App note: A simple alternative to analog isolation amplifiers


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


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


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


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


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


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.

App note: Driving MOSFET and IGBT switches using the Si828x


App note from Silicon Labs on their MOSFET and IGBT driver Si828x and how to determining its external components to achieve optimized performance. Link here (PDF)

The Si828x products integrate isolation, gate drivers, fault detection protection, and operational indicators into one package to drive IGBTs and MOSFETs as well as other gated power switch devices. Most Si828x products (except the Si8286) have three separate output pins to provide independent rise and fall time settings and low impedance clamping to suppress Miller voltage spikes. This application note provides guidance for selecting the external components necessary for operation of the driver. Although this application note discusses the topic of driving IGBTs and MOSFETs, users can apply the same concepts for driving other gate-based power switches, such as SiC (Silicon Carbide).

App note: Power supply rejection for low-jitter clocks


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: Safety considerations and layout recommendations for digital isolators


Application note from Silicon Labs about end user safety against high voltage shock that are designed together with digital isolators. Link here (PDF)

This application note details the creepage and clearance requirements of an isolator type component, such as a digital isolator, used to provide protection from electric shock. It also details layout recommendations to enhance a design’s robustness and ensure compliance with end safety standards.