High speed differential adc driver design considerations

High speed dc abstract this application note describes the design considerations for designing the lvds interface between the adc and fpga. High speed differential adc driver design considerations by john ardizzoni and jonathan pearson rev. Receivers are evolving and are increasingly using differential components, a trend that began at the adc and is gradually moving up the signal chain. Devices separated by more than a small fraction of a signal wavelength must be connected by electrical transmission lines with controlled impedance to avoid losing signal integrity. The afe consists of the highspeed signal chain and the associated pointof load pol.

Low noise, railtorail, differential adc driver ad89 farnell. Pcb and high speed serial interface hssi design guideline. Adc driverscircuits often specifically designed to provide such signalsperform. High speed differential adc driver design considerations an63. Dissecting the highspeed amplifieraafadc interface. Ti designs, tida01050, optimized analog front end daq system reference design for 18bit sar data converters. Evaluation board for ad82 low cost, high speed differential amplifier features ships. Using the analog devices active filter design tool data sheet ad89. Dc accuracy for high speed fully differential amplifiers fdas these fdas come in both cfa and vfa types. Differential pairs generally carry differential or semi differential signals, such as high speed digital serial interfaces including lvds differential ecl, pecl, lvpecl, hypertransport, ethernet over twisted pair, serial digital interface, rs422, rs485, usb, serial ata, tmds, firewire, and hdmi etc. Most modern high performance analogtodigital converters adcs use differential inputs to. This design incorporates ads64xx family of adcs from texas instruments and latticeecp3 fpga high speed lvds io.

This adc reference design rd1089 shows how the latticeecp3 or latticeecp2 fpga can be used to interface to a high speed adc device. Lowpower, high intercept interface to the ads5424, 105msps converter slyt223. The considerations differ between input and output coupling. Low distortion, differential adc driver data sheet ad88. Click the pdf above to read more about high speed design in this ebook. Differential adc driver data sheet ada49321ada49322.

Conventional high speed adc drivers are mainly accoupled by employing transformers baluns or fully differential amplifiers. High speed differential adc driver design considerations pdf. However, special considerations are required to ensure that the dynamic range of the circuit is not affected by the selected configuration. Advances in integrated rf circuit technology and expansion of differential rf building blocks allow differential architectures to be applied for high performance receiver designs.

Ultralow noise drivers for low voltage adcs documentation an1026. Pdf differential input range driver for sar adc measurement setup. Ada49601 is a high performance, differential amplifier. Lmh3401 7ghz, ultrawideband, fixedgain, fullydifferential. This second article in the jesd204 series covers the different types of outputs in terms of physical implementation, efficiency, and apps best suited for. Differential adc biasing techniques, tips and tricks. Rules of the road for highspeed differential adc drivers. An adc typically measures the voltage between the signal and ground but in differential mode, the ground pin is actually connected to another part of the circuit so the adc can measure the difference between the two signals. High speed amplifier application notes amplifiers forum. Ti designs designs are analog solutions created by. The output commonmode voltage of the ad8351 is set to avdd2. Each adc features wide bandwidth inputs supporting a variety of userselectable input ranges.

The shifted input stages add two transistors to allow the inputs to swing closer to the v s rail. Active filter evaluation board for differential amplifiers an282. Table of contents 1 integrated laser driver solutions. This white paper describes the design of fast driver circuits, pcb layouts and optical measurement considerations, as well as a solution to achieve an ideal design for pulses as short as 2. High speed amplifiers selection table documentation an1026. Some of the key considerations that are prevalent in communication. Analog devices highspeed differential adc drivers have two input stage configurations, centered and shifted. Rules of the road for high speed differential adc drivers. Read about evaluation board for ad82 low cost, high speed differential amplifier on. Its why more engineers choose adi data converters analogto digital converter and driver ics. Design considerations for lowpower, highspeed cmos. National semiconductors lmh6554 fully differential current feedback cfb operational amplifier is capable of performing the singletodifferential conversion required to drive these high speed adcs. Refer to the high speed 10bit analogtodigital converter adc chapter in the specific device data sheet for more information. This may seem like the obvious choice based on noise but sometimes the right fda may not exist and a.

