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Texas Instruments CD74HC4538M
- Part No.:
- CD74HC4538M
- Manufacturer:
- Texas Instruments
- Category:
- Multivibrators
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74HC4538M.pdf
- Description:
- IC MULTIVIBRATOR 21NS 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,902
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Product details
Overview
CD74HC4538M from Texas Instruments is a dual retriggerable/resettable monostable multivibrator in 16-pin SOIC package, operating from 2V to 6V with ±25mA output drive, -55°C to +125°C temperature range, and Schmitt-trigger inputs on A/B terminals. It delivers precision timing pulses for edge-triggered control circuits in industrial automation and test equipment.
For engineers reviewing the CD74HC4538M datasheet, CD74HC4538M pinout, CD74HC4538M application, or CD74HC4538M equivalent, key selection criteria include independent trigger/reset propagation delays, retrigger time independence from CX, leading/trailing-edge triggering capability, and buffered Q/Q outputs for noise-immune signal distribution.
Technical Context
The CD74HC4538M implements two independent monostable sections, each with separate A (leading-edge), B (trailing-edge), and R (asynchronous reset) inputs, plus RX/CX timing network pins. Propagation delay from A/B or R to Q/Q is independent of external RX and CX values, enabling stable timing across wide pulse-width ranges.
Each section supports retriggerable operation by default; non-retriggerable mode is achieved via internal feedback (Q→B for A-triggering or Q→A for B-triggering). Schmitt-trigger inputs ensure robust noise immunity, while buffered complementary outputs provide high fanout (10 LSTTL loads) without loading effects.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 2V to 6V - Enables direct interface with 3.3V and 5V logic systems without level shifting. |
| Operating Temperature | -55°C to +125°C - Qualified for extended industrial and aerospace environments without derating. |
| Propagation Delay | 43ns max at VCC=6V (A/B→Q) - Supports high-speed timing control up to ~10MHz repetition rates. |
| Output Drive | ±25mA per pin - Sufficient to directly drive LEDs, small relays, or logic inputs without external buffers. |
| Input Hysteresis | NIL/NIH = 30% of VCC at 5V - Rejects >1.5V noise spikes on trigger inputs in noisy industrial settings. |
| Pulse Width Range | τ = 0.7 × RX × CX, RX ≥5kΩ, CX ≥0pF - Enables programmable output durations from microseconds to seconds using standard RC components. |
Pinout & Package
CD74HC4538M is housed in a 16-pin SOIC (D) package, 7.5mm × 10.3mm body, 1.75mm max height, with 1.27mm pitch and gull-wing leads. Thermal resistance θJA = 73°C/W enables reliable operation at full load in compact PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 15 | 1CX / 2CX | External timing capacitor connection for Monostable 1 and 2 - sets pulse width with RX. |
| 2, 14 | 1RXCX / 2RXCX | Shared node for RX and CX - internal discharge path during reset; requires proper termination. |
| 3, 13 | 1R / 2R | Asynchronous active-low reset input - forces Q low and Q high regardless of trigger state. |
| 4, 12 | 1A / 2A | Leading-edge trigger input with Schmitt buffer - initiates pulse on rising edge. |
| 5, 11 | 1B / 2B | Trailing-edge trigger input with Schmitt buffer - initiates pulse on falling edge. |
| 6, 10 | 1Q / 2Q | True output - active-high pulse synchronized to trigger or reset event. |
| 7 | GND | Ground reference - must be low-impedance return path for all timing and output currents. |
| 8, 9 | 1Q / 2Q | Inverted output - complements Q; buffered for fanout and noise rejection. |
| 16 | VCC | Positive supply - decoupling capacitor (0.1µF) required within 10mm of pin for stable switching. |
Key Features
| Feature | Design Value |
|---|---|
| Retriggerable/Resettable Operation | Enables dynamic pulse extension during ongoing events (e.g., watchdog timeout extension) or hard reset recovery without power cycle. |
| Independent Trigger/Reset Delays | Eliminates timing uncertainty when adjusting RC networks - critical for deterministic response in safety-critical sequencers. |
| Schmitt-Trigger Inputs on A/B | Prevents multiple triggering from slow-rising or noisy signals (e.g., mechanical switch bounce or motor EMI). |
| Separate Resets per Section | Allows independent initialization of dual timing channels - essential for multi-stage process controllers or dual-sensor synchronization. |
| Wide Output Pulse Width Range | Supports single-chip implementation of both short-duration strobes (<1µs) and long-duration enable signals (>1s) via RC scaling. |
Applications
| Industrial PLC Timing Module | Automated Test Equipment (ATE) |
|---|---|
