ISO7220BDR

The ISO7220x and ISO7221x family devices are dual-channel digital isolators. Tofacilitate PCB layout, the channels are oriented in the same direction in the ISO7220x and inopposite directions in the ISO7221x. These devices have a logic input and output buffer separatedby TI’s silicon-dioxide (SiO2) isolation barrier, providing galvanicisolation of up to4000VPK per VDE. Used in conjunction with isolated power supplies, these devicesblock high voltage and isolate grounds, as well as prevent noise currents on a data bus or othercircuits from entering the local ground and interfering with or damaging sensitivecircuitry.

A binary input signal is conditioned, translated to a balanced signal, thendifferentiated by the capacitive isolation barrier. Across the isolation barrier, a differentialcomparator receives the logic transition information, then sets or resets a flip-flop and theoutput circuit accordingly. A periodic update pulse is sent across the barrier to ensure the properdc level of the output. If this dc-refresh pulse is not received every 4 μs, the input is assumedto be unpowered or not being actively driven, and the failsafe circuit drives the output to a logichigh state.

The small capacitance and resulting time constant provide fast operation with signalingrates available from 0 Mbps (DC) to 150 Mbps (The signaling rate of a line is the number of voltagetransitions that are made per second expressed in the units bps). The A-option, B-option, andC-option devices have TTL input thresholds and a noise filter at the input that prevents transientpulses from being passed to the output of the device. The M-option devices have CMOSVCC/2 input thresholds and do not have the input noise filter and theadditional propagation delay.

The ISO7220x and ISO7221x family of devices require two supply voltages of 2.8 V(C-Grade), 3.3 V, 5 V, or any combination. All inputs are 5-V tolerant when supplied from a 2.8-Vor 3.3-V supply and all outputs are 4-mA CMOS.

The ISO7220x and ISO7221x family of devices are characterized for operation over theambient temperature range of –40°C to +125°C.