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## IR3553 Datasheet(PDF) 17 Page - International Rectifier

 Part No. IR3553 Description 40A Integrated PowIRstage Download 22 Pages Scroll/Zoom 100% Manufacturer IRF [International Rectifier] Direct Link http://www.irf.com Logo

## IR3553 Datasheet(HTML) 17 Page - International Rectifier

 17 / 22 pageJuly 16, 2014 | DATASHEET V3.317IR355340A Integrated PowIRstage®12) Determine the case temperature with VCC = 5V, whichis +5.4° based on the dashed lines in Figure 13.13) Determine the case temperature with L=210nH, whichis -1.8° based on the dashed lines in Figure 14.14) Sum the case temperature adjustment from 9) to 13),+0.6° -3.0° -0.4° +5.4° -1.8° = +0.8°. Add the delta tothe required ambient temperature in step 8), 45°C +(+0.8°C) = 45.8°C, at which the maximum current isreducedto34Awhentheallowedjunctiontemperature is 125°C, as shown in Figure 9. If only105°C junction temperature is allowed, the requiredambient temperature is equivalent to 45.8°C + (125°C -105°C) = 65.8°C, which indicates 29.5A maximumcurrent at the 45°C required ambient temperature.INDUCTOR CURRENT SENSING CAPACITOR CCSAND RESISTOR RCSIf the IR3553 is used with inductor DCR sensing, care mustbe taken in the printed circuit board layout to make aKelvin connection across the inductor DCR. The DCresistance of the inductor is utilized to sense the inductorcurrent. Usually the resistor RCS and capacitor CCS in parallelwith the inductor are chosen to match the time constant ofthe inductor, and therefore the voltage across thecapacitor CCS represents the inductor current.Measure the inductance L and the inductor DC resistanceRL. Pre-select the capacitor CCS and calculate RCS as follows.CSLCSCRLRINPUT CAPACITORS CVINAt least two 10uF 1206 ceramic capacitors and one 0.22uF0402 ceramic capacitor are recommended for decouplingthe VIN to PGND connection. The 0.22uF 0402 capacitorshould be on the same side of the PCB as the IR3553 andnext to the VIN and PGND pins. Adding additionalcapacitance and use of capacitors with lower ESR andmounted with low inductance routing will improveefficiency and reduce overall system noise, especially insingle-phase designs or during high current operation.BOOTSTRAP CAPACITOR CBOOSTA minimum of 0.22uF 0402 capacitor is required for thebootstrap circuit. A high temperature 0.22uF or greatervalue 0402 capacitor is recommended. It should bemounted on the same side of the PCB as the IR3553 and asclose as possible to the BOOST pin. A low-inductance PCBrouting of the SW pin connection to the other terminal ofthe bootstrap capacitor is required to minimize the ringingbetween the BOOST and SW pins.VCC DECOUPLING CAPACITOR CVCCA 0.22uF to 1uF ceramic decoupling capacitor is required atthe VCC pin. It should be mounted on the same side of thePCB as the IR3553 and as close as possible to the VCC andPGND (pin 4). Low inductance routing between the VCCcapacitor and the IR3553 pins is required to minimize theringing between the BOOST and SW pins.BODY-BRAKING® PIN FUNCTIONThe BBRK# pin should be pulled up to VCC if the feature isnot used by the PWM controller. Use of a 4.7kΩ resistor ora direct connection to VCC is recommended.MOUNTING OF HEAT SINKSCare should be taken in the mounting of heat sinks so asnot to short-circuit nearby components.The VCC andBootstrap capacitors are typically mounted on the sameside of the PCB as the IR3553. The mounting height ofthese capacitors must be considered when selecting theirpackage sizes.HIGH OUTPUT VOLTAGE DESIGNCONSIDERATIONSThe IR3553 is capable of creating output voltages abovethe 3.3V recommended maximum output voltage as thereare no restrictions inside the IR3553 on the duty cycleapplied to the PWM pin. However if the current sensefeature is required, the common mode range of thecurrent sense amplifier inputs must be considered. Aviolation of the current sense input common mode rangemay cause unexpected IR3553 behavior. Also the outputcurrent rating of the device will be reduced as the dutycycle increases. In very high duty cycle applicationssufficient time must be provided for replenishment of theBootstrap capacitor for the control MOSFET drive.LAYOUT EXAMPLEContact International Rectifier for a layout examplesuitable for your specific application.