Power

Synchronous buck converters with noise reduction

19th November 2020
Alex Lynn

Diodes Incorporated has announced two highly integrated synchronous buck converters that simplify circuit design in automotive power systems with its Power Good output and its innovative EMI mitigation for noise-sensitive applications.

The AP63356Q and AP63357Q are 3.5A converters with an input voltage range of 3.8 to 32V. Leveraging peak current mode control as well as high-side and low-side power MOSFETs on-chip, the converters minimise external components to reduce bill of materials (BOM) costs and board size.

Both devices have a Power Good indicator with an internal 5MΩ pull-up resistor useful for power sequencing. To further aid sequencing, their enable pin has accurate voltage thresholds, which allows adjustment of the input voltage device power-on and undervoltage lockout (UVLO). The high-voltage capability of the EN pin allows direct connection to VIN to simplify the auto-start of the device. When disabled, the converter draws only 0.6µA shutdown current typical.

Their proprietary gate-driver scheme ensures clean switching transitions while preventing switch-node ringing to minimise high-frequency radiated noise. Frequency spread spectrum (FSS) contributes further to quiet performance by dispersing switching-noise energy.

The AP63356Q operates continuously in PWM mode at the nominal 450kHz switching frequency for all loads. The AP63357Q changes to PFM mode at light loads, keeping efficiency as high as 86% at 5mA load and drawing quiescent current of just 22µA under no load.

Both devices feature low-dropout (LDO) operation, which maintains their output-voltage regulation as the input reduces to a level near the output voltage. Built-in protection features include output undervoltage protection (UVP), cycle-by-cycle peak current limit, and thermal shutdown. The protection features, along with 40V (for 400ms) input voltage surge withstand capability, enable the devices to provide a robust Automotive POL solution.

The AP63356Q and AP63357Q are qualified to AEC-Q100 Grade 1, support PPAP documentation, and are manufactured in IATF 16949 certified facilities. The devices are each available in a 3x2mm V-DFN3020-13 (SWP) package with wettable flanks to aid in automated optical inspection. The unit price is $0.46 in 3,000 piece quantities.

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