IFX80471SKV Demo Board Users Manual
Contents
1. Di N Schottky Diode MBRD 360 3A 60V D2 Diode S3D 3A Mi P channel MOSFET BSP 613P 3 1 About the IFX80471SKV demo board The IFX80471SKV has open drain outputs at the pins RO and SO The pull up resistors R12 and R13 on the demo board are connected to the V_EXT pad V_EXT should be connected to an appropriate pull up voltage source usually the microcontroller I O voltage source The pull up resistors have been assembled with a value of R12 R13 5 1kQ This resistor value should be checked with respect to the actual I O voltage and microcontroller requirements The driving capability of the reset output and sense output are described in the datasheet under Electrical Characteristics item 5 1 40 and 5 1 55 The synchronizing function is disabled by the OQ resistor R8 connecting pin 5 directly to GND In case the synchronizing function is needed make sure R8 is removed before connecting a TTL Level frequency source to the SYNC connector of the demo board Mounted on PCB back side Pin 2 GND to be cut before assembly on demo board Demoboard 4 Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 4 Dimensioning of the external components The equations for the dimensioning of the external components L1 R1 are given in the datasheet in chapter 7 where the dimensioning of the feedback divider resistors R4 and R5 is discussed In this application note a practical approach how to apply these equations for given application requ2. Cinfineon IFX80471SKV Demo Board User s Manual Demoboard Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 1 Abstract Note The following information is given as a guideline for the implementation of the device only and shall not be regarded as a description or warranty of a certain functionality condition or quality of the device This Application Note is intended to provide support for using the demo board of the Step Down DC to DC Controller IFX80471SKV This document is written in order to help the reader understand the dimensioning of the external components needed for the proper functioning of the DC DC controller It will also enable the reader to change the external components to adapt the function of the controller to his her application needs 2 Introduction Selection of appropriate external components and the layout of the PCB are key factors when designing DC DC applications for various industrial environments The goal is to achieve optimum functionality with minimum output voltage ripple and good EMC performance This application note provides as an example 1 proposal for the components selection 2 recommendation for layout Lo PIN i Tam ma dr N uh ib iw rm ie a os gt tro oe gt rs am Figure 1 Photo of the demo board assembled with the IFX80471SKV DC DC Controller Demoboard 2 Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 3 Application schematic f
3. eference generating positive feedback that might cause instability Usage of low ESR ceramic capacitors in the range 220nF to 1uF is recommended For further details about the pin definitions and functions please refer to section 3 2 of the IFX80471 datasheet 7 Additional Information e For further information please refer to www infineon com industrial standard e For technical support please write to support infineon com Demoboard 9 Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 AP Number Revision History 2012 05 15 Rev 1 0 Previous Version none 1 0 Initial Rev Demoboard 10 Rev 1 0 2012 05 15 Edition 2009 Published by Infineon Technologies AG 81726 M nchen Germany Infineon Technologies AG 2006 All Rights Reserved LEGAL DISCLAIMER THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION INFINEON TECHNOLOGIES HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND INCLUDING WITHOUT LIMITATION WARRANTIES OF NON INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY WITH RESPECT TO ANY AND ALL INFORMATION GIVEN IN THIS APPLICATION NOTE Information For further
4. he maximum available load current according to the equation lpeak PWM ILoaqt 0 5 Al Demoboard 5 Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 To continue we select Ri as R1 22m0 Using this value we can calculate the maximum allowed ripple current assuming still a load current of 2 0A somV 22m0 2 0A ax mm 0 5 In order to keep the output voltage ripple as low as possible we choose a ripple current of 300mA in the typical operation condition with 13 5V VBAT corresponding to 15 of the 2 0A maximum load current In the datasheet chapter 7 8 1 we find the equation Vin Your Vour fsw Vin LI which we now use to define the buck inductance L1 _ 13 5V 5 0V 5 0V _ 30uH 370kKHz 13 5V 300mA Al_ 545mA Al We select the next norm value L1 33UH Now it remains to check if the stability conditions arising from the slope compensation are fulfilled The inequation from chapter 7 8 1 in the datasheet gives us 2 0x107 e Vour e Rsense lt LI lt 4 0x10 e Vour e Rense 2 0x107 e 7 1V e 22m0 lt L1 lt 4 0x107 e 7 1V e 22m0 3luH lt L1 lt 62uH which confirms that our selected inductance is good to maintain stability 5 Components placement and PCB layout of the Demo Board For EMC optimization the demo board comes with an input II Filter C4 L2 and C1 Thus emission from the VBAT line is largely suppressed For proper operation and to avoid stray inductance paths the exte
5. information on technology delivery terms and conditions and prices please contact your nearest Infineon Technologies Office www infineon com Warnings Due to technical requirements components may contain dangerous substances For information on the types in question please contact your nearest Infineon Technologies Office Infineon Technologies components may be used in life support devices or systems only with the express written approval of Infineon Technologies if a failure of such components can reasonably be expected to cause the failure of that life support device or system or to affect the safety or effectiveness of that device or system Life support devices or systems are intended to be implanted in the human body or to support and or maintain and sustain and or protect human life If they fail it is reasonable to assume that the health of the user or other persons may be endangered
