SMBus Accelerator (SMA)


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 with 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 de-activated, 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 voltage-time threshold. To activate the boost circuit, the input must exceed VTRIPL by 100Vns (typical)

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.


    • Active termination for SMBus lines
    • Enhances system bus signal rise time
    • Increases bus capacity while ensuring 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)


 Block Diagram


Basic Information
Production Status
Mass Production
Supply Voltage Vcc Range (V)
2.7 to 5.5
Accelerator Current
2.2 mA
Accelerator Trigger
Supply Current Icc
80 µA
Hot Swap
Qualification Level
Can Sample
Temperature Range
-40 to +85

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