Automotive, single-channel, 100-Mbps digital isolator

The ISO721-Q1 and ISO722-Q1 devices are digital

isolators with a logic input and output buffer separated by a silicon dioxide

(SiO2) insulation barrier. This barrier provides galvanic isolation

of up to 4000VPK per VDE 0884-17. Used in conjunction with isolated power

supplies, these devices 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 provide the proper dc level of

the output.

If this dc-refresh pulse is not

received for more than 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.

These devices require two supply

voltages of 3.3V, 5V, or any combination. All inputs are 5V tolerant when supplied

from a 3.3V supply and all outputs are 4mA CMOS.

The ISO722-Q1 devices include an active-low output

enable that when driven to a high logic level, places the output in a high-impedance

state and turns off internal bias circuitry to conserve power.

The ISO721-Q1 and ISO722-Q1 devices have TTL input

thresholds and a noise filter at the input that prevent transient pulses of up to

2ns in duration from being passed to the output of the device.

The ISO721-Q1 and ISO722-Q1 devices are

characterized for operation over the ambient temperature range of –40°C to

+125°C.