The SGM4551B is a 2-bit, SMbus, dual, bidirectional, I²C voltage translator with the ability of enable (EN) function. For VREF1, the typical operation range is from 1.2V to 3.3V and the typical operation for VREF2 is from 1.8V to 5.5V.

The signal can be transmitted bilaterally from 1.2V to 5V. The propagation delay is significant small as the low on-resistance of SGM4551B. Also, if the EN pin is in high position, the voltage translator is transparent and then it allows the connection between SCL1 and SCL2, SDA1 and SDA2 respectively. In addition, in this state, the transmitting direction is bidirectional. However, the transmitting will be suspended if the EN pin is in low state as the high-impedance property at this moment.

For the applications, the connections of the devices and bus length are limited as the 400pF capacitance of the bus pin. However, SGM4551B allows the isolation between two sides of I²C bus so that more and more I²C devices can be added and connected with SGM4551B.

Two different kinds of bus frequencies are supported by SGM4551B, one is 400kHz and the other is 100kHz. Also, if two frequencies for the buses are required, the priority of 400kHz should be always higher than that of 100kHz. Because of the adding of the additional delay, the operational frequency of the device must be lower than 400kHz if the frequency of the master is equal to 400kHz.

For the application of standard I²C, the pull-up resistor is required for the logic high levels, which means that the operation for I²C in this case is open-drain. Each side of the repeater requires a pull-up resistor and the value of resistor depends on the operation of SGM4551B. Also, when multiple masters are connected with SGM4551B, the standard operation current is 3mA, and high current can be taken into account under the specific conditions.

The resistance between SDA1 and SDA2 is low when the state of them is low. However, if the state of SDA1 or SDA2 is high, the level of high position depends on the corresponding voltage reference. In the transparent mode, when the position of SDA1 is high, SDA2 must be pulled to a high level through the pull-up resistor. In addition, the transition for high and low voltage is seamless which can be selected by the users.

Because of the same electrical characteristics for all the outputs of SGM4551B, so that the deviations of the propagation delay and voltage is extremely small. In addition, this advantage is good for the transition of discrete transistors as the symmetrical switch inside SGM4551B. On top of this, SGM4551B can also provide the protection of ESD for the devices with weak ESD ability.

The SGM4551B is available in a Green SOT-23-8 package. It operates over an ambient temperature range of -40℃ to +85℃.