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ISL88694IH5-TK

P1-P3P4-P6P7-P7
4
FN8239.1
January 21, 2005
Typical Performance Curves
FIGURE 1. ACTIVE PULL-UP CURRENT. SMBus PIN=0V
FIGURE 2. BOOST PULL-UP CURRENT. SMBus PIN = V
DD
/2.
FIGURE 3. STANDBY PULL-UP CURRENT. SMBus1,2=V
DD
-0.5V
FIGURE 4. V
TRIPL
VOLTAGE
290
310
330
350
370
270
250
230
210
-40-20 0 20406080100-60
TEMPERATURE (°C)
ACTIVE PULL-UP CURRENT, I
OUT_A
(µA)
VDD=5.5V
VDD=2.7V
2.15
2.30
2.45
2.60
3.75
2.00
1.85
1.70
1.55
-40-20 0 20406080100-60
TEMPERATURE (°C)
BOOST PULL-UP CURRENT, I
OUT_B
(µA)
VDD=5.5V
VDD=2.7V
80
90
100
110
120
70
60
50
40
-40-20 0 20406080100-60
TEMPERATURE (°C)
STANDBY PULL-UP CURRENT, I
OUT_SB
(µA)
VDD=5.5V
VDD=2.7V
0.75
0.80
0.85
0.90
0.95
0.70
0.65
0.60
0.55
-40-20 0 20406080100-60
TEMPERATURE (°C)
INPUT THRESHOLD LOW, V
TRIPL
(V)
VDD=5.5V
VDD=2.7V
ISL88694
5
FN8239.1
January 21, 2005
Functional Description
SMBus Overview
The SMBus or I
2
C bus is a 2-wire multimaster bus, meaning
that more than one device connected to the bus is capable of
controlling it. Master devices communicate to other master
or slave devices using one clock and one data line. These
are both bidirectional.
In order to allow multimaster operation without bus
contention, it is necessary to allow each bus to be connected
to a positive supply voltage via a current-source or pull-up
resistor (see “System Diagram” on page 2). When the bus is
free, both lines are HIGH. The output stages of devices
connected to the bus must have an open-drain or open-
collector to perform the wired-AND function.
Simple pull-up resistors on the clock and data lines work well
unless there are long signal lines or many devices
connected to the bus. Then, the combined capacitance of
the bus increases the rise time on the signal to such an
extent that the communication becomes unreliable or fails to
meet the bus timing specifications. Smaller resistors can
sometimes compensate for the extra capacitance, but this
increases the current consumption when the signal lines are
pulled LOW.
FIGURE 5. V
TRIPH
VOLTAGE
FIGURE 6. I
DD
CURRENT. SMBus1=SMBus2=OPEN.
FIGURE 7. BOOST PULL-UP CURRENT vs. SMBus VOLTAGE
Typical Performance Curves (Continued)
0.50
0.55
0.60
0.65
0.70
0.45
0.40
0.35
0.30
-40-20 0 20406080100-60
TEMPERATURE (°C)
INPUT THRESHOLD HIGH, V
TRIPH
(V
DD
-V)
VDD=5.5V
VDD=2.7V
75
80
85
90
95
70
65
60
55
-40-20 0 20406080100-60
TEMPERATURE (°C)
SUPPLY CURRENT, I
DD
(µA)
VDD=5.5V
VDD=2.7V
2.0
2.5
3.0
3.5
1.5
1.0
0.5
0
123450
SMBus VOLTAGE (V)
BOOST PULL-UP CURRENT, I
OUT_B
(mA)
6
VDD=5.0V
VDD=2.7V
ISL88694
6
FN8239.1
January 21, 2005
ISL88694 Operation
To improve the operation of the SMBus where larger bus
capacitance exists, the ISL88694 provides active pull-up
using switched current sources. When the bus is idle and
both lines are HIGH, a standby pull-up current of 100µA is
used to maintain the signal level while minimizing power
consumption. When either of the two signals is pulled LOW,
an active pull-up current of 275µA maintains a good V
OL
noise margin.
When the bus line is released, it is pulled high by the
ISL88694 active current until the voltage exceeds the
V
TRIPL
level for a period of time. This voltage-time
combination filters out noise on the signal line. Once the
ISL88694 detects a valid rising edge, a 2.2mA boost current
pulls the bus line high very quickly (see Figure 8). This boost
current turns off when the input level reaches the V
TRIPH
threshold and the pull-up current returns to the active level. If
both inputs are HIGH, the pull-up current drops to the
standby level of 100µA.
FIGURE 8. ISL88694 SMBus SYSTEM BOOST PULL-UP
COMPARED TO RESISTOR PULL-UP (V
DD
=
5.5V).
FIGURE 9. ISL88694 SMBus SYSTEM BOOST PULL-UP
COMPARED TO RESISTOR PULL-UP (V
DD
=
2.7V).
FIGURE 10. NOISE SUPPRESSION. BOOST CURRENT
APPLIED WHEN INPUT SIGNAL EXCEEDS 20Vns
(TYPICAL).
V
TRIPL
With RC
Pullup
With ISL88694 SMA
V
TRIPH
R=15.8K
C= 200pF
V
TRIPL
With RC
Pullup
With ISL88694 SMA
V
TRIPH
R=15.8K
C= 200pF
V
TRIPL
Gnd
t
SMBus1
>20Vns
SMBus2
V
DD
With SMA
Without SMA
(Typical)
V
TRIPH
ISL88694
P1-P3P4-P6P7-P7

ISL88694IH5-TK

Mfr. #:
Buy ISL88694IH5-TK
Manufacturer:
Renesas / Intersil
Description:
IC ACCELERATOR I2C 2CH SOT-5
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
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