My Inquiry
My Account
NXP Semiconductors 74HCT221DB,118
- Part No.:
- 74HCT221DB,118
- Manufacturer:
- NXP Semiconductors
- Category:
- Multivibrators
- Package:
- 16-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
74HCT221DB,118.pdf
- Description:
- IC MULTIVIBRATOR 31NS 16SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,370
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
74HCT221DB,118 from Nexperia is a dual non-retriggerable monostable multivibrator in SO16 package, featuring independent negative-edge (nA) and positive-edge (nB) trigger inputs per channel, active-low reset (nRD), complementary outputs (nQ/nQ), and external REXT/CEXT timing control. It delivers ±2% pulse width match between channels and supports output pulse widths from 140 ns to >700 µs depending on external components - used in precision timing, debounce, and delay generation circuits.
For engineers reviewing the 74HCT221DB,118 datasheet, 74HCT221DB,118 pinout, 74HCT221DB,118 application, or 74HCT221DB,118 equivalent, key selection criteria include HCT-level TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 4.5 V), propagation delays as low as 21 ns (tPHL, nB→nQ), Schmitt-triggered nB inputs for noise immunity, and dual-channel independence with no cross-talk in timing behavior.
Technical Context
The 74HCT221DB,118 implements two fully independent non-retriggerable monostables, each with separate nA (negative-edge), nB (positive-edge with hysteresis), and nRD (active-low asynchronous reset) inputs. Pulse width is determined solely by external REXT and CEXT values via tW ≈ 0.7 × REXT × CEXT, with internal compensation ensuring stability across VCC (4.5 V ±10%) and temperature (−40 °C to +125 °C).
Each channel provides true complementary outputs (nQ active-low, nQ active-high) with standard logic drive capability (IOH/ IOL = ±4 mA at VCC = 4.5 V). The SO16 package supports surface-mount assembly and thermal performance suitable for industrial ambient conditions up to +125 °C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74HCT - TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V @ VCC = 4.5 V) |
| Propagation Delay | tPHL = 21 ns (nB → nQ, VCC = 4.5 V, CL = 50 pF) - enables sub-50 ns timing resolution in fast digital systems |
| Pulse Width Match | ±2% between channels - ensures synchronized timing across dual outputs without calibration |
| Output Drive | Standard CMOS drive (±4 mA @ VCC = 4.5 V) - directly interfaces with 74-series logic and microcontroller GPIO |
| Timing Range | 140 ns to 805 µs (via REXT = 2–1000 kΩ, CEXT = 1 pF–100 nF) - covers debounce, delay, and one-shot needs in single device |
| Operating Temperature | −40 °C to +125 °C - qualified for automotive under-hood and industrial control environments |
| Supply Voltage | 4.5 V to 5.5 V - compatible with regulated 5 V rails; rejects supply ripple via internal voltage regulation |
Pinout & Package
74HCT221DB,118 is housed in a 16-pin SO (Small Outline) package with 1.27 mm pitch, JEDEC MS-012AC compliant, body width 3.9 mm, and moisture sensitivity level (MSL) 1 - suitable for reflow soldering without baking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 9 | 1A, 2A | Negative-edge trigger inputs - initiate monostable output on HIGH-to-LOW transition; no hysteresis |
| 2, 10 | 1B, 2B | Positive-edge trigger inputs with Schmitt hysteresis - reject noise on slow-rising signals; trigger on LOW-to-HIGH |
| 3, 11 | 1RD, 2RD | Active-low asynchronous reset - terminates ongoing output pulse immediately regardless of trigger state |
| 4, 12 | 1Q, 2Q | Active-low outputs - asserted LOW during monostable pulse; driven to GND when active |
| 5, 14 | 1CEXT, 2CEXT | External timing capacitor connections - tied to GND externally per channel for stable RC timing |
| 7, 15 | 1REXT/CEXT, 2REXT/CEXT | Shared REXT/CEXT node - connects external resistor to VCC and capacitor to GND to set pulse width |
| 8 | GND | Ground reference - must be low-impedance; pins 6 and 14 (CEXT) recommended to be grounded externally |
| 13, 5 | 1Q, 2Q | Active-high complementary outputs - asserted HIGH during monostable pulse; driven to VCC when active |
| 16 | VCC | Positive supply - 4.5–5.5 V; decoupling capacitor (100 nF) required within 10 mm of pin |
Key Features
| Feature | Design Value |
|---|---|
| Non-retriggerable operation | Prevents pulse extension from repeated triggers - essential for fixed-duration events like switch debouncing |
