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

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

510

34

nA

WARMUPC Voltage, Discharging

BYPASS = 8V

1.5

1.9

2.3

V

ADJ Bias Current

−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

Ω to GND, ADJ = 100kΩ

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

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 5

µA, 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