App note: BA45F55xx with power line transceiver

App note from Holtek on power line transceiver found on their BA45F55xx MCU. Link here (PDF)

A Power Line Transceiver is a fire protection dual-line bus which is used as a data transceiver. The master gives a command to the slave using a voltage signal modulation method while the slave responds to the master using a current modulation method. In this way a complete communication system between a master and slave only requires two lines. This communication method is very common in fire protection related products.

App note: Op amps for MEMS Microphone preamp circuits

App note from TDK on design considerations of preamps used on MEMS microphones. Link here

A microphone preamp circuit is used to amplify a microphone’s output signal to match the input level of the devices following it in the signal chain. Matching the peaks of the microphone’s signal level to the full-scale input voltage of an ADC makes maximum use of the ADC’s dynamic range and reduces the noise that subsequent processing may add to the signal.

App note: Analog and digital MEMS microphone design considerations

App note from TDK about the things to consider when integrating analog and digital MEMS microphones into a system design. Link here (PDF)

Microphones are transducers that convert acoustic pressure waves to electrical signals. Sensors have become more integrated with other components in the audio signal chain, and MEMS technology is enabling microphones to be smaller and available with either analog or digital outputs. Analog and digital microphone output signals obviously have different factors to consider in a design.

A sensitive, frequency-modulated dip meter capable of measuring resonator Q

Qrp Gaijin’s version of a dip meter to measure resonator Q:

A highly-sensitive, narrow-band frequency-modulated dip meter offers a simple way to measure resonator Q.
I have been working with an unusual dip meter circuit recently that has some interesting properties.
The dip meter, also called a grid dip meter, is a simple homebrew instrument that offers a wide range of measurement possibilities.

More details on Qrp Gaijin’s blog.

Check out the video after the break.

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Reverse engineering RAM storage in early Texas Instruments calculator chips

Reverse engineering RAM storage in early Texas Instruments calculator chips:

Texas Instruments introduced the first commercial single-chip computer in 1974, combining the CPU, RAM, ROM, and I/O into one chip. This family of 4-bit processors was called the TMS1000. A 4-bit processor now seems very limited, but it was a good match for calculators, where each decimal digit fit into four bits. This microcontroller was also used in hand-held games and simple control applications such as microwave ovens. Since its software was in ROM, the TMS1000 needed to be custom-manufactured for each application, but it was inexpensive and sold for $2-$4 in quantity.

See the full post on Ken Shirriff’s blog.

Powering up an HP YIG tuned oscillator

Kwong explained the operation principle of an YIG tuned oscillator and demonstrated the tuning characteristics:

I was going through some of the components I accumulated over the years and stumbled upon a Hewlett Packard YIG tuned oscillator (part number 5086-7023) that I bought a while back. This YIG oscillator was made for a frequency extension module for the HP 8660C synthesized signal generator and has a tunable range of between 2.7 to 4.2 GHz.

More details on Kerry Wong’s blog.

Check out the video after the break.

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App note: Driving electronic paper displays (E-paper)

Silicon Labs’ app note on driving E-paper with their EFM32 micro. Link here (PDF)

Electronic Paper Displays (EPDs) are types of displays that are reflective and bistable. Reflective in this case means that they rely solely on ambient light and does not use a backlight. Bistable is the property of retaining an image even when no power is connected.
EPDs are commonly used in e-readers, industrial signage and electronic shelf labels. Their properties are ideal for applications which do not update the image frequently. Since the display draws no current when showing a static image, they allow for a very long battery lifetime.

App note: Designing with an inverted-F 2.4 GHz PCB antenna

PCB design guide for an inverted-F 2.4 GHz antenna from Silicon Labs. Link here (PDF)

One of the main reasons to use a PCB antenna is to reduce cost. Since the antennas are printed directly on the board, they are generally considered to be free. On boards with room to spare, this will be true. On boards that need to grow to account for the increased size of the printed antenna, you must include the added cost of the larger PCB when calculating cost savings.

App note: Secure hash algorithms back to basics

Maxim Integrated’s introduction to SHA security. Link here (PDF)

This application note goes over the basics of Secure Hash Algorithms (SHA) and discusses the variants of the algorithm. It then briefly touches on how the algorithm is used for authentication, including the concept of a Hashed Message Authentication Code (HMAC). It concludes by looking at some of the Maxim secure authenticators that can be used to very easily deploy SHA algorithms for security applications.

App note: Optocouplers in on-board chargers and battery monitoring systems

App note from Vishay on how optocouplers play a role on safety for Electric vehicles. Link here (PDF)

The number of electric vehicles on the roads is steadily growing, increasing the need for safe and reliable battery systems and high efficiency battery chargers. Modern electric vehicles use battery systems with voltages up to 1000 V and charge times down to a few hours. This application note uses two examples to illustrate how optocouplers play a major role in on-board chargers battery monitoring systems, and explores the benefits they provide to designers and drivers.

