Linear Technology Introduces Inductorless High Current White LED Driver LTC3218
Linear Technology Corporation introduces the LTC3218, an inductorless high current white LED driver that delivers up to 400mA of LED current. Its multimode architecture automatically switches between 1x or 2x boost modes, it monitors the voltage across the LED current source and performs mode switching only when an ILED voltage drop is detected. The LTC3218 uses an internal high side sensing resistor to regulate the LED current. This enables low dropout operation and allows the device to stay in 1x mode for longer periods of time, maximizing efficiency over the entire Li-Ion/Polymer battery operating voltage range, thus extending battery run time and minimizing The noise.
The LTC3218 provides up to 400mA of pulse current for camera flash or up to 150mA of continuous current for camera flashlight applications with convenient single-resistor programming capability. An ultra low dropout current source begins to provide an accurate current to the LED when the input voltage of the integrated circuit approaches the forward voltage of the LED. The LTC3218 incorporates a built-in soft-start circuit that prevents excessive inrush current during startup and provides a two-second flash current timeout for LED protection. The device's inductorless charge pump architecture, high switching frequency of 1MHz, few external component counts (one jumper capacitor, one programming resistor, two bypass capacitors) and a compact DFN package ensure component economics and accountability The board's very slim solution makes it ideal for video and flash applications, digital cameras and Other portable lighting applications in camera phones. The LTC3218 requires only one wire to the LED, which is useful in flip phones where the driver IC and LED are located on either side of the hinge.
The LTC3218 is available from stock in a low profile (0.75mm) 2mm x 3mm 10-lead DFN package and is specified over the -40°C to +85°C temperature range. Buy in 1,000-piece quantities starting at $1.44 each.
Performance summary:
Multi-mode operation: 1x or 2x boost mode
?Automatic mode switching
?Output current
- Pulse: 400mA
- Continuous: 150mA
Low noise constant frequency operation
? Two seconds flash current timeout to protect the LED
Automatic soft start
Output disconnection
? No inductor
?220mΩ internal high side current sense resistor
Single-resistance programming capability for pulse/continuous mode
Slim application circuit (all components height <1mm)
2mm x 3mm 10-lead DFN package
Source: Electronic Engineering
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