DC Ground to Earth Connection in PCB design

 In electronics, "earth ground" refers to a direct connection to the Earth, which is a safety connection to the physical earth, often via the chassis. This connection is primarily designed to provide a stable reference voltage rather than to carry current during normal operation.

Under typical conditions, it shouldn't conduct current when devices are drawing power. Instead, it only comes into play to safely dissipate unwanted currents, such as electromagnetic interference (EMI) or electrostatic discharge (ESD) events. Essentially, think of the earth's ground as a safety net that helps manage electrical noise and protect sensitive equipment.

The standard method for connecting DC ground to Earth involves the use of a resistor-capacitor (RC) network, as illustrated below. A capacitor with sufficient capacitance is employed to effectively couple the two points for the attenuation of high-frequency noise. In parallel with this capacitor, a high-value resistor, typically around 1 megohm, is utilized to ensure that the DC ground does not float, thereby maintaining a stable reference potential. This configuration allows for effective noise suppression while preserving the integrity of the DC ground.

What is Encroached Vias?

The encroached via concept is one that uses soldermask on the bottom via pad without filling the via’s plated-through hole. Encroachment-type vias have the top-side soldermask open and the bottom-side soldermask opening adjusted, so that it is slightly larger than the via hole size (typically +0.06 mm).

If the mask is opened all the way around an EPAD via (OPEN via), then solder can flow out from under the QFN EPAD onto the bottom-side via pad as a big drop. This drop often drips off during the motion of the unit through the reflow oven, pulling solder from the EPAD joint. This solder “scavenging” can render the EPAD connection unreliable and/or cause the device to tilt, resulting in unreliable pin connections.

Encroached via can be created in Altium Design by defining Solder Mask Expansion setting with negative values as below. For best result, via with and Finished hole size, FHS of 0.25 to 0.3mm and bottom-side soldermask opening of 0.055 mm to 0.075mm larger than the FHS.

Ultra-Precise, Current-Sense Amplifier

 

The INAx290 is an ultra-precise, current-sense amplifier that can measure voltage drops across shunt resistors over a wide common-mode range from 2.7 V to 120 V. Depending on your application, different gains can be selected.

 – A1 devices: 20 V/V

 – A2 devices: 50 V/V 

– A3 devices: 100 V/V 

– A4 devices: 200 V/V 

– A5 devices: 500 V/V 

Using Simple Hall-effect Sensor as a position Sensor

 

The AH1806 is a high-sensitivity, micro-power Omnipolar Hall effect switch IC, designed for portable and battery powered consumer to home appliance and industrial applications such as smart-meter magnetic tamper detection

Schmitt trigger for cleaning up noisy or slow-rising digital signals

 

A Schmitt trigger is a circuit that converts an analog input signal into a digital output signal with hysteresis. It's characterised by two different threshold voltages, one for the rising input signal and another for the falling input signal, which provides noise immunity and prevents oscillations.