Analog Devices Inc./Maxim Integrated DG421DY

Overview

DG421DY from Maxim Integrated is a precision dual SPST CMOS analog switch with latched TTL/CMOS-compatible control inputs, 20Ω typical on-resistance, 15pC max charge injection, and rail-to-rail signal handling from ±4.5V to ±20V bipolar or +10V to +30V single supply. It operates in battery-powered test equipment and audio routing systems requiring low leakage (<5nA at +85°C) and fast switching (175ns tON).

For engineers reviewing the DG421DY datasheet, DG421DY pinout, DG421DY application, or DG421DY equivalent, key selection criteria include guaranteed 3Ω max on-resistance matching between channels, latch timing compliance (tWW/tDW ≤ 200ns), ESD tolerance (2000V min per Method 3015.7), and SO-16 package compatibility with industrial temperature range (–40°C to +85°C).

Technical Context

The DG421DY implements two independent, normally open SPST switches controlled by WR (Write) and RS (Reset) logic inputs that latch digital states-eliminating need for continuous microprocessor bus hold. Its silicon-gate 44V process enables true rail-to-rail analog conduction with matched channel performance.

Switch operation is decoupled from logic supply (VL = +5V required for TTL compatibility) and analog supplies (V+/V−), supporting mixed-signal system partitioning. Charge injection is minimized via matched transistor geometry, and off-leakage is characterized across –40°C to +85°C with 100% hot-temperature testing.

Key Specifications

Pinout & Package

Package: 16-pin SO (Small Outline), 3.9mm width, RoHS-compliant, rated for –40°C to +85°C operating temperature.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar analog switch applications.

Compared with ADG421BRZ and TS5A23157DCUR, the DG421DY uniquely combines latched TTL-compatible control, bipolar supply support, and guaranteed channel matching-making it the only option for industrial test equipment and telecom analog front-ends requiring microprocessor-driven, high-accuracy dual-channel switching.

Availability

DG421DY is available at Aetrix Electronics and suitable for test equipment multiplexing, audio signal routing, modem analog front-ends, battery-powered data loggers, and guidance and control systems requiring stable component supply across extended temperature ranges.

Supply support for DG421DY includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for industrial, communications, and computing applications.

The DG421DY belongs to the DG42x family of latched CMOS analog switches engineered for microprocessor-interfaced instrumentation where rail-to-rail signal integrity, low leakage, and latch-based control reduce system-level complexity.

FAQ

What is the maximum allowable voltage difference between V+ and V− for the DG421DY?

The DG421DY has an absolute maximum rating of 44V between V+ and V−. This limit applies regardless of individual rail voltages-for example, V+ = +25V and V− = –19V yields 44V differential and remains within specification. Exceeding this risks permanent damage due to junction breakdown, and proper power sequencing (V+ first, then VL, V−, and logic inputs) is mandatory to ensure reliability.

Does the DG421DY require a separate +5V logic supply (VL) when operated from ±15V analog supplies?

Yes, the DG421DY requires VL = +5V for TTL-compatible logic thresholds (VINH ≥ 2.4V, VINL ≤ 0.8V). Even with ±15V analog supplies, connecting VL to +5V ensures correct interpretation of microprocessor control signals. If VL is tied to V+, the device operates at CMOS thresholds instead, which may cause misreads in TTL-driven systems-so VL must be independently regulated to +5V for guaranteed interoperability.

Can the DG421DY be used in a single-supply configuration with V− grounded?

Yes, the DG421DY supports single-supply operation from +10V to +30V with V− connected to GND. In this mode, the analog signal range extends from 0V to V+, enabling use in +12V or +24V industrial systems. However, on-resistance matching (3Ω max) and flatness (4Ω max) are guaranteed only under bipolar-supply conditions per the datasheet-single-supply performance remains functional but not production-binned to those specs.

What is the purpose of the N.C. pins (3, 4, 5, 6) on the DG421DY SO-16 package?

The N.C. pins (3, 4, 5, 6) on the DG421DY have no internal connection and must remain unconnected-neither tied to GND, V+, nor left floating with pull resistors. These pins exist for package compatibility across the DG42x family (e.g., DG423 uses some as S3/S4) but serve no electrical function in the DG421DY. PCB layout must isolate these pads to prevent accidental shorts or parasitic coupling that could affect adjacent signal integrity.

How does the latch functionality of the DG421DY simplify microprocessor interface compared to non-latching analog switches?

The DG421DY's WR and RS inputs allow microprocessor GPIOs to set switch states with a single pulse-after which the internal latches retain the state without continuous bus drive. This eliminates timing-critical strobe windows, reduces I/O pin count (no need for dedicated OE or hold lines), and prevents glitches during bus contention or interrupt latency. For example, writing IN1=1, IN2=0, then pulsing WR once configures S1/D1 ON and S2/D2 OFF indefinitely until next WR cycle-freeing the µP for other tasks.