#I2c isolator driver

The voltage levels on Side A are completelycompatible with I2C requirements and there is no special considerationfor the side without the comparator circuit.įor side B, with the comparator circuit, the output of the isolatorshould not turn on the comparator but the open drain driver must turnon the comparator. Note that thecomparator circuit only needs to be used on one side, and could be usedon either side A or side B. If the low on side B is caused by the open drain driver on side B,Q1 and Q2 do turn on and the low is propagated. If the low on side B is caused by low on side A, Q1 or Q2will not turn on due the drop across diodes D2A,B and R1 or R2 and thelow is not propagated back to side A breaking the latch condition. Transistors Q1 and Q2 act as thecomparators. The latchup problem described above is solved by using a comparatorto sense whether the non-isolated side (side A) is causing the low onthe isolated side (side B).

#I2c isolator series

C8051Fxxx series MCUs at a bus speed ofapproximately 300KHz including bus transactions which require SCL clockstretching.įigure1: Diodes D1A, B and D2A, b convert the push-pull output of the Si8442to open drain. This circuit has been tested with SiliconLaboratories, Inc. It can be easily adjusted for otherbus pull up resistors. The circuit assumes 1K pull upresistors on the SCL and SDA lines. Si8442 high speedisolator is show in Figure 1 below.

#I2c isolator full

The full circuit using a Silicon Laboratories, Inc. They tend to be slow due to the slow response of the opto-couplers.Finally, when higher speed digital isolators with standard CMOS inputlevels are used, the circuit tricks using the diode input of theopto-couplers no longer apply. Some of these approaches are sensitive to bus capacitance. Previous attempts to solve this problem have used diodes inherent tothe opto-coupler input and additional circuitry to avoid the latch-upcondition. The open drain problem is easilysolved by putting a Schottky diode in series with the isolator output.However, the latch up problem is much more difficult to solve. This causes isolator B to pull low on side A and the circuit latcheswith both isolators pulling low. If, forexample, the side A driver pulls low then isolator A pulls low on sideB. All devices are rated for operation at ambient temperatures of -40☌ to +125☌.For the wires that need to be bidirectional, if digital isolatorsare inserted there are several problems the isolators must be opendrain, and there is a latch up condition that can occur. The MAX14933 is available in both a 16-pin wide-body (10.3mm x 7.5mm) and narrow-body (9.9mm x 3.9mm) SOIC package.

The device operates from DC to 1.7MHz and can be used in isolated I 2C busses with clock stretching. The device features independent 2.25V to 5.5V supplies on each side of the isolator.

The B side features conventional buffers that do not regulate logic-low output voltage. To prevent latch-up action, the A-side outputs comprise special buffers that regulate the logic-low voltage at 0.9V (max), and the input logic-low threshold is at least 50mV lower than the output logic-low voltage. The device offers two bidirectional, open-drain channels for applications, such as I 2C, that require data to be transmitted in both directions on the same line. The MAX14933 transfers digital signals between circuits with different power domains at ambient temperatures up to +125☌. For applications requiring 5kV RMS of isolation, refer to the MAX14937 data sheet. The MAX14933 is a two-channel, 2.75kV RMS I 2C digital isolator utilizing Maxim’s proprietary process technology.