PVIN. Test Point uF. RLIM 2k. RON 12.1k EN/MODE 70 ILIM 69 SS 74 BST BST BST PAD PVIN 65 PVIN 59 PVIN 60 PVIN 66 PVIN 61 PVIN 62 PVIN 63

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1 May 05 GENERAL DESCRIPTION The XR790 is a 0A synchronous step-down Power Module for point-of load supplies. A wide 4.5V to V input voltage range allows for single supply operation from industry standard 5V, V, and 9.6V rails. With a proprietary emulated current mode Constant On-Time (COT) control scheme, the XR790 provides extremely fast line and load transient response using ceramic output capacitors. It requires no loop compensation hence simplifying circuit implementation and reducing overall component count. The control loop also provides 0.% load and 0.7% line regulation and maintains constant operating frequency. A selectable power saving mode allows the user to operate in discontinuous mode (DCM) at light current loads thereby significantly increasing the converter efficiency. With a 9% peak efficiency and 84% for loads as low as 00mA, the XR790 is suitable for applications where low power losses are important. A host of protection features, including over-current, over-temperature, short-circuit and UVLO, help achieve safe operation under abnormal operating conditions. The XR790 is available in a RoHS compliant, green/halogen free space-saving 74-pin x4x4mm QFN package. With integrated controller, drivers, bootstrap diode and capacitor, MOSFETs, inductor, CIN and COUT, this solution allows the smallest possible 0A POL design. FEATURES EVALUATION BOARD MANUAL Rev. A Controller, drivers, bootstrap diode and capacitor, MOSFETs, Inductor, CIN and COUT integrated in one package 0A Step Down Module Wide 4.5V to V Input Voltage Range 0.6V Adjustable Output Voltage Proprietary Constant On-Time Control No Loop Compensation Required Ceramic Output Cap. Stable operation Programmable 00ns-µs On-Time Constant 400kHz-600kHz freq. Selectable CCM or CCM/DCM Operation 74-pin x4x4mm QFN package GND GND GND GND - --> DCM / CCM J - --> CCM PG D R 5.7k Optional MMSZ4685 R5 0.k EN R4 0k PG C 4 C 4.7uF R CSNB.5nF RSNB Ohm R 0k C 47nF LG LG RON.k EN RLIM k 74 TON EN/MODE 70 ILIM U XR790 Test Point C uF C7 0.47uF C8 500kHz, C C4 C9 C C C C0 C5 C6 CFF 0.47nF RFF 0k C7 C0 + - R 4.0k C C 0.uF R k Fig. : XR790 Evaluation Board Schematics Exar Corporation Kato Road, Fremont CA 9458, USA Tel Fax

2 PIN AIGNMENT TON EN/MODE ILIM PGN D Fig. : XR790 Pin Assignment 05 Exar Corporation /9 Rev. A

3 PIN DESCRIPTION Pin No. Pin Name Type Description OD, O Power-good output. This open-drain output is pulled low when is outside regulation. A Feedback input to feedback comparator. Connect with a set of resistors to and in order to program., 7, 7, Pad A Analog ground. Control circuitry of the IC is referenced to this pin. Should be connected to at a single point. 4 PWR Controller supply input. Provides power to internal LDO. 5 PWR The output of LDO. Bypass with a 4.7uF capacitor to. For operation from a 5 rail, should be tied to. 6, 7, pad O Driver output for Low-side N-channel synchronous MOSFET. It is internally connected to the gate of the FET. Leave this pin floating. 8 PWR Controller low-side driver ground. Connect with a short trace to closest pins or pad. -6, 57, 58, pads 9-, 7-, pad -56, pads PWR Ground of the power stage. Should be connected to the system s power ground plane. PWR Switching node. It is internally connected. Use thermal vias and/or sufficient PCB land area in order to heatsink the low-side FET and the inductor. PWR Output of the power stage. Place the output filter capacitors as close as possible to these pins , pad PWR Power stage input voltage. Place the input filter capacitors as close as possible to these pins. 67, 68, pad A Controller high-side driver supply pin. It is internally connected to via a 0.uF bootstrap capacitor. Leave these pins floating. 69 ILIM A Over-current protection programming. Connect with a short trace to pins. 70 EN/MODE I Precision enable pin. Pulling this pin above.9v will turn the IC on and it will operate in Forced CCM. If the voltage is raised above.0v, then the IC will operate in DCM or CCM depending on load. 7 TON A Constant on-time programming pin. Connect with a resistor to. 74 A Soft-start pin. Connect an external capacitor between and to program the soft-start rate based on the 0uA internal source current. Type: A = Analog, I = Input, O = Output, I/O = Input/Output, PWR = Power, OD = Open-Drain ORDERING INFORMATION Refer to XR790 datasheet and/or for exact and up to date ordering information. 05 Exar Corporation /9 Rev. A

