UNITRODE UCC2305, UCC3305 Technical data

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HID Lamp Controller
FEATURES DESCRIPTION
Regulates Lamp Power
Compensates For Lamp
Temperature Fixed Frequency Operation
Overcurrent Protected
Overvoltage Shutdown
Open and Short Protected
High Current FET Drive Output
Operates Over Wide Battery
Voltage Range: 5V to 18V
The UCC3305 integrates all of the functions required to control and drive one HID lamp.The UCC3305 is tailored to the demanding, fast turn-on requirements of automobile headlamps, but is also applicable to all other lighting applications where HID lamps are selected. HID lamps are ideal for any lighting applications that can benefit from very high efficiency, blue-white light color, small physical lamp size, and very long life.
The UCC3305 contains a complete current mode pulse width modulator, a lamp power regulator, lamp temperature compensation, and total fault protection. Lamp temperature compensation is critical for automobile headlamps, because without compensation, light output varies dramatically from a cold lamp to one that is fully warmed up.
The UCC2305 is tested for full performance with ambient temperature from –40°C to +105°C while the UCC3305 is tested with ambient temperature from 0°Cto+70°C. The UCC3305 is available in a 28 pin small-outline, surface mount plastic package (SOIC).
application
INFO
available
UCC2305 UCC3305
BLOCK DIAGRAM
SLUS297B - SEPTEMBER 1995 - REVISED APRIL 2004
UDG-94091-1
UCC2305 UCC3305
ABSOLUTE MAXIMUM RATINGS
VCC Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0V
BOOST Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 12.0V
PWMOUT Current, Peak ............................±1.0A
PWMOUT Energy, Capacitive Load . . . . . . . . . . . . . . . . . 5.0µJ
Input Voltage, Any Input. . . . . . . . . . . . . . . . . . –0.3V to +10.0V
Output Current, QOUT, QOUT
Output Current, 5VREF, LPOWER, COMP. . . . . . . . . ±10.0mA
ISET Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –1.0mA
Storage Temperature . . . . . . . . . . . . . . . . . . . 65°C to +150°C
Junction Temperature. . . . . . . . . . . . . . . . . . . 55°C to +150°C
Lead Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +300°C
ELECTRICAL CHARACTERISTICS
OSC = 200pF to GND, BAT = 4V, LOADISENSE connected to LPOWER, VOUTSENSE = 0.666V, BOOST = 10.5V, COMP connected to FB through a 100kΩresistor, –40°C<T
PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNITS
Overall Section
VCC Supply Current 0.1 1.0 mA BOOST Supply Current 3.0 5.0 mA BOOST Threshold to PUMP Stop 9.1 9.6 10.2 V BOOST Threshold to PUMP Start 9.2 9.7 10.3 V BOOST Threshold to PWMOUT 4.7 5.4 6.1 V
Battery Section
BAT Threshold to PWMOUT Stop 4.7 5.0 5.3 V BAT Threshold to PWMOUT Start 4.15 4.8 5.0 V BAT Input Current BAT = 4V –1 1
Oscillator & Divider Section
OSC Frequency 80 100 120 kHz OSC Pull-Up Current OSC = 1.5V DIVPAUSE Threshold to Pause 1.1 1.5 1.9 V DIVPAUSE Threshold to Divide 0.8 1.2 1.6 V DIVPAUSE Input Current 0V < DIVPAUSE < 6V –8 –5 –1
Reference Section
5VREF Voltage 4.85 5.0 5.1 V ISET Voltage 4.8 4.8 5.2 V
Error Amplifier Section
FB Voltage 2.4 2.5 2.6 V FB Input Current –1 0 1 FB Sink Current VOUTSENSE = 4V, FB = 4V 0.3 1.5 mA FB Release Delay VOUTSENSE Step from 4V to 1V 15 30 43 ms COMP Source Current FB = 2V, COMP = 4V –3.0 –0.2 mA COMP Sink Current FB = 3V, COMP = 1V 0.2 1.0 mA
, FLT . . . . . . . . . . . . . . ±10.0mA
Unless otherwise stated, VCC = 6.6V, ISET = 100kΩto GND, ADJ = 100kΩto GND,
A<+105°C for the UCC2305, 0°C<TA<+70°C for the UCC3305, and TA=TJ.
