Tag Archives: CMOS

Reverse engineering the popular 555 timer chip (CMOS version)


Ken Shirriff reverse engineer the CMOS version of 555 timer IC and explains how it works.

This article explains how the LMC555 timer chip works, from the tiny transistors and resistors on the silicon chip, to the functional units such as comparators and current mirrors that make it work. The popular 555 timer integrated circuit is said to be the world’s best-selling integrated circuit with billions sold since it was designed in 1970 by analog IC wizard Hans Camenzind[1].

Reverse engineering the popular 555 timer chip (CMOS version) – [Link]

Unipolar Stepper Motor Driver Circuit

This unipolar stepper motor driver circuit is used to drive a 12V unipolar stepper motor with a current rating of 1.25A. It uses PCA9537 IC, which is a 10-pin CMOS device that provides 4 bits of General Purpose I/O (GPIO) expansion with interrupt and reset for I2C-bus/SMBus applications. It consists of a 4-bit configuration register (input or output selection), 4-bit input port register, 4-bit output port register and a 4-bit polarity inversion register (active HIGH or active LOW operation). In addition, the device uses PCA9665 IC that serves as an interface between most standard parallel-bus microcontrollers/microprocessors and the serial I2C-bus allowing the parallel bus system to communicate bidirectionally with the I2C-bus.

The PCA9537 totem pole GPIO used in this circuit has a fixed I2C-bus slave address, 92H. The host controller’s firmware generates the I2C byte sequences needed to toggle the outputs and provide the waveforms at the gate inputs G1 to G4. The type of waveform will be one corresponding to wave, two-phase or half-step drive that is chosen by the user. The duration of the pulses is controlled by time delay implemented in the host controller firmware. It is shown as a reference for the various waveforms. The maximum I2C-bus speed supported by PCA9537 is 400kHz.

Motor drivers have various applications that are used when accurate positioning is required. Such applications are for use in holding or positioning, like packaging machinery, and positioning of valve pilot stages for fluid control systems. The device enhances the performance of machines and other simple devices that may significantly support industries, and other commercial entities to make the work easier.

Unipolar Stepper Motor Driver Circuit – [Link]

Tutorial on the Theory, Design and Characterization of a CMOS Transimpedance Amplifier

In this episode, Shahriar and Shayan discuss the design and characterization of a deceptively simple CMOS inverter-based transimpedance amplifier. The the large and small signal behavior of the CMOS inverter is discussed and measured using the Keithley 2450 and 2460 source meters. The transient response is also measured using a Keysight MSO-S series oscilloscope.

The small signal gain of the circuit is calculated from small signal parameters which are extracted directly by measuring the devices I/V characteristics. The NMOS/PMOS devices used are from an ADL1105 quad-discrete transistor IC. Through the use of a shunt-shunt feedback, the CMOS amplifiers is converted to a transimpedance amplifier which is capable of amplifying the current from a photo-detector diode by a gain of 30kV/A. The feedback theory is used to calculate the gain of the amplifier. The slides for this tutorial can be downloaded from The Signal Path website.

Tutorial on the Theory, Design and Characterization of a CMOS Transimpedance Amplifier – [Link]

iCoupler – Digital Signal Isolator


Clemens Valens @ elektormagazine.com discuss about the new iCoupler family of isolators from Analog Devices:

Digital isolators based on transformers and capacitors use magnetic and electric fields to couple data across isolation barriers where optocouplers use light. Digital isolators can be manufactured using CMOS technology allowing the integration of signal conditioning circuitry in the chip to greatly reduce power consumption and improve data transfer rates.

The iCoupler family from Analog Devices is a family of digital isolators that feature up to 16 kVpk surge protection and that can withstand voltages up to 5 kV. Signal speeds go up to 150 Mbit/s.

iCoupler – Digital Signal Isolator – [Link]


CCS811 – Digital CMOS gas sensors for wearables & IoT


by Graham Prophet @ edn-europe.com:

Cambridge CMOS Sensors is a semiconductor company that designs gas sensor solutions to monitor the local environment; its CCS811 is the first digital product in its CCS800 product family of ultra-low power miniature gas sensors.

The CCS811 integrates a metal oxide gas sensor with a microcontroller sub-system which enables Indoor Air Quality Monitoring, ease of design, extended battery life and reduced system cost for smartphones, wearables and connected home devices. It is based on CCS’s Micro-hotplate technology which enables a highly reliable solution for gas sensors, very fast cycle times and a significant reduction in average power consumption compared with traditional metal oxide gas sensors.

