LTC4307
Low Offset Hot Swappable
2-Wire Bus Buffer with Stuck
Bus Recovery
FEATURES
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DESCRIPTIO
Bidirectional Buffer with Stuck Bus Recovery
60mV Buffer Offset Independent of Load
30ms Stuck Bus Timeout
Compatible with Non-Compliant V
OL
I
2
C Devices
Prevents SDA and SCL Corruption During Live
Board Insertion and Removal from Backplane
±5kV Human Body Model ESD Protection
Isolates Input SDA and SCL Line from Output
Compatible with I
2
C
TM
, I
2
C Fast Mode and SMBus
READY Open-Drain Output
1V Precharge on All SDA and SCL Lines
High Impedance SDA, SCL Pins for V
CC
= 0V
Small 8-Lead (3mm
×
3mm) DFN and 8-Lead MSOP
Packages
The LTC
®
4307 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 LTC4307 provides
bidirectional buffering, keeping the backplane and card
capacitances isolated. Low offset and high V
OL
tolerance
allows multiple devices to be cascaded on the clock and
data busses. If SDAOUT or SCLOUT are low for 30ms, the
LTC4307 will automatically break the bus connection. At
this time the LTC4307 automatically generates up to 16
clock pulses on SCLOUT in an attempt to free the bus. A
connection will resume if the stuck bus is cleared.
During insertion, the SDA and SCL lines are pre-charged
to 1V to minimize bus disturbances. When driven high,
the ENABLE input allows the LTC4307 to connect after a
stop bit or bus idle. Driving ENABLE low breaks the con-
nection between SDAIN and SDAOUT, SCLIN and SCLOUT.
READY is an open-drain output which indicates that the
backplane and card sides are connected.
, 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 7032051, 6356140, 6650174
APPLICATIO S
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Live Board Insertion
Servers
Capacitance Buffer/Bus Extender
RAID Systems
ATCA
TYPICAL APPLICATIO
3.3V
0.01μF
10k
10k
V
CC
ENABLE
LTC4307
MICRO-
CONTROLLER
SCLIN
SCLOUT
2.7k
2.7k
V
CC
ENABLE
100k
10k
10k
0.01μF
LTC4307
SCLIN
SCLOUT
CARD_SCL
200mV/DIV
600
LOW
OFFSET
SDAOUT
SDAIN
SDAIN
SDAOUT
3.3V
10k
READY
GND
SDAIN
SDAOUT
3.3V
10k
READY
GND
CARD_SDA
4307 TA01a
CARD
BACKPLANE
CONNECTOR CONNECTOR
CARD
U
Rising Edge from Asserted Low
1000
800
400
200
0
0
100
200
300
400
100ns/DIV
500
600
4307 TA01b
U
U
4307f
1
LTC4307
ABSOLUTE
AXI U RATI GS
V
CC
to GND ................................................. – 0.3V to 6V
SDAIN, SCLIN, SDAOUT, SCLOUT,
READY, ENABLE .......................................... –0.3V to 6V
Maximum Sink Current (SDAIN, SCLIN, SDAOUT,
SCLOUT, READY) .............................................. 50mA
Operating Temperature Range
LTC4307C ................................................ 0°C to 70°C
LTC4307I .............................................– 40°C to 85°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
ENABLE 1
SCLOUT 2
SCLIN 3
GND 4
9
8
7
6
5
V
CC
SDAOUT
SDAIN
READY
ORDER PART
NUMBER
LTC4307CDD
LTC4307IDD
DD PART*
MARKING
LBTW
LBTW
TOP VIEW
ENABLE
SCLOUT
SCLIN
GND
1
2
3
4
8
7
6
5
V
CC
SDAOUT
SDAIN
READY
DD PACKAGE
8-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 9) CONNECTION TO GND IS OPTIONAL
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL
Power Supply
V
CC
I
CC
I
SD
V
PRE
t
IDLE
V
THR_ENABLE
I
ENABLE
t
PLH_EN
t
PHL_EN
t
PLH_READY
t
PHL_READY
V
OL_READY
I
OFF_READY
Positive Supply Voltage
Supply Current
Shutdown Supply Current
Precharge Voltage
Bus Idle Time
ENABLE Threshold
ENABLE Input Current
ENABLE Delay Off-On
ENABLE Delay On-Off
READY Delay Off-On
READY Delay On-Off
READY Output Low Voltage
READY Off Leakage Current
PARAMETER
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V, unless otherwise noted.
