1 description lt c6432-15 100khz to 1000mhz differential adc driver/if/rf amplifier demonstration circuit 2496a features the LTC6432-15 differential adc driver/if amplifier. the ltc ? 6432-15 has a fixed power gain of 15.9db and works from 100khz to 1400mhz . it is part of the high linearity ltc643x-yy amplifier series. as a differential amplifier, the ltc6432 -15 offers flat gain and impressive linearity from 100khz to 1ghz using a single output bias network. since high fidelity differen - tial test equipment is lacking, the dc2496 a offers single l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of analog devices, inc. all other trademarks are the property of their respective owners. ended inputs and outputs so that the ltc6432 -15 perfor - mance may be evaluated with standard test equipment. the native ltc6432 -15 has 100 differential source and load impedances, so the demo circuit uses 2 : 1 transform - ers to convert the differential input/output impedances to 50 single-ended impedance. design files for this circuit board are available at http://www.linear.com/demo/dc2496a-a dc2496aaf demo manual dc2496a-a/dc2496a-b
2 o peration demo circuit 2496a is a high linearity, fixed gain amplifier. it is designed for ease of use. the LTC6432-15 is inter - nally matched to 100 differential source and load imped - ances from 100khz to 1400mhz . due to the unpopularity of 100 differential test equipment, transformers have been added to convert these impedances to single-ended 50. hence, demo boards with various transformers are built for corresponding working frequency ranges. the frequency range of the 2496a evaluation circuit is limited by these input and output transformers. there are provi - sions for installing various smt transformers on either the top or bottom side of dc2496as pcb. because ltc6432 -15 has a very wide working frequency range, no single transformer can cover its full 13 octave frequency band. the dc2496 a pcb is quite versatile. there are footprints for various transformers on the pcb. two demo board versions cover most commonly used frequencies as shown in table 1. table 1. frequency ranges and suggested 2:1 transformers. dc number frequency (mhz) transformers part # manufacturer 2496a-a 0.1 to 20 sytx2-6t-1+ mini-circuits 2496a-b 1 to 250 adt2-1t+ -- 20 to 400 adt2-1t-1p+ -- 200 to 950 adtl2-18+ please note that the suggested frequency bands are narrower than small-signal s-parameters would indicate. at the edges of their useful band, these transformers contribute distortion that degrades the performance of the LTC6432-15. figure? 1 and figure? 2 show demo board dc2496a-a and dc2496 a-b schematics. each demo circuit s sche - matic shows the required passive support components. at the board s inputs and outputs are the low frequency transformer, sytx2- 6t-1+ or the mid-frequency trans- former, adt2- 2t+. each of these transformers has a 1:2 impedance transformation ratio. the input and output dc blocking capacitors ( c7, c9, c12 and c17) are required because this device is internally dc-biased for optimal operation. the v cc pull-up networks ( l1, l2, l3, l4, r1, r5, r9 and r13) and the de-coupling capacitors ( c2, c3, c4, c5, c19, c20, c21 and c22) provide the proper dc bias to the rf out nodes. a single 5v supply is required for the v cc pins on the device. a pair of stability networks have been added. they consist of a 1f capacitor (c6 and c15 ) and 348 resistor (r4 and r14 ) in parallel at the LTC6432-15 inputs to ensure low frequency stability. it is important to note that x8r capacitors are used in the rf signal path. the dc block and feedback caps have been specified as x8r capacitors. high capacitance den - sity (high capacitor values in a small package) typically contribute distortion products due to their poor voltage coefficient. film and npo capacitors have low distortion but are unwieldy at 1f values. as a compromise we have found that x8r capacitors exhibit low distortion at reason - able capacitance densities. if the user is concerned with thermal heating and the associated reliability, the chip provides a means to deter - mine the chip temperature. the t_diode pin (turret e4) can be forward biased to ground with 1ma of current. the measured voltage will be an indicator of the chip junction temperature (t j ). please