| Schmitt-trigger nB inputs | Input hysteresis (≈0.4 V typical) eliminates false triggering from EMI or slow signal edges |
| Overriding active-low reset | nRD forces immediate termination of output pulse - enables emergency stop or system synchronization |
| Pin-compatible with 74LS123 | Direct drop-in replacement in legacy LSTTL designs without PCB change - same pinout and function mapping |
| Low power dissipation | CPD = 96 pF - enables <1 mW static power at 1 MHz clock rate, reducing thermal load in dense logic layouts |
Applications
| Industrial Pushbutton Debounce | Automotive Door Lock Timing |
|---|---|
|
Use Scenario: Mechanical pushbuttons in PLC I/O modules generate contact bounce lasting 5–20 ms, causing spurious interrupts. IC Role / Device Role / Timing Role: 74HCT221DB,118 acts as hardware debounce filter - one-shot triggered by button press, generating clean 10–15 ms output pulse. Use Value: Eliminates need for firmware polling or software timers; guarantees single edge per press even with 10+ ms bounce. |
Use Scenario: Vehicle door lock actuators require precise 500 ms activation pulses to prevent motor stall or overtravel. IC Role / Device Role / Timing Role: 74HCT221DB,118 generates fixed-duration enable signal using REXT = 47 kΩ, CEXT = 10 nF (tW ≈ 330 µs) per channel. Use Value: Replaces discrete RC+transistor timers; achieves ±2% pulse consistency across temperature and unit-to-unit variation. |
| Dual-Channel Serial Data Delay | Reset-Synchronized Power Sequencing |
|
Use Scenario: FPGA configuration interfaces require staggered enable signals for multiple peripherals to avoid inrush current peaks. IC Role / Device Role / Timing Role: 74HCT221DB,118 provides two independent, non-overlapping delay pulses (e.g., 100 µs and 200 µs) from shared trigger. Use Value: Enables deterministic inter-peripheral timing without FPGA logic resources or external microcontroller intervention. |
Use Scenario: Multi-rail power supplies (e.g., 12 V, 5 V, 3.3 V) must sequence turn-on with 10–100 ms gaps to prevent latch-up. IC Role / Device Role / Timing Role: 74HCT221DB,118 uses global nRD to synchronize both channels' reset, then triggers sequentially via nA/nB to generate cascaded enable pulses. Use Value: Ensures strict monotonic sequencing even after brown-out recovery - no race conditions or metastability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar monostable multivibrator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LV221AIPWR | Lower VCC range (1.65–5.5 V); LV logic thresholds; 3.3 V optimized; tPHL = 3.5 ns faster at 3.3 V | Better suited for mixed-voltage 3.3 V systems; not TTL-compatible - requires level-shifting if interfacing with 5 V logic | Select when operating below 4.5 V or requiring sub-5 ns propagation; verify input threshold compatibility with driving source |
| 74HC221N,652 | HC family - CMOS input thresholds (VIH = 3.5 V min @ VCC = 5 V); higher noise margin but incompatible with TTL outputs | Requires 5 V-only systems with CMOS drivers; unsuitable for direct interface with 74LS/74F logic without buffers | Choose for pure CMOS designs where power supply is stable at 5 V and driver outputs meet HC VIH/VIL specs |
Compared with 74HCT221DB,118, SN74LV221AIPWR offers superior speed and voltage flexibility below 4.5 V but sacrifices TTL compatibility, while 74HC221N,652 provides higher noise immunity at 5 V but cannot accept standard TTL output levels - making 74HCT221DB,118 the optimal choice for legacy 5 V systems with mixed logic families.
Availability
74HCT221DB,118 is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and consumer appliance control systems requiring stable component supply, long-term lifecycle support, and guaranteed traceability.
Supply support for 74HCT221DB,118 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 leader in high-volume production of logic, discrete, and power MOSFET semiconductors, serving automotive, industrial, and computing markets with AEC-Q100-qualified components and ISO/TS 16949 manufacturing.
The 74HCT221DB,118 belongs to Nexperia's 74HCT logic family - engineered for seamless interoperability with legacy TTL systems while delivering CMOS power efficiency and robustness in harsh environments.
FAQ
What is the maximum recommended value for REXT when using 74HCT221DB,118?