CONDITIONS
●
V
CC
= 5.5V, V
SCLOUT
= V
SDAOUT
= 0V (Note 6)
SDA, SCL Floating
V
CC
= 5.5V, ENABLE = GND, SDA, SCL = 5.5V
●
●
●
●
ENABLE from 0V to V
CC
V
CC
= 3.3V (Figure 1)
V
CC
= 3.3V (Note 3) (Figure 1)
V
CC
= 3.3V (Note 3) (Figure 1)
V
CC
= 3.3V (Note 3) (Figure 1)
I
PULLUP
= 3mA, V
CC
= 2.3V
V
CC
= READY = 5.5V
2
U
U
W
W W
U
W
(Notes 1, 7)
Storage Temperature Range
DFN....................................................– 65°C to 125°C
MSOP ................................................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP ............................................................... 300°C
ORDER PART
NUMBER
LTC4307CMS8
LTC4307IMS8
MS8 PART*
MARKING
LTBTV
LTBTV
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 200°C/W
MIN
2.3
TYP
MAX
5.5
UNITS
V
mA
μA
V
μs
V
μA
μs
ns
ns
ns
●
8
900
0.8
55
0.8
1
95
1.4
0.1
95
10
10
10
11
1200
1.2
175
2
±5
●
●
0.4
0.1
±5
V
μA
4307f
LTC4307
ELECTRICAL CHARACTERISTICS
SYMBOL
t
PHL
t
PLH
t
RISE
t
FALL
I
PULLUPAC
PARAMETER
SDA/SCL Propagation Delay High to Low
SDA/SCL Propagation Delay Low to High
SDA/SCL Transition Time Low to High
SDA/SCL Transition Time High to Low
Transient Boosted Pull-Up Current
Propagation Delay and Rise-Time Accelerators
C
LOAD
= 50pF, 2.7k to V
CC
on SDA, SCL,
V
CC
= 3.3V (Notes 2, 3) (Figure 1)
C
LOAD
= 50pF, 2.7k to V
CC
on SDA, SCL,
V
CC
= 3.3V (Notes 2, 3) (Figure 1)
C
LOAD
= 100pF, 10k to V
CC
on SDA, SCL, V
CC
= 3.3V (See Notes 3, 4) (Figure 1)
C
LOAD
= 100pF, 10k to V
CC
on SDA, SCL, V
CC
= 3.3V (See Notes 3, 4) (Figure 1)
Positive Transition on SDA, SCL, V
CC
= 3.3V
(Note 5)
2.7k to V
CC
on SDA, SCL, V
CC
= 3.3V,
Driven SDA/SCL = 0.2V
Rising Edge
(Note 3)
(Note 3)
SDA, SCL, Pins
SDA, SCL Pins, I
SINK
= 4mA,
Driven SDA/SCL = 0.2V, V
CC
= 2.7V
2.7k to V
CC
on SDA, SCL, V
CC
= 3.3V,
Driven SDA/SCL = 0.1V
V
ILMAX
t
TIMEOUT
f
I2C,MAX
t
BUF
t
HD,STA
t
SU,STA
t
SU,STO
t
HD,DATI
t
SU,DAT
Buffer Input Logic Low Voltage
Bus Stuck Low Timer
I
2
C Maximum Operating Frequency
Bus Free Time Between Stop and Start
Condition
Repeated Start Condition Set-Up Time
Stop Condition Set-Up Time
Data Hold Time Input
Data Set-Up Time
V
CC
= 3.3V
V
CC
= 3.3V, SDAOUT, SCLOUT = 0V
(Note 3)
(Note 3)
Bus Stuck Low Timeout
●
●
●
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V, unless otherwise noted.
