1FEATURES
• 1-, 5- and 25-Mbps Signaling Rate Options
– Low Channel-to-Channel Output Skew;
1 ns max
– Low Pulse-Width Distortion (PWD);
1 ns max
– Low Jitter Content; 1 ns Typ at 150 Mbps
• 4000-Vpeak Isolation, 560 Vpeak VIORM
– UL 1577 Approved
– 50-kV/μs Typical Transient Immunity
• Operates with 3.3-V or 5-V Supplies
• 4-kV ESD Protection
• High Electromagnetic Immunity

APPLICATIONS
• Down-Hole Drilling
• High Temperature Environments

SUPPORTS EXTREME TEMPERATURE
APPLICATIONS
Controlled Baseline
One Assembly and Test Site
One Fabrication Site
Available in Extreme (–55°C to 175°C)
Temperature Range (1) (2)
Extended Product Life Cycle
Extended Product-Change Notification
Product Traceability
Texas Instruments high temperature products
utilize highly optimized silicon (die) solutions
with design and process enhancements to
maximize performance over extended
temperatures.

DESCRIPTION
The ISO7221 is a dual-channel digital isolator. To facilitate PCB layout, the channels are oriented in the opposite
directions. This device has 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, this device
blocks high voltage, isolates grounds, and prevents 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 μs, 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. (3) 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.