LM3552 Datasheet | National Semiconductor

Description The LM3551 and LM3552 are fixed frequency, current mode step-up DC/DC converters with two integrated NFETs that can be used for precision LED brightness control. The devices are capable of driving loads up to 1A from a single-cell Li-Ion battery. The LM3551 and LM3552 can drive one or more high current flash LEDs either in a high power Flash mode or a lower power Torch mode using the TORCH/FLASH pin. A programmable Timeout function on the FTO pin forces the internal NFETs to turn off after a certain user defined time. An external SD pin (LM3551) or EN pin (LM3552) is available to put the device into low power shutdown mode. During shutdown, the feedback resistors and the load are disconnected from the input to avoid leakage current paths to ground. User programmable soft-start circuitry has been integrated to eliminate large inrush currents at start-up. Over-voltage protection circuitry and a 1.25MHz switching frequency allow for the use of small, low-cost output capacitors with lower voltage ratings. The LM3551 and LM3552 are available in a low profile 14 pin LLP package. Features n n n n n n n n n Up to 1A total drive current Flash timeout protection Independent Torch/Flash/Shutdown modes LED disconnect in shutdown Programmable soft-start limits inrush current Over-voltage protection Wide voltage range 2.7 to 5.5V 1.25MHz constant switching frequency Small, low profile package, non-pullback LLP14 (4mm x 4mm) Applications n n n n n n White LED Camera Flash White LED Torch (Flashlight) DSC (Digital Still Camera) Flash Cellular Camera Phone Flash PDA Camera Flash Camcorder Torch (Flashlight) lamp Typical Application Circuits © 2005 National Semiconductor Corporation DS201512 .national. LM3551/LM3552 Connection Diagram 14 Pin Dual LLP Package NS Package Number SDA14B Pin Descriptions Pin 9 13 8 10 3 5 12 11 4 14 2 1,7,DAP 6 Name VIN T/F SW OVP VC SD(LM3551) EN(LM3552) FTO SS FB FET-T FET-F GND AGND Input Voltage. Input range:...