AN723 データシートの表示（PDF） - Vishay Semiconductors

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AN723

Design A High Performance Buck or Boost Converter With Si9165

Vishay Semiconductors 

AN723

Vishay Siliconix

Other Issues

Sometimes higher input capacitance values are required

when ultra-high-speed, large-scale load transients occur at a

2.7-V or lower input voltages. If the voltage level at VDD drops

below 2.3 V, the UVLO circuit will instantaneously shut off the

IC and collapse the output. Best results can be achieved

when a higher-value R-C filter is used on VDD pin in

conjunction with higher input capacitance.

The PSM feature is designed to increase efficiency under light

load conditions and extend battery life. It does not offer an

efficiency advantage over PWM mode when the load exceeds

100 mA and a 1.5-µH inductor is used. (Efficiency data are

given in the “Experimental Results” section.) However, with a

maximum of 1.5-µH inductance, the Si9165 PSM mode

guarantees output regulation up to a 150-mA load for both

buck and boost converters under any input/output condition.

EXPERIMENTAL RESULTS

The Si9165 controller has been fully tested in both buck and

boost modes on demo boards. Some test results are

summarized here. For the waveforms shown, the channel

lineup from top to bottom is:

• Channel 2 - VOUT voltage ripple

• Channel 4 - inductor current, 200 mA/div.

• Channel 1 - coil pin voltage, 2 V/div.

PWM Operation

• Buck mode VIN = 3.6 V, VOUT = 2.7 V, load = 300 mA

• Boost mode VIN = 3.3 V, VOUT = 3.7 V, load = 300 mA

FIGURE 10. Buck PWM Waveforms

PSM Operation

• Buck mode VIN = 3.6 V, VOUT = 2.7 V, load = 50 mA

FIGURE 11. Boost PWM Waveform

• Boost mode VIN = 3.3 V, VOUT = 3.7 V, load = 50 mA

FIGURE 12. Buck PSM Waveform

FaxBack 408-970-5600, request 70823

www.siliconix.com

FIGURE 13. Boost PSM Waveform

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