However, above about 500 mhz, its return loss is inadequate for the needs of the ltc2107 adc. The ad8351s simplifies adc driving allowing the user to adjust the gain up to 26 db through one external resistor and incorporates output common mode adjustment circuit to ease the drive levels into the adc. Jan 27, 2014 at very high frequencies, every trace and pin is an rf emitter and receiver. Most modern highperformance adcs use differential inputs to reject commonmode noise. Circuit topologies and systemlevel parameters slaa416. Active filter evaluation board for differential amplifiers an649.

Although they can be driven singleended as previously described, a fully differential driver usually optimizes overall performance. Ultralow distortion differential adc driver data sheet. Evaluation board for ad82 low cost, high speed differential. Design considerations for avoiding timing errors during high. Considerations for the creation of powerefficient hybrid data.

Circuit for driving highvoltage sar adcs for highvoltage. Successive approximation adc saadc successive approximation adc has been used long time as a low power and low speed adc. High speed adc layout considerations cocopa on aug 20, 2015 hello, im designing a board with 5 high speed adcs ad6643 driven by ada49302 and im having some concerns regarding pcb layout and especially ground connections. Differential circuit design techniques for communication.

The adc driver amplifier and the antialiasing filter aaf prepare the signal to be. Design guidelines for implementing lvds interfaces. Terminating a differential amplifier in singleended input applications an0992. Using op amps with data converters part 3 ee times. Additionally, understanding the relationship between common mode voltage and the adc voltage reference. Analog devices high speed axi adc driver core analog devices ad9208 and similar high speed adcs snip hardware configuration.

Use small form factor capacitors, no larger than 0402, c 1 nf. Terminating a differential amplifier in singleended input applications. Low cost, low power, differential adc driver data sheet ad87. Driving high performance adcs in communication applications carlos calvo analog device june 2008 2 agenda communications system overview system performance metrics rf versus adc terminology system budgeting different adc driver implementations filter design considerations and techniques singleended versus balance drive driver. Evaluation board for ada49321 differential adc driver.

Understanding differential amplifiersand paying attention to the details of adc driver design at the outset of a. Universal evaluation board for single differential amplifiers documentation application notes an0990. Input and output voltage range issues for high speed cfas and. Introduction for the discussions that follow, some definitions are in order. Active filter evaluation board for differential amplifiers an1026. Highspeed adc driver amplifier with singleended to differential input conversion. Multiple feedback bandpass design example peak highspeed performance even at low power. The ad8351s is fully differential amplifier, designed to drive high resolution 1014 bits high speed adcs 240 msps at if frequencies within communications receivers. An integrated voltage reference eases design considerations. High speed board design advisor high speed channel design and layout november 2007, ver. Ada49601 is a high performance, differential amplifier optimiz ed for rf and if applications. This reference design shows the ability of the high speed amplifier, ths4509 to perform singleended to differential conversion to drive high speed analogtodigital converters adcs while maintaining excellent noise and distortion performance. Ultralow power, 18bit, differential pulsar adc driver mt218.

Inputoutput range issues for fully differential amplifiers fdas. This work presents a detailed systemlevel design methodology for a lowpower ct adc. Input range driver for measurement of a differential 10 bit. This reference design focuses on the operation of the ths4509 device. Active filter evaluation board for differential amplifiers.

In the past, the performance advantages of fully differential signal chains were. Low noise, railtorail, differential adc driver data sheet. High speed differential adc driver design considerations source. Adc drivers have become essential signal conditioning elements in data conversion stages and are key factors in enabling the adc function to achieve its rated performance. This may seem like the obvious choice based on noise but sometimes the right fda may not exist and a custom circuit using a dual amplifier is a better fit. Are there considerations on utilizing the maximum powerdown mode of the ad9249.

