ZXSC310E5TA

The ZXSC310 is a single or multi cell LED driver designed for LCD backlighting applications. The input voltage range of the device is between 0.8V and 8V. This means the ZXSC310 is compatible with single NiMH, NiCd or Alkaline cells, as well as multi-cell or LiIon batteries. The device features a shutdown control, resulting in a standby current less than 5μA, and an output capable of driving serial or parallel LED’s. The circuit generates constant power output, which are ideal for driving single or multiple LED’s over a wide range of operating voltages. These features make the device ideal for driving LED’s particularly in LCD backlight applications for Digital Still cameras and PDA’s. The ZXSC310 is PFM, controller IC which, when combined with a high performance external transistor, enables the production of a high efficiency boost converter for LED driving applications. The on chip comparator forces the driver circuit and therefore the external switching transistor off if the voltage at ISENSE exceeds 19mV. An internal reference circuit and divider set this threshold. The voltage at ISENSE is taken from a current sense resistor connected in series with the emitter of the switching transistor. A monostable following the output of the comparator forces the turn - off time of the output stage to be typically 1.7us. This ensures that there is sufficient time to discharge the inductor coil before the next on period. With every on pulse the switching transistor is kept on until the voltage across the current - sense resistor exceeds the threshold of the ISENSE input. The on - pulse length, and therefore the switching frequency, is determined by the programmed peak current, the input voltage and the input to output voltage differential. The driver circuit supplies the external switching transistor with a fixed drive current. To maximise efficiency the external transistor switched quickly, typically being forced off within 30ns.

Applications

• LCD backlights: Digital still camera, PDA, Mobile phone
• LED flashlights and torches
• White LED driving
• Multiple LED driving

Key features

• 94% efficiency
• Minimum operating input voltage 0.8V
• Maximum operating input voltage 8V
• Standby current less than 5μA
• Programmable output current
• Series or parallel LED configuration
• Low saturation voltage switching transistor
• SOT23 - 5 package