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UCC2305 Datasheet(PDF) 4 Page - Texas Instruments |
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UCC2305 Datasheet(HTML) 4 Page - Texas Instruments |
4 / 14 page 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 IWARMUPC = –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 510 34 nA WARMUPC Voltage, Discharging IWARMUPC = 25nA, VCC = 0V, BOOST = 0V, BYPASS = 8V 1.5 1.9 2.3 V ADJ Bias Current VADJ = 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 = 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 Ω resistor, –40°C<TA<+105°C for the UCC2305, 0°C<TA<+70°C for the UCC3305, and TA=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 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 |
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