Nexperia USA Inc. HEF4021BT,653

Overview

HEF4021BT,653 from Nexperia is an 8-bit static parallel-to-serial shift register with asynchronous parallel load (PL), synchronous serial data input (DS), edge-triggered clock (CP), and buffered Q5–Q7 outputs. It operates from 3 V to 15 V, features Schmitt-trigger CP input for noise immunity, and supports industrial temperature range (−40 °C to +125 °C) in SO16 package. Used in digital control logic, LED multiplexing, and serial data expansion.

For engineers reviewing the HEF4021BT,653 datasheet, HEF4021BT,653 pinout, HEF4021BT,653 application, or HEF4021BT,653 equivalent, key selection factors include its wide VDD range (3–15 V), asynchronous PL capability, Q5–Q7 output buffering, Schmitt-trigger clock tolerance, and SO16 thermal derating profile (12.4 mW/K above 110 °C).

Technical Context

The HEF4021BT implements eight cascaded D-type master-slave flip-flops, each with independent SD and CD inputs. Parallel loading occurs asynchronously when PL = HIGH, overriding clock and serial input behavior. Serial shifting advances data rightward on LOW-to-HIGH CP transitions when PL = LOW.

Schmitt-trigger action on CP enables robust operation with slow-rising signals (Δt/ΔV as low as 0.08 μs/V at VDD = 15 V). Output drive strength scales with supply voltage: IOL = 2.4 mA (min) at VDD = 15 V, VOL ≤ 0.05 V (|IO| < 1 μA), supporting TTL- and CMOS-level interfacing across all rated VDD points.

Key Specifications

Pinout & Package

HEF4021BT,653 is housed in a plastic small outline package (SO16, SOT109-1) with 16 leads and 3.9 mm body width. The package meets JEDEC MS-012 and is RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit parallel-to-serial shift register applications.

Compared with CD4021BE and 74HC165PW, the HEF4021BT,653 uniquely combines asynchronous parallel load, Schmitt-trigger clock tolerance, and three buffered mid-chain outputs-making it optimal for real-time capture and flexible serial streaming in harsh or timing-critical environments.

Availability

HEF4021BT,653 is available at Aetrix Electronics and suitable for LED matrix controllers, industrial I/O expanders, legacy bus interface adapters, and test equipment pattern generators requiring stable component supply across extended temperature and voltage ranges.

Supply support for HEF4021BT,653 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

Nexperia is a global semiconductor expert delivering high-performance logic, discrete, and MOSFET solutions optimized for efficiency, reliability, and manufacturability in high-volume applications.

The HEF4021B belongs to Nexperia's legacy CMOS logic portfolio designed specifically for industrial control, instrumentation, and retrofit systems where wide supply range, robust noise immunity, and long-term availability are critical.

FAQ

What is the minimum pulse width required for the PL input?

The minimum high-time pulse width for PL is 24 ns at VDD = 15 V and 70 ns at VDD = 5 V, as specified in Table 7. This ensures reliable asynchronous capture of all eight parallel inputs without metastability. Shorter pulses may result in incomplete or indeterminate latching of D0–D7 values.

Can unused inputs be left floating?

No. All unused inputs-including SD, CD, DS, CP, and PL-must be tied to VDD, VSS, or a defined logic level. Floating CMOS inputs cause increased power consumption, oscillation, and potential latch-up due to undefined gate voltages, violating JEDEC JESD 13-B compliance requirements.

Does the HEF4021BT,653 support hot insertion?

No. The device lacks hot-swap protection circuitry. Applying VDD before establishing stable VSS or connecting inputs while power is ramping may exceed absolute maximum ratings (e.g., VI > VDD + 0.5 V), risking permanent damage per Table 4 limiting values.

How does the Schmitt-trigger CP input improve system reliability?

The Schmitt-trigger input provides hysteresis (typical 0.8 V at VDD = 5 V), rejecting noise spikes and slow-edge interference on the clock line. This eliminates false triggering in electrically noisy environments-such as motor drive cabinets or relay-controlled panels-where rise/fall times can exceed 1 μs without compromising timing accuracy.