LTM2886 datasheet(17/38 Pages) AD

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LTM2886

Rev C

For more information www.analog.com/LTM2886

APPLICATIONS INFORMATION

Overview

The LTM2886 digital µModule isolator provides a

galvanically-isolated robust logic interface, powered by

an integrated, regulated DC/DC converter, complete with

decoupling capacitors. The LTM2886 is ideal for use in

networks where grounds can take on different voltages.

Isolation in the LTM2886 blocks high voltage differences,

eliminates ground loops and is extremely tolerant of com-

mon mode transients between ground planes. Error-free

operation is maintained through common mode events

greater than 30kV/μs providing excellent noise isolation.

Isolator µModule Technology

The LTM2886 utilizes isolator µModule technology to

translate signals and power across an isolation barrier.

Signals on either side of the barrier are encoded into

pulses and translated across the isolation boundary using

coreless transformers formed in the µModule substrate.

This system, complete with data refresh, error checking,

safe shutdown on fail, and extremely high common mode

immunity,providesarobustsolutionforbidirectionalsignal

isolation. The µModule technology provides the means to

combinetheisolatedsignalingwithmultipleregulatorsand

a powerful isolated DC/DC converter in one small package.

DC/DC Converter

The LTM2886 contains a fully integrated DC/DC converter,

including the transformer, so that no external components

are necessary. The logic side contains a full-bridge driver,

running at 1.6MHz, and is AC-coupled to a single trans-

former primary. A series DC blocking capacitor prevents

transformer saturation due to driver duty cycle imbal-

ance. The transformer scales the primary voltage, and is

rectified by a voltage quadrupler. This topology eliminates

transformer saturation caused by secondary imbalances.

The quadrupler is grounded in the middle producing sym-

metrical positive and negative voltage rails. The positive

rail is post regulated with two low dropout regulators

(LDOs) producing VCC2 and V+, the negative rail also has

an LDO producing V–.

Each voltage rail is capable of producing 100mA of output

current,totaloutputpowercapabilityisapproximately 1W.

Allvoltagerailsarebypassedwith2.2µFceramiccapacitors.

VL Logic Supply

AseparatelogicsupplypinVLallowstheLTM2886tointer-

facewithanylogicsignalfrom1.62Vto5.5V(LTM2886-S)

or 3V to 5.5V (LTM2886-I) as shown in Figure 4. Simply

connect the desired logic supply to VL.

There is no interdependency between VCC and VL; they

may simultaneously operate at any voltage within their

specified operating ranges and sequence in any order. VL

is bypassed internally by a 1µF capacitor.

Hot-Plugging Safely

Caution must be exercised in applications where power is

plugged into the LTM2886’s power supplies, VCC or VL,

due to the integrated ceramic decoupling capacitors. The

parasitic cable inductance along with the high Q char-

acteristics of ceramic capacitors can cause substantial

ringing which could exceed the maximum voltage ratings

and damage the LTM2886. Refer to Linear Technology Ap-

plication Note 88, entitled Ceramic Input Capacitors Can

Cause Overvoltage Transients for a detailed discussion

and mitigation of this phenomenon.

2886 F04

DI1

LTM2886-I

ANY VOLTAGE FROM

1.62V TO 5.5V LTM2886-S

3V TO 5.5V LTM2886-I

3V TO 3.6V LTM2886-3

4.5V TO 5.5V LTM2886-5

EXTERNAL

DEVICE

VCC

GND

GND2

SDA

SDA2

SCL

SCL2

V–

AVCC2

V+

VCC2

DO2

DO1

Figure 4. VCC and VL Are Independent

LTM2886 Datasheet(PDF) 17 Page - Analog Devices

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