16 w which exceeds the specification for ixd409pi so

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Unformatted text preview: ication, keeping other parameters the same as above, now the dissipation would be 1.16 W, which exceeds the specification for IXD_409PI. So in this case, it is recommended to use either the IXD_409YI (TO -263 package) or IXD_409CI (TO220) package. Both these packages can dissipate about 17 W with proper heat sinking arrangement. The TO-263 is a surface mount package and can be soldered onto a large pad on a copper surface of a PCB for achieving good heat transfer. For TO -220 package, a heat sink can be used. Let us take another example of a boost converter, using IXFK55N50 at VDS = 250 VDC and at I = D 27.5 Amps. Assuming sw = 500 kHz, Vcc = 12 V. f From the curve of Gate Charge for IXFK55N50 in the Data Sheet one can determine that Qg = 370 nC. Let us set R Gext = 1.0 Ohm. We use IXD_414YI or IXD_414CI here, which can dissipate 12W. Here typical value of ROH = ROL = 0.6 Ohm. Substituting the above values in our equation, we compute the power dissipation to be: PD = 0.6 x 12 x 370 x 500 kHz x 10-9 0.6 + 1.0 + 0.0 PD = 0.83 W. With adequate air circulation, one may just be able to use the PDIP Package. However, it is recommended to use TO -263 or TO -220 package for reliable performance. For the third example, considering driving a large size MOSFET module VMO 580-02F at fsw = 250 kHz. Let Vcc = 10 V, ROH = ROL = 0.6 Ohm, RGext= 0.0 Ohm. We read that Qg =2750 nC at Vcc = 10 V off the VMO 580-02F data sheet. Now: PD = 0.6 x 10 x 2750 x 250kHz x 10 -9 0.6+ 0.0 + 0.0 PD = 6.86 W IXAN0009 IXD_414YI (TO-263) or IXD_414CI (TO-220) can easily drive this load provided adequate heat sinking and proper airflow is maintained. Comments above for mounting TO-263 and/or TO-220 packages apply here as well. For derating use 0.1 W/o C. So for an ambient temperature of 50 o C, it works out to be 2.5 W. As the limit of IXD_414YI or IXD_414CI is 12 W, subtracting 2.5 W from this yields 9.5 W. So 6.86 W is still within limit. Thermal Impedance (Junction to Case) is 0.55o C/W for TO -263 and TO-220, hence a rise in case temperature should be within limit. If we increase Vcc to 15V, conduction losses in MOSFET could reduce due to lower RDS(on), but obtaining the same rise...
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This note was uploaded on 01/15/2014 for the course ECE 624 taught by Professor Staff during the Winter '08 term at Ohio State.

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