One，Overview:

The LM43603 regulator is an easy-to-use synchronous step-down DC/DC converter capable of driving up to 3A of load current with an input voltage range of 3.5V to 36V (42V absolute maximum). The LM43603 provides excellent efficiency, output accuracy and voltage drop in a very small solution size. The extended family is available in pin-to-pin compatible packages with 0.5A, 1A and 2A load current options. Peak current mode control is employed for simple control loop compensation and cycle-by-cycle current limiting. Optional features include programmable switching frequency, synchronization, power good flag, precision enable, internal soft-start, scalable soft-start and tracking, providing a flexible and easy-to-use platform for a variety of applications. Discontinuous conduction and automatic frequency modulation at light loads improve light load efficiency. This family requires few external components and the pinout allows for simple, optimal printed circuit board (PCB) layout. Protection features include thermal shutdown, VCC undervoltage lockout, cycle-by-cycle current limit, and output short-circuit protection. The LM43603 device is available in a HTSSOP/PWP 16-lead package (5.1mm × 6.6mm × 1.2mm) and a VSON-16 package with wettable sides. The HTSSOP package is pin-to-pin compatible with the LM43600, LM43601, LM43602, LM46000, LM46001, LM46002. The VSON-16 package is pin-to-pin compatible only with the LM43602.

Applications • Industrial Power Supplies • Telecom Systems • Sub-AM Automotive Applications • General Purpose Wide VIN Regulation • High Efficiency Point-of-Load Regulation

Second, the schematic diagram of LM43603:

Three， Features of LM43603:

27µA Regulated Quiescent Current

High Efficiency (DCM and PFM) at Light Load Conditions

Complies with EN55022/CISPR 22 Electromagnetic Interference (EMI) Standards

Integrated Synchronous Rectification

Adjustable frequency range: 200kHz to 2.2MHz (default 500kHz)

Synchronized to external clock frequency

Internal compensation

Stable with almost any combination of ceramic, solid electrolytic, tantalum, and aluminum capacitors

power good sign

Soft Start to Prebiased Load

Internal soft-start: 4.1ms

Soft-start time extended by external capacitors

Output voltage tracking function

Program System Undervoltage Lockout (UVLO) Accurate Enable

Output Short-Circuit Protection with Hiccup Mode

Thermal Shutdown Protection