Differential line-driver ICs for balanced serial outputs

01

Map complementary outputs and the shared enable state

TI’s AM26C31 has four differential drivers with shared active-high and active-low enables. In its enabled state, Y follows the logic input and Z takes the opposite level; disabling places both outputs at high impedance. Its function table applies to each channel, while the enables control the group. [1]

For AM26C31, the recommended supply is 4.5–5.5 V. Its industrial I suffix has a −40 to +85°C free-air range; other suffixes have separate temperature limits. Order the complete suffix and package rather than treating the family name as an electrical specification. [1]

Define which controller signal drives each input and how the enable pins are held during reset. Include the asserted, deasserted and unpowered cases in the interface drawing. A disabled differential output needs its own system-level idle-state review.

Use the maker’s internal diagrams to understand the input buffer and output stage. The supplied item is the packaged IC: its bias and clamp structures are internal design features, rather than a list of separately orderable transistors, resistors or protection diodes. Record any additional board-level protection explicitly.

02

Evaluate the waveform with its cable and receiver attached

TI’s AM26C31 application discussion places an RS-422 termination, when used, at the far end near the last receiver. Select the termination from the cable and link arrangement, then check the waveform at the receiving end. [1]

Separate differential output magnitude from output common-mode voltage. TI’s AM26LV31E test drawing measures the former between the output wires and the latter at the centre of the split load relative to ground. These quantities describe different parts of the receiver’s electrical environment. [2]

For a timing comparison, retain the data sheet’s load circuit, probe capacitance, supply and temperature, plus its distinction between propagation delay, edge transition and channel skew. AM26LV31E provides separate measurement diagrams for propagation and output-enable timing. A headline switching frequency alone leaves those conditions unspecified. [2]

Estimate supply demand with all used channels, termination and switching activity included. Request the loaded current or power result for that setup; a quiescent, unloaded current figure serves a different operating condition.

Define protection by pin group and test method. The AM26LV31E bus pins are rated ±15 kV HBM, ±8 kV IEC 61000-4-2 contact and ±15 kV IEC 61000-4-2 air discharge. These are distinct component ratings; include the external connector and complete board in any equipment-level immunity verification. [2]

03

Keep the receiver’s input range on the receiving side

Renesas’ FN7529 describes the ISL32173E family as receivers, with a −7 to +12 V bus common-mode range. That is a named receiver family’s input capability; it does not establish the output-voltage allowance of a driver-only IC. Check both ends against their respective data sheets. [3]

The same receiver document specifies open-input fail-safe operation. This illustrates why the remote receiver’s idle response must be selected together with the driver’s disabled state. Obtain the behaviour for the actual receiver under the intended open, disconnected and terminated-idle conditions. [3]

For a replacement, reconcile input thresholds and leakage, output polarity and loading, channel grouping, package pinout and power sequencing. Complete the comparison with the specified data pattern, link length, ground relationship and acceptance waveform, rather than a shared RS-422 label.

04

Driver-channel and cable acceptance schedule

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Driver identity: [complete part/suffix, driver-only function, channel count, package code, pin map and quantity]
Logic side: [controller supply, thresholds/input current, polarity, enable group and reset defaults]
Power and environment: [recommended rail, loaded supply budget, temperature grade and power-sequence conditions]
Cable circuit: [pair assignment, length, impedance, termination, receiver model/load and ground relationship]
Waveform acceptance: [differential swing, output common mode, output current/loading, data pattern/rate, propagation delay, edge time and channel skew]
Inactive states: [enable timing, power-off leakage/terminal limits and receiver idle behaviour]
Protection evidence: [bus versus logic pins, HBM/contact/air methods, external network and equipment-level verification]

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