CONNECTION DIAGRAM
PDIP-28 or SOIC-28 (Top View)
N or DW Package
70 50 40 µA
µA
µA
µA
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UCC2305 UCC3305
ELECTRICAL CHARACTERISTICS (cont.) Unless otherwise stated, VCC = 6.6V, ISET = 100k
to GND, ADJ = 100k
to GND, OSC = 200pF to GND, BAT = 4V, LOADISENSE connected to LPOWER, VOUTSENSE = 0.666V, BOOST = 10.5V, COMP connected to FB through a 100kΩresistor, –40°C<T T
A=TJ.
A<+105°C for the UCC2305, 0°C<TA<+70°C for the UCC3305, and
PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNITS
Load Power Amplifier Section
LOADISENSE Input Current –2.5 –0.1 2.5 LPOWER Source Current LPOWER = 0V –8.0 –0.4 mA LPOWER Sink Current LPOWER = 1V 0.4 1.3 mA LPOWER Voltage VOUTSENSE = 0.0V 0.32 0.40 0.48 V
VOUTSENSE = 0.45V 0.32 0.40 0.48 V VOUTSENSE = 0.65V 0.41 0.46 0.51 V VOUTSENSE = 0.88V 0.43 0.51 0.59 V VOUTSENSE = 2.0V 0.43 0.51 0.59 V VOUTSENSE = 0.7V, SLOPEC = 0V 0.29 0.34 0.41 V
Input Current Sense Section
ISENSEIN Threshold COMP = 5V, WARMUPC = 0V 0.16 0.21 0.28 V
COMP = 5V, WARMUPC = 10V 0.10 0.19 0.27 V COMP = 1V, WARMUPC = 0V 0.07 0.10 0.2 V
ISENSEIN Bias Current OSC = 0V –15 –5 –2
OSC = 2V –80 –40 –15
VOUTSENSE Section
VOUTSENSE Threshold to PWMOUT 4.2 5.0 5.2 V VOUTSENSE Threshold to FB 1.7 1.9 2.1 V VOUTSENSE Threshold to NOTON 0.035 0.083 0.140 V VOUTSENSE Input Current –1 1
OUTPUTS SECTION
PWMOUT High Voltage I PWMOUT Low Voltage I PUMPOUT High Voltage I PUMPOUT Low Voltage I
PWMOUT = –100mA 9.15 10.0 V PWMOUT = 100mA 0.3 0.5 V PUMPOUT = –10mA 5.3 5.8 V PUMPOUT = 10mA 1.0 1.8 V
PUMPOUT Frequency BOOST = 9.5V 35 50 60 kHz NOTON High Voltage I NOTON Low Voltage I QOUT, QOUT QOUT, QOUT QOUT, QOUT
High Voltage IQOUT = –1mA or IQOUT = –1mA 5.0 6.3 V Low Voltage IQOUT = 1mA or IQOUT = 1mA 0.1 0.45 V
Frequency 150 200 250 Hz FLT High Voltage I FLT Low Voltage I
NOTON = –1mA 5.0 6.3 V NOTON = 1mA 0.1 0.3 V
FLT = –1mA 6.0 6.3 V FLT = 1mA 0.1 0.3 V
Timing Capacitor Section
FLTC Discharge Current FLTC = 2.5V 35 60 100 nA FLTC Charge Current FLTC = 2.5V –430 –300 –220 nA FLTC Threshold to FAULT 4.65 4.9 5.1 V SLOPEC Charge Current SLOPEC = 0.5V –165 –90 –60 nA
SLOPEC = 2.2 –105 –60 –40 nA SLOPEC = 4.2 –50 –30 –10 nA
SLOPEC Voltage I
SLOPEC = –125nA 1.3 1.5 1.7 V SLOPEC = –50nA 2.8 3.0 3.2 V
I
µA
µA µA
µA
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UCC2305 UCC3305
ELECTRICAL CHARACTERISTICS (cont.) Unless otherwise stated, VCC = 6.6V, ISET = 100k
to GND, OSC = 200pF to GND, BAT = 4V, LOADISENSE connected to LPOWER, VOUTSENSE = 0.666V, BOOST = 10.5V, COMP connected to FB through a 100kΩresistor, –40°C<T T
A=TJ.
