DEMO MANUAL DC1833A LTC6362 Fully Differential Amplifier DESCRIPTION The LTC®6362 is a low power, low noise differential op amp with rail-to-rail input and output swing that has been optimized to drive low power SAR ADCs. The amplifier may be configured to buffer a fully differential input signal or convert a single-ended input signal to a differential output signal. Demo circuit 1833A contains the LTC6362 amplifier configured as a unity gain amplifier with 1kΩ feedback and input resistors, where both inputs are AC-coupled by a 1μF capacitor. The differential outputs of the DC1833A can be configured with a first order RC network for driving PERFORMANCE SUMMARY differential input, as given in Table 1. (TA = 25°C) the differential inputs of an ADC. The LTC6362 differential output can be DC-coupled or AC-coupled (AC-coupled is the default configuration). Onboard jumpers configure the DC1833A for dual or single power supply. In addition, there are several optional surface mount pads that can be used to change the LTC6362 configuration. Design files for this circuit board are available at http://www.linear.com/demo L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. This demo board is factory tested by measuring distortion with an 8VP-P, 2kHz Table 1. LTC6362 Noise and Distortion Differential Input, Referred Noise Voltage Density 3.9nV/√Hz Distortion, 8VP-P Differential Input, VS = 5V, FIN = 2kHz, RLOAD = 1000Ω 2nd Harmonic 3rd Harmonic –128dBc –114dBc 2kHz Sine Wave, VIN Diff 8VP-P 16384 –Point FFT R6, 1k R3, 1k V+ 0.1μF – + VOCM 0.1μF VIN+ R5, 1k R15 LTC6362 + – C18 CDIFF R14 C19 C15 VOUT+ VOUT– R4, 1k DC1833A F01a MAGNITUDE (dB) VIN– 0 –10 –20 –30 –40 –50 –60 –70 V+ = 5V V– = 0V HD2 = –128dBc HD3 = –114dBc –80 –90 –100 –110 –120 –130 –140 –150 0 2 4 6 8 10 12 14 FREQUENCY (kHz) 16 18 20 DC1833A FO1b Figure 1. Typical Application for an LTC6362 dc1833af 1 DEMO MANUAL DC1833A QUICK START PROCEDURE Check to ensure that both jumpers, JP1 and JP2, are set as shown in Figure 2. Power the DC1833 from a single power supply, V+ = 5V and V– = 0V. For distortion measurements, a low noise, low distortion generator and an analyzer such as Audio Precision SYS-2722 or Stanford Research SR1 should be used with the LTC6362 configured as shown in Figure 1, the resulting distortion for an 8VP-P sine wave input is shown in the FFT plot. 5V POWER SUPPLY + – AUDIO PRECISION SYS - 2722 ANALOG GENERATOR ANALOG OUTPUT A+ ASIN(WT) VIN 2kHz 8VP-P –ASIN(WT) COMPUTER –DISPLAY AP SYS-2722 RESULTS ANALOG ANALYZER +INPUT –INPUT ANALOG OUTPUT A– DC1833A F02 USB CABLE Figure 2. DC1833A Connection Diagram dc1833af 2 DEMO MANUAL DC1833A QUICK START PROCEDURE Single-Ended to Differential Output Definitions The DC1833A can be configured for single-ended input to differential output by populating R1 with 0Ω, removing C1, and replacing C8 with a 0Ω resistor. In this configuration, the input, J2, is now DC-coupled to the LTC6362 input. The differential output is AC-coupled in the default setting. Driving the single-ended input of the LTC6362 at full scale 10VP-P, each output will swing from 0.5V to 4.5V when configured with gain of AV = –0.8 (AV = –0.8 is set by changing the R5 and R6 values to 1.25k). JP1: Toggles the LTC6362 ON and OFF. Part ON is the default setting. Differential Input to Differential Output E3: Negative Power Supply Voltage, V–. In the default configuration V– is tied to Ground. Populate C1 and C8 pads with 0Ω resistors to set the differential input mode. DC-Coupled Output The DC1833 is configured for an AC-coupled output via C16 and C17. For DC-coupled output, replace these capacitors with 0Ω resistors. Layout A ground plane is necessary to obtain maximum performance. Keep bypass capacitors as close to supply pins as possible. Use individual low impedance returns for all bypass capacitors. Use a symmetrical layout around the analog inputs to minimize the effects of parasitic elements. Shield analog input traces with ground to minimize coupling from other traces. Keep traces as short as possible. JP2: Toggles between single and dual power supplies for the LTC6362. The single supply is the default configuration for the DC1833A. E1: Positive Power Supply Voltage. In the default configuration, V+ = 5V. E2: Ground. E4: Sets the input common mode voltage. In the default the input common mode voltage is set by the output common mode reference voltage. Please refer to the input common mode voltage range section in the LTC6362 data sheet for more details. E5: The voltage on this pin sets the output common mode voltage level. If left floating (default setting), an internal resistor divider develops a default voltage of 2.5V with a 5V supply. E6: Ground. E7: Externally drives the SHDN pin. The default configuration the EXT SHDN pin is left floating (LTC6362 power on). Use EXT SHDN only after JP1 is removed. 