6. irements is shown IFX80471 SKV Rsense 90m2 5 TINT ITIN 0 25 05 0 75 Figure 4 Example of typ characteristic of the output current limit foldback 4 1 Variable output voltage For the IFX80471SKV variable device demo board we use the same output current target as for the fixed voltage version 2 0A with permission to be in the foldback current limit range see Fig 4 The desired output voltage should be typ 7 10V We should now fix the feedback output voltage divider The datasheet chapter 7 3 allows a range from 5kQ to 500kQ2 for R5 corresponds to Rrg gt We have selected a value of R5 47kQ Using the feedback voltage value of 1 25V item 5 1 12 of the electrical characteristics in the datasheet we can calculate R4 as R4 47kQ 7 10V 1 25V 1 220k0 The following procedure is very similar to component dimentioning for the 5V versions The shunt resistor is given by the current limitation target From the datasheet Chapter 7 8 2 the equation for R1 is R1 Vim 2 IpEaK PwM Vim is specified in the electrical characteristics as item 5 1 27 peak current limit threshold voltage 50mV 90mV To get the worst case lowest current we apply the equation above but we leave out the factor 2 since we have accepted to enter the foldback part of the current characteristic We get R1 max 50mV 2 0A 25mQ We have to take into account that we have not yet considered the ripple current which reduces t
7. or Adjustable version Figure 2 shows the minimum application circuit as proposed in the IFX80471 Datasheet which applies for the adjustable output voltage version IFX80471SKV Infineon BSO 613SPV or Infineon BSP 613P CS GDRV VOUT SO IFX80471SKV Figure 2 Minimum application circuit for IFX80471SKV The complete circuitry used for the demo board is shown in Figure 3 Compared to the minimum circuitry it e covers a wider load current range e improves EMC performance e enables to use only one PCB to evaluate other voltage variants of the device C4_1 4 7uF C4 2 4 7uF C2 100nF 100 uF C1 CS IFX80471SKV _ MPH Figure 3 Schematic of the demo board for IFX80471SKV Demoboard 3 Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 Table 1 E recommendation BOM for IFX80471SKV Device Supplier Type Value amp Remark 12 224H 2 5A 66m0 Ci 100NF 63V C2 Ceramic capacitor X7R 100nF gt 60V C3 o capacitor X7R 2 2nF 16V C4 1 C4 2 TDK Ceramic capacitor C4532X7R1H475M X7R 4 7uF 50Vq C5 a Tantalum electrolytic capacitor Low ESR Speed Power B45010D1076M506 C6 Ceramic capacitor X7R 100nF 16V C7 TDK Ceramic capacitor C3216X7R2A224 X7R 220nF 100V C8 Ceramic capacitor X7R 220nF 16V C9 not assembled RI pf Resistor 22m 21 ow i R3 EEE Resistor Jeg R4 pf Resistor 1 220k0 R7 R9 not assembled fo R10 Resistor RA RI pf Resistor OK R12R13 Resistor ET
8. re 7 as the green highlighted area and the blue trace respectively The Input and Output capacitors should have a short low inductance link small area ground area second layer Figure 6 Layout Recommendations Blue Line Short Connection Green Small Area The supply voltage should be routed via the pins of the input capacitors The output voltage should be routed via the pins of the output capacitors It is recommended to design the ground as a ground area ina an layer There should be a direct connection of all GND terminals of input capacitors free wheeling diode D1 output capacitors the IC RC elements and filter capacitors Use a star shaped ground link to avoid ground looping Separate the ground system connect to external wiring ground only via a single trace Connect the current sensing IC terminals pin 13 and 14 directly to the shunt R1 and design to be short Please also make sure the following pins are free from any switching noise Demoboard 8 Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 e Pin 2 FB Feedback Input Keep the PCB traces far from switching nodes to prevent from coupled switching noise Use of low ESR ceramic capacitors recommended e Pin 3 VOUT Buck Output Voltage Input Use low ESR ceramic capacitors e Pin 5 SYNC Input for external frequency synchronization e Pin 8 COMP Compesation Input e Pin 13 VS Device Supply Input Spikes at VS may influence the Bandgap r
9. rnal catch diode the Buck inductance and the input capacitor Cin have to be connected as close as possible to the PMOS device Also the GDRV path from the controller to the switching transistor should be as short as possible Best suitable for the connection of the cathode of the catch diode and one terminal of the inductance would be a small plain located next to the drain of the PMOS The GND connection of the catch diode must be also as short as possible In general the GND level should be implemented as surface area over the whole PCB as second layer The most sensitive points for coupled switching noise are the feedback path to the pins FB and VOUT and the input path Also switching noise coupled back to the SYNC input must be avoided These paths should be kept away from the switching node On the demo board also the ceramic capacitor C6 helps to suppress potential noise on the feedback line Demoboard 6 Rev 1 0 2012 05 15 Cinfineon Demo Board IFX80471 at E T co Figure5 PCB Layout Front and Back Demoboard Rev 1 0 2012 05 15 Infineon Demo Board IFX80471 6 General Layout Recommendations It is important to follow the layout recommendations given in this section The commutation circuit input capacitor C1 the PMOS M1 and the free wheeling diode D1 should be as compact as possible in order to have low inductance The area of the connection M1 L1 D1 should be as small as possible This can be seen in the Figu
Download Pdf Manuals
Related Search