The design of analog circuit is different from the design of processor, FPGA and PLD in architecture. For analog circuits as long as you set the topology layout and parameters of the circuit, the signal processing function of the circuit is basically fixed. Of course, some off-the-shelf functional circuit blocks, such as various filters, you can adjust the clock (for the switch capacitor design) or adjust through the DAC of various circuit factors, digital means such as cutoff frequency, roll drop and other functions, but these adjustments can only be counted as exceptions. Most designs are functionally fixed and can be almost immutable in their performance.
This invariant character is not a bad thing, and in fact it is often true. This fixed performance can make the performance of the analog signal processing channel stable, and becomes a channel with little change in the system. However, in the simulation of the designer, as long as the FPGA or PLD reprogramming, or often do not need to change the printed circuit board or any device on the board, and by modifying the software can easily be modified, the superior or adjust the circuit function, naturally will not be able to suppress the programmable device generated goodwill.
In fact, the simulation designer in the programmability of really have a choice of room! There are several vendors of analog ICS that allow you to set or modify the performance of these devices as a one-time production step, or after your system has entered the field, you can still create or modify the device layout or performance parameters. This programmability provides the benefit of being configurable, even reconfiguration, or the ability to adapt your circuit's performance to the dynamic performance of your application system. Analog ICS enable you to use the same parts in different designs, and to provide some degree of protection to the security of analog circuit design to prevent others from observing active devices and passive devices and their interconnection methods to explore or estimate the security of the circuit you designed.
You should consider carefully the ramifications and limitations of these programmable analog devices, and the transverse effects of using this number of unique analog devices in the system.
As with many technical terms, the two words "programmable" and "programmable" have different interpretations, depending on what kind of device the user and discussion object is. Programmable digital devices can be processors that perform fixed code or change code (Programs). It can be a programmable device, its circuit interconnect before the factory has been programmed, or by the OEM on-site programming, such as gate array or logic devices. It may also mean that the user defines certain functional parameters, such as bit rate, and that they exist in the internal registers.
Some of these definitions do not apply to analog programmability; You do not execute sequential code directives. When using programmable analog circuits, you can interconnect the analog units either by the factory or by the OEM in the desired mode, or even in the field, to reprogram the units. The other way is that the circuit is fixed topology on the main parameters, but some you can set and change as required by the application, such as filter bandwidth or roll down. However, in this case, the signal processing channel and the basic function to remain unchanged, the change is only the parameters.
The desire and ability to program analog circuits is not uncommon. Early analog computers have connectors and wiring boards, allowing engineers to use basic unit modules for various configurations and to swap subassemblies of passive components to meet various requirements. In the use of IC mixed signal processing field, engineers have long used the number/mode converter (DAC) to digitally set the analog circuit parameters, especially to the filter, has already been used analog switch to the analog signal processing channel reconfiguration and reroute. This configurable and configurable routing architecture requires careful analysis of structural planning, printed circuit board design and error budgeting.
When you need programmability, it seems to mean that only digital is the only way out. However, if you are not biased against the processor and executable code, there are several reasons why you should choose to simulate. For example, almost every signal processing application requires the use of filters, and even digital filters need to simulate Nyquist (nyqaist) frequency filters to avoid confusion during sampling. Low-level signals usually need to be amplified to be compatible with the frequency converter signal and obtain maximum Snr (signal-to-noise ratio) and dynamic range. Even if you can filter and reshape the signals with all the digital techniques, the modular approach is still less expensive and less power-consuming. In the case of the peak detector, if the simulation scheme is used, it is only one or two operational amplifiers and a few diodes, but if the digital method to do, it is necessary to include a filter, a number/mode converter, but also a processor.
Do not confuse the programmable module ICS with the module ASIC and mask programming array. Some manufacturers provide the model of the various analog Unit circuit libraries, the unit circuit interconnection can meet the user's application requirements. Over the years, manufacturers and users believe that the Unit circuit through the selection of the unit circuit, can be more easily paired with the required analog IC. Or more specifically, pick an op-amp unit, a comparator unit, and a multiplier unit better.
However, your requirements for high-performance analog design add to the difficulty of designers in configuring and producing these high-performance ICS, as there are clearly many subtle and interacting factors, such as heating problems, and the various factors that are associated with design layout and process. Many module circuit OEM manufacturers, using the Unit Circuit Library as the starting point of the standard product design, but at the same time to use their experience to the final unit interconnect design to make a substantial adjustment in order to enable the IC to achieve the desired purpose.
The varieties supplied by manufacturers are limited
When you compare the basic analog components of different sources, such as operational amplifiers and inverters, they are found to differ in architecture and performance. However, in general, these differences can be analyzed and resolved, to make a meaningful comparison, starting with the comparison of the basic technical specifications, such as bandwidth, stability time, linear error, and performance and other major measurement parameters, and then look at the more subtle and more critical of the secondary measurement parameters.
For programmable analog IC, each manufacturer provides the product according to the basic principle. Some are basic analog functions, such as amplifiers, while others contain more functions that can be run as subsystems for handling analog signals. You have to carefully review their application requirements, and then look at the market model of the product can be effectively applied to your design. Existing products may be just right or close to your requirements, and may not be used at all. You may also need a free array that can be configured for almost any selected signal channel, or only a filter with a certain choice of layout and parameters.
If you start with the basic functionality of the view, the MOSFET transistor should be the first. This kind of epad plays the role of electrically controlled micro-potentiometer in the transducer preamplifier and sensor signal adjusting channel. If your application system needs to be protected, you can also seal the device or place it in a location where you can't touch or work. But once set, the internal bias voltage can be saved. The programming level of the dual ALD 1108E and four ald110e devices, the current is 0.1 to 3mA, and the voltage range is 1 to 3V, which can be programmed by 0.1V. (Please note: Increasing the threshold voltage is equivalent to reducing leakage current.) ）
From the basic physical point of view, the externally injected charge will change the epad parameter into the floating gate substrate; These injected charges increase the threshold level. If your design requires two-way control, you should set up two back-to-back epad, because this programming is a single function. Also, Epad cannot be reprogrammed indefinitely. Standard epad circuits generally allow only 20 to 50 times to reprogram. Of course, this is enough for many application projects. For example, this is probably the number that matches the characteristics of the preamplifier to the sensor or the cycle of the factory calibration.
The advantage of using epad to replace the trimmer potentiometer is that the epad has no active parts, the environment is rugged, and the resolution is higher than the 10-turn device with a standard size of 2000. Alternatively, you can seal the epad first and then adjust them through the software. However, you also have to consider certain factors, such as Epad's limited time to fine-tuning cycles, there are a number of challenges to application, and limited numbers of optional values.
Epad varieties are not just basic MOSFET. Manufacturers also provide operational amplifiers ald1722e and micro-power ald1726e, allowing you to set the starting bias voltage vos. By setting this voltage, it can reduce or eliminate the VOS error caused by the bias state, and some consequences due to the power supply rejection ratio, the common mode rejection ratio and the vos temperature coefficient error. ald1726e start input vos at Factory 50mV, you can increase this voltage to 610mV. The operating voltage of the $1 operational amplifier can be as low as 2V and the standard input current is less than 0.01pA, the bandwidth is 200kHz, and the conversion rate is 0.17v/ms.
When programming to Epad, use a E100 programmer that sells for $499. The programmer is operated by a PC using Windows, and the purpose of running the programming algorithm is to shorten the programming time by speeding up the stability of the threshold voltage. At the same time, the programmer reduces the overshoot to its target value. Programmers have a variety of epad templates, and you can use it with a dedicated module priced at $199 to fit a variety of dedicated Epad series.
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