PARAMETER TEST CONDITIONS MIN. TYP. MAX. UNITS
Timing Capacitor Section (cont.)
SLOPEC Discharge Current SLOPEC = 2.2V, VCC = 0V, BOOST = 0V,
BYPASS = 8V
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 Discharge Current WARMUPC = 5V, VCC = 0V, BOOST = 0V,
WARMUPC Voltage, Discharging I
ADJ Bias Current V WARMUPV Voltage WARMUPC = 1V 0.05 0.125 0.25 V
BYPASS Voltage VCC = 0V 8.8 9.6 V BYPASS Current VCC = 0V, BOOST = 0V, BYPASS = 8V 2.5 7
WARMUPC = –250nA 3.39 3.8 4.1 V
BYPASS = 8V
WARMUPC = 1V, VCC = 0V, BOOST = 0V,
BYPASS = 8V
WARMUPC = 25nA, VCC = 0V, BOOST = 0V,
BYPASS = 8V
ADJ = 0V
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
A<+105°C for the UCC2305, 0°C<TA<+70°C for the UCC3305, and
to GND, ADJ = 100k
40 100 200 nA
23 50 126 nA
51034nA
1.5 1.9 2.3 V
38 20 12 µA
µA
PIN DESCRIPTIONS
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
=5 A
V
60s
5V
=60 F••
µµ
COMP: Differences between commanded lamp power and desired lamp power are amplified by an error ampli
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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.
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PIN DESCRIPTIONS (cont.)
DIVPAUSE: The QOUT and QOUT outputs can be used
to switch lamp polarity in an AC ballast. It is important to stop polarity switching when the lamp is being lit, so that the arc across the electrodes can form in the correct place. Pulling high on DIVPAUSE stops the internal di vider which generates the QOUT and QOUT thereby freezes the QOUT and QOUT
To stop the divider when the lamp is being lit and start af ter the lamp has lit, connect a resistor from NOTON to DIVPAUSE and a capacitor from DIVPAUSE to GND.
FLTC: The voltage on VOUTSENSE is proportional to lamp voltage. If that voltage is too high or too low, the lamp is either open, shorted, or not yet running. During normal operation, there is a capacitor connected to FLTC, and this capacitor is discharged to 0V by a current source inside the UCC3305.
The UCC3305 monitors the voltage on VOUTSENSE and compares it to an internal 83mV lower threshold and a 2V upper threshold. If the voltage is outside this win dow, then the IC will pull up on FLTC with a current of ap­proximately 250nA. If the fault remains long enough to charge the external FLTC capacitor over 5V, the control­ler declares a catastrophic fault and shuts the IC down. The IC will stay shut down until power is removed from BOOST.
If the fault clears before the FLTC capacitor reaches 5V, the capacitor discharges down to 0V. This discharge cur­rent is approximately 50nA, representing a five times lon­ger discharge rate than charge rate.
FLT: If the voltage on the FLTC pin exceeds 5V, indicat ing a severe fault, then a latch in the UCC3305 sets and PWM drive is halted. In addition, the FLT output goes high to VCC, indicating a serious system fault.
FB: Differences between commanded lamp power and desired lamp power are amplified by an error amplifier. This amplifier senses the difference between the voltage at FB and 2.5V, and drives COMP with an amplified error voltage.
GND: Ground for all functions is through this pin.
signals, and
signals.
UCC2305 UCC3305
to normal operation is accomplished by the rise of the WARMUPC capacitor.
Current mode control has an advantage over voltage mode control in that a current mode loop is easier to
­compensate. Current mode control has a disadvantage
compared to voltage mode control in that the loop can enter into chaotic oscillations at high duty cycles. These chaotic oscillations can be prevented using slope com
­pensation. The UCC3305 contains internal slope com pensation in the form of a current proportional to OSC voltage on ISENSEIN. This current combined with an ex ternal resistor from ISENSEIN to the current sense resis tor creates a voltage drop proportional to OSC voltage, which gives slope compensation.
