SKY73201-364LF SKY73202-364LF - Datasheet Archive

 

Interfacing to the SKY73201-364LF and SKY73202-364LF Filters Figure 1 shows a simplified schematic of the inputs to the

 

APPLICATION NOTE Interfacing to the SKY73201-364LF SKY73201-364LF and SKY73202-364LF SKY73202-364LF Filters Figure 1 shows a simplified schematic of the inputs to the SKY73201-364LF SKY73201-364LF filter. The input stage is a 2-stage op-amp with bipolar input, which implies that the preceding stage must supply base current and a common-mode voltage. We suggest a common-mode base voltage of 1.65 V be applied to the inputs. Any external resistance in series with pins 7 and 8 will reduce the gain of the filter. (The same recommendations apply to the inputs of the SKY73202-364LF SKY73202-364LF filter.) Figure 2 shows a simplified schematic of the output buffer of the SKY73201-364LF SKY73201-364LF. The device generates a common-mode voltage of 1.65 V at the output and the output buffers are designed to drive a minimum of 5 k impedance. If the device is loaded with a resistance lower than 5 k, it will cause loss in signal swing, which may reduce the gain and affect the signal-linearity. (The same recommendations apply to the SKY73202-364LF SKY73202-364LF filter.) Pin 7 1.66 V Pin 8 1.65 V ib Pin 26 1.65 V ib CM Feedback Amplifier Pin 25 1.65 V SKY73201-364LF SKY73201-364LF SKY73201-364LF SKY73201-364LF Figure 1. Simplified Schematic of Input Figure 2. Simplified Schematic of the Filter Output Skyworks Solutions, Inc. · Phone [781] 376-3000 · Fax [781] 376-3100 · sales@skyworksinc.com · www.skyworksinc.com 200760 Rev. B · Skyworks Proprietary Information · Products and Product Information are Subject to Change Without Notice. · October 11, 2007 1 APPLICATION NOTE · INTERFACING TO THE SKY73201-364LF SKY73201-364LF AND SKY73202-364LF SKY73202-364LF FILTERS If the stage following the SKY73201-364LF SKY73201-364LF or SKY73202-364LF SKY73202-364LF requires a common-mode voltage that is lower or higher than 1.65 V, the new common-mode voltage can be established by simple resistive-division. Figure 3 shows a simple application circuit in which the SKY73201-364LF SKY73201-364LF filter is used to drive a 1.8 V data converter with an input common mode voltage of 0.9 V. It is important to design adequate supply bypassing by means of bypassing capacitors as any noise coupled into the device may affect the corner frequency accuracy. The exact values of the bypass capacitors will depend on the application environment. 3.3 V Bypass Capacitors 29 28 27 26 2.7 k Out_n VDD 30 Out_p VDD 31 Clk_sel Enable 32 Ref_Clk VSS VDD for 40 MHz VSS for 20 MHz 3.3 k 25 NC 1 24 2 23 HighEdge NC 3 22 LowEdge NC 4 21 Tuned 3.3 k ManSel/Cal_EN NC SKY73201-364LF SKY73201-364LF 7 18 SPI_CLK In_p 8 17 SPI_LE 9 10 11 12 13 14 15 From SPI Controller 16 VSS In_n VSS SPI_Data ManSel_5 19 ManSel_4 6 ManSel_3 VSS Turn Ref_Clk OFF when High CLR_reg ManSel_2 20 ManSel_0 5 ManSel_1 NC VIN 2.7 k VOUT Figure 3. SKY73201-364LF SKY73201-364LF Application Circuit with 0.9 V Output Common-mode Voltage Skyworks Solutions, Inc. · Phone [781] 376-3000 · Fax [781] 376-3100 · sales@skyworksinc.com · www.skyworksinc.com 2 October 11, 2007 · Skyworks Proprietary Information · Products and Product Information are Subject to Change Without Notice. · 200760 Rev. B APPLICATION NOTE · INTERFACING TO THE SKY73201-364LF SKY73201-364LF AND SKY73202-364LF SKY73202-364LF FILTERS Copyright © 2007, Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. ("Skyworks") products or services. These materials, including the information contained herein, are provided by Skyworks as a service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. 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Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper use or sale. Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters. Skyworks, the Skyworks symbol, and "Breakthrough Simplicity" are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. Skyworks Solutions, Inc. · Phone [781] 376-3000 · Fax [781] 376-3100 · sales@skyworksinc.com · www.skyworksinc.com 200760 Rev. B · Skyworks Proprietary Information · Products and Product Information are Subject to Change Without Notice. · October 11, 2007 3