Dual-channel, 2/0, 5-Mbps digital isolator

The ISO7220x and ISO7221x family devices are

dual-channel digital isolators. To facilitate PCB layout, the channels are oriented

in the same direction in the ISO7220x and in opposite directions in the ISO7221x.

These devices have a logic input and output buffer separated by TI’s silicon-dioxide

(SiO2) isolation barrier, providing galvanic isolation of up to

4000VPK per VDE. Used in conjunction with isolated power supplies,

these devices block high voltage and isolate grounds, as well as 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 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 verify that the proper dc level

of the output. If this dc-refresh pulse is not received every 4µs, 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 resulting time constant provide fast operation

with signaling rates available from 0Mbps (DC) to 150Mbps (The signaling rate of a

line is the number of voltage transitions that are made per second expressed in the

units bps). The A-option, B-option, 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.

The ISO7220x and ISO7221x family of devices

require two supply voltages of 2.8V (C-Grade), 3.3V, 5V, or any combination. All

inputs are 5V tolerant when supplied from a 2.8V or 3.3V supply and all outputs are

4mA CMOS.

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