LTC1694
2
SMBus/I C Accelerator*
FEATURES
DESCRIPTIO
n
Improves SMBus Rise Time Transition
The LT C 1694 is a dual SMBus active pull-up designed to
n
Ensures Data Integrity with Multiple Devices
enhance data transmission speed and reliability under all
on the SMBus
specified SMBus loading conditions. The LTC1694 is also
TM
n 2
Improves Low State Noise Margin
compatible with the Philips I C Bus.
n
Auto Detect Low Power Standby Mode
The LTC1694 allows multiple device connections or a
n
Wide Supply Voltage Range: 2.7V to 6V
longer, more capacitive interconnect, without compro-
TM
n
Low Profile (1mm) SOT-23 (ThinSOT ) Package
mising slew rates or bus performance, by using two
U
bilevel hysteretic current source pull-ups.
APPLICATIO S
During positive bus transitions, the LTC1694 current
n
Notebook and Palmtop Computers sources provide 2.2mA to quickly slew the SMBus line.
n
Portable Instruments During negative transitions or steady DC levels, the cur-
n
Battery Chargers rent sources decrease to 275m A to improve negative slew
n
Industrial Control Application rate and improve low state noise margins. An auto detect
n
TV/Video Products standby mode reduces supply current if both SCL and
n
ACPI SMBus Interface SDA are high.
The LTC1694 is available in a 5-pin SOT-23 package,
requiring virtually the same space as two surface mount
resistors.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
2
I C is a trademark of Philips Electronics N.V.
*U.S. Patent No. 6,650,174
TYPICAL APPLICATIO
Comparison of SMBus Waveforms for
V
CC the LTC1694 vs Resistor Pull-Up
5V
V SMBus1
CC
C1
LTC1694
0.1F
GND SMBus2
LTC1694
SCL
SMBus
SDA
1V/DIV
R
PULL-UP
= 15.8k
CLK DATA CLK DATA
IN IN IN IN
CLK DATA CLK DATA
OUT OUT OUT OUT
V = 5V 1m s/DIV
CC
DEVICE 1 DEVICE N
C = 200pF
LD
f = 100kHz 1694 TA02
SMBus
1694 TA01
1694fa
1
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ULTC1694
UUW
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
Supply Voltage (V ) ................................................. 7V
CC
TOP VIEW NUMBER
SMBus1, SMBus2 Inputs ............ 0.3V to (V + 0.3V)
CC
V 1 5 SMBus1
CC
Operating Ambient Temperature Range
LTC1694CS5
GND 2
LTC1694C ............................................... 0 C to 70 C
LTC1694IS5
NC 3 4 SMBus2
LTC1694I............................................ 40 C to 85 C
S5 PART MARKING
S5 PACKAGE
Junction Temperature........................................... 125 C
5-LEAD PLASTIC TSOT-23
Storage Temperature Range ................. 65 C to 150 C
T = 125 C, q = 256 C/ W LTEE
JMAX JA
Lead Temperature (Soldering, 10 sec).................. 300 C
LTA8
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The l denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25 C.
A
V = 2.7V to 6V unless otherwise noted.
CC
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Supply Voltage Range 2.7 6 V
CC
I Supply Current SMBus1 = SMBus2 = Open l 20 60 100 m A
CC
I Pull-Up Current SMBus1 = SMBus2 = 0V l 125 275 350 m A
PULL-UP
Boosted Pull-Up Current Positive Transition on SMBus ( Figure 1) l 1.0 2.2 mA
Slew Rate = 0.5V/m s, SMBus > V
THRES
V Input Threshold Voltage Slew Rate = 0.5V/m s (Figure 1) l 0.4 0.65 0.9 V
THRES
SR Slew Rate Detector Threshold SMBus > V l 0.2 0.5 V/m s
THRES THRES
t SMBus Rise Time Bus Capacitance = 200pF (Note 2) l 0.32 1.0 m s
r
2
Standard Mode I C Bus Rise Time Bus Capacitance = 400pF (Note 3) l 0.30 1.0 m s
f SMBus Maximum Operating Frequency (Note 4) l 100 kHz
MAX
2
Note 1: Absolute Maximum Ratings are those values beyond which the life Note 3: The rise time of an I C bus line is calculated from V to
IL(MAX)
of a device may be impaired. V or 1.5V to 3V (with V = 5V). This parameter is guaranteed by
IH(MIN) CC
design and not tested. With a minimum boosted pull-up current of 1mA:
Note 2: The rise time of an SMBus line is calculated from (V
IL(MAX)
0.15V) to (V + 0.15V) or 0.65V to 2.25V. This parameter is Rise Time = (3V 1.5V) 400pF/1mA = 0.6m s
IH(MIN)
guaranteed by design and not tested. With a minimum pull-up current of
Note 4: This parameter is guaranteed by design and not tested.
125m A, a minimum boosted pull-up current of 1mA and a maximum input
threshold voltage of 0.9V:
Rise Time = [(0.9V 0.65V)/125m A + (2.25V 0.9V)/1mA] 200pF
= 0.67m s
1694fa
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