App note: Hand soldering tutorial for fine pitch QFP devices

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No SMD tools removal and soldering of QFP packages tutorial from Silicon labs. Link here (PDF)

This document is intended to help designers create their initial prototype systems using Silicon Lab’s TQFP and LQFP devices where surface mount assembly equipment is not readily available. This application note assumes that the reader has at least basic hand soldering skills for through-hole soldering. The example presented will be the removal, cleanup and replacement of a TQFP with 48 leads and 0.5 mm lead pitch.

App note: Replacing traditional optocouplers with Si87xx digital isolators

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Digital isolator from Silicon Labs app note shows pin compatible plus high performance replacment of incumbent optoisolators, link here (PDF)

Opto-couplers are a decades-old technology widely used for signal isolation, typically providing safety isolation, signal level shifting, and ground loop mitigation. They are commonly used in a wide range of end applications, including data communication circuits, switch mode power systems, measurement and test systems, and isolated data acquisition systems. Optocouplers have several weaknesses, including parametric instability with temperature and device aging, significant internal parasitic couplings, long propagation delay times, narrow operating temperature ranges, and relatively low reliability.

Today’s advanced CMOS signal isolation products offer better timing performance, higher reliability, and lower power consumption compared to optocouplers and are capturing sockets traditionally held by optocouplers. However, converting to CMOS isolation devices has, most often, required circuit changes and PCB modifications that cost money and create design risks, until now.

App note: Introduction to gapped clocks and PLLs

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App note from Silicon Labs on the introduction of gapped clocks, how they can be used in network timing, and their impact upon phase locked loop (PLL) technology. Link here (PDF)

Gapped clocks are periodic clock signals of a single clock frequency that have clock pulses removed from their stream. Well-formed gapped clocks do not have reduced width pulses (known as runt pulses). Rather, each individual clock pulse is either completely present or completely absent.

App note: A simple alternative to analog isolation amplifiers

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A linear isolation amplifier from Silicon Labs app note. Link here (PDF)

Analog circuits sometimes require linear (analog) signal isolation for safety, signal level shifting, and/or ground loop elimination. Linear signal isolation is typically difficult to implement, costly, and often exhibits mediocre performance. While the design community thirsts for a flexible and inexpensive linear isolator solution, it is the analog isolation amplifier (ISOamp) that most often captures the socket.

App note: High-speed lithium-ion battery charger

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C8051F300 implementation of Li-Ion battery charger from Silicon Labs. Link here (PDF)

Driven by the need for untethered mobility and ease of use, many systems rely on rechargeable batteries as their primary power source. The battery charger is typically implemented using a fixedfunction IC to control the charging current/voltage profile.

The C8051F300 family provides a flexible alternative to fixed-function linear battery chargers. This note discusses how to use the C8051F300 device in Li-Ion battery charger applications. The Li-Ion charging algorithms can be easily adapted to other battery chemistries.

App note: Sub-1 V current sensing with the TS1001, A 0.8 V, 0.6 µA OP-AMP

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Another TS1001 op-amp application from Silicon Labs on sensing nano currents. Link here (PDF)

Current-sense amplifiers can monitor battery or solar cell currents, and are useful to estimate power capacity and remaining life. However, if the battery or solar source is a single cell, it’s difficult to find a low voltage solution that works below 1V and draws just microamps. A new class of nanopower analog ICs, namely the TS1001 0.8 V/0.6 µA op amp, makes a sub-1 V supply current sense amplifier possible. This discrete circuit operates from as low as 0.8 V and draws 860 nA at no load while providing a 0–500 mV output for measured currents of 0–100 mA, though the scale can be adjusted by changing the values of a few resistors. With its extremely low power, the circuit can simply remain “always on,” providing a continuously monitored, averaged indication of current which can subsequently be read periodically by a microcontroller, without causing too much current drain in the battery.

App note: A microwatt charge pump boosts 1 V to 1.8 V at 90% efficiency, providing “Always On” standby power for microcontrollers

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Interesting app note from Silicon Labs on high efficiency charge pump utilizing their nanopower TS1001 op amp. Link here (PDF)

Boosting the output voltage of common alkaline button-cells to at least 1.8 V needed by microcontrollers provides an “always on” standby power source sufficient for low-power oscillator interrupt/sleep state operation. Two ultralow power op amps are used in a charge pump configuration to double an input voltage, creating an output voltage of approximately 2x the input voltage. Output currents up to 100 µA are available at 90% efficiency; even load currents as low as 10 µA achieve 80% efficiency, beating commercially available charge pump ICs and inductorbased boost regulators.

App note: Buried capacitive sensors for tamper protection

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A short app note from Silicon Labs on burying pads to prevent snopping on keypads. Link here (PDF)

An individual’s financial matters are increasingly electronic in nature and decreasingly interpersonal. As financial institutions replace human interaction with electronic interfaces such as ATMs, the need to make electronic circuits tamper-proof becomes critical. A typical numeric keypad for financial transactions may contain up to hundred or more tamper prevention and detection features. Tamper detection circuits raise alarms and disable functionality, while tamper prevention features are designed to prevent intrusions and breaches. This application note addresses the elimination of copper pads on the accessible top surface of printed circuit boards (PCBs). Burying traces to internal layers of a PCB prohibits electrical contacts from snooping on copper elements within the PC board.

App note: Selecting a FET for use with the Si875x driver

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Another application note from Silicon Labs on determining the proper FET used on their Si875x driver based on its application. Link here (PDF)

The Si875x enables creating custom solid state relay (SSR) configurations. Supporting customer-selected external FETs, the Si875x combines robust isolation technology with a FET driver to form a complete, isolated, switch. Versatile inputs provide digital CMOS pin control (Si8751) or diode emulation (Si8752) to best suit the application, plus flexible outputs to support driving ac or dc load configurations. A floating secondary side dc voltage source is unnecessary as the product generates its own self contained gate drive output voltage, reducing cost, size, and complexity.