As logic systems get larger and more complex, theirsupply CURRENT requirements continue to rise. Systemsrequiring 100A are fairly common. A high CURRENT powersupply to meet such requirements usually requires parallelingseveral power regulators to alleviate the thermalstress on the individual power components. A powersupply designer is left with the choice of how to drive theseparalleled regulators: brute-force single-phase or smartPolyPhaseTM.
Photomultipliers (PMT), avalanche photodiodes (APD),ultrasonic transducers, capacitance microphones, radiationdetectors and similar devices require high voltage,low CURRENT bias. Additionally, the high voltage must bepristinely free of noise; well under a millivolt is a commonrequirement with a few hundred microvolts sometimesnecessary. Normally, switching regulator confi gurationscannot achieve this performance level without employingspecial techniques. One aid to achieving low noise is thatload CURRENTs rarely exceed 5mA. This freedom permitsoutput fi ltering methods that are usually impractical
鎖定放大是微弱信號檢測的重要手段。基于相關檢測理論，利用開關電容的開關實現鎖定放大器中乘法器的功能，提出開關電容和積分器相結合以實現相關檢測的方法，并設計出一種鎖定放大器。該鎖定放大器將微弱信號轉化為與之相關的方波，通過后續電路得到正比于被測信號的直流電平，為后續采集處理提供方便。測量數據表明鎖定放大器前級可將10-6 A的電流轉換為10-1 V的電壓，后級通過帶通濾波器級聯可將信號放大1×105倍。該方法在降低噪聲的同時，可對微弱信號進行放大，線性度較高、穩定性較好。
Abstract:
Lock-in Amplifying（LIA）is one of important means for weak signal detection. Based on cross-correlation detection theory， switch in the swithched capacitor was used as multiplier of LIA， and a new method of correlation detection was proposed combining swithched capacitor with integrator. A kind of LIA was designed which can convert the weak signal to square-wave， then DC proportional to measured signal was obtained through follow-up conditioning circuit， providing convenience for signal acquisition and processing. The measured data shows that the electric CURRENT（10-6 A） can be changed into voltage（10-1 V） by LIA， and the signal is magnified 1×105 times by cascade band-pass filter. The noise is suppressed and the weak signal is amplified. It has the advantages of good linearity and stability.
Sensing and/or controlling CURRENT flow is a fundamental requirement in many electronics systems, and the tech-niques to do so are as diverse as the applications them-selves. This Application Note compiles solutions to cur-rent sensing problems and organizes the solutions by general application type. These circuits have been culled from a variety of Linear Technology documents
HIGH SPEED 8051 μC CORE
- Pipe-lined Instruction Architecture; Executes 70% of Instructions in 1 or 2
System Clocks
- Up to 25MIPS Throughput with 25MHz System Clock
- 22 Vectored Interrupt Sources
MEMORY
- 4352 Bytes Internal Data RAM (256 + 4k)
- 64k Bytes In-System Programmable FLASH Program Memory
- External Parallel Data Memory Interface – up to 5Mbytes/sec
DIGITAL PERIPHERALS
- 64 Port I/O; All are 5V tolerant
- Hardware SMBusTM (I2CTM Compatible), SPITM, and Two UART Serial
Ports Available ConCURRENTly
- Programmable 16-bit Counter/Timer Array with 5 Capture/Compare
Modules
- 5 General Purpose 16-bit Counter/Timers
- Dedicated Watch-Dog Timer; Bi-directional Reset
CLOCK SOURCES
- Internal Programmable Oscillator: 2-to-16MHz
- External Oscillator: Crystal, RC, C, or Clock
- Real-Time Clock Mode using Timer 3 or PCA
SUPPLY VOLTAGE ........................ 2.7V to 3.6V
- Typical Operating CURRENT: 10mA @ 25MHz
- Multiple Power Saving Sleep and Shutdown Modes
100-Pin TQFP (64-Pin Version Available)
Temperature Range: –40°C to +85°C
利用單片機具有的智能程序控制的特點，設計了基于STC89C52單片機的"二極管特性測試器"，可對二極管一般特性進行快速測試。通過穩定線性電流源給二極管加載恒定電流，然后由高精度模數轉換器測試其壓降，以此為基礎可判斷二極管好壞、檢測二極管極性和測試二極管伏安特性等，避免了用萬用表測試只能測得極性而不知其特性這一缺點。可用于電子設計制作過程中對二極管進行快速測試，以確定被測二極管是否滿足電路的設計要求。
Abstract:
By making good use of the intelligent control function of the Micro Controller Unit (MCU)， the diode trait tester was designed based on the STC89C52，which could be used to test the trait of a diode rapidly. By loading constant CURRENT to diode through the stable linear CURRENT source， and measuring the voltage drop of the diode by high-precision analogue-to-digital converter (ADC)， it can judge whether the diode is good or not， distinguish the polarity of the diode， and test the trait that the diode， which can avoid the fault of using a multimeter can only measure the polarity but not the trait. This device can be used to test the trait of a diode quickly，and to make sure that whether a diode can be used in the electronic design or not.
現有基于MAX7219芯片的數碼管驅動電路只適用于小尺寸LED，為擴展其使用范圍，在介紹動態顯示芯片MAX7219功能的基礎上，提出了一個基于該芯片的8位高亮度8英寸數碼管驅動電路。電路保留了MAX7219芯片的功能強大、編程簡單等優點，通過74LS273鎖存器和ULN2803達林頓驅動器，實現了對任意大尺寸數碼管提供較高電壓和電流驅動的靜態顯示，并亮度可調。
Abstract:
The existing display-driving circuit based on MAX7219 was only applicable to small-size LED. To expand its use, based on the function introduction of dynamic display chip MAX7219, a display-driving circuit for high-brightness 8-bit LED with the size of 8-inch was proposed. The advantages of MAX7219 were retained, such as powerful function and simple programming. Static display with adjustable brightness for large-size LED with higher voltage and CURRENT was achieved with the help of 74LS273 and ULN2803.