ISET: Many functions inside the UCC3305 require pre cise currents to give well controlled performance. These controlled currents are programmed by a resistor from ISET to GND. A resistor of 100k programs the IC to nor mal operating current. Lower resistor values increase the
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internal currents. Some of the functions which are influ­enced by this resistor are WARMUPC charging and dis­charging, SLOPEC charging and discharging, FLTC charging and discharging, and error amplifier bandwidth
LOADISENSE: Just as ISENSEIN is normally connected to a current sense resistor which monitors battery cur­rent, LOADISENSE is normally connected to a resistor which monitors lamp current. Lamp current is then regu­lated by the controller such that the correct lamp power is supplied at every lamp temperature, in conjunction with the lamp voltage sensed by VOUTSENSE.
­LPOWER: LOADISENSE directly drives one input of an
op amp in the UCC3305. This amplifier amplifies the dif ference between the desired load current and the actual load current, and generates an output signal on LPOWER which feeds the error amplifier.
NOTON: While the lamp is in a fault condition, such as excessively high or low lamp voltage, NOTON is pulled high to VCC, indicating that the arc is not yet correct. When the voltage on VOUTSENSE is within the 83mV to 2V window, NOTON is pulled low.
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ISENSEIN: The power regulating algorithm in the UCC3305 HID Controller computes a function of lamp current and lamp voltage and commands the appropriate battery current to keep lamp power constant. This appro priate battery current is sensed by a connection from I-SENSEIN to a current sense resistor. This current sensed pulse width modulation scheme is often referred to as current mode control.
In addition to this current regulation, the UCC3305 con tains peak input current limiting. This limiting is set to
0.2V across the ISENSEIN resistor during normal opera tion and 0.4V during starting. The transition from starting
OSC: The fixed frequency PWM in the UCC3305 oper ates at the frequency programmed by the OSC pin. Typically, a a 200pF capacitor from OSC to GND pro grams the PWM frequency at 100kHz. In addition, this
­programs the charge pump at 50kHz and the QOUT QOUT signals at 192Hz. The actual oscillator frequency is a function of both the capacitor from OSC to GND and the resistor from ISET to GND.
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PUMPOUT: Although the UCC3305 is powered from the VCC input, most functions of the device operate from a
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supply voltage of approximately 10V connected to BOOST. In normal operation, this 10V supply is gener
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and
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PIN DESCRIPTIONS (cont.)
ated by a voltage doubler using the PUMPOUT pin as an AC signal and external diodes as switches. PUMP-OUT is a square wave which swings from VCC to GND at half of the OSC frequency.
PWMOUT: The output of the pulse width modulator is a command signal to a power MOSFET switch. This sig nal appears on PWMOUT. In normal systems, PWM-OUT can be directly connected to the gate of an N-channel power MOSFET such as the IRF540. If the lead between the UCC3305 and the MOSFET is longer than a few cm, a 10 ohm resistor from PWMOUT to gate may be required to dampen overshoot and under shoot.
: The UCC3305 is immediately configured for DC
QOUT
HID lamps. To operate with AC HID lamps, it is neces sary to add a power H-bridge which will toggle lamp voltage. A practical switching frequency for this toggle function is the OSC frequency divided by 512, or 192Hz for a 100kHz oscillator.
The QOUT OSC frequency divided by 512, 180 degrees out of phase with the QOUT pin.
QOUT: The QOUT pin is a logic output which toggles at the OSC frequency divided by 512, 180 degrees out of phase with the QOUT
SLOPEC: To track lamp warm-up and cool down, two capacitors connected to the UCC3305 charge and dis­charge. One is connected to SLOPEC.The other is con nected to WARMUPC. The capacitor connected to SLOPEC charges up to 5V with a rate controlled by the resistor from ISET to GND. With a nominal 100k ISET resistor the charging current into SLOPEC is equivalent to the current from a 50Meg resistor to 5V.
When power is removed from VCC, SLOPEC dis charges at a constant current, nominally 100nA.
pin is a logic output which toggles at the
pin.
