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2 Apr 2014

The PCA9508 is a CMOS integrated circuit that supports hot-swap with zero offset and provides level shifting between low voltage (down to 0.9 V) and higher voltage (2.7 V to 5.5 V) for I2C-bus or SMBus applications. While retaining all the operating modes and features of the I2C-bus system during the level shifts, it also permits extension of the I2C-bus by providing bidirectional buffering for both the data (SDA) and the clock (SCL) lines, thus enabling two buses of 400 pF. Using the PCA9508 enables the system designer to isolate two halves of a bus for both voltage and capacitance, and perform hot-swap and voltage level translation. Furthermore, the dual supply pins can be powered up in any sequence; when any of the supply pins are unpowered, the 5 V tolerant I/O are high-impedance.

PCA9508 has B-side and A-side bus drivers. The 2.7 V to 5.5 V bus B-side drivers behave much like the drivers on the PCA9515A device, while the adjustable voltage bus A side drivers drive more current and incur no static offset voltage. This results in a LOW on the B-side translating into a nearly 0 V LOW on the A side.

The hot swap feature allows an I/O card to be inserted into a live backplane without corrupting the data and clock buses. Control circuitry prevents the backplane from being connected to the card until a stop command or bus idle occurs on the backplane without bus contention on the card. Zero offset output voltage allows multiple PCA9508s to be put in series and still maintains an excellent noise margin.


  • PCA9508D CMOS integrated circuit (3 units)
  • BUS Master
  • Slave 400kHz (3 units)
  • 10kΩ Resistor (6 units)
  • Ground Source

Hot swap level translating I2C repeater - [Link]

26 Mar 2014


This Design Idea describes a simple two-chip CMOS circuit that can sort capacitors into 20 bins over a wide range (100pF to 1μF), using 10 LEDs to display the value range. The circuit is power efficient and can be run using two CR2032 cells. As such, it can be built into a handheld probe. by Raju Baddi

Simple capacitance meter bins parts - [Link]

10 Mar 2014

With the rapid development of GPS (Global Positioning System) techniques, GPS gets wider application in many fields. GPS has features such as high precision, global coverage, convenience, high quality, and low cost. Recently, the use of GPS extends speedily from military to civilian applications such as automobile navigation systems which combine the GPS system, e-map, and wireless network. GPS is getting popular, and the market for GPS techniques is extending continuously.

UARTs provide serial asynchronous receive data synchronization, parallel-to-serial and serial-to-parallel data conversion for both the transmitter and receiver sections. These functions are necessary for converting the serial data stream into parallel data that is required with digital systems. Synchronization for the serial data stream is accomplished by adding start and stop bits to the transmit data to form a data character. Data integrity is ensured by attaching a parity bit to the data character. The parity bit is checked by the receiver for any transmission bit errors.

The circuit describes how to combine GPS into a navigation system by using a Philips 2-channel UART, the SC16C2552B.  The SC16C2552B is a two channel Universal Asynchronous Receiver and Transmitter (UART) used for serial data communications. Its principal function is to convert parallel data into serial data, and vice versa. The UART can handle serial data rates up to 5 Mbit/s.


  • SC16C2552BIA44 Dual UART, 5 Mbps (max.), with 16-byte FIFOs
  • 80C51 CMOS 0 to 42 MHz Single-Chip 8 Bit Microcontroller
  • 12 MHz Oscillator Clock
  • 1.8432 MHz Oscillator Clock
  • 22pF Capacitor – 2 Units
  • 33pF Capacitor – 2 Units
  • 0.1µF Capacitor – 2 Units
  • 10 µF Capacitor – 2 Units
  • 74LV04 Hex Inverter – 2 Units

UART in GPS navigation system – [Link]

30 Sep 2013


by Steven Keeping:

LEDs have many advantages over traditional lighting including efficacy, longevity, and robustness, but price is not one of them.

The reason why LEDs are expensive is partly because the manufacturing process used to fabricate the wafers from which the individual chips are cut is difficult and employs exotic materials such as gallium nitride (GaN) deposited on sapphire or silicon-carbide (SiC) substrates.

But recently, some manufacturers have proposed using silicon, the material routinely used to fabricate billions of integrated circuits (ICs) every year, as an LED substrate. Apart from potentially reducing the cost of LEDs, the use of mature complementary metal oxide semiconductor (CMOS) IC technology would allow fabrication in conventional wafer fabs that have spare capacity.

