DG421CJ - Dual SPST Analog Switch | Analog Devices
Référence : DG421CJ ✗ Fin de vieDG421CJ Présentation
An analog switch is a semiconductor device that connects or isolates signal paths under digital control. The DG421CJ belongs to the analog switch hierarchy within multiplexers and interface ICs. Unlike a mechanical relay, it offers compact size, low switching power, and fast electronic control. Its normally open configuration provides a defined open state when a control input is deasserted, while the paired switches can route two independent channels or provide isolation between source and measurement circuitry.
Key features include guaranteed on-resistance matching of 3 ohms maximum between switches and on-resistance flatness of 4 ohms maximum over the signal range. Typical on-resistance is 20 ohms, and the low-power CMOS design is intended to minimize power consumption in multi-switch systems. The 16-PDIP package uses a 0.300-inch, 7.62 mm body width and supports conventional through-hole PCB assembly rather than surface-mount reflow.
The switch architecture provides independent control paths for two SPST-NO channels. Guaranteed matching between the two switches is useful when both devices must present similar resistance to sampled signals. Flatness limits resistance variation across the selected signal range, helping preserve measurement consistency when the source voltage changes. Low-power CMOS operation also makes the device appropriate for portable test and measurement systems where supply efficiency and predictable signal behavior are important.
Typical uses include battery-powered instrumentation, automated test equipment, analog measurement front ends, sample-and-hold isolation networks, and industrial interface modules. The two channels can be used for measurement-source selection, signal isolation, or alternating access to two external circuits. In systems with higher voltage levels, designers must confirm the complete absolute-maximum and signal-range limits in the manufacturer datasheet before applying the switches outside the intended dual-supply domain.
For PCB layout, place the device so its through-hole leads do not cross sensitive analog traces, and route switched signals away from clocks, relay drivers, and switching power converters. Use a common ground reference for control and analog circuitry. Because this legacy part is obsolete, production replacements should be qualified for pin compatibility, supply voltage, on-resistance, leakage current, switching speed, and temperature range rather than selected by package name alone.
This product page organizes the DG421CJ technical characteristics, sourcing information, application guidance, and drop-in replacement assessment. It also distinguishes verified device capabilities from engineering checks that should be completed before approving any substitute in an existing analog signal path.
Alternatives de remplacement direct pour DG421CJ — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Aucune alternative de remplacement direct disponible pour ce produit.
Demander des alternativesDG421CJ Valeurs maximales et caractéristiques électriques
| Switch Type | 2 Circuit SPST-NO |
| Number of Switches | 2 |
| Maximum On-Resistance | 35 ohm |
| Typical On-Resistance | 20 ohm |
| On-Resistance Matching Between Switches | 3 ohm maximum |
| On-Resistance Flatness Over Signal Range | 4 ohm maximum |
| Tension d'alimentation | 15 V maximum per supply rail |
| Switching Time | 250 ns |
| Leakage Current | 500 pA |
| Plage de température de fonctionnement | 0 C to +70 C |
| Boîtier | 16-PDIP (0.300 inch, 7.62 mm) |
| Type de montage | Through Hole |
| Nombre de broches | 16 pins |
| Number of Terminals | 16 |
| Control Interface | Latched CMOS control inputs |
| Technology | Low-power CMOS |
Guide de configuration des broches du DG421CJ 16-pdip (0.300 inch, 7.62 mm)
Configuration des broches du DG421CJ (boîtier 16-pdip (0.300 inch, 7.62 mm)). La numérotation des broches, les fonctions et les schémas de connexion sont définis dans la fiche technique du fabricant. Consultez-la pour l'empreinte exacte et les directives de soudage.
Aucune donnée de brochage détaillée disponible pour DG421CJ.
Consultez la fiche technique pour la configuration complète des broches.
Applications typiques
DG421CJ convient pour 6 applications: Automated Test Equipment, Battery-Powered Instrumentation, Analog Signal Routing, Sample-and-Hold Isolation, Industrial Control Interface, Data Acquisition Front End.
Automated Test Equipment
The DG421CJ fits automated test equipment when two low-voltage analog paths must be isolated or selected under digital control. Its two independently controlled SPST-NO channels simplify fixture routing, while the 20-ohm typical on-resistance is suitable for many medium-impedance sources and the 35-ohm maximum provides a defined worst-case limit. The guaranteed 3-ohm maximum matching between channels helps compare measurements made through different routes. Designers should include input buffering when the tester samples a high-impedance node, because switch resistance and 500 pA leakage can create measurable loading. The 250 ns switching time also supports controlled sequencing when the test system changes sources between measurement phases.
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Battery-Powered Instrumentation
The DG421CJ is useful in battery-powered instrumentation when two analog inputs must be connected or disconnected without continuous electromechanical wear. Its low-power CMOS implementation and 500 pA leakage specification help preserve accuracy in high-impedance measurement paths. The 20-ohm typical on-resistance should be included in the source-impedance calculation because it can create gain error when the selected source has meaningful output impedance. Use the device within the 0 C to +70 C operating range and verify that control-logic thresholds are compatible with the host microcontroller. Local supply bypassing and a single ground reference near the DIP will improve switching predictability.
