LTC4300-1/LTC4300-2
Hot Swappable
2-Wire Bus Buffers
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DESCRIPTIO
FEATURES
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Bidirectional Buffer for SDA and SCL Lines
The LTC®4300 series hot swappable 2-wire bus buffers
allow I/O card insertion into a live backplane without cor-
ruptionofthedataandclockbusses. Whentheconnection
is made, the LTC4300-1/LTC4300-2 provide bidirectional
buffering, keeping the backplane and card capacitances
isolated. Rise-time accelerator circuitry* allows the use of
weaker DC pull-up currents while still meeting rise-time
requirements. During insertion, the SDA and SCL lines are
precharged to 1V to minimize bus disturbances.
Increases Fanout
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Prevents SDA and SCL Corruption During Live
Board Insertion and Removal from Backplane
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Isolates Input SDA and SCL Lines from Output
Compatible with I2CTM, I2C Fast Mode and SMBus
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Standards (Up to 400kHz Operation)
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Small MSOP 8-Pin Package
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Low ICC Chip Disable: <1µA (LTC4300-1)
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READY Open Drain Output (LTC4300-1)
The LTC4300-1 incorporates a CMOS threshold digital
ENABLE input pin, which forces the part into a low current
modewhendriventogroundandsetsnormaloperationwhen
driven to VCC. It also includes an open drain READY output
pin, which indicates that the backplane and card sides are
connected together. The LTC4300-2 replaces the ENABLE
pin with a dedicated supply voltage pin, VCC2, for the card
side, providinglevelshiftingbetween3.3Vand5Vsystems.
Both the backplane and card may be powered with supply
voltages ranging from 2.7V to 5.5V, with no contraints on
whichsupplyvoltageishigher.TheLTC4300-2alsoreplaces
the READY pin with a digital CMOS input pin, ACC, which
enables and disables the rise-time accelerator currents.
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1V Precharge on all SDA and SCL Lines
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Supports Clock Stretching, Arbitration and
Synchronization
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5V to 3.3V Level Translation (LTC4300-2)
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High Impedance SDA, SCL Pins for VCC = 0V
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APPLICATIO S
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Hot Board Insertion
Servers
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Capacitance Buffer/Bus Extender
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Desktop Computer
, LTC and LT are registered trademarks of Linear Technology Corporation.
I2C is a trademark of Philips Electronics N. V.
*U.S. Patent No. 6,650,174
The LTC4300 is available in a small 8-pin MSOP package.
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TYPICAL APPLICATIO
Input–Output Connection tPLH
V
3.3V
CC
C1
0.01µF
R1
R2
R3
R4
8
24k
24k
24k
24k
3
6
2
SCLIN
SCLOUT
C4*
OUTPUT
SIDE
50pF
INPUT
SIDE
150pF
C2*
7
5
SDAIN
SDAOUT
C5*
C3*
LTC4300-1
1
ENABLE
READY
GND
4
*CAPACITORS NOT REQUIRED
IF BUS IS SUFFICIENTLY LOADED
4300-1/2 TA01
sn430012 430012fs
1