pre
-
determined level. Connect BAT to a voltage divider
across the input supply. The UCC3305 shuts down when
this input voltage exceeds 5V. To protect the IC in the
event of very high or negative inputs, keep divider imped
-
ance higher than 10k.
BOOST: Although the UCC3305 is powered from the
VCC input, most functions of the device operate from a
supply voltage of approximately 10V connected to
BOOST. This 10V supply can be generated by a voltage
doubler using PUMPOUT as an AC signal and external
diodes as switches.
BYPASS: The UCC3305 compensates for lamp tempera
-
ture changes by changing the voltage on the SLOPEC
and WARMUPC capacitors. These voltages rise as the
lamp warms up. An internal calculation determines what
power should be applied to the lamp.
When the HID lamp is turned off, power to the lamp and
the controller is removed, leaving these two critical ca
-
pacitors charged to specific voltages. Also, with power
off, the lamp will cool down at a controlled rate. It is es
-
sential that the two capacitors discharge at a similarly
controlled rate so that if the lamp is restarted before the
lamp is fully cooled, the controller will have an estimate
of new lamp temperature, and can again command the
correct power for the lamp.
Power to control the discharge of these capacitors comes
from energy stored in a large capacitor connected to BY
-
PASS. The value of the capacitor required can be esti
-
mated assuming a maximum BYPASS current of 5µA, a
discharge time of 60s, and a maximum allowable droop
of 5V by:
C=I
t
V
=5 A
60s
5V
=60 F••
∆
∆
µµ
COMP: Differences between commanded lamp power
and desired lamp power are amplified by an error ampli
-
fier. This amplifier senses the difference between the
voltage at FB and 2.5V, and drives COMP with an ampli
-
fied error voltage. A capacitor is normally connected from
COMP to FB to compensate the overall feedback loop so
that the system will be stable.
PIN DESCRIPTIONS