The ISO7220 and ISO7221 are dual-channel digital isolators. To facilitate PCB layout, the channels are oriented
in the same direction in the ISO7220 and in opposite directions in the ISO7221. These devices have a logic input
and output buffer separated by TI’s silicon-dioxide (SiO2) isolation barrier, providing galvanic isolation of up to
4000 V. Used in conjunction with isolated power supplies, these devices block high voltage, isolate grounds, and
prevent noise currents on a data bus or other circuits from entering the local ground and interfering with or
damaging sensitive circuitry.
A binary input signal is conditioned, translated to a balanced signal, then differentiated by the capacitive isolation
barrier. Across the isolation barrier, a differential comparator receives the logic transition information, then sets or
resets a flip-flop and the output circuit accordingly. A periodic update pulse is sent across the barrier to ensure
the proper dc level of the output. If this dc-refresh pulse is not received every 4 ms, the input is assumed to be
unpowered or not being actively driven, and the failsafe circuit drives the output to a logic high state.
The small capacitance and resulting time constant provide fast operation with signaling rates available from 0
Mbps (dc) to 150 Mbps.(1)The A-, B- and C-option devices have TTL input thresholds and a noise filter at the
input that prevents transient pulses from being passed to the output of the device. The M-option devices have
CMOS VCC/2 input thresholds and do not have the input noise-filter and the additional propagation delay.
These devices require two supply voltages of 3.3 V, 5 V, or any combination. All inputs are 5-V tolerant when
supplied from a 3.3-V supply and all outputs are 4-mA CMOS.
These devices are characterized for operation over the ambient temperature range of –40°C to 125°C.