VCC: VCC is the main supply input to the UCC3305. Many functions in the UCC3305 are powered by VCC, while others are powered by BOOST. VCC should be clamped to 6.8V by an external zener diode and kept as close to 6.8V as practical with a low value resistor to the input supply.
­VOUT-SENSE: The VOUTSENSE input is used to
sense lamp voltage, commonly through a 120:1 voltage divider. For a normal, running HID lamp, the voltage across the lamp is between 60V and 110V. It takes higher than 300V to break down the lamp, and it is de sirable to limit the voltage on the starter input to 600V
­maximum. A lamp voltage less than 10V is indicative of
a shorted lamp. The UCC3305 regulates lamp power by commanding
the correct lamp current for a given lamp voltage. In ad
­dition, a comparator in the UCC3305 terminates a PWM cycle if VOUTSENSE reaches 5V, corresponding to 600V on the lamp. This regulates lamp voltage at 600V when the lamp is not lit. Comparators in the UCC3305 also compare VOUTSENSE to 83mV corresponding to 10V lamp voltage and 2V, corresponding to a 240V lamp voltage. When the VOUTSENSE voltage is out­side this window, the lamp is either not lit, shorted, or open.
WARMUPC: In addition to the capacitor from SLOPEC to GND, lamp temperature is estimated by the voltage on a capacitor from WARMUPC to GND. This capacitor is charged by a 200nA current source to 4.2V and by a 100nA current source from 4.2V to 10V when the lamp is on, and discharged by 39nA current sink to 2.5V and
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11nA current sink to GND when the lamp is off. WARMUPV: The voltage on WARMUPC is used to
modulate the signal fed to the error amplifier through FB. However, the impedance on WARMUPC is too high to be directly used. The UCC3305 contains a buffer am plifier which buffers the voltage on WARMUPC and pro
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cesses it to WARMUPV, making a signal appropriate for driving FB.
UCC2305 UCC3305
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APPLICATIONS INFORMATION
Typical Application
This circuit shows the UCC3305 HID Lamp Controller IC in a flyback converter. The output of the converter is reg ulated at constant power, so that lamp intensity is rela tively constant regardless of small lamp manufacturing variations.
Full Bridge Output Stage
The output of the flyback converter is directed to the AC lamp through a full bridge inverter. The full bridge is switched at a low frequency (typically 195Hz), so that the average lamp voltage is zero. The low frequency switch
ing is derived from the PWM oscillator. It is desirable to switch lamp polarity when running, but switching lamp polarity can interfere with clean starting. The UCC3305
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has a logic output called NOTON which is high when the
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lamp is not running (Not On) and low when the lamp is running. This output is connected to the DIVPAUSE input so that the low frequency switching stops until the lamp is fully lit.
The UCC3305 HID Controller IC has two low frequency outputs, QOUT and QOUT driving low-side MOSFETs directly at 195Hz, but
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high-side MOSFETs require a level-shifted drive. This
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. These outputs are capable of
APPLICATIONS INFORMATION (cont.)
can be as simple as a high voltage transistor and a resis tor pull-up, combined with the correct choice of phases.
UCC2305 UCC3305
regulated 10V supply on the BOOST output. This 10V
­supply drives all other functions on the UCC3305.
Regulated Lamp Input Power Gives Constant Intensity
The LPOWER output of the UCC3305 is a voltage roughly proportional to lamp input power. The UCC3305 regulates constant lamp power over a wide range of lamp voltages.The range of lamp voltages which produce con stant lamp power is set by the limiting amplifier on VOUTSENSE.
For inputs to VOUTSENSE below 0.5V, such as would occur with a shorted lamp, the loop regulates constant load current. For inputs to VOUTSENSE greater than
0.82V, as might occur with a lamp that is open or not yet lit, the loop also regulates constant load current, but at a lower current than for a shorted lamp. In between those two voltages, the amplifier driving the LPOWER pin will sum the load current and load voltage and produce a sig nal roughly proportional to load power.The summing am­plifier approximates power well enough to hold power within±10% over a factor of two in lamp voltage.
