IRS27951S IRS27952(4)S - International Rectifier
IRS27951S IRS27952(4)S - International Rectifier
IRS27951S IRS27952(4)S - International Rectifier
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
<strong>IRS27951S</strong><br />
<strong>IRS27952</strong>(4)S<br />
- For closed loop systems with feedback control, a resistor Rfmax can be connected between the RT<br />
pin and the collector of the (emitter-grounded) phototransistor. The feedback loop modulates the<br />
current through the phototransistor and hence, the oscillator frequency for output voltage regulation.<br />
- The converter maximum frequency is set by (Rmax//RT) and CT.<br />
VCCON<br />
VCC<br />
2V<br />
RT<br />
5V<br />
CT<br />
3V<br />
VEN1<br />
HO<br />
LO<br />
UVLO<br />
SLEEP<br />
NORMAL<br />
Figure 2: Typical startup waveforms with soft-start<br />
Frequency and Dead-time Calculation<br />
The dead time is calculated by the following equation:<br />
t<br />
DT<br />
2V<br />
= ( 0.85CT<br />
+ 40 pF)<br />
⋅<br />
2mA<br />
15 www.irf.com © 2012 <strong>International</strong> <strong>Rectifier</strong> November 8 th , 2012