CONDITIONS
MIN
TYP
70
10
30
30
5
8
300
300
MAX
UNITS
ns
ns
ns
ns
mA
Input-Output Connection
V
OS
V
THR
V
HYS
C
IN
I
LEAK
V
OL
Input-Output Offset Voltage
SDA, SCL Logic Input Threshold Voltage
SDA, SCL Logic Input Threshold Voltage
Hysteresis
Digital Input Capacitance SDAIN, SDAOUT,
SCLIN, SCLOUT
Input Leakage Current
Output Low Voltage
20
60
100
mV
V
mV
10
±5
0
120
160
0.4
205
1.2
25
400
30
600
1.3
100
0
0
0
100
35
pF
μA
V
mV
V
ms
kHz
μs
ns
ns
ns
ns
ns
0.45V
CC
0.55V
CC
0.65V
CC
50
Timing Characteristics
Hold Time After (Repeated) Start Condition (Note 3)
(Note 3)
(Note 3)
(Note 3)
(Note 3)
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
See “Propagation Delays” in the Operations section for a
discussion of t
PHL
and t
PLH
as a function of pull-up resistance and bus
capacitance.
Note 3:
Determined by design, not tested in production.
Note 4:
Measure points are 0.3 • V
CC
and 0.7 • V
CC
.
Note 5:
I
PULLUP
varies with temperature and V
CC
voltage as shown in the
Typical Performance Characteristics section.
Note 6:
I
CC
test performed with connection circuitry active.
Note 7:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise specified.
4307f
3
LTC4307
TIMING DIAGRAMS
ENABLE, CONNECT, READY Timing
t
PLH_READY
t
PLH_EN
ENABLE
t
PHL_READY
t
PHL_EN
CONNECT
READY
4307 TD01
Rising and Falling Propagation Delay and Rise and Fall Times for SDAIN, SDAOUT and SCLIN, SCLOUT
t
RISE
t
PLH
SDAIN/SCLIN
t
PHL
t
RISE
t
FALL
t
FALL
SDAOUT/SCLOUT
4307 TD02
Figure 1. Timing Diagrams
4307f
4
LTC4307
TYPICAL PERFOR A CE CHARACTERISTICS
I
CC
vs Temperature
8.3
V
CC
= 5.5V
8.0
16
7.7
7.4
I
CC
(mA)
7.1
6.8
V
CC
= 2.3V
6.5
6.2
5.9
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
4307 G01
I
PULLUPAC
(mA)
V
CC
= 3.3V
8
I
SD
(μA)
V
CC
= 3.3V
Input-Output High to Low
Propagation Delay vs Temperature
100
V
CC
= 5.5V
80
V
CC
= 2.3V
110
V
CC
= 3.3V
t
PHL
(ns)
t
PHL
(ns)
60
100
90
130
120
40
20
C
IN
= C
OUT
= 50pF
R
PULLUPIN
= R
PULLUPOUT
= 10k
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
4307 G04
Connection Circuitry V
OUT
– V
IN
(V
OS
)
85
34
75
V
OUT
– V
IN
(mV)
t
TIMEOUT
(ms)
65
55
45
1
2
3
4
6
7
R
PULLUP
(kΩ)
5
8
9
10
U W
T
A
= 25°C, V
CC
= 3.3V, unless otherwise indicated.
I
SD
vs Temperature
950
V
CC
= 5.5V
I
PULLUPAC
vs Temperature
20
V
CC
= 5.5V
900
12
850
800
V
CC
= 3.3V
4
750
V
CC
= 2.3V
0
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
4307 G02
700
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
4307 G02
Input-Output High to Low
Propagation Delay vs C
OUT
C
IN
= 50pF
R
PULLUPIN
= R
PULLUPOUT
= 10k
V
CC
= 5.5V
V
CC
= 3.3V
80
70
60
0
200
400
600
C
OUT
(pF)
800
1000
4307 G07
Bus Stuck Low Timeout vs V
CC
32
30
28
26
2
2.5
3
4
3.5
V
CC
(V)
4.5
5
5.5
4307 G06
4307 G05
4307f
5