4 USING THE EVALUATION BOARD POWERING UP Connect the +/- with short/thick leads to power supply. Use test pins and GND to monitor + and - respectively. Connect +/- with short/thick leads to an electronic load. Use test pins and GND to monitor + and - respectively. Apply V using the power supply. The XR790EVB should power up and regulate the output at.8v. Input voltage range is from 4.5V to V. Maximum rated current for XR790 is 0A. JUMPER J If the jumper is set to CCM position (left side) the Module will operate in forced CCM. If the Jumper is set to DCM/CCM position (right side) the Module will operate in DCM at light load. Transition from DCM to CCM is at approximately 5A. OPERATION FROM A 5V RAIL (V IN=4.5V-5.5V) For operation from a 5V rail it is recommended to tie output of the LDO to V IN by populating R with a 0Ω resistor. This enhances the operation of the drivers at V IN<5V. Please remember to remove R for operation at higher V IN. PROGRAMMING THE OUTPUT VOLTAGE V OUT can be programmed by changing R according to: R = R V OUT 0.6 Where R has a nominal value of kω. 05 Exar Corporation 4/9 Rev. A

5 EVALUATION BOARD SCHEMATICS D MMSZ4685 R 0k GND GND GND GND PG - --> DCM / CCM J - --> CCM Optional R 5.7k EN R4 0k PG C 4 C 4.7uF 5 6 LG 7 LG 8 R CSNB.5nF RSNB Ohm R5 0.k C 47nF RON.k 74 TON 7 EN RLIM k 7 7 EN/MODE 70 ILIM U XR790 Test Point C6 C uF 0.47uF C8 500kHz, C C4 C9 C5 C C C C0 C6 RFF 0k C7 CFF 0.47nF C0 + - R 4.0k C C 0.uF R k 05 Exar Corporation 5/9 Rev. A

6 XR790EVB BILL OF MATERIAL Reference Qty. Manufacturer Manufacturer Size Component Designator Part Number PCB Exar XR790 XR790 Evaluation kit U Exar XR790 x4x4mm 0A Power Module D ON SEMI MMSZ4685TG SOD- Diode Zener.6V, 500MW, C,C8,C9 MURATA GRMER7E6KE5L 0 CERAMIC CAP., 5V, X7R, 0% C MURATA GRMBR7C475KA7L 0805 CERAMIC CAP, 4.7uF, 6V, X7R, 0% C6 MURATA GRM55R7E47KA88D 040 CERAMIC CAP., 0.047uF, 5V, X7R, 0% C7 MURATA GRM88R7E474KAD 060 CERAMIC AP., 0.47uF, 5V, X7R, 0% CFF MURATA GRM88R7H47KA0D 060 CERAMIC CAP., 470pF, 50V, X7R, 0% CSNB MURATA GRM88R7H5KA0D 060 CERAMIC CAP.,.5nF, 50V, X7R, 0% C MURATA GRM88R7H47KA6D 060 CERAMIC CAP uF, 50V,X7R,0% C4,C5,C6,C7 4 MURATA GRMER60J07ME0L 0 CERAMIC CAP., 6.V, 0%, X5R C MURATA GRM88R7H04KA9D 060 CERAMIC CAP., 0.uF, 50V, 0%, X7R R4,R PANASONIC ERJ-EKF00V 060 Resistor 0.0K Ohm, /0W, % R5 PANASONIC ERJ-EKF0V 060 Resistor 0.K Ohm, /0W,%,SMD R PANASONIC ERJ-EKF57V 060 Resistor 5.7K Ohm, /0W, %, SMD RFF PANASONIC ERJ-GEY0R00V 060 Resistor Jumper, 0 Ohm, /0W R PANASONIC ERJ-EKF40V 060 Resistor 4.0K Ohm, /0W, %, SMD RLIM PANASONIC ERJ-EKF00V 060 Resistor.0K Ohm, /0W, %, SMD R PANASONIC ERA-YEB0V 060 Resistor.0K Ohm, /0W, 0.%, SMD RON PANASONIC ERJ-EKFV 060 Resisrtor.K Ohm, /0W,%, SMD RSNB PANASONIC ERJ-6RQFR0V 0805 Resistor.0 Ohm,/8W,%,SMD J Wurth Elektronik 600 -PIN CONNECTOR +, +, -,- 4 Wurth Elektronik CONNECTOR BLADE TERMINAL,,,GN D,,GND,,GND,VO UT, GND,GND4, Wurth Elektronik 600 SINE Test Point Post 05 Exar Corporation 6/9 Rev. A

7 EVALUATION BOARD LAYOUT Fig. : Assembly Top Fig. 4: Assembly Bottom Fig. 5: Top Fig. 6: Bottom 05 Exar Corporation 7/9 Rev. A

8 Fig. 7: Layer, GND Fig. 8: Layer, Fig. 9: Layer 4, GND Fig. 0: Layer 5, 05 Exar Corporation 8/9 Rev. A

9 DOCUMENT REVISION HISTORY Revision Date Description A /5 Initial release of document BOARD REVISION HISTORY Board Revision Date Description REV. /5 Initial release of evaluation board FOR FURTHER AISTANCE Exar Technical Documentation: customersupport@exar.com powertechsupport@exar.com EXAR CORPORATION HEADQUARTERS AND SALES OFFICES 4870 Kato Road Fremont, CA 9458 USA Tel.: + (50) Fax: + (50) NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained herein are only for illustration purposes and may vary depending upon a user s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. 05 Exar Corporation 9/9 Rev. A