DEMO MANUAL DC1833A LTC6362 Fully Differential Amplifier DESCRIPTION The LTC®6362 is a low power, low noise differential op amp the differential inputs of an ADC. The LTC6362 differential with rail-to-rail input and output swing that has been output can be DC-coupled or AC-coupled (AC-coupled is optimized to drive low power SAR ADCs. The amplifier may the default configuration). Onboard jumpers configure be configured to buffer a fully differential input signal or the DC1833A for dual or single power supply. In addition, convert a single-ended input signal to a differential output there are several optional surface mount pads that can be signal. Demo circuit 1833A contains the LTC6362 amplifier used to change the LTC6362 configuration. configured as a unity gain amplifier with 1kΩ feedback Design files for this circuit board are available at and input resistors, where both inputs are AC-coupled by http://www.linear.com/demo a 1μF capacitor. The differential outputs of the DC1833A L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear can be configured with a first order RC network for driving Technology Corporation. All other trademarks are the property of their respective owners. PERFORMANCE SUMMARY This demo board is factory tested by measuring distortion with an 8VP-P, 2kHz differential input, as given in Table 1. (TA = 25°C) 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 –128dBc 3rd Harmonic –114dBc 2kHz Sine Wave, VIN Diff 8VP-P 16384 –Point FFT 0 V+ = 5V –10 V– = 0V –20 HD2 = –128dBc R6, 1k R3, 1k – –30 HD3 = –114dBc VIN + –40 V 0.1μF –50 –60 – + R15 + –70 VOUT –80 VOCM C18 C19 LTC6362 C –90 – DIFF + R14 C15 MAGNITUDE (dB) 0.1μF – VOUT –100 –110 R5, 1k R4, 1k –120 + V DC1833A F01a IN –130 –140 –150 0 2 468 10 12 1416 18 20 FREQUENCY (kHz) 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 as Audio Precision SYS-2722 or Stanford Research SR1 shown in Figure 2. Power the DC1833 from a single power should be used with the LTC6362 configured as shown in + – supply, V = 5V and V = 0V. For distortion measurements, Figure 1, the resulting distortion for an 8VP-P sine wave a low noise, low distortion generator and an analyzer such input is shown in the FFT plot. 5V POWER SUPPLY + – AUDIO PRECISION SYS - 2722 ANALOG GENERATOR ANALOG ANALYZER ANALOG OUTPUT A+ ASIN(WT) +INPUT VIN 2kHz COMPUTER 8VP-P –DISPLAY AP SYS-2722 –ASIN(WT) –INPUT RESULTS 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 JP1: Toggles the LTC6362 ON and OFF. Part ON is the to differential output by populating R1 with 0Ω, removing default setting. C1, and replacing C8 with a 0Ω resistor. In this configu- JP2: Toggles between single and dual power supplies for ration, the input, J2, is now DC-coupled to the LTC6362 the LTC6362. The single supply is the default configuration input. The differential output is AC-coupled in the default for the DC1833A. setting. Driving the single-ended input of the LTC6362 at full scale 10VP-P, each output will swing from 0.5V to 4.5V E1: Positive Power Supply Voltage. In the default con- + when configured with gain of AV = –0.8 (AV = –0.8 is set figuration, V = 5V. by changing the R5 and R6 values to 1.25k). E2: Ground. Differential Input to Differential Output E3: Negative Power Supply Voltage, V–. In the default Populate C1 and C8 pads with 0Ω resistors to set the configuration V– is tied to Ground. differential input mode. E4: Sets the input common mode voltage. In the default the input common mode voltage is set by the output DC-Coupled Output common mode reference voltage. Please refer to the input The DC1833 is configured for an AC-coupled output via