Low power Pushbutton ON/OFF Controller solution from Linear Technology

 

All of the flexible timing circuitry required to debounce the on/off pushbutton is integrated within the LTC2950. For applications that need additional time during power down, it also provides an adjustable timer.

The LTC2950 can handle a wide range of input power supply because it runs across a broad input voltage range of 2.7V to 26.4V. The LTC2950 is perfectly suited for battery-powered applications due to its extremely low quiescent current (6µA average). The part comes in two versions to support either positive or negative enable polarities. 

The turn-on time can be adjusted by placing an external capacitor on the ONT pin and the turn-off time on the OFFT pin. Open-drain interrupt output INT pin triggers after the pushbutton turn-off event is detected. LTC2950 interrupts the system (µP) by bringing the INT pin low. Once the system finishes its power-down and housekeeping tasks, it sets KILL low, which in turn releases the enable output. If at the end of the power-down timer (1024ms) KILL is still high, the enable output is released immediately.

Power ON/OFF Control with Push button (Ref: TI Application Report)

 

This simple push-button circuit allows a system to turn on with a short button press and turn off when the button is held down. Essentially, the circuit employs D-type flip-flops with asynchronous clear (U2), inverting (U3), and non-inverting (U1) Schmitt-Trigger buffers.

At the initial state, CLR is set to HIGH, U2's clear data input is HIGH and output Q (POWER ENABLE ) is at Q0, which is latched into the last state as Pin D transferred to the output Pin Q is waiting for CLK rising edge.

To set the output Q, POWER ENABLE HIGH, press the button, B1 which forces the PB signal to go LOW and the CLK signal to go HIGH as U3 inverts the logic and causing the CLK rising edge. At the same time, The CLR signal starts to go LOW, but because the R1 resistor and C1 capacitor create an RC delay, which causes the CLR signal to decay slowly.  With this short button press, the CLR signal does not go LOW, which allows for the output Q, POWER ENABLE signal to go HIGH with input D is tied to HIGH.  The POWER ENABLE signal remains HIGH even if the button is pressed again after the initial press.

The power-off process begins with holding down the button for an extended period of time. The button must be held for longer than the RC delay specified by R1 and C1. When the button is pressed long enough, the CLR signal goes LOW enough to meet the conditions for the asynchronous clear to occur, causing the POWER ENABLE signal to be low. 

Furthermore, D1 is present within the RC circuit, allowing the short time between turnoff and turn-on to bypass R1 and rapidly charge C1. 

The delay time can be adjusted using different values for C1 as below.

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 Sesnor 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