note that eight dnc pins are connected on the demo board. these connections are not utilized for normal operation and should be left open circuit on the final pcb. table 2 shows the function of each input and output on the board. table 2. dc2496a board i/o descriptions connector function j1 (in) single-ended input. impedance matched to 50. drive from a 50 network analyzer or signal source. j4 (out) single-ended output. impedance matched to 50. drives a 50 network analyzer or spectrum analyzer. e4 (t_diode) when forward biased, the measured voltage will be an indicator of the chip junction temperature (t j ). e2 (v cc ) positive supply voltage source. e3 (gnd) supply ground. dc2496aaf demo manual dc2496a-a/dc2496a-b
3 o peration 5 5 4 4 3 3 2 2 1 1 d d c c b b a a 1. all resistors are in ohms, 0603 all capacitors are 0603. note: unless otherwise specified 2. all dnc pins on u1 are for linear use only ppt4 ppt5 t_diode ppt ppt1 ppt2 vcc vcc vcc vcc vcc date: ic no. sheet of title: demo circuit schematic, approvals pcb des. app eng. fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice 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. scale = none www.linear.com size: sku no. schematic no. and revision: pca bom: pca ass'y: 11 n/a ak john c. LTC6432-15 100khz to 1000mhz differential adc driver/amplifier dc2496a 700-dc2496a_rev02 710-dc2496a_rev 02 705-dc2496a_rev02 friday, march 17, 2017 date: ic no. sheet of title: demo circuit schematic, approvals pcb des. app eng. fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice 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. scale = none www.linear.com size: sku no. schematic no. and revision: pca bom: pca ass'y: 11 n/a ak john c. LTC6432-15 100khz to 1000mhz differential adc driver/amplifier dc2496a 700-dc2496a_rev02 710-dc2496a_rev 02 705-dc2496a_rev02 friday, march 17, 2017 date: ic no. sheet of title: demo circuit schematic, approvals pcb des. app eng. fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice 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. scale = none www.linear.com size: sku no. schematic no. and revision: pca bom: pca ass'y: 11 n/a ak john c. LTC6432-15 100khz to 1000mhz differential adc driver/amplifier dc2496a 700-dc2496a_rev02 710-dc2496a_rev 02 705-dc2496a_rev02 friday, march 17, 2017 c19 1000pf 0402 c14 1uf 0805 r5 0603 280 c16 1uf 0805 x8r u1 LTC6432-15 dnc 2 ident 14 dnc 1 +in 24 dnc 4 nfilt1 6 gnd 8 dnc 10 dnc 21 +fdbk 19 gnd 17 vcc 22 dnc 20 +out 18 ppt 16 nfilt2 5 -in 7 vcc 9 dnc 11 t_diode 15 -fdbk 12 -out 13 dnc 3 gnd 23 gnd 25 p5 e3 gnd c6 1uf 0805x8r p16 r1 0603 249 p6 j1 +in r9 0603 280 c12 1uf 0805x8r c20 0.1uf 0603 c3 0.1uf 0603 c13 1uf 0805 c17 1uf 0805 x8r t2 sytx2-6t-1+ 6 4 1 3 2 5 7 8 c21 1uf 0805 p1 l2 240nh p21 c5 10uf 0805 j4 out- c22 10uf 0805 c7 1uf 0805 x8r r13 0603 249 c8 1uf 0805 x8r r14 348 0805 c4 1uf 0805 z1 cmz5920b 1 2 r8 opt c15 1uf 0805 x8r p2 l3 240nh c1 1000pf 0402 c9 1uf 0805 x8r p10 p4 c18 1000pf 0402 e4 t_diode p3 p20 l4 470uh r4 348 0805 l1 470uh e2 vcc 4.75v-5.25v c2 1000pf 0402 t1 * sytx2-6t-1+ 6 4 1 3 2 5 7 8 p11 figure?1. dc2496a-a simplified schematic dc2496aaf demo manual dc2496a-a/dc2496a-b
4 o peration 5 5 4 4 3 3 2 2 1 1 d d c c b b a a 1. all resistors are in ohms, 0603 all capacitors are 0603. note: unless otherwise specified 2. all dnc pins on u1 are for linear use only ppt4 ppt5 t_diode ppt ppt1 ppt2 vcc vcc vcc vcc vcc date: ic no. sheet of title: demo circuit schematic, approvals pcb des. app eng. fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice 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. scale = none www.linear.com size: sku no. schematic no. and revision: pca bom: pca ass'y: 11 n/a ak john c. LTC6432-15 100khz to 1000mhz differential adc driver/amplifier dc2496a 700-dc2496a_rev02 710-dc2496a_rev 02 705-dc2496a_rev02 friday, march 17, 2017 date: ic no. sheet of title: demo circuit schematic, approvals pcb des. app eng. fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice 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. scale = none www.linear.com size: sku no. schematic no. and revision: pca bom: pca ass'y: 11 n/a ak john c. LTC6432-15 100khz to 1000mhz differential adc driver/amplifier dc2496a 700-dc2496a_rev02 710-dc2496a_rev 02 705-dc2496a_rev02 friday, march 17, 2017 date: ic