Operating Frequency Information
Operating frequency information for a typical device (Figure
10) is presented as a guide for estimating device performance
for a speciﬁc application. Other typical frequency vs collector
current (ICE) plots are possible using the information shown
for a typical unit in Figures 7, 8 and 9. The operating
frequency plot (Figure 10) of a typical device shows fMAX1 or
fMAX2 whichever is smaller at each point. The information is
based on measurements of a typical device and is bounded
by the maximum rated junction temperature.
fMAX1 is deﬁned by fMAX1 = 0.05/tD(OFF)I. tD(OFF)I deadtime
(the denominator) has been arbitrarily held to 10% of the on-
state time for a 50% duty factor. Other deﬁnitions are possible.
tD(OFF)I is deﬁned as the time between the 90% point of the
trailing edge of the input pulse and the point where the
collector current falls to 90% of its maximum value. Device
turn-off delay can establish an additional frequency limiting
condition for an application other than TJMAX. tD(OFF)I is
important when controlling output ripple under a lightly loaded
fMAX2 is deﬁned by fMAX2 = (PD - PC)/WOFF. The allowable
dissipation (PD) is deﬁned by PD = (TJMAX - TC)/RθJC. The sum
of device switching and conduction losses must not exceed PD.
A 50% duty factor was used (Figure 10) and the conduction
losses (PC) are approximated by PC = (VCE • ICE)/2. WOFF is
deﬁned as the integral of the instantaneous power loss starting
at the trailing edge of the input pulse and ending at the point
where the collector current equals zero (ICE = 0A).
The switching power loss (Figure 10) is deﬁned as fMAX2 •
WOFF. Turn-on switching losses are not included because they
can be greatly inﬂuenced by external circuit conditions and com-
All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certiﬁcation.
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or speciﬁcations at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate
and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which
may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see web site http://www.intersil.com
Sales Ofﬁce Headquarters
P. O. Box 883, Mail Stop 53-204
Melbourne, FL 32902
TEL: (407) 724-7000
FAX: (407) 724-7240
100, Rue de la Fusee
1130 Brussels, Belgium
TEL: (32) 2.724.2111
FAX: (32) 2.724.22.05
Intersil (Taiwan) Ltd.
7F-6, No. 101 Fu Hsing North Road
Republic of China
TEL: (886) 2 2716 9310
FAX: (886) 2 2715 3029