Datasheet IXRFD630 (IXYS) - 8

30 A Low-Side RF MOSFET Driver
IXRFD630 Applications Information Output Lead Inductance
Of equal importance to supply bypassing and grounding are issues related to the output lead
Introduction
inductance. Every effort should be made to keep Circuits capable of very high switching speeds and the leads between the driver and its load as short high frequency operation require close attention to sev- and wide as possible, and treated as coplanar eral important issues. Key elements include circuit loop transmission lines. In configurations where the inductance, Vcc bypassing, and grounding. optimum configuration of circuit layout and by- passing cannot be used, a series resistance of a
Circuit Loop Inductance
few ohms in the gate lead may be necessary to The Vcc to Vcc Ground current path defines the loop dampen ringing. that generates the inductive term. This loop must be kept as short as possible. The output lead must be
Heat Sinking
no further than 0.375 inches (9.5 mm) from the gate of For high power operation, the bottom side metal- the MOSFET. Furthermore, the output ground leads ized substrate should be placed in compression must provide a balanced symmetric coplanar ground against an appropriate heat sink. The substrate return for optimum operation. is metalized for improved heat dissipation, and is not electrically connected to the device or to
Vcc Bypassing
ground. See the technical note “DE-Series MOS- In order to turn a MOSFET on properly, the IXRFD630 FET and IC Mounting Instructions” on the IXYS must be able to draw up to 30 A of current from the Vcc Colorado website at www.ixyscolorado.com for power supply in 2-6 ns (depending upon the input ca- detailed mounting instructions. pacitance of the MOSFET being driven). Good per- formance requires very low impedance between the driver and the power supply. The most common method of achieving this low impedance is to bypass the power supply at the driver with a capacitance value much larger than the load capacitance. Usually, this is achieved by placing two or three different types of by- passing capacitors, with complementary impedance curves, very close to the driver itself. (These capacitors should be carefully selected for low inductance, low resistance, and high pulse current service.) Care should be taken to keep the lengths of the leads be- tween these bypass capacitors and the IXRFD630 to an absolute minimum. The bypassing should be comprised of several values of MLC (Multi-Layer Ceramic) capacitors symmetrically placed on either side of the IC. Recommended values are 0.01uF and 0.47uF for bypass and at least two 4.7uF tantalums for bulk storage.
Grounding
In order for the design to turn the load off properly, the IXRFD630 must be able to drain 30 A of current into An
IXYS
Company 1609 Oakridge Dr., Suite 100 an adequate grounding system. There are two paths Fort Collins, CO USA 80525 for returning current that need to be considered: Path 970-493-1901 Fax: 970-232-3025 Email: sales@ixyscolorado.com one is between the IXRFD630 and its load, and path Web: http://www.ixyscolorado.com two is between the IXRFD630 and its power supply. © 2013 Both of these paths should be as low in resistance and inductance as possible, and thus as short as practical. 8