no. sheet of title: demo circuit schematic, approvals pcb des. app eng. fax: (408)434-0507 milpitas, ca 95035 phone: (408)432-1900 1630 mccarthy blvd. ltc confidential-for customer use only customer notice 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. scale = none www.linear.com size: sku no. schematic no. and revision: pca bom: pca ass'y: 11 n/a ak john c. LTC6432-15 100khz to 1000mhz differential adc driver/amplifier dc2496a 700-dc2496a_rev02 710-dc2496a_rev 02 705-dc2496a_rev02 friday, march 17, 2017 p16 e3 gnd c6 1uf 0805 x8r c12 1uf 0805 x8r r9 0603 280 j1 +in p6 r1 0603 249 z1 cmz5920b 1 2 c20 0.1uf 0603 c13 1uf 0805 c3 0.1uf 0603 p1 c21 1uf 0805 c17 1uf 0805 x8r adt2-1t+ 6 4 1 5 3 p21 l2 240nh j4 out- c10 1uf 0805 c5 10uf 0805 c8 1uf 0805 x8r r13 0603 249 c7 1uf 0805 x8r c22 10uf 0805 c4 1uf 0805 r14 348 0805 r8 opt e2 vcc 4.75v-5.25v c1 1000pf 0402 l3 240nh p2 c15 1uf 0805 x8r p4 p10 adt2-1t+ 6 4 1 5 3 c9 1uf 0805 x8r e4 t_diode c18 1000pf 0402 r4 348 0805 l4 470uh p20 p3 p11 c2 1000pf 0402 l1 470uh c16 1uf 0805 x8r r5 0603 280 c14 1uf 0805 c19 1000pf 0402 c11 1uf 0805 p5 u1 LTC6432-15 dnc 2 ident 14 dnc 1 +in 24 dnc 4 nfilt1 6 gnd 8 dnc 10 dnc 21 +fdbk 19 gnd 17 vcc 22 dnc 20 +out 18 ppt 16 nfilt2 5 -in 7 vcc 9 dnc 11 t_diode 15 -fdbk 12 -out 13 dnc 3 gnd 23 gnd 25 figure?2. dc2496a-b simplified schematic dc2496aaf demo manual dc2496a-a/dc2496a-b
5 figure?3. demo board dc2496a-a s-parameters performance figure?4. demo board dc2496a-b s-parameters performance figure?5. dc2496a-a oip3, gain and noise figure performance figure?6. dc2496a-b oip3, gain and noise figure performance o peration figure?3 and figure?4 show the two port dc2496a-a s and dc2496a-b s s-parameters performances, and figure?5 and figure?6 show demo boards typical linearity, noise figures and gain performances. frequency (mhz) |s12|, |s11| and |s22| (db) dc2496 f02 ?50 ?40 ?45 ?35 ?30 ?25 ?20 ?15 ?10 ?5 0 0 28 12108642 24 262220181614 |s22| |s11| |s12| frequency (mhz) |s12|, |s11| and |s22| (db) dc2496 f03 ?50 ?35 ?30 ?45 ?40 ?25 ?20 ?15 ?10 ?5 0 0 35030025020015010050 |s22| |s11| |s12| frequency (mhz) oip3 (dbm) dc2496 f04 0 28 32 20 24 12 16 4 8 36 40 44 48 56 52 60 64 0 3 6 9 12 15 18 21 24 0.1 10 1 |s21| and noise figure (db) oip3 noise figure |s21| frequency (mhz) oip3 (dbm) dc2496 f05 0 28 32 20 24 12 16 4 8 36 40 44 48 56 52 60 64 0 3 6 9 12 15 18 21 24 1 100 10 |s21| and noise figure (db) oip3 noise figure |s21| dc2496aaf demo manual dc2496a-a/dc2496a-b
6 o peration setup signal sources and spectrum analyzer the ltc6432 -15 is an amplifier with high linearity per - formance. therefore, the output intermodulation prod - ucts are very low. even using high dynamic range test equipment, third-order intercept (i p3 ) measurements can drive test setups to their limits. consequently, accurate measurement of ip3 for a low distortion ic such as the ltc6432 -15 requires certain precautions to be observed in the test setup as well as the testing procedure. set up signal sources figure?7 shows a proposed i p3 test setup. this setup has low phase noise, good reverse isolation, high dynamic range, sufficient harmonic filtering and wideband imped - ance matching. the setup is outlined below: a . high per formance signal generators 1 and 2 (hp8644 a) are used. these suggested generators have low har - monic distortion and very low phase noise. b. hig h linearity amplifers are used to improve the reverse isolation. this prevents cross talk between the two signal generators and provides higher output power. c. a low pass flter is used to suppress the harmonic content from interfering with the test signal. note that second order inputs can mix with the fundamental frequency to form intermodulation ( im) products of their own. we suggest fltering the harmonics to C50 dbc or better. d. for improved vswr, distortion and isolation, the h-6287-10 signal combiner from werlatone covers the 100 khz to 50 mhz band. it features >30 db isolation over this band. from 20 mhz to 1400 mhz, we suggest the h9 signal combiner from ma/com which features >40db isolation. passive devices ( e.g. combiners) with magnetic elements can contribute nonlinearity to the signal chain and should be used cautiously. e. the attenuator pads on all three ports of the signal combiner will further support isolation of