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LTC4310-1/LTC4310-2

431012fa

Typical applicaTion

DescripTion

Hot-Swappable

C Isolators

The LTC

4310 provides bidirectional I

C communications

between two I

C buses whose grounds are isolated from

one another. Each LTC4310 encodes I

C bus logic states

into signals that are transmitted across an isolation barrier

to another LTC4310. The receiving LTC4310 decodes the

transmission and drives its l

C bus to the appropriate logic

state. The isolation barrier can be bridged by an inexpensive

Ethernet, or other transformer, to achieve communications

across voltage differences reaching thousands of volts, or

it can be bridged by capacitors for lower voltage isolation.

The LTC4310-1 is intended for use in 100kHz I

C systems.

The LTC4310-2 is intended for 400kHz I

C systems.

Rise time accelerators provide strong pull-up currents on

SCL and SDA rising edges to meet rise time speciﬁcations

for heavily loaded systems. Data and clock Hot Swap™

circuitry prevent data corruption when a card is inserted

into or removed from a live bus. When a bus is stuck low

for 37ms, the LTC4310 turns off its pull-down devices

and generates up to sixteen clocks and a STOP bit in an

attempt to free the bus. Driving EN low sets the LTC4310

in a very low current shutdown mode to conserve power.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

1500V Isolated I

C System

FeaTures

applicaTions

Bidirectional I

C Communication Between Two

Isolated Buses

Full Isolation with Inexpensive Ethernet

Transformers or Capacitors

Low Voltage Level Shifting

C Maximum Operating Frequency:

100kHz for LTC4310-1

400kHz for LTC4310-2

C Speciﬁcation Compliant V

, V

±5kV Human Body Model ESD Protection

Rise Time Accelerators

SDA, SCL Hot-Swapping

Very Low Shutdown Current

Stuck Bus Disconnect and Recovery

Thermal Shutdown

10-Lead MSOP and 3mm × 3mm DFN Packages

Isolated I

C, SMBus and PMBus Interfaces

Isolated Power Supplies

Positive-to-Negative Rail Communications

Power-over-Ethernet

LTC4310 Operating Through

20kV/µs Common Mode Transient

RXP

10/100Base-TX

ETHERNET TRANSFORMER

EPF8119S

RXN

TXP

SDA

SCL

TXN GND

READY

0.01µF0.01µF

ISOLATED

3.3V

3.3k 3.3k3.3k 3.3k

LTC4310-1

SDA2

SCL2

SDA1

SCL1

0.01µF

431012 TA01a

TXP

TXN

RXP

RXN

SDA

SCL

READY

GND

LTC4310-1

2µs/DIV

20kV/µs

500V/

DIV

2V/DIV

431012 TA01b

SDA

SCL

Summary of content (20 pages)

