GENERAL DESCRIPTION. FEATURES 3A step-down power module

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1 XR7903 April 06 GENERAL DESCRIPTION The XR7903 is part of a family of 40V synchronous step-down power modules combining the controller, drivers, inductor, passive components and MOSFETs in a single package for point-of-load supplies. This module requires very few external components leading to ease of design and fast time to market. The XR7903 has load current rating of 3A. A wide 5V to 40V input voltage range allows for single supply operation from industry standard 4V ±0%, 8V to 36V and rectified 8VAC and 4VAC rails. With a proprietary emulated current mode Constant On-Time (COT) control scheme, the XR7903 provides extremely fast line and load transient response using ceramic output capacitors. It requires no loop compensation, simplifying circuit implementation and reducing overall component count. The control loop also provides 0.% load and 0.% line regulation and maintains constant operating frequency. A selectable power saving mode, allows the user to operate in Discontinuous Current Mode (DCM) at light current loads significantly increasing the converter efficiency. A host of protection features, including overcurrent, over temperature, short-circuit and UVLO, helps achieve safe operation under abnormal operating conditions. The XR7903 is available in a RoHS-compliant, green/halogen-free space-saving 8mm x 8mm x 4mm QFN package. FEATURES EVALUATION BOARD MANUAL 3A step-down power module o o Rev. A 5V to 40V wide single input voltage 0.6V adjustable output voltage Controller, drivers, inductor, passive components and MOSFETs integrated in one package Proprietary constant on-time control o No loop compensation required o Stable with ceramic output capacitors o Programmable 00ns to µs ontime o Constant 400kHz to 800kHz frequency o Selectable CCM or DCM/CCM operation Precision enable and power-good flag Programmable soft-start 8mm x 8mm x 4mm QFN package Exar Corporation Kato Road, Fremont CA 94538, USA Tel Fax

2 XR7903 April 06 Rev. A D MMSZ4685-TP C A R 0k R 30.K -3=DCM/CCM 3 -=CCM J SS PGOOD C3 R3 35.7K 0.uF CSS 47nF RON.5k RLIM.8k EN CBST C = 4V nominal C C3 C4 C5 C6 T3 Lin (short) + RPGOOD 0k UA SS 3 PGood TON ENMode ILIM 5 5 BST 50 BST NC 44 BST RR k nf CAC CR nf 0.uF 0uF 0uF T4 500kHz, 3.3V, 3A C7 C8 C9 C0 47uF C 0.uF - T + C - T XR7903 C4 CFF 0pF R 9.09k 6 60 CSNB nf 0.uF RFF 0.8k R 0 R5 k CIN 0.uF C 4.7uF 58 6 BST RSNB Ohm R k UB XR7903 Fig. : XR7903 Evaluation Board Schematics PIN CONFIGURATION Fig. : XR7903 Pin Assignment Exar Corporation Kato Road, Fremont CA 94538, USA Tel Fax

3 XR7903 PIN FUNCTIONS ORDERING INFORMATION Refer to XR7903 datasheet and/or for exact and up to date ordering information. 06 Exar Corporation 3/9 Rev. A

4 XR7903 USING THE EVALUATION BOARD POWERING UP Connect the +/- with short leads to power supply. Use T3 and T4 pins to monitor + and respectively. Connect +/- with short leads to an electronic load. Use T and T pins to monitor + and - respectively. Apply 4V using the power supply. The XR7903 EVB should power up and regulate the output at 3.3V. Input voltage range is from 5V to 40V. Maximum rated current for XR7903 is 3A. PROGRAMMING THE OUTPUT VOLTAGE V OUT can be programmed by changing R according to: RRRRRR = RRRRRR VV OOOOOO 0.6 Where R has a nominal value of kω. R ON must be set correspondingly, as explained in the datasheet, in order to get the desired switching frequency. JUMPER J If the jumper is set to CCM position, the Module will operate in forced CCM. If the Jumper is set to DCM/CCM position, the Module will operate in DCM at light load. 06 Exar Corporation 4/9 Rev. A

