Analog Devices’ LTM2887 – If a Digital Bus Needs Galvanic Isolation

In theory, digital buses are intended to connect things to one another. Sadly, one sometimes wants but a logical connection – in many cases, galvanic isolation helps out. Should you ever feel like isolating very fast buses, definitely give the LTM2887 a chance.

From a technical point of view, Linear Technologies attempt at entering the galvanic isolator IC fray is relatively simple. Figure one tells us that the LTM2887 has a total of three transcievers for one direction, which can be used to route arbitrary signals across the isolation border at the middle. It provides for an isolation voltage of up to 2500Vdc.

Adding galvanic isolation to an SPI bus could not be easier

Linear Technologies experience in the degree of sensor design shows itself in the adding of a two-output power supply which can provide small amounts of energy (100mA at 5V per channel) across the isolation border. This measure is useful in that it lets you power small bits of electronics without needing an additional transformer wiring or a similar galvanic isolator. One of the two output channels can furthermore be regulated, removing the need for an additional voltage regulator inside of the “isolation island”.

I2C’s open drain architecture has always had the dubious distinction of making a galvanic isolator designers life interesting. The LTM2887 works around this problem via the design trick shown in figure two – one of the transcievers is provided with a feedback path, thereby allowing the two sides of the circuit to interact with one another. This pair of pins can then be used to route the SDA pin – as clock generation is the master’s sole responsibility in most I2C buses, SCL can simply run from master to slave.

From a space point of view, deploying the (somewhat pricey) part is not too difficult – the 15mm × 11.25mm × 3.42mm BGA housing should fit even the tightest of PCBs. Sadly, hand-soldering the LTM2887 is not really possible due to the BGA housing.

Recent Articles
Go with OPTO! Watch this free Webinar about Broadcom’s Isolation Products in Electrical Chargers
Broadcom Webinar: Isolation Products for High Speed Inverters/Converters in Electrical Chargers DC fast chargers shorten charging time from hours to mere minutes. Such high-powered equipment requires... Read Article
Efficient DC Power Distribution in Data Centres
The consistent use of direct current in a data centre makes sense. Losses can be massively reduced. On the power side, the IEC has defined the... Read Article
AC/DC Power Supplies 15 – 450 W from Traco Power
Engineered to stay cool High performance, ultra-compact AC/DC power supplies with minimal heat dissipation. Available in four different mechanical packages, these high-efficiency power supplies utilize industrial grade... Read Article
Bluetooth Mesh Solutions for IoT Based Designs
Cypress Best-in-class Bluetooth Mesh Cypress’ Bluetooth Mesh Eval Kit is a multi-node platform featuring a certified Bluetooth 5 module, sensors, and multiple mesh example projects with... Read Article
Check out the newly expanded TE Connectivity Online Store!
Buy Now with PayPal The TE Store now accepts PayPal! This feature gives you a wider range of payment options and the ability to pay for... Read Article
Compact, low power microphone with IC Interface.
This high performance MEMS audio sensor from STMicroelectronics is desigined with an IC Interface and capacitive sensing element. Ideal for a number of applications such as... Read Article