Diodes High efficiency step-down converters offer POL design diversity

     Diodes announced new additions to its portfolio of synchronous step-down converters. The AP62500 and AP62800 have continuous output current ratings of 5A and 8A, respectively, giving engineers more flexibility when developing point-of load (POL) solutions optimized for efficiency or size. These devices enable compact implementation with a minimum number of components and are used primarily in mass-market consumer products. Examples include 5V and 12V distributed power bus providers, television sets and displays, white goods and small appliances, FPGA, DSP, and ASIC power supplies, home stereos, networking systems, game consoles, consumer electronics, and general purpose load points.

     Both the AP62500 and AP62800 are packaged with 12-pin V-QFN2030. Both step-down converters have a wide input voltage range: the AP62500 covers 4.5V to 18V, and the AP62800 covers 4.5V to 17V (both for product applications with 5V and 12V rails). The output voltage of both can be reduced to 0.6V. Three different switching frequencies (400kHz, 800kHz, and 1.2MHz) are available, allowing engineers to prioritize conversion efficiency or focus on a compact form factor.

     In addition, these units have three operating modes to choose from; Pulse frequency modulation (PFM) improves light-load efficiency, pulse width modulation (PWM) reduces output voltage ripple, and ultrasonic (USM) avoids the audible frequency range while ensuring that the switching frequency is maintained above 20kHz.

     This product remains low due to the associated on-resistance (RDS(ON)) values: high side mosFETs (AP62500 at 47 Mω; AP62800 is 22 Mω) and low side mosFETs (AP62500 is 18 Mω; AP62800 is 10mΩ), which helps to improve the step-down conversion efficiency. Ultra-low static current (IQ) is also achieved in PFM mode (typical value 195μA), further improving light load efficiency.

     These step-down converters are designed to dramatically reduce electromagnetic interference (EMI) problems. A special cartridge driver design can slow the switching node's ringing without prolonged MOSFET on/off time, which may interfere with the high frequency switching function. Constant on-time (COT) control enables fast instantaneous response and low output voltage ripple, and helps to make the loop more stable. Another important feature is the adjustable soft start time to prevent the risk of damage from surge current.