Reverse-engineering the classic MK4116 16-kilobit DRAM chip

Ken has written an article on reverse-engineering the classic MK4116 16-kilobit DRAM chip:

Back in the late 1970s, the most popular memory chip was Mostek’s MK4116, holding a whopping (for the time) 16 kilobits. It provided storage for computers such as the Apple II, TRS-80, ZX Spectrum, Commodore PET, IBM PC, and Xerox Alto as well as video games such as Defender and Missile Command. To see how the chip is implemented I opened one up and reverse-engineered it. I expected the circuitry to be similar to other chips of the era, using standard NMOS gates, but it was much more complex than I expected, built from low-power dynamic logic.

See the full post on Ken Shirriff’s blog.

FV-1 based mini SDR radio

FV-1 based mini SDR radio @

I have really enjoyed my FV-1 based mini SDR radio but it has one problem…its too small! I made the thing so small; it’s hard to operate and assemble. So I decided to make it a little larger, allowing for all the controls to be larger and more spaced out. It has a larger display and the circuit board layout provides for the switches, encoder, volume control and display all to be soldered directly to the board. All of the circuit components are now on the top side of the board as well. Along with these physical changes, I made some minor circuit changes.

Check out the video after the break.

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App note: Control solution using logic, analog switches, and discrete semiconductor devices for reversing a one-phase motor

App note from Littelfuse on solution to control split-phase motor using logic devices and triacs. Link here (PDF)

In the huge variety of the AC motors, one-phase motors are an excellent option when only the single-phase power is available to supply electrical energy which motors require to operate. One of the most common single-phase motors is the split-phase motor which is used in many applications, such as pumps, bench drills, compressors, vacuum cleaners, electrical sewing machines, etc.
In some if these applications it is necessary to reverse the motor which requires two conditions. The first condition is the removal of power to the motor in order to stop it. The second condition is to change the electrical connections between the mainand the start winding.

App note: Circuit protection solution for lithium cells

App note from Littelfuse on PolySwitch PPTC for lithium cells protection. Link here (PDF)

Primary lithium cells (i.e., AA and 2/3A) and rechargeable lithium cells (i.e., 18650, 17500, and prismatic) are used in many portable electronics applications, such as laptop or notebook computers. Their popularity is based on the fact that they offer high energy density, high capacity and long cycle life, with no memory effect.
Lithium cells are sensitive to faults caused by overcurrent and overtemperature conditions that may result from accidental shorting of the cell terminals and, in the case of rechargeable lithium cells, abusive charging or charger failure. For this reason, lithium cells generally require individual protection.

Reverse-engineering the carry-lookahead circuit in the Intel 8008 processor

Reverse-engineering the carry-lookahead circuit in the Intel 8008 processor:

The 8008 was Intel’s first 8-bit microprocessor, introduced in 1972. While primitive by today’s standards, the 8008 is historically important because it essentially started the microprocessor revolution and is the ancestor of the modern x86 processor family. I’ve been studying the 8008’s silicon die under the microscope and reverse-engineering its circuitry.

More details on Ken Shirriff’s blog.

App note: How to determine if an eFuse system can be safely hot−plugged

This app note from ON Semiconductors linked here (PDF)

System designers must account for voltage surges that occur when supplies or loads are connected. eFuses are integrated circuits with many features to protect loads from these surges. However, it is important to ensure that the eFuse itself will not receive excessive voltage on its input.
This application note uses mathematical calculations, simulations, and actual lab data to illustrate the voltage surge as an eFuse is suddenly connected on the input side. System designers can use this information to make certain that the eFuse will be within its limits.

App note: Analysis of power dissipation and thermal considerations for high voltage gate drivers

App note from ON Semiconductors on ways to dissipate thermals or reduce junction temperature of HVIC. Link here (PDF)

Gate drivers used to switch MOSFETs and IGBTs at high frequencies can dissipate significant amount of power depending on the operating conditions. It is important to determine the driver power dissipation and the resulting junction temperature in the application to ensure that the part is operating within acceptable temperature limits.

Low-cost open source ventilator-ish device

Johnny made a low-cost ventilator-ish device, that is available on GitHub:

In the event that COVID-19 hospitalizations exhaust the availability of FDA approved ventilators. This project documents the process of converting a low-cost CPAP (Continuous Positive Airway Pressure) blower into a rudimentary non-invasive pressure support ventilator that could help with breathing during respiratory distress. It’s an evolving project, but in it’s current form, it most aligned with the definition of a non-invasive pressure support BiPAP ventilator.
This same project can also be used to create a reasonable low-cost Powered Air Purifying Respirator (PAPR) with filter adapter and mask.

See the full post on Johnny Chung Lee’s project blog.

Check out the video after the break.

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App note: Termination recommendations for single-ended oscillator driving single or multiple Loads

Proper clock signal terminations app note from SiTime. Link here (PDF)

Clock signals with fast edges see traces on Printed Circuit Boards (PCB) as transmission lines rather than simple wire connections. If the length of PCB trace exceeds certain limit it requires matching of the trace impedance to one or both of the source and load impedances. Impedance mismatch causes signal reflections travelling back and forth the transmission line causing signal distortions such as ringing, overshoots, and undershoots.