C16 common mode voltage range section in the LTC6362 data and C17. For DC-coupled output, replace these capacitors sheet for more details. with 0Ω resistors. E5: The voltage on this pin sets the output common mode voltage level. If left floating (default setting), an internal Layout resistor divider develops a default voltage of 2.5V with a A ground plane is necessary to obtain maximum perfor- 5V supply. mance. Keep bypass capacitors as close to supply pins E6: Ground. as possible. Use individual low impedance returns for all bypass capacitors. Use a symmetrical layout around the E7: Externally drives the SHDN pin. The default configura- analog inputs to minimize the effects of parasitic elements. tion the EXT SHDN pin is left floating (LTC6362 power on). Shield analog input traces with ground to minimize cou- Use EXT SHDN only after JP1 is removed. pling from other traces. Keep traces as short as possible. 4.5V 4V V + 4.5V DIFFERENTIAL OUT V 5V + INPUT IN 0.5V VOUT R3, 1k C19 –4V C VIN CM 0.5V C19 R3, 1k 5V R15 –5V CCM – R6, 1k + RFILT 5V C17 + R6 R15 C17 VOUT – 1.25k + RFILT 1μF VOCM C18 + LTC6362 R14 VOUT C – SHDN + DIFF RFILT VOCM C18 C16 – LTC6362 R14 C16 VOUT VIN C – SHDN + DIFF RFILT 1μF V – OUT R5, 1k R4, 1k C15 R5 4.5V CCM 1.25k R4, 1k C15 C – 4.5V CM VOUT – 0.5V DC1833A F04 VOUT 0.5V 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 3 2 C4, C5 CAP, CER X5R 4.7μF 16V, 0805 TAIYO YUDEN, EMK212ABJ475MG-T 4 0 C6, C7, C9, C10, C15, C18, CAP, 0603 C19 (OPT) 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 RES, 0603 (OPT) 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 SCHEMATIC DIAGRAM 1 2 3 4 5 6 7 8 REVISION HISTORY V + / - = 2.8V - 5.25V ECO REV DESCRIPTION APPROVED DATE V+ GND V- - 2PRODUCTION FAB ERJON Q . 10-13-11 E1 E2 E3 C2 C3 0.1uF 0.1uF 0805 0805 A V+ V- A C4 C5 4.7uF 4.7uF 0805 0805 C1 VIN+ 1uF R2 tion that the interconnection of its circuits asdescribed hereinwillnotinfringe onexistingpatentrights. ofitscircuits tion thatthe interconnection Corporation makesnorepresenta- noresponsibility isassumed for itsuse.LinearTechnology However, Corporationisbelieved tobeaccurateandreliable. Information furnished byLinearTechnology 0 C6 C7 E6 J1 OPT R1 OPT GND OPT C9 OPT R3 R4 1K U1 1K C8 LTC6362CMS8 SHDN VIN- 1uF R7 R6 R5 B 0 1K 1K PWR_ON B 1 IN- IN+ 8 EXT JP1 J2 R11 SHDN R8 2 7 R9 R10 C11 VOCM SHDN OPT OPT OPT V+ 0 0.1uF V- E7 3 6 V+ V- SUPPLY EXT C10 C12 C13 DUAL VCM OPT R12 0.1uF 0.1uF 4 5 E4 OPT OUT+ OUT- SINGLE JP2 C16 DEMO MANUALDC1833A R14 VOUT- C14 0 1uF EXT 0.1uF VOCM R13 C15 OPT J3 E5 C18 OPT C C OPT C17 R15 1uF VOUT+ 0 C19 J4 OPT NOTE: UNLESS OTHERWISE 1630 McCarthy Blvd. CUSTOMER NOTICE APPROVALS Milpitas, CA 95035 SPECIFIED LINEAR TECHNOLOGY HAS MADE A BEST EFFORT TO DESIGN A Phone: (408)432-1900 www.linear.com CIRCUIT THAT MEETS CUSTOMER-SUPPLIED SPECIFICATIONS; TECHNOLOGY Fax: (408)434-0507 1. ALL RESISTORS ARE IN OHMS, 0603 HOWEVER, IT REMAINS THE CUSTOMER'S RESPONSIBILITY TO PCB DES. NC LTC Confidential-For Customer Use Only ALL CAPACITORS ARE IN MICROFARADS, 0603. D VERIFY PROPER AND RELIABLE OPERATION IN THE ACTUAL APP ENG. ERJON Q . TITLE: SCHEMATIC D APPLICATION. COMPONENT SUBSTITUTION AND PRINTED CIRCUIT BOARD LAYOUT MAY SIGNIFICANTLY AFFECT CIRCUIT FULLY DIFFERENTIAL AMPLIFIER PERFORMANCE OR RELIABILITY. CONTACT LINEAR SIZE IC NO. REV. TECHNOLOGY APPLICATIONS ENGINEERING FOR ASSISTANCE. LTC6362CMS8 N/A 2 THIS CIRCUIT IS PROPRIETARY TO LINEAR TECHNOLOGY AND DEMO CIRCUIT 1833A SUPPLIED FOR USE WITH LINEAR TECHNOLOGY PARTS. SCALE = NONE DATE: 10-13-11 SHEET1 OF 1 1 2 3 4 5 6 7 8 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.