NR263S Datasheet, PDF(11/29 Page) Sanken electric – Light Load High Efficiency Synchronous Buck Regulator IC

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NR263S Datasheet, PDF (11/29 Pages) Sanken electric – Light Load High Efficiency Synchronous Buck Regulator IC

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7. Operational Descriptions

The Characteristic value of, unless otherwise noted, it writes the TYP value in accordance with the NR263S

specifications.

7.1 PWM(Pulse Width Modulation) Output Control

The PWM control circuit of the NR263S consists of the current sense amplifier, the error amplifier, the PWM

comparator, the slope superimposing circuit. The Vtrip is the drain current feedback signal detected by current sense

amplifier. And the VCOMP is the error amplification signal generated by the error amplifier with the output voltage

and the reference voltage. By comparing with the Vtrip and the VCOMP in the PWM comparator, it performs control

of the ON-Duty. In the slope superimposition circuit, by superimposing the slope signal with respect to the current

feedback signal Vtrip, it can avoid the sub-harmonic oscillation that occur at ON-Duty 50% or more.

Fig. 7-1 Basic Structure of Buck Regulator with PWM Control by Current mode Control

When the UVLO was released or, the EN terminal voltage exceeded threshold, the SS terminal voltage starts to rise.

In the period until the SS terminal voltage reaches to 0.6V (typ), to drive the High-side driver and the High-side

switch (the following M1), by turning on the Low-side switch (the following M2), the boost capacitor CBS is

charged. After that, the switching operation is started when the SS terminal voltage exceeds 0.6V (typ). M1 and M2

are the switching-MOSFET for suppling the power to the Output. By M1&M2 repeating ON and OFF alternately,

and energy is supplied to the Output stage. In the period when M1 turns on, the current of Inductor L increase, and

the output of the current sense amplifier is raised, too. In the PWM comparator, the error amplifier output VCOMP

signal is compared with the Vtrip signal which is the addition of the current sense amplifier signal and the slope

compensation signal. When the Vtrip exceeds the VCOMP, M1 turns OFF, and M2 turns ON, the regenerative current

of the inductor L flows via M2 from the GND. Then, upon receiving a set signal from the oscillator OSC, M1 is

turned ON again.

NR263S series-DSE Rev.1.0

SANKEN ELECTRIC CO.,LTD

2016.03.09

http://www.sanken-ele.co.jp/en/

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