LTC4331 datasheet(22/26 Pages) AD

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LTC4331

Rev 0

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on both sides of the link. For transformer applications,

series resistors must be added to the A and B pins on

each side of the link. Use resistor values from 25 to

50. See Figure21.

Table6. Typical Resistor Values for Transformer Applications

VCC (V)

RB ()

RS ()

RT2 ()

3.3

200

110

5.0

270

110

For capacitive isolation, select RB such that 200 ≤ RB ≤

320 . C = 1F rated capacitors support all SPEED INDEX

values. Smaller value capacitors can be used if the appli-

cation only utilizes higher SPEED INDEX values. Ensure

the capacitors’ working voltages are much higher than the

expected ground offset voltage. See Figure25.

Multiple Local Extender Network

Multiple LTC4331 devices operating in slave device mode

can be connected to the same local SMBus network unlike

other extension solutions which typically restrict usage to

one extender device. This allows a star network of paral-

lel LTC4331 devices extending separate remote SMBus

networks.

LINK indicates when the remote system is ready. Optionally

RDY can also be monitored to determine when the local

side control interface is ready to access in the absence of

a link. See Figure23.

Multi-Tier Extender Network

The LTC4331 also supports chaining remote segments

into a single multi-tiered network. The maximum depth of

the I2C link network is limited only by the tTIMEOUT param-

eters of the I2C devices on the network. As the depth

increases, the clock-stretched low time of the devices

increases. No other I2C timing parameter is affected by

depth. See Figure24.

Auxiliary Protection for 5kV Surge, 5kV EFT, and 30kV

IEC ESD

An interface transceiver used in an industrial setting

may be exposed to extremely high levels of electrical

overstress due to phenomena such as lightning surge,

electrical fast transient (EFT) from switching high cur-

rent inductive loads, and electrostatic discharge (ESD)

from the discharge of electrically charged personnel or

equipment. The LTC4331 is designed for high robustness

against ESD, but the on-chip protection is not able to

absorb the energy associated with the 61000-4-5 surge

transients. Therefore, a properly designed external pro-

tection network is necessary to achieve a high level of

surge protection, and can also extend the ESD and EFT

performance of the LTC4331 to extremely high levels.

Refer to section Auxiliary Protection for IEC Surge,

EFT and ESD on page 17 of Analog Devices LTC2862A

Datasheet for a detailed description and diagram of the

external protection network.

The network provides the following protection:

• EC 61000-4-2 ESD Level 4: ±30kV contact, ±30kV air

(line to GND, direct discharge to bus pins with trans-

ceiver and protection circuit mounted on a ground

referenced test card per Figure 4 of the standard)

• IEC 61000-4-4 EFT Level 4: ±5kV (line to GND, 5kHz

repetition rate, 15ms burst duration, 60 second test

duration, discharge coupled to bus pins through

100pF capacitor per paragraph 7.3.2 of the standard)

• IEC 61000-4-5 Surge Level 4: ±5kV (line to GND,

line to line, 8/20µs waveform, each line coupled to

generator through 80 resistor per Figure 14 of the

standard)

Table7. Recommended Transformers

MANUFACTURER

PART NUMBER

ISOLATION VOLTAGE

CENTER TAP

CM CHOKE

SPEED INDEX SUPPORTED

Murata

78601/9JC

1kVRMS

ALL

Pulse

PE-68386NL

1500VRMS

3, 4, 5, 6, 7, 8

APPLICATIONS INFORMATION

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