5 XR7903 EVALUATION BOARD SCHEMATICS D MMSZ4685-TP C A R 0k R 30.K -3=DCM/CCM 3 -=CCM J SS PGOOD C3 R3 35.7K 0.uF CSS 47nF RON.5k RLIM.8k EN CBST C = 4V nominal C C3 C4 C5 C6 T3 Lin (short) + RPGOOD 0k UA SS 3 PGood TON ENMode ILIM 5 5 BST 50 BST NC 44 BST RR k nf CAC CR nf 0.uF 0uF 0uF T4 500kHz, 3.3V, 3A C7 C8 C9 C0 47uF C 0.uF - T + C - T XR7903 C4 CFF 0pF R 9.09k 6 60 CSNB nf 0.uF RFF 0.8k R 0 R5 k CIN 0.uF C 4.7uF 58 6 BST RSNB Ohm R k UB XR7903 XR7903 EVB Schematics 06 Exar Corporation 5/9 Rev. A

6 XR7903 XR7903EVB BILL OF MATERIAL PCB Exar XR7906 Evaluation Board U Exar XR7903EL-F 8mmX8MM D ON SEMI MMSZ4685TG SOD3 DIODE ZENER 3.6V 500MW SOD3 C3,C4 MURATA GRM3CR6H06KAL 06 CERAMIC CAP. 0uF, 50V, X5R, 0% C7 MURATA GRM3CR6A476KE5L 06 CERAMIC CAP. 47uF, 0V, X5R, 0% C,C MURATA GRM55R7H04KE4D 040 CERAMIC CAP. 0.uF, 50V, X7R, 0% CIN MURATA GRM88R7H04KA93D 0603 CERAMIC CAP. 0.uF, 50V, X7R, 0% C MURATA GRM88R6A475KE5D 0603 CERAMIC CER, 4.7uF, 0V, X5R, 0% C3 MURATA GRM88R7C4KA0D 0603 CERAMIC CAP, 0.uF, 6V, X7R, 0% CSS MURATA GRM88R7H473KA6D 0603 CERAMIC CAP, 47nF, 50V, X7R, 0% CFF MURATA GRM88R7HKA0D 0603 CERAMIC CAP, 0pF, 6V, X7R, 0% RFF PANASONIC ERJ-3EKF800V 0603 Resistor 80 Ohm, /0W,%,SMD R,RPGOOD PANASONIC ERJ-3EKF00V 0603 Resistor 0.0K Ohm, /0W,%,SMD R PANASONIC ERJ-3EKF30V 0603 Resistor 30.K Ohm, /0W,%,SMD R3 PANASONIC ERJ-3EKF357V 0603 Resistor 35.7K Ohm, /0W,%,SMD R PANASONIC ERJ-3EKF909V 0603 Resistor 9.09K Ohm, /0W,%,SMD R PANASONIC ERJ-3EKF00V 0603 Resistor.0K Ohm, /0W,%,SMD R PANASONIC ERJ-3GEY0R00V 0603 Resistor 0.00 Ohm, Jumper, /0W, SMD RLIM PANASONIC ERJ-3EKF8V 0603 Resistor.8K Ohm, /0W,%,SMD RON PANASONIC ERJ-3EKF5V 0603 Resistor.5K Ohm, /0W,%,SMD LIN VISHAY/DALE CRCW00000Z0EAHP 00 Resistor 0.00 Ohm, Jumper, 3/4W, SMD T-T4,,PGOOD,SS,EN, 9 Wurth Elektronik mm Header pin J Wurth Elektronik mm Header 3 pin -, +, -, + 4 Wurth Elektronik Mountin Tab WA-MTAB 06 Exar Corporation 6/9 Rev. A

7 XR7903 EVALUATION BOARD LAYOUT Fig. 3: Assembly Top Fig. 4: Assembly Bottom Fig. 5: Top Layer Fig. 6: Bottom Layer 06 Exar Corporation 7/9 Rev. A

8 XR7903 Fig. 7: Layer Fig. 8: Layer 3 06 Exar Corporation 8/9 Rev. A

9 XR7903 DOCUMENT REVISION HISTORY Revision Date Description A 4/5/6 Initial release of document BOARD REVISION HISTORY Board Revision Date Description REV.0 /3/5 Initial release of evaluation board FOR FURTHER ASSISTANCE Exar Technical Documentation: customersupport@exar.com powertechsupport@exar.com EXAR CORPORATION HEADQUARTERS AND SALES OFFICES 4870 Kato Road Fremont, CA 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. 06 Exar Corporation 9/9 Rev. A