PAGE 1
LTC4310-1/LTC4310-2 Hot-Swappable I2C Isolators Features Description Bidirectional I2C Communication Between Two Isolated Buses n Full Isolation with Inexpensive Ethernet Transformers or Capacitors n Low Voltage Level Shifting n I2C Maximum Operating Frequency: 100kHz for LTC4310-1 400kHz for LTC4310-2 n I2C Specification Compliant V , V OL IL n ±5kV Human Body Model ESD Protection n Rise Time Accelerators n SDA, SCL Hot-Swapping n Very Low Shutdown Current n Stuck Bus Disconnect and Recovery n Ther
PAGE 2
LTC4310-1/LTC4310-2 Absolute Maximum Ratings (Notes 1, 4) Input Supply Voltage (VCC)........................... –0.3V to 6V Input and Bidirectional Pin Voltages SCL, SDA, EN, RXP, RXN........................... –0.3V to 6V Output Voltages READY...................................................... –0.3V to 6V TXP, TXN....................... –0.3V to VCC + 0.3V (6V Max) Maximum Sink Current (SDA, SCL, READY)...........30mA Operating Ambient Temperature Range LTC4310C.......................................
PAGE 3
LTC4310-1/LTC4310-2 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Supplies VCC Input Supply Range 5.5 V ICC Input Supply Current, LTC4310-1 Input Supply Current, LTC4310-2 EN = VCC = 5.5V, SDA = SCL = VSDA,SCL(OL) EN = VCC = 5.5V, SDA = SCL = VSDA,SCL(OL) l l 6.5 7 8 8.
PAGE 4
LTC4310-1/LTC4310-2 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted. SYMBOL PARAMETER tMAX(TX) tMAX(RX) CONDITIONS MIN TYP MAX UNITS Maximum Time Between TXP, TXN Transmit Events l 0.85 1.15 1.45 ms Maximum Time Between RXP, RXN Receive Events l 3.4 4.6 5.8 ms 1.5 5 mV 0.95 1.25 1.
PAGE 5
LTC4310-1/LTC4310-2 Typical Performance Characteristics SDA = 0V SCL = VCC 2.0 ICC (mA) 4.8 4.6 VCC = 3.3V 4.4 4.2 4.0 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 1.8 1.6 1.4 VCC = 3.3V 1.2 –50 125 25 50 75 100 125 431012 G02 SDA, SCL Rise Time Accelerator Pull-Up Current vs Temperature 11 5.0 10 VCC = 5V PULL-UP CURRENT (mA) CONTROLLED RISE RATE (V/µs) 0 TEMPERATURE (°C) 5.5 4.5 4.0 3.5 VCC = 3.3V VCC = 5V 9 8 7 VCC = 3.3V 6 3.0 2.
PAGE 6
LTC4310-1/LTC4310-2 Pin Functions EN (Pin 1): Device Enable Input. Pulling EN up to VCC sets the device in normal operation mode, allowing bus information to be sent and received across the barrier. Grounding EN disables communication across the barrier and debiases all internal circuitry, setting the device in a very low current shutdown mode. Connect to VCC if unused. SDA (Pin 2): Serial Bus Data Input/Output. This is the bidirectional data line for the two-wire bus.
PAGE 7
LTC4310-1/LTC4310-2 FUNCTIONAL Diagram + – LOGIC 0.45 • VCC 1.25V 8 0.45 • VCC VCC IBOOST 2 0.35 • VCC SDA 0.35V + – + – FALLING VIL RISING VIL – + 3 SCL + – + – – + 0.45 • VCC –+ RXP –+ RXN 9 10 0.5V 0.45 • VCC + – 0.35 • VCC + – 0.35V FALLING VIL STOP BIT AND BUS IDLE DETECTORS RXP RXN RISING VIL RX – + RISE RATE LIMITER dV/dtRISE 150µA 1 6 LOGIC 0.5V + – IBOOST TXN RX 150µA LOGIC 7 1.
PAGE 8
LTC4310-1/LTC4310-2 Operation (LTC4310 refers to both LTC4310-1 and LTC4310-2) The LTC4310 provides fully bidirectional communications between two I2C or SMBus buses whose grounds are isolated from one another. Clock stretching, clock synchronization, arbitration and data acknowledging all work seamlessly across the barrier, regardless of the locations of the master(s) and slave(s). bus rise rate to dV/dtRISE via the rise rate limiter circuitry. It also transmits a high to the other LTC4310.
PAGE 9
LTC4310-1/LTC4310-2 Operation 3.3V C1 0.01µF R1 7.5k R3 10k READY TXP R2 7.5k 1 10/100Base-TX ETHERNET TRANSFORMER LTC4310-1 VCC EN CBUS = 40pF SCL1 µP SDA TXN SCL RXP 15 3 14 6 READY RXP 16 11 IS0LATED 5V C4 0.01µF R4 10k R5 7.5k R6 7.5k LTC4310-1 C3 0.01µF VCC EN RXN SDA TXP SCL CBUS = 80pF SCL2 SLAVE#1 . . . SLAVE#4 SLAVE 7 GND RXN C2 0.01µF 8 9 TXN GND 431012 F01 EPF8119S Figure 1.
PAGE 10
