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MAX16823 Datasheet(PDF) 6 Page - Maxim Integrated Products |
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MAX16823 Datasheet(HTML) 6 Page - Maxim Integrated Products |
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6 / 12 page  Detailed Description of Hardware The MAX16823 three-channel current regulator operates from a 5.5V to 40V input voltage range and delivers up to 100mA per channel to one or more strings of HB LEDs. The output currents are programmable using external current-sense resistors in series with the LEDs. Three DIM inputs allow a wide range of independent pulsed dimming in addition to providing the on and off control of the outputs. The MAX16823 offers an LED-GOOD output that indicates an open-circuit condition when one or more LED channels are open. Integrated pass elements minimize external components while providing ±5% output current accuracy. Additional features include a 3.4V (±5%) voltage regulator with 4mA output current capability, short-circuit and thermal protection. The MAX16823 uses a feedback loop to linearly control the current from each output. The voltage across each sense resistor is compared to a fixed reference voltage and the error is amplified to drive the internal power pass device for a particular channel. See the Block Diagram. The regulation point is factory-set at 203mV. The regulated current is adjusted by the value of RCS_. The MAX16823 is a constant-current LED driver internally optimized for driving the impedance range expected from one or more HB LEDs. 3.4V Regulator (REG) The MAX16823 includes a fixed 3.4V voltage regulator that delivers up to 4mA of load current for auxiliary appli- cations throughout the 5.5V to 40V input voltage range. Connect a 0.1μF compensation capacitor from REG to ground. Shorting REG to ground disables the thermal shutdown. Thermal Protection The MAX16823 enters a thermal-shutdown mode in the event of overheating. This typically occurs in overload or output short-circuit conditions. When the junction temperature exceeds TJ = +155°C, the internal thermal protection circuitry turns off the series pass elements. The MAX16823 recovers from thermal-shutdown mode once the junction temperature drops by 23°C. The part will therefore protect itself by low-frequency thermal cycling in the event of a short-circuit or overload condition. Applications Information Programming the LED Current The MAX16823 uses sense resistors to set the output current for each channel. To set the LED current for a particular channel, connect a sense resistor across the corresponding current-sense input (CS_) and GND. For optimal accuracy, connect the low-side of the current- sense resistors to the IC’s ground pin with short traces. The value needed for the sense resistor for a given current can be calculated with the equation below: CS_ CS_ OUT_ V (V) R () I (A) Ω= where VCS_ is 203mV and IOUT_ is the desired LED cur- rent (ILED). Input-Voltage Considerations For proper operation, the minimum input voltage must always be: VIN(MIN) ≥ VCS_(MAX) + VFT(MAX) + VDO(MAX) where VFT(MAX) is the total forward voltage of all series- connected LEDs. The minimum operating voltage of the device is 5.5V. LEDGOOD The MAX16823 features an active-low, open-drain LEDGOOD output that goes low either when one or more LED channels are open or when a signal at any of the dimming inputs remains low for a period greater than the programmed LEDGOOD delay time tDELAY. Program tDELAY with a capacitor connected between LGC and ground. The LEDGOOD output goes low after the programmed delay period tDELAY has elapsed. Use the following formula to set the delay period: tCK = 112,000 x CLGC (F) 4 x tCK < tDELAY < 6 x tCK where CLGC is the capacitor connected between LGC and ground. The LEDGOOD output goes low during the thermal shutdown. The minimum recommended value of the capacitance that can be used on the LGC pin is 100pF. MAX16823 High-Voltage, 3-Channel Linear High-Brightness LED Driver with Open LED Detection www.maximintegrated.com Maxim Integrated │ 6 |
Similar Part No. - MAX16823_15 |
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Similar Description - MAX16823_15 |
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