LM3477A Datasheet | National Semiconductor

Description The LM3477/A is a high-side N-channel MOSFET switching regulator controller. It can be used in topologies requiring a high side MOSFET such as buck, inverting (buck-boost) and zeta regulators. The LM3477/A’s internal push pull driver allows patibility with a wide range of MOSFETs. This, the wide input voltage range, use of discrete power ponents and adjustable current limit allows the LM3477/A to be optimized for a wide variety of applications. The LM3477/A uses a high switching frequency of 500k Hz to reduce the overall solution size. Current-mode control requires only a single resistor and capacitor for frequency pensation. The current mode architecture also yields superior line and load regulation and cycle-by-cycle current limiting. A 5µA shutdown state can be used for power savings and for power supply sequencing. Other features include internal soft-start and output over voltage protection. The internal soft-start reduces inrush current. Over voltage protection is a safety feature to ensure that the output voltage stays within regulation. The LM3477A is similar to the LM3477. The primary difference between the two is the point at which the device transitions into hysteretic mode. The hysteretic threshold of the LM3477A is one-third of the LM3477. n Frequency pensation optimized with a single capacitor and resistor n Internal softstart n Current mode operation n Undervoltage lockout with hysteresis n 8-lead Mini-SO8 (MSOP-8) package Applications n n n n n n n n Local Voltage Regulation Distributed Power Notebook and Palmtop puters Internet Appliances Printers and Office Automation Battery operated Devices Cable Modems Battery Chargers Hysteretic Threshold LM3477 ) 36% of programmed current limit ) 12% of programmed current limit Features n n n n 500k Hz switching frequency Adjustable current limit 1.5% reference Thermal shutdown - See Hysteretic Threshold and section for more information. Typical Application Circuit Typical...