LTC3452

peculiarity

• High efficiency: ≥85% across the entire lithium-ion battery range
• Wide V_INRange: 2.7V to 5.5V
• Independent master/camera current control
• Up to 425mA continuous output current
• Internal soft start
• Open/short LED protection
• PWM brightness control
• LED current matching error is typical
• 1MHz constant frequency operation
• Low shutdown current: 6.5μA
• Overtemperature protection

  description

  LTC^®The 3452 is a synchronous buck-boost DC/DC converter optimized for driving two sets of white LEDs from a single-cell Li-Ion battery input. In a low-power LED bank, the device can drive up to five LEDs in parallel, each with up to 25mA, while in a high-power LED bank, it can drive two LEDs with up to 150mA each (or one LED, 300mA). Depending on the input voltage and the maximum forward voltage of the LED, the regulator can operate in synchronous buck, synchronous boost, or buck-boost mode. Optimum efficiency is achieved by detecting which LED needs the largest forward voltage drop at its set current and then adjusting the shared output voltage to achieve the lowest dropout voltage. 85% efficiency can be achieved over the entire usable range of the lithium-ion battery (2.7V to 4.2V).
  
  The maximum LED current for each LED display can be set using a single external resistor. Dual enable pins allow PWM brightness control in low-power LED banks and independent on/off control in high-current LED banks (best suited for LED photoflash applications). In shutdown, the supply current is only 6.5μA.
  
  The high constant operating frequency of 1MHz allows the use of small external inductors. The LTC3452 is available in a low profile (only 0.75mm height) thermally enhanced 20-lead (4mm × 4mm) QFN package.

• apply

  • Cellular
  • Digital cameras
  • PDA
  • Portable devices
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• Small, thermally enhanced 20-pin (4mm x 4mm) QFN package
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