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Numéro de sérieHT7937
CategoriePower Management => Lighting Controllers
DescriptionBuilt-in OVP White LED Step-up Converter
The HT7937 is high efficiency boost converter with a constant current output to provide back light functions in handheld devices. Applications with series connected LEDs ensure constant and identical LED currents resulting in uniform brightness. A continuous LED output current is setup using the FB pin regulated voltage across an external sense resistor, RFB connected between the FB pin and ground.
SociétéHoltek Semiconductor Inc.
DatasheetTélécharger HT7937 datasheet
 
 
  • Description courte
  • Features

    · Integrated open-circuit protection· Over voltage protection· to 84% efficiency VIN=3V, 3LEDs,· Low standby current: 0.1mA (typ.) (VSHDN=0V)· Matches LED current· Small value inductor and capacitors· Small outline SOT23-6 package

    Applications
    · Cellular phones· PDAs· DSCs· Handheld devices· White LED display backlighting

    The HT7937 is high efficiency boost converter with a constant current output to provide back light functions in handheld devices. Applications with series connected LEDs ensure constant and identical LED currents resulting in uniform brightness. A continuous LED output current is setup using the FB pin regulated voltage across an external sense resistor, RFB connected between the FB pin and ground. The integrated open load protection circuitry prevents damage resulting from an open circuit condition. The low 95mV feedback voltage minimises power losses in the current setting resistor which improves efficiency. The HT7937 has a high switching frequency to 1.2MHz which permits the use of lower value extremely small outline inductor and filter capacitor. The HT7937 is supplied in a space-saving, 6-lead SOT23-6 package type.

    Pin No. Pin Name SW GND FB SHDN OVP VIN Switching pin Ground pin Output voltage sense node. Connect the cathode of the LED to this pin. A resistor from this pin to ground sets the LED current. Internally compares to 95mV (Typ.). Shutdown device pin. Connect 1.5V or higher to enable device (ON), 0.3V or lower to disable device (OFF). For over voltage protection connect to the output. Input voltage pin. to 5.5V for internal circuitry. Description

    Input FB Voltage.................................................................6V OVP Voltage............................................................30V Maximum Junction Temperature..........................125°C Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maximum Ratings² may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability. Voltage..............................................................29V SHDN........................................................................6V Operating Temperature to 85°C

    Symbol VIN Parameter Input Voltage Switching IIN Supply Current Non-switching VSHDN= 0V VFB fOSC DC RDS(ON) ISW(OFF) VIH VIL VOVP Note: Feedback Voltage Switching Frequency Measurement at SW pin Maximum Duty Cycle SW On Resistance Switch Leakage Current SHDN Voltage High SHDN Voltage Low OVP Threshold No load VSW= 29V LEDs VIN=3V; Ta=25°C (Unless otherwise specified)(Note) Test Conditions ¾ Min. Typ. Max. Unit mA mV MHz mA V

    Specifications are production tested at Ta=25 degree. Specifications over to 85 degree operating temperature range are assured by design, characterization.