Document
FEATURES
n Bidirectional Buffer for SDA and SCL Lines Increases Fanout
n Prevents SDA and SCL Corruption During Live Board Insertion and Removal from Backplane
n Isolates Input SDA and SCL Lines from Output n Compatible with I2C, I2C Fast Mode and SMBus
Standards (Up to 400kHz Operation) n Low ICC Chip Disable: <1μA (LTC4300A-1) n READY Open Drain Output (LTC4300A-1) n 1V Precharge on all SDA and SCL Lines n Supports Clock Stretching, Arbitration and
Synchronization n 5V to 3.3V Level Translation (LTC4300A-2) n High Impedance SDA, SCL Pins for VCC = 0V n Small MSOP 8-Pin Package
APPLICATIONS
n Hot Board Insertion n Servers n Capacitance Buffer/Bus Extender n Desktop Computer
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and Hot Swap and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. Patents, including 6650174.
LTC4300A-1/LTC4300A-2
Hot Swappable 2-Wire Bus Buffers
DESCRIPTION
The LTC®4300A series hot swappable 2-wire bus buffers allow I/O card insertion into a live backplane without corruption of the data and clock busses. When the connection is made, the LTC4300A-1/LTC4300A-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.
The LTC4300A-1 incorporates a CMOS threshold digital ENABLE input pin, which forces the part into a low current mode when driven to ground and sets normal operation when driven to VCC. It also includes an open drain READY output pin, which indicates that the backplane and card sides are connected together. The LTC4300A-2 replaces the ENABLE pin with a dedicated supply voltage pin, VCC2, for the card side, providing level shifting between 3.3V and 5V systems. Both the backplane and card may be powered with supply voltages ranging from 2.7V to 5.5V, with no constraints on which supply voltage is higher. The LTC4300A-2 also replaces the READY pin with a digital CMOS input pin, ACC, which enables and disables the rise-time accelerator currents.
The LTC4300A is available in a small 8-pin MSOP package.
TYPICAL APPLICATION
VCC 3.3V
R1 R2 10k 10k
C1 0.01μF
SCLIN
R3 R4 10k 10k
SCLOUT
Input–Output Connection tPLH
OUTPUT SIDE 50pF
INPUT SIDE 150pF
SDAIN
LTC4300A-1 ENABLE GND READY
4300a12 TA01
SDAOUT
4300a12 TA02
4300a12fa
1
LTC4300A-1/LTC4300A-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VCC to GND .................................................... –0.3 to 7V VCC2 to GND (LTC4300A-2)............................ –0.3 to 7V SDAIN, SCLIN, SDAOUT, SCLOUT.................. –0.3 to 7V READY, ENABLE (LTC4300A-1)...................... –0.3 to 7V ACC (LTC4300A-2)......................................... –0.3 to 7V Operating Temperature Range
LTC4300A-1C/LTC4300A-2C.................... 0°C to 70°C LTC4300A-1I/LTC4300A-2I ..................–40°C to 85°C Storage Temperature Range .................. –65°C to 125°C Lead Temperature (Soldering, 10 sec)................... 300°C
PIN CONFIGURATION
TOP VIEW
ENABLE/VCC2* 1 SCLOUT 2
SCLIN 3
GND 4
8 VCC 7 SDAOUT
6 SDAIN
5 READY/ACC*
MS8 PACKAGE 8-LEAD PLASTIC MSOP
*LTC4300A-2
TJMAX = 125°C, θJA = 200°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
LTC4300A-1CMS8#PBF LTC4300A-1CMS8#TRPBF LTABF
8-Lead Plastic MSOP
LTC4300A-1IMS8#PBF LTC4300A-1IMS8#TRPBF LTABG
8-Lead Plastic MSOP
LTC4300A-2CMS8#PBF LTC4300A-2CMS8#TRPBF LTACF
8-Lead Plastic MSOP
LTC4300A-2IMS8#PBF LTC4300A-2IMS8#TRPBF LTACG
8-Lead Plastic MSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
TEMPERATURE RANGE 0°C to 70°C –40°C to 85°C 0°C to 70°C –40°C to 85°C
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.7V to 5.5V, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX UNITS
Power Supply
VCC
Positive Supply Voltage
l
2.7
5.5
V
ICC
Supply Current
VCC = 5.5V, VSDAIN = VSCLIN = 0V, LTC4300A-1 l
5.1
7
mA
ISD
Supply Current in Shutdown Mode VENABLE = 0V, LTC4300A-1
0.1
μA
VCC2
Card Side Supply Voltage
LTC4300A-2
l
2.7
5.5
V
IVCC1
VCC Supply Current
VSDAIN = VSCLIN = 0V, VCC1 = VCC2 = 5.5V, LTC4300A-2
3
4.1
mA
IVCC2
VCC2 Supply Current
VSDAOUT = VSCLOUT = 0V, VCC1 = VCC2 = 5.5V, LTC4300A-2
2.1
2.9
mA
Start-Up Circuitry
VPRE
Precharge Voltage
tIDLE
Bus Idle Time
VEN
.