AN2728 datasheet(4/20 Pages) STMICROELECTRONICS

Il numero della parte	AN2728

Spiegazioni elettronici	ST1S12 small synchronous buck converter

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Produttore elettronici	STMICROELECTRONICS [STMicroelectronics]

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ST1S12 description

AN2728

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ST1S12 description

The ST1S12 is an adjustable current mode PWM synchronous step-down DC-DC converter

with an internal 0.7 A power switch. It is a complete 0.7 A switching regulator with internal

compensation which eliminates the need for additional components.

The device operates with typically 1.7 MHz fixed frequency, and in order to guarantee the

lowest switching ripple, operates in pulse width modulation (PWM) mode even at low-load

condition. (Figure 2 and Figure 3)

To clamp the error amplifier reference voltage, a soft-start control block generating a voltage

ramp is implemented. When switching on the power supply, it allows controlling the inrush

current value (Figure 4).

Figure 2.

Inductor current at no load

Figure 3.

Inductor current at medium load

VEN=VIN=5 V, VOUT=1.8 V, no load, CH1=SW,

CH2=VOUT, CH4=IL

VEN=VIN=5 V, VOUT=1.8 V, RLOAD=4.7 Ω, CH1=SW,

CH2=VOUT, CH4=IL

OUT (AC)

Vout (AC)

Figure 4.

Inrush current

OUT

VEN=VIN=5 V, VOUT=1.8 V, RLOAD =15 Ω,

Ch1=SW, CH2=VOUT, CH3=EN, CH4=IIN

AN2728 Scheda tecnica(PDF) 4 Page - STMicroelectronics