LTM2883 View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTM2883

SPI/Digital or I2C µModule Isolator with Adjustable ±12.5V and 5V Regulated Power

Linear Technology 

LTM2883

Applications Information

Overview

The LTM2883 digital µModule isolator provides a gal-

vanically-isolated robust logic interface, powered by an

integrated, regulated DC/DC converter, complete with

decoupling capacitors. The LTM2883 is ideal for use in

networks where grounds can take on different voltages.

Isolation in the LTM2883 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.

Performance of the –12.5V supply is enhanced by loading

the 12.5V supply. A load current of 1.5mA is sufficient to

improve static and dynamic load regulation characteristics

of the –12.5V output. The increased load allows the boost

regulator to operate continuously and in turn improves the

regulation of the inverting charge pump.

The internal power solution is sufficient to provide a mini-

mum of 20mA of current from VCC2 and V+, and 15mA

from V–. VCC and VCC2 are each bypassed with 2.2µF

ceramic capacitors, and V+ and V– are bypassed with 1µF

ceramic capacitors.

Isolator µModule Technology

The LTM2883 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, provides a robust solution for bidirectional

signal isolation. The µModule technology provides the

means to combine the isolated signaling with multiple

regulators and a powerful isolated DC/DC converter in

one small package.

DC/DC Converter

The LTM2883 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 2MHz, and is AC-coupled to a single trans-

former primary. A series DC blocking capacitor prevents

transformer saturation due to driver duty cycle imbalance.

The transformer scales the primary voltage, and is recti-

fied by a full-wave voltage doubler. This topology allows

for a single diode drop, as in a center tapped full-wave

bridge, and eliminates transformer saturation caused by

secondary imbalances.

The DC/DC converter is connected to a low dropout regula-

tor (LDO) to provide a regulated 5V output.

An integrated boost converter generates a regulated 14V

supply and a charge pumped –14V supply. These rails are

regulated to ±12.5V respectively by low dropout regulators.

16

VL Logic Supply

A separate logic supply pin VL allows the LTM2883 to in-

terface with any logic signal from 1.62V to 5.5V 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 2.2µF capacitor.

3V TO 3.6V LTM2883-3

4.5V TO 5.5V LTM2883-5

LTM2883-S

VCC

ANY VOLTAGE FROM

1.62V TO 5.5V

VL

VCC2

AVCC2

V+

AV+

V–

AV–

EXTERNAL

DEVICE

ON

SDOE

CS

SDI

SCK

DO2

SDO

DO1

CS2

SDI2

SCK2

I2

SDO2

I1

GND

GND2

2883 F04

Figure 4. VCC and VL Are Independent

Hot-Plugging Safely

Caution must be exercised in applications where power

is plugged into the LTM2883’s power supplies, VCC or VL,

due to the integrated ceramic decoupling capacitors. The

2883f

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