4.5V 4V 4.5V 5V R6 1.25k VOCM SHDN R5 1.25k 5V R15 RFILT C17 1μF C18 R14 CDIFF RFILT C16 1μF – + LTC6362 + – C19 CCM R4, 1k 4.5V 0.5V R3, 1k –4V 0.5V R3, 1k –5V VIN DIFFERENTIAL V INPUT IN VOUT+ VIN VOUT+ 5V R6, 1k VOUT+ VOUT– VOCM SHDN R5, 1k R15 RFILT C17 VOUT+ C18 R14 CDIFF RFILT C16 VOUT– – + LTC6362 + – C19 CCM R4, 1k 4.5V C15 CCM C15 CCM VOUT– VOUT– 0.5V 0.5V DC1833A F04 DC1833A F03 Figure 4. Differential Input to Differential Output Figure 3. Single-Ended to Differential Output dc1833af 3 DEMO MANUAL DC1833A PARTS LIST ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER Required Circuit Components 1 4 C1, C8, C16, C17 CAP, CER X5R 1μF 16V, 0603 AVX, 0603YD105KAT 2 2 C2, C3 CAP, CER 0.1μF 25V 10% X7R, 0805 MURATA, GRM21BR71E104KA01L TAIYO YUDEN, EMK212ABJ475MG-T 3 2 C4, C5 CAP, CER X5R 4.7μF 16V, 0805 4 0 C6, C7, C9, C10, C15, C18, C19 (OPT) CAP, 0603 5 4 C11, C12, C13, C14 CAP, CER X7R 0.1μF 16V, 0603 AVX, 0603YC104KAT 6 2 JP1, JP2 HEADER, 3PIN 1 ROW 0.079CC SAMTEC, TMM-103-02-L-S 7 2 JP1, JP2 SHUNT, 0.079” CENTER SAMTEC, 2SN-BK-G 8 4 J1 TO J4 CONN SMA 50Ω EDGE LAUNCH AMPHENOL/CONNEX 132357 9 7 E1 TO E7 TP, TURRET, 0.064” MILL-MAX, 2308-2-00-80-00-00-07-0 10 0 R1, R8, R9, R10, R12, R13 (OPT) RES, 0603 11 5 R2, R7, R11, R14, R15 RES, CHIP 0, 1%, 0603 NIC, NRC06ZOTRF 12 4 R3, R4, R5, R6 RES, CHIP 1k, 1%, 0603 NIC, NRC06F1001TRF 13 1 U1 IC, FULLY DIFFERENTIAL AMPLIFIER IC, LINEAR TECH. LTC6362CMS8 14 2 STENCIL FOR BOTH SIDES STENCIL, DC1833A-2 15 1 FAB, PRINTED CIRCUIT BOARD DEMO CIRCUIT 1833A-2 dc1833af 4 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. D C B A C8 1uF C1 1uF 2 R1 OPT R8 OPT R7 0 R2 0 1 2 1. ALL RESISTORS ARE IN OHMS, 0603 ALL CAPACITORS ARE IN MICROFARADS, 0603. NOTE: UNLESS OTHERWISE SPECIFIED J2 VIN- J1 VIN+ 1 E5 E4 R9 OPT V+ E1 R10 OPT 0805 V+ C4 4.7uF R13 OPT R12 OPT GND C12 0.1uF 3 4 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. 4 3 2 1 ERJON Q . 5 SCALE = NONE NC PCB DES. IN+ OUT- V- SHDN 5 6 7 8 2 - DATE: N/A SIZE 6 10-13-11 IC NO. 7 R15 0 R14 0 J4 J3 VOUT+ VOUT- E7 EXT SHDN GND 8 DATE 10-13-11 7 LTC6362CMS8 DEMO CIRCUIT 1833A 8 SHEET 1 OF 1 2 REV. 1630 McCarthy Blvd. Milpitas, CA 95035 Phone: (408)432-1900 www.linear.com Fax: (408)434-0507 LTC Confidential-For Customer Use Only C17 1uF C16 1uF SINGLE C19 OPT C15 OPT JP2 SUPPLY DUAL PWR_ON SHDN E6 ERJON Q . APPROVED FULLY DIFFERENTIAL AMPLIFIER V- JP1 PRODUCTION FAB DESCRIPTION REVISION HISTORY TECHNOLOGY C18 OPT C13 0.1uF 0 R11 R5 1K R4 1K C7 OPT REV ECO 6 TITLE: SCHEMATIC C14 0.1uF OUT+ V+ VOCM IN- U1 LTC6362CMS8 V- E3 APPROVALS 0805 0805 V- 5 APP ENG. C11 0.1uF R6 1K R3 1K C6 OPT C5 4.7uF C3 0.1uF LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT PERFORMANCE OR RELIABILITY. CONTACT LINEAR TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. E2 V + / - = 2.8V - 5.25V C2 0.1uF 0805 C10 OPT V+ 4 CUSTOMER NOTICE EXT VOCM EXT VCM C9 OPT 3 D C B A DEMO MANUAL DC1833A SCHEMATIC DIAGRAM dc1833af 5 DEMO MANUAL DC1833A DEMONSTRATION BOARD IMPORTANT NOTICE Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions: This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations. If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES. The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind. LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive. Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and observe good laboratory practice standards. Common sense is encouraged. This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer. Mailing Address: Linear Technology 1630 McCarthy Blvd. Milpitas, CA 95035 Copyright © 2004, Linear Technology Corporation dc1833af 6 Linear Technology Corporation LT 0312 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2012