The ISL88694 SMBus accelerator (SMA) is a dual active
pull-up bus terminator designed to improve data
transmission speed on SMBus or similar 2-wire serial bus
interfaces. The ISL88694 is also compatible to the I2C serial
bus.
The SMA detects rising input transitions with two internal
voltage references and two comparators per channel. After
the voltage on a data line crosses the first threshold
(VTRIPL), the boost pull-up current source is activated to
speed transition. After the voltage crosses the second
threshold (VTRIPH), the boost pull-up current source is deactivated, leaving an active pull-up current of 275µA on the
line. When both channels are HIGH, the pull-up current for
both lines is reduced to 100µA to save power. Internal logic
ensures that the active and boost pull-up current sources are
not activated during downward transitions.
The level for VTRIPH is controlled by a bandgap voltage
referred to VDD. This feature makes the switching behavior
invariant for all power supply voltages between 2.7V and
5.5V.
A noise filter on each channel prevents the circuit from
responding to input transitions that do not exceed a voltagetime threshold. To activate the boost circuit, the input must
exceed VTRIPL by 100Vns (typical) (See Figure 10).
The SMA permits operation of the bus at frequencies up to
100kHz, despite the capacitive loads of multiple devices
and/or long PC board traces. Enhanced ESD protection on
the accelerator pins are guaranteed to withstand 8kV ESD
(HBM) events.
The SMBus Accelerator provides an essential function in
SMBus applications because of distributed capacitance of
SMBus and multiple device input capacitances at various
nodes. By incorporating SMA, systems using SMBus or I2C
can reliably increase their bus load without the risk of data
loss.

Features
• Active Termination for SMBus lines
• Enhances System Bus Signal Rise Time
• Increases Bus Capacity While Guaranteeing Data Integrity
• 2.2mA Rise Time Supply Current
• 8kV ESD Protection on SDA and SCL Pins
• Wide Operating Voltage Range: 2.7V to 5.5V
• 2-Wire SMBus and I2C Compatible (100kHz)
• Small Package - SOT23-5
• Pin-for-Pin Compatible with the LTC1694
• Pb-Free Available (RoHS Compliant)

Target Applications
• Servers
• Data Acquisition
• Routers
• Battery Chargers
• Portable Instrumentation
• Notebook
• PC
• Facilities Tracking System