LTC4307 Просмотр технического описания (PDF) - Linear Technology

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LTC4307

Low Offset Hot Swappable 2-Wire Bus Buffer with Stuck Bus Recovery

Linear Technology 

LTC4307

APPLICATIONS INFORMATION

Live Insertion and Capacitance Buffering Application

Figures 4 and 5 illustrate applications of the LTC4307 that

take advantage of the LTC4307’s Hot SwapTM , capacitance

buffering and precharge features. If the I/O cards were

plugged directly into the backplane without the LTC4307

buffer, all of the backplane and card capacitances would

add directly together, making rise-time and fall-time re-

quirements difficult to meet. Placing an LTC4307 on the

edge of each card, however, isolates the card capacitance

from the backplane. For a given I/O card, the LTC4307

drives the capacitance of everything on the card and the

backplane must drive only the capacitance of the LTC4307,

which is less than 10pF.

Hot Swap is a trademark of Linear Technology Corporation.

In most applications the LTC4307 will be used with a

staggered connector where VCC and GND will be long

pins. SDA and SCL are medium length pins to ensure that

the VCC and GND pins make contact first. This will allow

the precharge circuitry to be activated on SDA and SCL

before they make contact. ENABLE is a short pin that is

pulled down when not connected. This is to ensure that

the connection between the backplane and the card’s data

and clock busses is not is not enabled until the transients

associated with live insertion have settled.

Figure 4 shows the LTC4307 in an application with a stag-

gered connector. The LTC4307 receives its VCC voltage

from one of the long “early power” pins. Establishing

early power VCC ensures that the 1V precharge voltage is

present at SDAIN and SCLIN before they make contact.

BACKPLANE

VCC

SDA

SCL

ENA1

READY

R1 R2 R3

10k 10k 10k

BACKPLANE

CARD

CONNECTOR CONNECTORS

I/O PERIPHERAL CARD 1

SDAIN

C1

0.01μF

R5 R6

10k 10k

VCC

SDAOUT

CARD1_SDA

SCLIN LTC4307 SCLOUT

ENABLE

CARD1_SCL

READY

R4

GND

10k

ENAn

•

•

•

I/O PERIPHERAL CARD N

SDAIN

C2

0.01μF

R8 R9

10k 10k

VCC

SDAOUT

CARDn_SDA

SCLIN LTC4307 SCLOUT

ENABLE

CARDn_SCL

READY

R7

GND

10k

4307 F04

Figure 4. The LTC4307 in an Application with a Staggered Connector

4307f

10

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