The need for ac or dc coupling can have a significant impact on the choice of a differential adc driver. Is fr4 the best board material choice for high speed pcb design. Offsetfree dccoupled analog frontend circuit for high. The analog input and clock signals are differential inputs. In this paper, a 14bit low power selftimed differential sar adc with a new structure high precision multisegment bandgap reference bgr is presented. Low cost, low power, differential adc driver data sheet. Active filter evaluation board for differential amplifiers pdf an282. Input and output voltage range issues for high speed cfas.

This design translates an input bipolar signal of 20v into a fully differential adc differential input scale of. Using the analog devices active filter design tool. Planet analog dc precision considerations for high speed. Pcb and high speed serial interface hssi design guidelines ap32174 high speed board design application note 9 v1. High speed differential adc driver design considerations cn0237. Using the analog devices active filter design tool an584. The analog frontend afe coupling circuit is a crucial processing element for data acquisition systems based on analogtodigital converters adcs. Low distortion differential adc driver data sheet ad88dscc. A differential analogto digital converter adc measures the voltage difference between two signals. The ltc6430 highlinearity, differential rfif amplifieradc driver is a wideband differential gain block, matched to 50 a 100 a in differential hookups. A fully differential adc design offers the advantages of good cm rejection, reduction in secondorder distortion products, and simplified dc trim algorithms. This document assumes familiarity with the following tools and support collateral. Q the figure 40 in the datasheet of ad9245 is similar with the evb schematic in figure 49,50. Nov 26, 2014 designing with fdas is described in much greater detail in this application note an1026.

A fully differential adc design offers the advantages of good commonmode rejection, reduction in secondorder distortion products, and simplified dc trim algorithms. Optimum performance is achieved when a transmission line is. The technique sends the same electrical signal as a differential pair of signals, each in its own conductor. High speed differential adc driver design considerations an0992.

Adc driver design analog to digital converter signal. The adc data outputs are internally connected to four digital downconverters ddcs through a crossbar mux. This document includes the general considerations when driving an adc with an amplifier, such as commonmode voltages, power. According to walt kesters high speed design seminar, 2 an analogto digital converter adc can sample above 0. Contents introduction technology scaling and performance of pipelined adcs performance model of pipelined adc design challenge of high speed adcs pipelined adcs optimization of opamp comparator controlled current source in stead of opamp subranging adc successive approximation adcs.

Optimizing ths4509 to drive high speed adcs reference design. High speed adc analog input interface considerations pdf. Ad88 low distortion differential adc driver data sheet. High speed differential interfaces in cyclone ii devices chapter in volume 1 of the cyclone ii device handbook high speed differential signaling in cyclone devices chapter in volume 1 of the cyclone device handbook fpga design flow this section describes the design flow to implement an lvds interface in a cyclone series. Fully differential amplifier design in high speed data acquisition systems slyt119.

Design considerations for wide bandwidth continuoustime. The first pipeline adc utilizes a new high speed currentmode amplifier in openloop configuration in order to reach a samplerate of 2. Differential adc driver element14 community design. Differential signaling is a method for electrically transmitting information using two complementary signals. Voltage considerationsdccoupled input section, for driving adcs with low. The differentialsignal advantage for communications. At very high frequencies, every trace and pin is an rf emitter and receiver. Analog devices single and fully differential adc drivers offer precision dc specs and are designed to better reject high frequency psrr and cmrr through their differential input and output architectures. High speed board design advisor altera corporation 4 how to design with dc blocking capacitors use cutouts under the smt launch pads to a depth at least equal to the pad diameter or within 10 mils under the capacitor. National semiconductors lmh6554 fully differential current feedback cfb operational amplifier is capable of performing the singleto differential conversion required to drive these high speed adc s. Reference designs for highspeed adc interfacing to fpga. High speed differential adc driver design considerations pdf terminating a differential amplifier in singleended input applications pdf. Analog devices ad9208 and similar jesd204b analogtodigital converter adc.