The UCC3305 HID Controller contains a current mode PWM similar to the industry standard UC3842 and UCC3802 circuits. This controller uses a high gain op amp to regulate the output of the LPOWER circuit. This op amp drives a high speed PWM comparator, which compares converter input current to the output of the op amp and uses this signal to set duty cycle.
Slope Compensation
In addition to a complete current mode PWM, the UCC3305 HID Controller contains internal slope com pensation, a valuable function which improves current loop stability for high duty cycles. Slope compensation is accomplished with an on-chip current ramp and an off-chip resistor RSL. Larger values of RSL give more slope compensation and a more stable feedback loop.
Powering The UCC3305
Conventional power MOSFETs require at least 8V of gate drive to ensure high efficiency and low on resis tance. Despite this requirement, the UCC3305 HID Con troller can be used to build a ballast that will drive power MOSFETs well with input supplies as low as 5V! The UCC3305 does this using a charge pump.
Protection From Over Voltage
The most significant stresses in an automotive environ ment are the overvoltage conditions which can occur dur ing load dump and double-battery jump start. At these times, the voltage into the ballast can go so high that even the most overdesigned power stage will be dam
­aged. The UCC3305 is inherently immune to damage
from this when operated with a zener regulated supply.In addition, the UCC3305 will protect the ballast compo nents by shutting down the PWM in the presence of ex cessive voltage on the BAT input.
This typical application shows a voltage divider consist ing of a 270k resistor and a 100k resistor driving the BAT input. The threshold of the BAT input is approximately 5V, so this divider sets the shutdown voltage at approxi mately 18.5V.
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Programming the UCC3305
All circuitry on the UCC3305 HID Lamp Controller is op­erated from a bias current set by the resistor from ISET to ground.For best operation, this resistor (RSET) should be between 75k and 150k.
Oscillator Frequency
The UCC3305 HID Lamp Controller PWM oscillator is set by the resistor from ISET to ground and by the capacitor from OSC to ground. Oscillator frequency can be esti­mated by the equation:
­For operation at 100kHz, RSET should be 100k and
C The PWM oscillator also determines the low frequency
lamp switching rate for AC lamps. The exact lamp switch ing rate is the PWM frequency divided by 512.
Lamp Temperature Compensation
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Automobile headlights must come up to full intensity very
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quickly, but HID lamps require many minutes to stabilize. The UCC3305 HID Controller contains sophisticated in ternal circuitry to anticipate lamp temperature and also to compensate for lamp temperature.
FOSC =
OSC should be 200pF.
2
RSET COSC
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In this typical application, power for the UCC3305 HID Controller IC is derived from a 6.8V zener supply. This zener regulated supply gives the application overvoltage protection, reverse battery protection, low parts count, and low cost. The output of the 6.8V zener supply drives the VCC pin of the UCC3305. VCC is the input to the UCC3305 charge pump. The charge pump generates a
The circuits anticipate lamp temperature by monitoring charge on capacitors which charge when the lamp is on and discharge when the lamp is off. The UCC3305 HID Controller compensates for lamp temperature by driving the lamp with a higher lamp power when the lamp is cold and reducing the power to a normal operating level when the lamp is warmed up. The capacitors which set these
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APPLICATIONS INFORMATION (cont.)
time constants are external film capacitors CS and CW, and are connected to SLOPEC and WARMUPC. CS and CW are critical capacitors and must be selected to match the time-temperature relationship of the lamp.
In addition to changing the power regulation point, the WARMUPC capacitor voltage also changes the short cir cuit lamp current. The ratio of cold short circuit current to warmed-up short circuit current is set by the resistor from ADJ to ground.
FLYBACK HID BALLAST
When power is removed from the ballast, CS and CW must discharge at a controlled rate. The discharge cur rents are programmed by current sources on the UCC3305 HID Controller. These current sources are powered by the power supply connected to BYPASS. In a typical application, a non-critical electrolytic capacitor
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from BYPASS to ground stores energy when the ballast is on and uses this energy to control the discharge rate when the ballast is off.
UCC2305 UCC3305
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UDG-94092-1
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Telephony www.ti.com/telephony Video & Imaging www.ti.com/video Wireless www.ti.com/wireless
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