DEMO MANUAL DC845A LTC2448: 24-Bit, High Speed, 8-/16-Channel ADC with Selectable Speed/Resolution Description The LTC(R)2448 is an 8-/16-channel, high speed, 24-bit ADC with ten selectable speed/resolution modes from 6.9Hz/280nVRMS to 3.5kHz/25VRMS. Key DC specifications include 5ppm INL, 5V offset, 10ppm full-scale error and 20nV/C offset drift. In the 6.9Hz/280nVRMS mode, an input normal mode rejection of 50Hz and 60Hz noise is better than a 87dB. The accuracy (offset, full-scale, linearity, drift) and power dissipation are independent of the speed selected. easy evaluation of the LTC2448 and may be connected directly to the target application's analog signals while using the DC590 USB serial controller board and supplied software to measure performance. The exposed ground planes allow proper grounding to prototype circuitry. After evaluating with LTC's software, the digital signals can be connected to the application's processor/controller for development of the serial interface. Design files for this circuit board are available at http://www.linear.com/demo DC845A is a member of Linear Technology's QuikEvalTM family of demonstration boards. It is designed to allow Board Photo L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and QuikEval is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. REFERENCE MONITOR (OR EXTERNAL SOURCE; SEE HARDWARE SET-UP) - + RIBBON CABLE TO DC590 - - SINGLE-ENDED SIGNALS COM BIAS (OR TIE COM TO GROUND) + - - + + + - + DC845A F01 DIFFERENTIAL SIGNALS (OBSERVE COMMON-MODE LIMITATIONS) Figure 1. DC845A Connection Diagram dc845af 1 DEMO MANUAL DC845A Quick Start Procedure n n n n Connect the DC845A to a DC590 USB serial controller using the supplied 14-conductor ribbon cable. Connect the DC590 to a host PC with a standard USB A/B cable. Run the evaluation software supplied with the DC590, or download it from www.linear.com/software. The correct program will be loaded automatically. n Click the slider at the bottom of the strip chart display to change the oversample ratio (OSR) which will, in turn, change the data output rate. Tools are available for logging data, changing reference voltage, changing the number of points in the strip chart and histogram, and changing the number of points averaged for the DVM display. Click the COLLECT button to start reading the input voltage. Figure 1. DC847A Evaluation Software 2 dc845af DEMO MANUAL DC845A Hardware Setup Jumpers JP1, JP3: Select the source for REF + and REF -, respectively. REF + can be 5.00V from the on-board LT1236 reference (default) or supplied externally. REF - can be ground (0V, default) or supplied externally. JP2: Select the source for analog COM input, either tied to ground or supplied externally to the COM turret post. JP4: Trigger mode; either normal (default) or externally triggered. JP7: Trigger input signal. Pin 1 is a 5V logic signal, Pin 2 is ground. When trigger mode is selected on JP3, a rising edge starts a new conversion. Note: Since a conversion cannot be terminated once started, this signal can only be used to slow down the conversion rate. CONNECTION TO THE DC590 USB SERIAL CONTROLLER J2 is the power and digital interface connector. Connect to the DC590 USB serial controller with the supplied 14-conductor ribbon cable. ANALOG CONNECTIONS Channels 0-7 have 1F capacitors from the inputs to ground. Channels 8-15 do not have capacitors installed, however there are pads for these capacitors on the back of the board. The reason for this is that some applications benefit from a large capacitance at the inputs while others require no capacitance. Analog