MIC2291 1.2A PWM Boost Regulator Photo Flash LED Driver General Description Features The MIC2291 is a 1.2MHz Pulse Width Modulation (PWM), 2.5V to 10V input voltage boost-switching regulator that is optimized for high-current, Output voltage up to 34V white LED photo ash applications. With a guaranteed 1.2A switch current switch current of 1.2A, the MIC2291 easily drives a string 1.2MHz PWM operation of 3 white LEDs in series at 100mA, ensuring a high level of brightness and eliminating several ballast resistors. 95mV feedback voltage The MIC2291 implements a constant frequency, 1.2MHz Overvoltage protection (OVP) PWM control scheme. The high frequency PWM operation Options for 15V and 34V saves board space by reducing external component sizes. Stable with ceramic capacitors The added benet of the constant frequency PWM <1% line and load regulation scheme, in contrast to variable frequency topologies, is 1A shutdown current much lower noise and input ripple injected back to the battery source. Over temperature protection To optimize efficiency, the feedback voltage is set to only UVLO 95mV. This reduces the power dissipation in the current Low-prole Thin SOT23-5 package option set resistor, and allows the lowest total output voltage, 2mm 2mm MLF package option hence minimal current draw from the battery. 40C to +125C junction temperature range The MIC2291 is available with 2 levels of over-voltage protection, 15V, and 34V. This allows designers to choose the smallest possible external components with the Applications appropriate voltage ratings for their applications. Photo Flash LED driver The MIC2291 is available in low-prole, Thin SOT23 5-pin Cell phones and 8-pin 2mm 2mm MLF package options. The PDAs MIC2291 has a junction temperature range of 40C to +125C. GPS systems Data sheets and support documentation can be found on Digital cameras Micrels web site at www.micrel.com. IP phones LED ashlights Typical Application 10H 10H 100mA 100mA MIC2291xD5 MIC2291-15xML 5 1 VIN SW VIN SW 1-Cell 1F 1-Cell 1F 0.22F EN OVP Li Ion 0.22F 4 3 Li Ion ceramic EN FB 3V to 4.2V 3V to 4.2V 95mV FB 95mV GND GND 2 Thin SOT23 Flash LED Driver 2mm x 2mm Flash LED Driver with Output OVP PowerPAK is a trademark of Siliconix, Inc. MLF and MicroLeadFrame are registered trademarks of Amkor Technology, Inc. Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC2291 Ordering Information Overvoltage Junction Part Number Marking* Package Lead Finish Protection Temp. Range MIC2291BD5 SSAA 40 to +125C 5-Pin Thin SOT23 Standard MIC2291YD5 SSAA 40 to +125C 5-Pin Thin SOT23 Pb-Free MIC2291-15BML STA 15 40 to +125C 8-Pin 2mm x 2mm MLF Standard MIC2291-15YML STA** 15 40 to +125C 8-Pin 2mm x 2mm MLF Pb-Free MIC2291-34BML STC 34 40 to +125C 8-Pin 2mm x 2mm MLF Standard MIC2291-34YML STC** 34 40 to +125C 8-Pin 2mm x 2mm MLF Pb-Free Notes: * Under bar / Over bar symbol may not be to scale. ** Over bar symbol located after Pin 1 identifier. Pin Configuration FB GND SW OVP 1 8 PGND 1 3 2 VIN 2 SW 7 EN 3 6 FB AGND 4 EP 5 NC 4 5 EN VIN 5-Pin TSOT23 (D5) 8-Pin 2mm x 2mm MLF (ML) Pin Description Pin Number Pin Number Pin Name Pin Name TSOT23-5 2x2 MLF-8 1 7 SW Switch node (Output): Internal power BIPOLAR collector. 2 GND Ground (Return): Ground. 3 6 FB Feedback (Input): Output voltage sense node. Connect the cathode of the LED to this pin. Connect current set resistor from this pin to ground. 4 3 EN Enable (Input): Logic high (1.5V) enables regulator. Logic low ( 0.4V) shuts down regulator. 5 2 VIN Supply (Input): Input Voltage. 1 OVP Overvoltage protection (Input): Connect to the output to clamp the maximum output voltage. 4 AGND Analog ground. Internally connected to ground. 8 PGND Power ground. 5 NC No connect (no internal connection to die). EP GND Ground (Return): Exposed backside pad. M9999-051507 May 2007 2