Will Silicon Substrates Push LED Lighting Into the Mainstream? - [Link]

19 Jul 2013


by Steve Taranovich

The following is a white paper by Silicon Labs with an innovative new process and technology that I believe deserves some level of detail and explanation for informative and educational purposes for EDN readers. Learning about this technology will help all designers give birth to new ideas and architectures as well as help those other designers to effectively integrate this type of product into their systems,

CMEMS® technology is an innovative CMOS + MEMS manufacturing process developed by Silicon Labs, a leading supplier of timing solutions. The term CMEMS is a contraction of the acronyms CMOS and MEMS (microelectromechanical systems). CMEMS technology offers many benefits over traditional oscillator approaches, ranging from scalability, customer-specific programmability and 0-day samples, to long-term reliability and performance. This white paper describes CMEMS process technology, existing hybrid oscillator architectures and the Si501/2/3/4 (Si50x) CMEMS oscillator architecture.

CMEMS oscillator architecture - [Link]

5 Jul 2013


New Si50x CMEMS® Oscillators Leap Ahead of Quartz-Based Timing Devices with Superior Frequency Stability, Reliability and Programmability

Silicon Labs has developed a new low-drift, single-die MEMS oscillator fabricated using a CMOS process. By porting low-temperature MEMS technology to the SMIC foundry, they managed to build a SiGe structure on top of the passivation layer of a CMOS logic chip using an existing CMOS production line. The drift problems of dual-die devices are eliminated by selecting specific materials to counteract thermal drift. The programmable oscillators operate at up to 100 MHz with frequency stability down to 20 ppm. Higher speed devices are planned, according to a Silicon Labs’ source.

CMOS MEMS (CMEMS) technology allows data sheet performance for frequency stability to be guaranteed for ten years, including solder shift, load pulling, supply voltage variation, operating temperature range, vibration and shock. This is ten times longer than typically offered by comparable crystal and MEMS oscillators. The oscillators tightly couple the MEMS resonator with CMOS temperature sensing and compensation circuitry, ensuring a highly stable frequency output despite thermal transients and over the full industrial temperature range. [via]

New MEMS Oscillators Boast Long-term Stability - [Link]

4 Jun 2013

Here’s a video describing CMOS current sources.

CMOS current source circuits are examined. The voltage versus current and layout are presented. The channel region versus the voltage/current curve is explained. The equation to calculate the Gate-Source voltage is given. The CMOS cascode current source is also explored.


App note: CMOS current source - [Link]

29 Mar 2013


The C10988MA-01 sensor from Hamamatsu Photonics is an ultra-compact spectrometer built with Micro-Opto-Electro-Mechanical Systems (MOEMS) technology. Measuring only 27.6 x 13 x 16.8 mm and weighing just 9 grams, the device is intended to be used in portable and hand-held devices where a standard mini-spectrometer would be too large and consume too much power. [via]

The new device features an aberration-corrected concave grating with a very short focal length and blazed grating profile for high diffraction efficiency. The grating is replicated onto a convex glass lens using nano-print technology. Directly opposite the grating there is a dedicated CMOS silicon image sensor with an on-chip slit. This 75 x 750 µm slit is formed in the CMOS chip using MEMS technology. The distance between the sensor and slit is only 1 mm, and the distance between the grating and the image sensor distance a mere 8.5mm. Thanks to its novel design, the sensor offers a spectral resolution of 14 nm in the wavelength range of 340 to 750 nm, making it suitable for a variety of visible light applications requiring a miniaturized spectrometer head.

Ultra-Compact Spectrometer Sensor Targets Visible Light - [Link]

12 Dec 2012


The LTC6090 is a high voltage precision operational amplifier. The low noise, low bias current input stage is ideal for high gain configurations. The LTC6090 has low input offset voltage, a rail-to-rail output stage, and can be run from a single 140V or split ±70V supplies.

The LTC6090 is internally protected against overtemperature conditions. A thermal warning output, TFLAG, goes active when the die temperature approaches 150°C. The output stage can be turned off with the output disable pin OD. By tying the OD pin to the thermal warning output, the part will disable the output stage when it is out of the safe operating area. These pins easily interface to any logic family.

The LTC6090 is available in an 8-lead SO and 16-lead TSSOP with exposed pad for low thermal resistance.

LTC6090 – 140V CMOS Rail-to-Rail Output, Picoamp Input Current Op Amp - [Link]

28 Jun 2012

Dilshan developed a precision event logger based on the PIC16F73 and some binary ripple counters from the CMOS logic family. The project uses a 2Mhz reference clock, and is capable of measuring events from 0.02 to 6.8 seconds long. [via]

The counter gets activate and deactivate in positive edge of the input signal. Thanks to the wider operating voltage of the CMOS ICs this counter may be able to handle +5V to +15V of input signal. At the end of the counter session system release total tick count to the RS232 interface and it can receive through any serial terminal software. When applying the inputs it is recommended to maintain minimum of 100ms of interval between each session.

Precision event logger measures 0.02 to 6.8 seconds - [Link]





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