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Analog Signal Routing
The DG421CJ provides two normally open channels for routing low-level analog signals in a modular measurement or control system. Each switch can independently connect a source to a downstream instrument, and the specified 3-ohm maximum difference between switches reduces channel-dependent variation when paired measurements are compared. The 4-ohm maximum flatness over the signal range supports more consistent behavior as source voltage changes. The 250 ns transition time is fast enough for ordinary sequencing, although system designers should allow for control settling before taking a reading. Keep switched traces short and isolated from digital clock and power-converter return currents.
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Sample-and-Hold Isolation
The DG421CJ can isolate a sampled capacitor or measurement node by disconnecting the source during the acquisition and conversion interval. Its SPST-NO configuration provides a natural open state, while the 250 ns switching time allows the analog front end to settle before conversion begins. The 500 pA leakage figure is important when holding a high-impedance node because leakage introduces a time-dependent charge error. Designers should calculate settling time from the switch resistance, downstream capacitance, and amplifier bias current. An input buffer is preferable when the source impedance is high enough that the 20-ohm typical on-resistance would materially affect accuracy.
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Industrial Control Interface
The DG421CJ can route control or monitor signals in industrial interface modules that operate from dual supplies. Its two latched SPST-NO channels allow a controller to connect field-side signals only during a defined interval, reducing unwanted loading of inactive channels. The 35-ohm maximum on-resistance is useful for relatively low-impedance industrial inputs, although sensitive sensor lines may require buffering. The commercial 0 C to +70 C temperature range covers many indoor control cabinets but not harsh or automotive environments. Protective grounding, supply bypassing, and physical separation from relay coils and motor drivers are essential for reliable operation.
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Data Acquisition Front End
The DG421CJ is applicable to the front end of a multichannel data-acquisition system where two sources share a converter input. The normally open channels provide isolation from an unselected source, and the guaranteed on-resistance matching of 3 ohms maximum helps reduce channel-to-channel measurement variation. Designers should compare the 20-ohm typical switch resistance with the source impedance and ADC input capacitance to determine the required settling time. The 500 pA leakage may also affect very high-impedance sources. Place the DIP near the analog input section, route switched signals as short as practical, and keep converter and digital return currents away from the measurement node.
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Récapitulatif des produits recommandés
Données de référence d'ingénierie pour DG421CJ — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit |
|---|---|
| Brand | Analog Devices / Maxim Integrated |
| Package | 16-PDIP (0.300 inch, 7.62 mm) |
| Switch Configuration | 2 Circuit SPST-NO |
| Number of Switches | 2 |
| Maximum On-Resistance | 35 ohm |
| Typical On-Resistance | 20 ohm |
| On-Resistance Matching | 3 ohm maximum between switches |
| On-Resistance Flatness | 4 ohm maximum over signal range |
| Switching Time | 250 ns |
| Leakage Current | 500 pA |
| Operating Temperature | 0 C to +70 C |
| Lifecycle Status | Obsolete |
Principaux différenciateurs
- Two matched SPST-NO channels in one device (vs Single-channel analog switch)
- Defined resistance matching between channels (vs Discrete SPST switch pair)
- Low-power CMOS construction (vs Mechanical relay)
Notes de conception
Do not select a replacement from switch count and package dimensions alone. Confirm that each control input uses the same active logic, that the normally open behavior is preserved, and that supply rails remain within the 15 V maximum per rail. Also compare leakage, on-resistance, switching time, and the 0 C to +70 C temperature range. The obsolete DG421CJ footprint is 16-PDIP, so a surface-mount substitute requires PCB redesign and is not a drop-in replacement.
Place the DG421CJ close to the switched analog nodes and keep its control traces away from sensitive measurement traces. Maintain a low-impedance ground reference, place supply bypass capacitors near the device pins, and route relay-coil, clock, and motor-drive return currents away from the switch inputs. Because the specified 20-ohm typical on-resistance can alter high-impedance measurements, use a nearby buffer when source impedance is appreciable.
Include switch resistance, source impedance, downstream capacitance, and amplifier input bias current in the settling-time calculation. Allow the 250 ns switching transition to finish before sampling, and use additional acquisition delay when the selected source has substantial capacitance or leakage. The 500 pA leakage specification is particularly important for high-impedance nodes because it can produce a charge-related measurement error over long acquisition intervals.
The published commercial operating range of 0 C to +70 C applies to the DG421CJ and should not be extended into industrial, automotive, or outdoor extremes without an explicitly qualified alternative. Review the maximum power and signal limits in the manufacturer datasheet for the selected supply voltage. Keep the through-hole package away from heat sources and provide conventional copper paths that carry current without creating excessive temperature rise at the device.
Informations de conformité
The DG421CJ is a legacy commercial-temperature device. RoHS, REACH, lead-free, halogen-free, and conflict-minerals declarations were not stated in the cited manufacturer information and are therefore recorded as unknown.