LTC4310-1/LTC4310-2 Applications Information SDA, SCL Bus Pull-Up Resistor Value Selection Rise Time Accelerators When the SDA (or SCL) bus is rising between 0V and 0.35 • VCC, the LTC4310 controls the bus rise rate to (0.35 • VCC)/900ns for the LTC4310-1 and to (0.35 • VCC)/ 300ns for the LTC4310-2.
PAGE 11
LTC4310-1/LTC4310-2 Applications Information Bus Rising Edge Waveform Start-Up, Data and Clock Hot Swap Circuitry When all external pull-downs on SCL1 (Figure 1) turn off, the SCL1 rising waveform will resemble that shown in Figure 4. The LTC4310-1 senses that SCL1 is rising and transmits a message to the other LTC4310-1 to release SCL2 high. During the transmission, the first LTC4310-1 also drives SCL1 to 0.35V, so that when the transmission is complete, both buses will rise simultaneously from 0.
PAGE 12
LTC4310-1/LTC4310-2 Applications Information quiet if it has been idle high for at least 115µs, or if a STOP bit has occurred and both data and clock have remained high since the STOP bit. This functionality makes the LTC4310 ideal for hot-swapping cards into and out of a live I2C system. The threshold voltages for the STOP bit and bus idle comparators are 0.5 • VCC. Stuck Bus Disconnect and Recovery An internal timer runs whenever SDA, SCL or both are low.
PAGE 13
LTC4310-1/LTC4310-2 Applications Information Once a STOP bit or bus idle occurs on both the local and isolated buses, the LTC4310 reactivates its buffers and rise time accelerators. READY Digital Output The READY pin provides a digital output flag that pulls low to indicate that the LTC4310 is driving its SDA and SCL pins with the logic state information it is receiving on its RXP and RXN pins from the other LTC4310.
PAGE 14
LTC4310-1/LTC4310-2 Applications Information must be connected between ground and –5V to provide a return path for the transmitted current. Typical Applications Figure 8 shows the LTC4310-1 providing I2C communications between an I2C bus referenced to system ground and an I2C bus using –5V for its ground reference. Ceramic coupling capacitors, C1-C5, are used to bridge the isolation barrier.
PAGE 15
LTC4310-1/LTC4310-2 Applications Information BACKPLANE CONNECTOR CARD CONNECTOR I/O PERIPHERAL CARD BACKPLANE 5V C6 0.01µF R1 2k R2 2k R3 10k C1 VCC TXP LTC4310-1 SDA C = 400pF SCL BUS READY EN SDA SCL TXN READY EN RXP R7 100k R4 6.8k VCC C2 C3 C4 RXN GND 3.3V C7 0.01µF R5 6.8k R6 10k RXP LTC4310-1 RXN SDA SCL TXP READY EN CBUS = 50pF SDA2 SCL2 READY2 EN2 TXN C5 GND C1 TO C5 = 47pF, 100V 431012 F10 Figure 10.
PAGE 16
LTC4310-1/LTC4310-2 Applications Information Using the LTC4310-1 at Frequencies Above 100kHz Table 1 shows a recommended list of transformers for use with the LTC4310. 10/100BaseTX Ethernet transformers are inexpensive and work very well in this application for isolation voltages up to 1500V. For applications requiring 4000V isolation, the Würth Electronics Midcom 749014012 transformer is recommended.
PAGE 17
LTC4310-1/LTC4310-2 Package Description DD Package DD Package 10-Lead Plastic DFN (3mm × 3mm) 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev C) (Reference LTC DWG # 05-08-1699 Rev C) 0.70 ±0.05 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (4 SIDES) R = 0.125 TYP 6 0.40 ± 0.10 10 1.65 ± 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.
PAGE 18
LTC4310-1/LTC4310-2 Package Description MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661 Rev E) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.50 0.305 ± 0.038 (.0197) (.0120 ± .0015) BSC TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 10 9 8 7 6 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) DETAIL “A” 0.497 ± 0.076 (.0196 ± .003) REF 0° – 6° TYP GAUGE PLANE 1 2 3 4 5 0.53 ± 0.152 (.021 ± .
PAGE 19
LTC4310-1/LTC4310-2 Revision History REV DATE DESCRIPTION PAGE NUMBER A 4/11 Revised conditions for ISDD,SCL(OH) in the Electrical Characteristics section. 3 431012fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
PAGE 20
LTC4310-1/LTC4310-2 Typical Application Breaking Ground Loops Using Capacitors 3.3V C6 0.01µF R1 5.1k R2 5.1k R3 10k C1 VCC TXP LTC4310-1 CBUS = 100pF 5V C7 0.