Tag Archives: app notes

App note: Interfacing to analog switches: Driving the control input of an analog switch with 1.8 V or lower − Is it safe?

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ON Semiconductor’s analog switches let you drive with an input control voltage lower than Vcc. Link here (PDF)

Analog switches are everywhere today. Due to their small size and low current consumption, they are popular in portable devices where they are effective in a variety of subsystems including audio and data communications, port connections, and even test. They can be used to facilitate signal routing, allow multiple data types to share an interface connector, or permit temporary access to internal processors during manufacturing. Analog switches are often used to give portable system designers a convenient method of increasing their features or accessibility without duplicating any circuitry. Understanding the key specifications and tradeoffs can make the difference between a temporary fix and a truly optimized solution.

App note: Consideration of self-pollution reduction for electronic systems

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App note from ON Semiconductors discussing how locally generated EMI affects its own system and how to prevent it. Link here (PDF)

This application note will address the problem of Electro Magnetic Interference (EMI) self pollution in which one part of an electrical systems such as cell phones and consumer electrical products emit radiation that interferes with the operation of other parts of the system.

App note: Active capacitor discharge circuit considerations for FPGAs

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Power down sequencing and discharging on FPGAs app note from Diodes Incorporated. Link here (PDF)

FPGA’s need the different power rails to be powered up and down in a defined sequence. For power down, each sequenced rail needs to be fully off before the next rail is turned off. With large high speed and high functionality FPGA’s, the power rails have large bulk capacitors to be discharged quickly and safely within a total time of 100ms and up to 10 rails each to be discharged within 10ms.

This application note shows a methodology and considerations for safe open ended shutdown to be controlled by a power sequencing circuit and using correctly chosen MOSFET to discharge the capacitor bank.

App note: Power supply rejection for low-jitter clocks

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Method of rejecting noises from power supply, an app note from Silicon Labs. Link here (PDF)

Hardware designers are routinely challenged to increase functional density while shrinking the overall PCB footprint of each new design. One significant challenge is minimizing clock jitter through careful board design while meeting the design’s functional and space requirements. Since jitter is a measure of signal fidelity, it requires an understanding of diverse analog concepts, such as transmission line theory, interference, bandwidth, and noise, in order to manage their impact on performance. Among these, density impacts sensitivity to external noise and interference the most. Since noise and interference are everywhere and since multiple components share a common power supply, the power supply is a direct path for noise and interference to impact the jitter performance of each device. Therefore, achieving the lowest clocking jitter requires careful management of the power supply. Sensitivity to power supply is commonly referred to as power supply ripple rejection or power supply rejection ratio (PSRR). For jitter, ripple rejection is more appropriate.

App note: Single-pushbutton ON/OFF power control

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With the help of an MAX6816 debouncer from Maxim Integrated to form a single push button power switch. Link here (PDF)

This application note presents a single-pushbutton power-control circuit. The design consists of an ON/OFF control circuit comprised of a push button, debouncer, and flip-flop. This circuit toggles the power output voltage by controlling an LDO.