SDC2921 datasheet(10/13 Pages) SDC

Part #	SDC2921

Description	Voltage Mode PWM Controller

PDF	13 Pages

Scroll/Zoom	100%

Manufacturer	SDC [Shaoxing Devechip Microelectronics Co., Ltd]

Direct Link	http://www.sdc-semi.com/e/index.asp

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10 / 13 page

Datasheet

December, 2013 Rev. 1.2

10/13

2013 Shaoxing Devechip Microelectronics Co., Ltd.

www.sdc-semi.com

Voltage Mode PWM Controller

SDC2921

Under Voltage Protection Delay Time

REM

REMON

UVP

tUVP

Figure 6. Delay Time

Pulse Width Modulation Block

The output pulse width modulation is generated by

comparison of the sawtooth waveform from the capacitor

CT to the feedback of the voltage. Therefore, an increase

in feedback control signal amplitude cause a linear

decrease of the output pulse width. Also, the SS(Soft-Start)

limits the output pulse width. The timing diagram is

shown as below:

PWM OUT

DTC

FF-CLK

FF-Q

FF-QN

Figure 7. PWM Block

The function of PT

This signal is prepared for extra OVP/OPP (VPT > 1.25V) or disable under voltage protection function (VPT < 0.62V)

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SDC2921 Datasheet(PDF) 10 Page - Shaoxing Devechip Microelectronics Co., Ltd