Analog Devices Inc./Maxim Integrated DS1021S-25/T&R

Overview

DS1021S-25/T&R from Dallas Semiconductor (now Maxim Integrated) is a programmable 8-bit all-silicon delay line IC used for precise digital signal timing adjustment in high-speed logic systems. It delivers a nominal step-zero delay of 10 ns, maximum delay of 73.75 ns, and 0.25 ns incremental resolution. The device supports both 3-wire serial and 8-bit parallel programming, operates at 5 V, and maintains rising/falling edge accuracy for TTL/CMOS-compatible signals.

For engineers reviewing the DS1021S-25/T&R datasheet, DS1021S-25/T&R pinout, DS1021S-25/T&R application, or DS1021S-25/T&R equivalent, key selection criteria include programmable delay resolution (0.25 ns), dual-mode configuration (serial/parallel), SOIC-16 package compatibility, edge-accurate propagation, and CMOS-level power consumption with 5 V supply tolerance.

Technical Context

The DS1021S-25/T&R implements an 8-bit user-programmable delay register controlling a silicon-based analog delay path. Delay values are set via parallel pins P0–P7 (when S = 1) or serially shifted MSB-first via D/C/Q (when S = 0), with enable (E) gating register updates. Settling time after reprogramming is 50 µs (tEDV).

It features dual-edge accuracy-measured at 1.5 V crossing for both tPLH and tPHL-with ±6 ns max deviation from programmed delay. The device drives up to 10 × 74LS loads, exhibits 10 pF input capacitance, and requires defined logic levels on unused pins (D, C, P1–P7) to prevent floating CMOS inputs.

Key Specifications

Pinout & Package

DS1021S-25/T&R is housed in a 16-pin SOIC (300-mil) surface-mount package, auto-insertable and compatible with vapor phase, IR, and wave soldering processes.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar programmable delay line applications.

Compared with DS1021S-25/T&R, DS1021S-50/T&R offers double the delay range at half the resolution and identical packaging, while MC100EP195DG provides superior resolution and speed but demands differential layout, PECL biasing, and 3.3 V infrastructure-making it unsuitable for direct replacement in 5 V TTL/CMOS designs.

Availability

DS1021S-25/T&R is available at Aetrix Electronics and suitable for FPGA timing calibration, memory bus skew compensation, logic analyzer trigger alignment, and digital test equipment signal deskew requiring stable component supply and long-term obsolescence management.

Supply support for DS1021S-25/T&R 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

Dallas Semiconductor, acquired by Maxim Integrated in 2001, specialized in precision timing, nonvolatile memory, and mixed-signal interface ICs for industrial and communications applications.

The DS1021S-25/T&R belongs to the DS1021 programmable silicon delay line family, designed to replace hybrid delay modules with monolithic CMOS solutions for accurate, reconfigurable digital signal timing in commercial-grade systems.

FAQ

What is the minimum and maximum delay achievable with the DS1021S-25/T&R?

The DS1021S-25/T&R has a fixed inherent delay of 10.00 ns (step zero), and its maximum programmable delay is 73.75 ns. Each increment adds exactly 0.25 ns, yielding 256 discrete delay values from 10.00 ns to 73.75 ns in 0.25 ns steps. These values are confirmed in Table 2 of the official datasheet and validated under 5 V, 25°C test conditions.

Does the DS1021S-25/T&R support both rising and falling edge delay accuracy?

Yes, the DS1021S-25/T&R guarantees edge-accurate delay for both rising (tPLH) and falling (tPHL) transitions, with measured deviation ≤±6 ns from the programmed value. This is explicitly stated in the "DESCRIPTION" section and verified in AC Electrical Characteristics under Note 2, making DS1021S-25/T&R suitable for bidirectional or clock/data strobe applications.

Can the DS1021S-25/T&R be programmed dynamically during system operation?

Yes, the DS1021S-25/T&R supports real-time reprogramming via its 3-wire serial interface (C/D/Q pins) under active system control. When S = 0 and E is pulsed, new 8-bit delay values can be loaded MSB-first without interrupting signal flow-though a 50 µs settling time (tEDV) is required before the updated delay becomes valid.

What is the purpose of the Q pin on the DS1021S-25/T&R, and how is it used?

The Q pin on the DS1021S-25/T&R serves as serial data output, shifting out the current 8-bit delay register contents MSB-first during read operations. It is designed for daisy-chaining-connecting Q of one DS1021S-25/T&R to D of the next-and supports destructive readback with automatic restoration via a 1 kΩ–10 kΩ pull-up resistor, as detailed in Figure 2 and SERIAL MODE description.

Is the DS1021S-25/T&R pin-compatible with other members of the DS1021 family?

Yes, all DS1021 variants-including DS1021S-25/T&R, DS1021S-50/T&R, and DS1021M (metal can)-share identical 16-pin SOIC pinouts and functional pin assignments. Differences are limited to internal delay range and resolution; no PCB layout change is needed when substituting between -25 and -50 versions, provided timing requirements align.