Texas Instruments CD74HC221M96E4

Overview

CD74HC221M96E4 from Texas Instruments is a dual monostable multivibrator with independent reset, Schmitt-trigger B inputs, and buffered Q/Q̅ outputs. It operates from 2V to 6V, supports edge-triggering on A (trailing) and B (leading), delivers pulse widths from ~140ns to >800µs via external RX/CX, and is rated for -55°C to +125°C operation in industrial and aerospace timing applications.

For engineers reviewing the CD74HC221M96E4 datasheet, CD74HC221M96E4 pinout, CD74HC221M96E4 application, or CD74HC221M96E4 equivalent, key selection criteria include its dual independent monostable architecture, wide VCC range, temperature-hardened SOIC-16 package, and compatibility with both HC-logic-level and LSTTL-driven systems via external timing components.

Technical Context

The CD74HC221M96E4 implements two fully independent monostable circuits, each with separate A (edge-triggered), B (Schmitt-triggered), and R (active-low reset) inputs. Pulse width is determined solely by external RX and CX values using t_W ≈ 0.7·R_XC_X at V_CC = 4.5V, with minimum C_X = 0 pF and minimum R_X = 500 Ω.

Each monostable features internal masking logic that isolates outputs from subsequent triggers after activation, and power-up reset ensures deterministic initial state. Propagation delays range from 14 ns (t_PLH/t_PHL, CL = 15 pF, V_CC = 5V) to 63 ns (CL = 50 pF, V_CC = 4.5V), with output transition times as low as 13 ns under same conditions.

Key Specifications

Pinout & Package

CD74HC221M96E4 is supplied in a 16-pin SOIC (D) package, 7.5 mm × 10.3 mm body, 1.2 mm max height, with 1.27 mm pitch leads and RoHS-compliant NiPdAu finish. Moisture sensitivity level is Level-1 (unlimited floor life at ≤30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual monostable multivibrator applications.

Compared with CD74HC221M96E4, CD74HCT221M96 trades wide voltage flexibility for guaranteed TTL compatibility, while SN74LV221AD improves speed and low-voltage operation but removes Schmitt-trigger noise rejection - choice depends on system voltage architecture and signal integrity requirements.

Availability

CD74HC221M96E4 is available at Aetrix Electronics and suitable for industrial motor control, aerospace power sequencing, automotive body electronics, and test equipment requiring stable component supply across extreme temperature ranges and long production lifecycles.

Supply support for CD74HC221M96E4 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic ICs, with decades of heritage in high-reliability timing and interface solutions.

The CD74HC221M96E4 belongs to TI's High-Speed CMOS Logic family, designed specifically for precision timing, pulse generation, and waveform shaping in harsh-environment applications demanding wide temperature range, noise immunity, and predictable RC-based timing.

FAQ

What is the minimum external timing capacitor value supported by CD74HC221M96E4?

The CD74HC221M96E4 supports a minimum external timing capacitor (CX) value of 0 pF. This allows ultra-short pulse widths down to ~140 ns when paired with minimum RX = 500 Ω and VCC = 4.5V. For stable operation below 100 ns, layout parasitics and PCB trace capacitance must be accounted for as part of the effective CX.

Does CD74HC221M96E4 require external pull-up or pull-down resistors on unused inputs?

Yes - per the datasheet, all unused inputs on CD74HC221M96E4 (including A, B, and R pins of an unused monostable) must be terminated either high or low. Floating inputs can cause increased ICC, erratic triggering, or unintended oscillation due to CMOS input sensitivity. A 10 kΩ pull-up to VCC or pull-down to GND is recommended for unused A/B/R pins.

Can CD74HC221M96E4 generate asymmetric waveforms using a single monostable?

No - each monostable in CD74HC221M96E4 produces a single positive-going pulse (Q) and its inverse (Q̅) of identical width. Asymmetric waveforms (e.g., different high/low durations) require cascading two monostables or combining with external logic; the device does not support variable-duty-cycle generation from one trigger event.

Is CD74HC221M96E4 pin-compatible with CD74HCT221M96?

Yes - CD74HC221M96E4 and CD74HCT221M96 share identical SOIC-16 pinout, package dimensions, and terminal functions. They differ only in electrical specifications: HC supports 2–6V operation with CMOS input thresholds, while HCT is 4.5–5.5V only with TTL-compatible inputs. No PCB changes are needed for substitution within 5V systems.

What is the maximum recommended external timing resistor value for CD74HC221M96E4?

The datasheet does not specify a maximum RX value for CD74HC221M96E4, but practical limits arise from leakage current and noise sensitivity. At VCC = 6V, input leakage ≤ ±1 µA implies RX > 10 MΩ may cause timing drift or failure to trigger. For stable operation across -55°C to +125°C, TI recommends RX ≤ 1 MΩ when using standard film or metal-film resistors with low tempco.