signal connections are made via the row of turret posts along the edge of the board. Also, if connecting the board to an existing circuit, the exposed ground planes along the edges of the board may be used to form a solid connection between grounds. GND: Ground turrets are connected directly to the internal analog ground plane. PWR GND: Power ground; connected to the power return trace. VCC: This is the supply for the ADC. Do not draw any power from this point. External power may be applied to this point after disabling the switching supply on the DC590. If the DC590 USB serial controller is being used, the voltage must be regulated 5V only, as the isolation circuitry will also be powered from this supply. See the DC590 Quick Start Guide for details. REF +, REF - : These turrets are connected to the LTC2448 REF + and REF - pins. If the on-board reference is being used, the reference voltage may be monitored from this point. An external reference may be connected to these terminals if JP1 and JP3 are configured for external reference. Note: The REF + and REF - terminals are decoupled to ground with 0.1F and 10F capacitors in parallel. Thus, any source connected to these terminals must be able to drive a capacitive load and have very low impedance at DC. Examples are series references that require an output capacitor and C-load stable op amps, such as the LT1219 and LT1368. CH0-CH15: Differential inputs to the LTC2448. These inputs may be configured either as single-ended inputs with respect to the COM pin, or adjacent pairs may be configured as differential inputs (CH0-1, CH2-3, etc.). See note about loading capacitors on CH0-7. Experiments INPUT NOISE COMMON MODE REJECTION Solder a short wire from CH0 to CH1. Set the demo software to OSR32768 (6.8 samples per second) and check the 2x box. Noise should be approximately 0.056ppm of VREF (280nV). Next, select different oversample ratios. Measured noise for each oversample ratio should be close to the values given in the LTC2448 data sheet. Tie the two inputs (still connected together from the previous experiment) to ground through a short wire, and note the indicated voltage. Tie the inputs to REF +; the difference should be less than 5V due to the 120dB CMRR of the LTC2448. dc845af 3 DEMO MANUAL DC845A Experiments INPUT NORMAL MODE REJECTION The LTC2448's SINC4 digital filter is trimmed to strongly reject both 50Hz and 60Hz line noise when operated with the internal conversion clock and oversample ratio 32768 (6.8 samples per second). To measure input normal mode rejection, connect COM to a 2.5V source such as an LT1790-2.5 reference or a power supply. Connect any other input (CH0-CH15) to the same supply through a 10k resistor. Apply a 10Hz, 2V peak-to-peak sine wave to the input through a 1F capacitor. Select OSR32768 (6.8 samples per second) and 2x mode in the demo software and start taking data. The input noise will be quite large, and the graph of output vs time should show large variations. Next, slowly increase the frequency to 55Hz. The noise should be almost undetectable in the graph. Note that the indicated noise in ppm may still be above that of the data sheet specification because the inputs are not connected to a DC source. Change the OSR to 16384 (13.75 samples per second). The noise will increase substantially, as the first notch at this OSR is at 110Hz. Increase the signal generator frequency to 110Hz, and the noise will drop again. Parts List ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER 1 4 C3, C7, C10, C13 CAP., CHIP, X7R, 00.01F, 16V AVX, 0603YC103KAT1A, 0603 2 3 C11, C14, C15 