Resistor networks are networks of… resistors. Obviously. They combine groups of three to over twenty resistors in a single IC-like package. An array is a subset of networks, all of which have the same ohmic value.
Networks are especially useful when the design needs multiple pull-up, line-termination, or gain-setting resistors. One strong case for using a resistor network is the inherent matching it offers in terms of changes in resistance due to things like temperature shifts, a consequence of the common thermal substrate. This is an important consideration for many sensor- and interface-related applications where balanced or ratiometric circuits facilitate cancellation of drift-related errors. While discrete resistors can provide close TCR matching through selection or tight absolute TCR, they can never offer matching of actual element temperatures.
This does not mean that all such networks are prone to large drift; some are able to combine both stability and precision. The QSOP-C and SOIC-C resistor networks, for instance, combine a ceramic substrate, large feature size, and a self-passivating tantalum nitride film technology for an inherently moisture-proof film system. These networks can ease some of the pressure from a project’s error budget.
Resistor networks also have the advantage of saving PC board “real estate” since a multi-resistor package typically takes less space than individual resistors. They can also reduce needed PC traces if some or all of the resistors have a common connection. Networks also support a routing discipline which enables a cleaner, more logical layout arrangement.
In terms of production, using a network results in a shorter Bill of Materials, which means fewer items to order, stock, and risk being unavailable. Networks also simplify the production process as there are fewer reels components to use, and they speed assembly since a single pick-and-place step is needed to put the resistors on the board, rather than multiple steps.
Resistor networks are not always the best way to go, however. Placing all resistors in a single package and location can end up requiring longer PC-board traces, which can lead to board crowding and layout challenges, and increasing noise pickup and affect signal integrity. Custom networks offer the ultimate design flexibility, but arrays are easier to source off of the shelf. All the resistors having the same value can also be a design constraint.
Two other factors to keep in mind are thermal impact and crosstalk. Although the network package may be operating within its dissipation ratings, it does concentrate this dissipation in a small localized area. If this location is in a thermal “shadow” zone with marginal airflow, some resistor-network thermal derating may be needed. Crosstalk can occur since, unlike individual devices, multiple resistors share the common substrate. While this is a potential issue with networks using silicon substrates, ceramic-based substrates feature larger sizes and therefore crosstalk.
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