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Product Description

The UM3212 is a dual bidirectional I2C-bus and SMBus voltage-level translator with an enable (EN) input, and is operational from 1.0V to 3.6V (Vref(1)) and 1.8V to 5.5V(Vbias(ref)(2)).

The UM3212 allows bidirectional voltage translations between 1.0V and 5V without the use of a direction pin. The low ON-state resistance (Ron) of the switch allows connections to be made with minimal propagation delay. When EN is HIGH, the translator switch is on, and the SCL1 and SDA1 I/O are connected to the SCL2 and SDA2 I/O, respectively, allowing bidirectional data flow between ports. When EN is LOW, the translator switch is off, and a high-impedance state exists between ports.

The UM3212 is not a bus buffer which provides both level translation and physically isolates the capacitance to either side of the bus when both sides are connected.The UM3212 only isolates both sides when the device is disabled and provides voltage level translation when active.

The UM3212 can also be used to run two buses, one at 400 kHz operating frequency and the other at 100 kHz operating frequency. If the two buses are operating at different frequencies, the 100 kHz bus must be isolated when the 400 kHz operation of the other bus is required. If the master is running at 400 kHz, the maximum system operating frequency may be less than 400 kHz because of the delays added by the translator.

As with the standard I2C-bus system, pull-up resistors are required to provide the logic HIGH levels on the translator’s bus. The UM3212 has a standard open-collector configuration of the I2C-bus. The size of these pull-up resistors depends on the system, but each side of the translator must have a pull-up resistor. The device is designed to work with Standard-mode, Fast-mode and Fast-mode Plus I2C-bus devices in addition to SMBus devices. The maximum frequency is dependent on the RC time constant, but generally supports