CAP., CHIP, X7R, 0.1F, 16V AVX, 0603YC104MAT1A, 0603 3 10 C1, C4, C6, C16-C21, C29 CAP., CHIP, X5R, 1F, 10V TAIYO YUDEN, LMK107BJ105MG, 0603 4 3 C2, C9, C12 CAP., CHIP, X5R, 4.7F, 6.3V TAIYO YUDEN, JMK212BJ475MG, 0805 TDK, C2012X5R0J106M, 0805 5 1 C8 CAP., CHIP, X5R, 10F, 6.3V 6 0 C22-C28 OPT. 7 24 TP1-TP6, TP8, TP10-TP12, TP14-TP27 TURRET, TESTPOINT, 0.064" 8 0 TP13, TP28, TP29 OPT. (SURFACE MOUNT PAD ONLY ) MILL-MAX, 2308-2 9 4 JP1-JP4 HEADER, 3-PIN, 1 ROW, 0.079" COMM-CON, 2802S-03G2 10 4 FOR (JP1-JP4) SHUNT, 0.079" CENTER COMM-CON, CCIJ2MM-138GW 11 0 JP7 OPT. 12 0 J1 (OPT.) CONN., SMA COAXIAL, STRAIGHT JACK CONNEX, 132134 13 1 J2 HEADER, VERTICAL DUAL, 2x7, 0.079" MOLEX, 87831-1420 14 1 R7 RES., CHIP, 100, 5% AAC, CR16-101JM, 0603 15 3 R8, R9, R10 RES., CHIP, 4.99k, 1% VISHAY CRCW0603 16 2 R5, R11 RES., CHIP, 10k, 5% AAC, CR16-103JM, 0603 17 0 R6 OPT. 18 1 U1 I.C., 24-BIT 8-/16-CHANNEL DELTA SIGMA ADCs LINEAR TECHNOLOGY, LTC2448UHF, 38QFN 19 1 U4 I.C., PRECISION REFERENCE LINEAR TECHNOLOGY, LT1236ACS8-5, SO8 20 1 U3 I.C., SERIAL EEPROM MICROCHIP, 24LC025-I/ST, TSSOP-8 21 1 U2 I.C., NONINVERTING MULTIPLEXER FAIRCHILD, NC7SZ157P6X, SC70 22 1 U5 I.C., SINGLE D FLIP-FLOP ON SEMICONDUCTOR, NL17SZ74US, US8 4 dc845af 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 TP12 TP11 TP10 TP8 TP6 TP5 TP4 TP3 TP21 2 1 C28 Opt. C27 Opt. C26 Opt. VIN VOUT U4 LT1236ACS8-5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 NOTES: C15 0.1uF TP24 V+ REF- TP22 REF+ COM TP19 CH15 TP18 CH14 TP17 CH13 TP16 CH12 TP15 CH11 TP14 CH10 CH9 CH8 CH7 CH6 CH5 CH4 CH3 CH2 6 1 C25 Opt. C23 Opt. 3 JP1 REF+ C24 Opt. 5V 1 2 Ext. TP2 2 1 C22 Opt. 3 C19 1uF C29 1uF C20 1uF JP2 COM C21 1uF Ext. TP1 2 GND 1 C18 1uF C12 4.7uF 6.3V C10 0.01uF 30 29 7 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 C13 0.01uF C1 1uF REF- REF+ COM CH15 CH14 CH13 CH12 CH11 CH10 CH9 CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 CH0 4 C3 0.01uF GND CS SDO SCK FO SDI EXT BUSY NC NC NC NC U1 LTC2448UHF center pad bottom C2 4.7uF 6.3V Vcc JP7 (Opt.) 39 36 37 38 35 34 3 2 25 24 26 27 1 5 C14 0.1uF 1 2 D IO GND I1 3 5 1 U5 NL17SZ74US Q Q 4 5 6 Vcc 3 R7 100 CMOS LEVEL J1 FO (Opt.) JP4 Trig. Mode Z VCC S U2 NC7SZ157P6X R6 (Opt.) R12 50 1 6 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. This Circuit Is Proprietary To Linear Technology And Supplied For Use With Linear Technology Parts. Customer Notice LTC CONFIDENTIAL - FOR CUSTOMER USE ONLY CP Vcc 3 2 1 SMT Pad TP13 R11 10K CS SDO SCK FO SDI R5 10K 6 Figure 3. 24-Bit High Speed 8-/16-Channel Delta Sigma ADC 3 3 JP3 REF- C9 4.7uF 6.3V C17 1uF C16 1uF C6 1uF C4 1uF GND 1 CH1 Ext. GND 5 1 GND 4 2 GND GND 4 28 VCC GND 6 GND 31 GND 32 GND 33 CH0 2 1 8 5 Trig. 4 1 3 5 7 9 11 13 + + + + + + + + + + + + + + J2 HD2X7 2 4 6 8 10 12 14 7 A2 A1 A0 VSS U3 24LC025 SDA SCL WP VCC 4 3 2 1 C11 0.1uF C7 .01uF Vcc TP29 SMT Pad C8 10uF 6.3V 1 1 1 1 1 8 FAX (408) 434-0507 Pwr GND TP27 GND TP26 GND TP23 GND TP25 Demo Circuit 845A Document Number 7 Sheet 1 8 of LTC2448UHF 1 Rev 24-Bit High Speed 8-/16-Channel Delta Sigma ADC Date:Wednesday, November 24, 2004 Size Title 1630 McCARTHY BLVD. MILPITAS, CA. 95035-7487 VOICE (408) 432-1900 Vcc TP20 LINEAR TECHNOLOGY CORPORATION TP28 SMT Pad 5 6 7 8 R8-R10 Are 4.99K 1% V+ R8 3 R9 2 3 4 5 2 Normal 7 PR VCC GND 4 CLR 6 R10 1 2 1 1 D C B A DEMO MANUAL DC845A Schematic Diagram dc845af 5 DEMO MANUAL DC845A 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 (c) 2004, Linear Technology Corporation 6 dc845af Linear Technology Corporation LT 0613 * PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LINEAR TECHNOLOGY CORPORATION 2013