CCS811 – Digital CMOS gas sensors for wearables & IoT – [Link]

5V & 12V Regulated Power Supply


This project can be used to power up TTL and CMOS based projects, it provides 5 VDC & 12 VDC outputs with an onboard mains transformer.  The project is based on the industry popular 7800 series voltage regulator in TO220 packages.


  • Input: 240 VAC
  • Output: 5 V, 12 V @ 600 mA regulated low ripple DC voltage
  • Thermal overload/short circuit protection (provided by IC feature)
  • Power Battery Terminal (PBT) for easy input and output connection
  • External On/Off switch connection possible
  • LED indication for outputs
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 87 mm x 49 mm

5V & 12V Regulated Power Supply – [Link]

2 Channel Relay Board


2 channel Relay driver project can be controlled by feeding 2-12V trigger voltage, Very useful project for application like Micro-Controller based projects, Remote controller, Lamp on Off, and any circuits which required isolated high current and high voltage switching by applying any TTL or CMOS level voltage. Two LED works as operation indicator while in , 3 pins screw terminals to connect load and provides both normally open and normally closed switching.

Input: 12 VDC @ 84 mA
Output: Two SPDT relay
Relay specification: 5 A @ 230 VAC
Trigger level : 2 to 12 VDC
Header connector for connecting power and trigger voltage
LED on each channel indicates relay status
Power Battery Terminal (PBT) for easy relay output connection
Four mounting holes of 3.2 mm each
PCB dimensions 49 mm x 68 mm

2 Channel Relay Board – [Link]

CMOS Image Sensors Surpassing Moore’s Law


R. Colin Johnson @ eetimes.com:

PORTLAND, Ore. — Complementary metal oxide semiconductor (CMOS) imaging chips are becoming the industry’s leader in advanced process technology — instead of the traditional leaders (processors and memory) — thanks to strong demand for CMOS imaging chips in everything from smartphones to tablets to medical equipment and automobiles. Apparently, now the innovation surpasses Moore’s Law, says analyst firm Yole Développement.

Imaging was once done by film, but with the advent of solid-state sensors the technology breakthroughs seem to be growing exponentially, doubling with each new innovation (see slide 1), thus surpassing the traditional interpretation of Moore’s Law, argues Yole Développement (Lyon, France) in a new paper. Yole calls this effect “More than Moore.”

CMOS Image Sensors Surpassing Moore’s Law – [Link]

Clocked 8-bit random pattern generator for CMOS synth


by acidbourbon @ acidbourbon.wordpress.com:

Soon after I played around with some simple sequencers and multiplexers to generate more complex sound patterns. I thought it would be cool to have a device to gate oscillators or switch multiplexers with a random sequence. But the the output should change at a defined rate. Can we build a simple random pattern/number generator that works synchronized with an external clock signal? I believe so.

Clocked 8-bit random pattern generator for CMOS synth – [Link]

PCA8565 Application Circuit

The PCA8565 plays a very important role in the real time systems like digital clock, attendance system and tariff switching. In applications where timestamp is needed, PCA8565 real time clock is a good option. It provides the following benefits: low power consumption, allows the main system for time-critical tasks, and more accurate than other methods.

The PCA8565 is a CMOS real time clock and calendar optimized for low power consumption. A programmable clock output, interrupt output and voltage-low detector are also provided. All address and data are transferred serially via a two-line bidirectional I2C-bus with a maximum bus speed of 400kbps. The built-in word address register is incremented automatically after each written or read data byte. It provides a year, month, day, weekday, hours, minutes and seconds based on a 32.768kHz quartz crystal. It features alarm and timer functions, low current, and extended operating temperature range of -40 degrees Celsius to +125 degrees Celsius. It further contains an 8-bit year register that can hold values from 00 to 99 in BCD format, which also compensates for leap years, thus leap year is automatically corrected.

From the application circuit, the PCA8565 can be used to perform standard RTC functions, such as tracking the actual time and date, or acting as a reference timer. To support power management, the PCA8565 can be used to wake the microcontroller from hibernation mode. In systems that use a PLL, it can serve as a system reference clock for the PLL input. The PCA8565 can also be used as a watchdog timer, or as an activation timer to start measurements or initiate other functions.

PCA8565 Application Circuit – [Link]