The datasheet specifies REXT up to 1000 kΩ for reliable operation at VCC = 5 V. Using higher values increases susceptibility to leakage current errors and temperature drift, potentially causing pulse width inaccuracy beyond ±5%. For stable timing above 100 kΩ, use metal-film resistors with ±1% tolerance and low TC, and confirm performance across −40 °C to +125 °C in final design validation. Always pair with low-leakage ceramic or film capacitors.
Can 74HCT221DB,118 operate with a 3.3 V supply?
No - the 74HCT221DB,118 is specified only for VCC = 4.5 V to 5.5 V. At 3.3 V, input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) become invalid, propagation delays increase unpredictably, and output drive falls below specification. For 3.3 V systems, use the pin-compatible SN74LV221AIPWR or 74LVC221APW,118, both rated down to 1.65 V and maintaining full functionality.
How does the Schmitt-trigger input on nB improve noise immunity in 74HCT221DB,118?
The nB inputs of 74HCT221DB,118 feature built-in Schmitt-trigger hysteresis (~0.4 V typical), meaning the rising threshold (Vt+) is ~1.3 V and falling threshold (Vt−) is ~0.9 V at VCC = 4.5 V. This prevents multiple triggering from slowly rising or noisy signals - e.g., mechanical switch bounce or EMI-coupled transients - by requiring a clean 400 mV swing to cross both thresholds. Standard CMOS inputs would misfire on such signals.
Is 74HCT221DB,118 pin-compatible with the older 74LS123?
Yes - the 74HCT221DB,118 has identical pinout, function mapping, and DC/AC timing behavior to the 74LS123, enabling direct replacement in existing LSTTL designs. No PCB changes are needed. However, note that 74HCT221DB,118 draws significantly less quiescent current (ICC ≈ 4 µA vs. 74LS123's 15 mA) and offers improved pulse width stability across temperature and supply voltage.
What happens if CEXT is left unconnected on 74HCT221DB,118?
If CEXT is unconnected or floating, the 74HCT221DB,118 fails to generate a defined output pulse - the internal timing circuit lacks the necessary capacitance to establish tW = 0.7 × REXT × CEXT, resulting in erratic or missing output transitions. Always connect CEXT from pin 5 or 14 to GND (pin 8), and tie pins 6 and 14 externally to GND as recommended in the datasheet to prevent parasitic coupling and ensure stable monostable operation.
74HCT221DB,118 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- 74HCT
- Package/Case:
- 16-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Monostable
- Independent Circuits:
- 2
- Schmitt Trigger Input:
- Yes
- Propagation Delay:
- 31 ns
- Current - Output High, Low:
- 4mA, 4mA
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SSOP
74HCT221DB,118 FAQ
1.How can I place an order for 74HCT221DB,118 through Aetrix?
Please submit a Request for Quotation (RFQ) for 74HCT221DB,118 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for 74HCT221DB,118 reliable?
The price and inventory of 74HCT221DB,118 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74HCT221DB,118 is usually 5 days.
3.What payment methods are accepted for 74HCT221DB,118?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74HCT221DB,118 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74HCT221DB,118?
74HCT221DB,118 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74HCT221DB,118 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for 74HCT221DB,118?
For technical support, including 74HCT221DB,118 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74HCT221DB,118 requirements.
6.How does Aetrix verify that 74HCT221DB,118 is sourced from the original manufacturer or authorized distributors?
All 74HCT221DB,118 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 74HCT221DB,118 meets industry standards.
7.What is the process for return or replacement of 74HCT221DB,118?
All 74HCT221DB,118 units undergo pre-shipment inspection (PSI). If there is an issue with 74HCT221DB,118, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The 74HCT221DB,118 part is unused and in its original packaging.
Return procedure for 74HCT221DB,118:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
74HCT221DB,118 Tags
-
SN74LVC1G123DCUR
Texas Instruments
-
CD4047BM96
Texas Instruments
-
SN74LVC1G123DCTR
Texas Instruments
-
CD74HC221M96
Texas Instruments
-
CD14538BE
Texas Instruments
-
SN74LVC1G123YZPR
Texas Instruments
-
SN74LVC1G123DCUT
Texas Instruments
-
MC14538BDR2G
onsemi
-
74VHC123AMX
onsemi
-
LTC6993CS6-2#TRMPBF
Analog Devices Inc.
-
LTC6993CS6-3#TRMPBF
Analog Devices Inc.
-
LTC6993CS6-1#TRMPBF
Analog Devices Inc.
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
