LTC4309 Datasheet, PDF (1/16 Pages) Linear Technology – Level Shifting Low Offset Hot Swappable 2-Wire Bus Buffer with Stuck Bus Recovery

FEATURES
n _{Bidirectional Buffer Increases Fanout}
n _{60mV Buffer Offset Independent of Load}
n _{Optional Disconnect when Bus is Stuck Low}
n _{Prevents SDA and SCL Corruption During Live}
Board Insertion and Removal from Backplane
n _{Level Shift 2.5V, 3.3V and 5V Busses}
n _{Compatible with Non-Compliant VOL I}²_{C Devices}
n _{±6kV Human Body Model ESD Ruggedness}
n _{Isolates Input SDA and SCL Lines from Output}
n _{Compatible with I}²_{C™, I}²_{C Fast-Mode and SMBus}
n _{READY Open Drain Output}
n _{FAULT Open Drain Output}
n _{1V Precharge on All SDA and SCL Lines}
n _{Optional Rise Time Accelerators}
n _{High Impedance SDA, SCL Pins for VCC = 0}
n _{Available in Small 12-Pin DFN (4mm x 3mm) and}
16-Lead SSOP Packages
APPLICATIONS
n _{Live Board Insertion}
n _Servers
n _{Capacitance Buffer/Bus Extender}
n _{RAID Systems}
n _ATCA
LTC4309
Level Shifting Low Offset Hot
Swappable 2-Wire Bus Buffer
with Stuck Bus Recovery
DESCRIPTION
The LTC^®4309 hot swappable 2-wire bus buffer allows
I/O card insertion into a live backplane without corrup-
tion of the data and clock busses. The LTC4309 provides
bidirectional buffering, keeping the backplane and card
capacitances isolated. Low offset and high V_OL tolerance
allows cascading of multiple devices on the clock and data
busses. If SDAOUT or SCLOUT are low for 30ms, FAULT
will pull low indicating a stuck bus low condition. If DISCEN
is tied high, the LTC4309 will automatically break the bus
connection and generate up to 16 clock pulses and a stop
bit in an attempt to free the bus. A connection will resume
if the stuck bus is cleared. If DISCEN is connected to GND,
the busses will remain connected with no clock or stop
bit generation. ACC input enables rise-time accelerators
for high capacitively loaded busses.
During insertion, the SDA and SCL lines are precharged to
1V to minimize bus disturbances. When driven high, the
ENABLE input allows the LTC4309 to connect after a stop
bit or bus idle. Driving ENABLE low breaks the connection
between SDAIN and SDAOUT, SCLIN and SCLOUT. READY
is an open drain output which indicates that the backplane
and card sides are connected.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
6356140, 6650174, 7032051.
TYPICAL APPLICATION
3.3V
10k 10k
EN
0.01μF
V_CC2 ^VCC
ENABLE ACC
LTC4309
5V
2.7k 2.7k
SCL1
SCLIN SCLOUT
SDA1
SDAIN SDAOUT
3.3V
3.3V
DISCEN
10k
FAULT
10k
READY
FAULT
GND
FAULT
V_CC2 ^VCC
ENABLE
ACC
100k
LTC4309
SCLIN SCLOUT
0.01μF
10k 10k
SCL2
SDAIN SDAOUT
5V
5V
DISCEN
10k
10k
READY
FAULT
GND
SDA2
Rising Edge from Asserted Low
1000
800
600
LOW
OFFSET
400
200
SDAOUT
SDAIN
0
0 100 200 300 400 500 600
100ns/DIV
4309 G01
BACKPLANE CARD
CONNECTOR CONNECTOR
4309 TA01
4309fa
1