Many high performance adcs are now being designed with differential inputs. Adc drivers are frequently used in systems that process high speed signals. According to walt kesters high speed design seminar, 2 an analogtodigital converter adc can sample above 0. The centered adc drivers have about 1 v of headroom from each supply rail hence centered. An 8bit 1gss hybrid analogtodigital converter adc for high speed lowpower applications is introduced in this dissertation. For the wide range of accoupled signal path application using cfabased fda solutions, this poor dc precision will not matter. The world leader in high performance signal processing solutions. Input range driver for measurement of a differential 10. The signal must be sampled at a rate equal to or greater than twice its bandwidth to preserve all of its information. Draxelmayr, a 6b 600mhz 10mw adc array in digital 90nm cmos, ieee, isscc 2004, dig. In general, it doesnt matter where the dc blocking capacitors are placed on the tx or rx side.

The two different methods of driving the converter, pseudo differential and true differential mode, each have their own biasing circuitry. Meeting biasing requirements of externally biased rfmicrowave amplifiers with active bias controllers an282. Ad88 low distortion differential adc driver data sheet teson. Adc driver reference design improving full scale thd using. If careful design practices are not followed, the unwanted signals can easily mask those a designer is trying to handle. If careful design practices are not followed, the unwanted signals can easily mask those a. According to walt kesters high speed design seminar,2 an analogtodigital converter adc can sample above 0. Recommended adc driver and clock distribution devices for the ad9645. The pair of conductors can be wires typically twisted together or traces on a circuit board.

Ultralow power, low distortion fully differential adc driver. Most modern high performance analogtodigital converters adcs use differential inputs to reject commonmode noise and. High speed differential adc driver design considerations rev. Lvds low voltage differential signaling is a more widely accepted standard for adcs digital data output along with lvcmos. According to walt kesters high speed design seminar,2 an analogto digital converter adc can sample above 0. Rules of the road for highspeed differential adc drivers maximize performance. Designing with fdas is described in much greater detail in this application note an1026. Meeting biasing requirements of externally biased rfmicrowave amplifiers with active bias controllers an584. High speed differential adc driver design considerations pdf an0992. High voltage signal conditioning for differential adcs sboa096. Edn singledual amplifier configurations for driving. Design guidelines for implementing lvds interfaces in. Board layer stackup considerations for high speed board design.

This second article in the jesd204 series covers the different types of outputs in terms of physical implementation, efficiency, and apps best suited for each type. It has a subranging architecture with a 3bit flash adc as a first stage and a 5bit 4channel timeinterleaved comparatorbased asynchronous binary search cabs adc as a. The cfabased versions will have phenomenal slew rates but relatively poor dc precision terms. High speed differential adc driver design considerations. An842 ds00842apage 2 2002 microchip technology inc. Ad88 low distortion differential adc driver data sheet rev. Design of highspeed analogtodigital converters using. Low noise, railtorail, differential adc driver ad89. Design guidelines for implementing lvds interfaces in cyclone series devices july 20 an4791. Analog devices adc drivers configured for both precision and high speed differential amps come with a vocm pin, providing a critical but convenient solution when interfacing with analogtodigital converters adcs. Low noise, railtorail, differential adc driver data. Refer to the high speed 10bit analogtodigital converter adc chapter in the specific device data. High speed differential adc driver design considerations an0990.

Design considerations for avoiding timing errors during. Eight interleaved saadcs with 90nm cmos attain 600mhz operation. With a multitude of analogtodigital converters adcs available for designers to choose from, an important parameter to consider in the selection process is the type. Printed circuit board was designed to test the functionality of the sar adc. Tutorial differential drivers for high speed adcs overview. Currently, high speed and high resolution adcs are predominantly designed with differential input stages. Microcircuit, linear, low distortion differential adc driver, monolithic silicon military data sheet an1026. Design considerations and tradeoffs at the systemlevel are. This design proceeds from a target input impedance matched to rs, signal gain av, and. Most modern highperformance adcs use differential inputs to reject common mode noise. Many modern analogtodigital converters adcs use differential inputs to reject commonmode noise and interference, to increase the dynamic range, and to improve the overall system performance. Ti regulator, low noise negative bias generator, lm7705. Todays designers have a multitude of adc choices that provide different digital outputs.