the two input signal sources. they also reduce refections and promote maximum power transfer with wideband impedance matching. set up the spectrum analyzer a. adjust the spectrum analyzer for maximum possible resolution of the intermodulation products amplitude in dbc. a narrower resolution bandwidth will take a longer time to sweep. b. optimize the dynamic range of the spectrum analyzer by adjusting the input attenuation. first increase the spectrum analyzers input attenuation ( normally in steps of 5 or 10db). if the im product levels decrease when the input attenuation is increased, then the input power level is too high for the spectrum analyzer to make a valid measurement. most likely, the spectrum analyzers 1 st mixer was overloaded and producing its own im products. if the im reading holds constant with increased input attenuation, then a suffcient amount of attenuation was present. adding too much attenua - tion will bury the intended im signal in the noise foor. therefore, select just enough attenuation to achieve a stable and valid measurement. c. in order to achieve this valid measurement result, the test system must have lower total distortion than the duts intermodulation. for example, to measure a 53dbm oip3, the measured intermodulation products will be C102 dbc below a C13 dbm/tone input level and the test system must have intermodulation products approximately C108 dbc or better. for best results, the im products and noise foor should measure at least C112dbc before connecting the dut. dc2496aaf demo manual dc2496a-a/dc2496a-b
7 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 representa - tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. quick s tart p roce d ure demo circuit 2496a-a can be set up to evaluate the per - formance of the ltc6432 -15. refer to figure?7 for proper equipment connections and follow the procedure below: two-tone measurement: connect all test equipment as suggested in figure?7. 1. the power labels of vcc 4.75 v-5.25v and gnd di - rectly correspond to the power supply. typical current consumption of the LTC6432-15 is about 166ma. 2. apply two independent signals f1 and f2 from signal generator 1 and signal generator 2 at 5 mhz and 5.2mhz, while setting the amplitude to C13dbm/tone at the demo board input (j1). 3. mo nitor the output tone level on the spectrum ana - lyzer . a djust t he signal generator levels such that the output power measures +2 dbm / tone at the amplifer output j 4, after correcting for external cable losses and attenuations . 4. change the spectrum analyzers center frequency and observe the two im3 tones at 0.2 mhz below and above the input frequencies. the frequencies of im3 _low and im3 _high are 4.8 mhz and 5.4 mhz, respectively. the measurement levels should be approximately C102dbc; + 53dbm is typical oip3 performance for the dc 2496 a-a demo board at 5 mhz. the oip3 calculation is: oip3 = p out + ?imd3/2 where: p out is the lower of the two fundamental output signal products. ? imd3 = p out C p im3 ; p im3 is the higher of the two third-order intermodulation products. single-tone measurement: 5. continue with step 4 above, turn off one signal source to measure gain and harmonic distortions. a dditiona l d ocument ation refer to the demo board link from the ltc6432 -15 prod - uct page for bom, pcb, gerber, check plots and full unabridged schematic. figure?7. proper measurement equipment setup amplifier (mini-circuits, zhl-32a-s+ or equivalent) low-pass filter signal generator 1 amplifier (mini-circuits, zhl-32a-s+ or equivalent) werlatone h-6278-10 signal generator 2 (hp8644a) dc2496 f01 spectrum analyzer v cc = 4.75v to 5.25v rohde & schwarz fsu8 15db attenuation pad 3db attenuation pad 6db attenuation pad (optional) 6db attenuation pad (optional) low-pass filter dc power supply v + gnd (hp8644a) dc2496aaf demo manual dc2496a-a/dc2496a-b
8 ? linear technology corporation 2017 lt 0417 ? printed in usa 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 deve l opment or eva l uation purposes on l y 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 users 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 whatsoeve r. l tc 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 dc2496aaf demo manual dc2496a-a/dc2496a-b
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