Use Scenario: Generating precise on-time windows for solenoid actuation in packaging machinery with variable cycle times. IC Role / Device Role / Timing Role: Dual monostable provides independent gate-enable and fault-clear pulses synchronized to encoder edges. Use Value: Retriggerable mode extends valve-open duration if sensor feedback indicates incomplete motion, improving throughput without firmware changes. | Use Scenario: Controlling stimulus application and measurement sampling windows during IC parametric testing. IC Role / Device Role / Timing Role: One section triggers DUT power-up sequence; second generates calibrated test pulse with sub-50ns jitter. Use Value: Independent RX/CX control allows simultaneous optimization of power sequencing delay and test pulse width without cross-coupling. |
| Motor Control Fault Detection | Power Supply Sequencing |
Use Scenario: Detecting overcurrent latch conditions in BLDC inverters and initiating safe shutdown with defined hold-off time. IC Role / Device Role / Timing Role: B-input triggered by comparator output; Q drives gate driver disable, Q enables fault LED with adjustable blink rate. Use Value: Schmitt-trigger input rejects noise from PWM switching, preventing false trips during normal commutation. | Use Scenario: Enforcing strict power-up order across 3.3V, 5V, and 12V rails in FPGA-based systems. IC Role / Device Role / Timing Role: Cascaded monostables generate staggered enable signals with programmable inter-rail delays. Use Value: External RC tuning allows field adjustment of sequencing intervals without PCB redesign or firmware update. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual monostable applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| CD74HC4538M96 | Identical electrical specs and pinout; supplied in 2500-unit tape-and-reel (SOIC-D package). | No functional difference - optimized for automated SMT assembly rather than manual prototyping. | Select CD74HC4538M96 for volume production; CD74HC4538M is obsolete but may be available in legacy stock. |
| CD74HCT4538M96 | HCT version: TTL-compatible inputs (VIH=2V min), 4.5–5.5V only, identical timing behavior and SOIC-D footprint. | Required when interfacing with legacy 5V TTL logic without level shifters; not suitable for mixed 3.3V/5V systems. | Choose CD74HCT4538M96 only when input compatibility with 74LS-series devices is mandatory. |
Compared with CD74HC4538M, CD74HC4538M96 offers identical performance in production-ready packaging, while CD74HCT4538M96 trades voltage flexibility for guaranteed TTL input thresholds - making the HC variant preferable for modern low-voltage designs requiring broad supply range.
Availability
CD74HC4538M is available at Aetrix Electronics and suitable for industrial automation, test equipment, motor control, and power sequencing applications requiring stable component supply across extended temperature ranges.
Supply support for CD74HC4538M 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 delivering analog, embedded processing, and logic solutions with emphasis on reliability, longevity, and industrial-grade qualification.
The CD74HC4538M belongs to TI's High-Speed CMOS Logic family, designed specifically for precision timing, edge-sensitive control, and noise-immune signal conditioning in harsh industrial and aerospace environments.
FAQ
What is the minimum external timing resistor value supported by CD74HC4538M?
The CD74HC4538M requires a minimum external timing resistor (RX) of 5kΩ per section, as specified in the Absolute Maximum Ratings table. Using lower values risks exceeding the 30mA maximum current into pins 2 or 14 during timing capacitor discharge, potentially damaging the internal circuitry. Always verify RX selection against the actual CX leakage and board layout parasitics.
Can CD74HC4538M operate reliably at 3.3V supply voltage?
Yes, CD74HC4538M is fully specified for 2V to 6V operation, including 3.3V. At VCC = 3.3V, it maintains VIH = 2.31V (min), VIL = 0.99V (max), and propagation delay ≤110ns (typical), making it compatible with standard 3.3V CMOS logic families without level translation.
How does the retriggerable mode function in CD74HC4538M?
In retriggerable mode, CD74HC4538M extends the output pulse width by one full τ period upon each new trigger event before the prior pulse expires. This behavior is inherent and requires no external feedback - unlike non-retriggerable mode, which locks the pulse duration after the first trigger. The retrigger time (trT) is independent of CX and remains ≤175ns at 5V.
What is the purpose of the Schmitt-trigger inputs on CD74HC4538M A and B pins?
The Schmitt-trigger inputs on CD74HC4538M A and B pins provide hysteresis (30% of VCC at 5V), ensuring clean, single-event triggering even with slow-rising or noisy input signals. This eliminates contact bounce issues in switch interfaces and prevents false triggering from EMI in motor control or industrial sensor applications.
Is CD74HC4538M pin-compatible with CD74HCT4538M?
Yes, CD74HC4538M and CD74HCT4538M share identical 16-pin SOIC (D) package dimensions, pinout, and functional terminal assignments. However, they differ electrically: HC supports 2–6V operation with CMOS input thresholds, while HCT is limited to 4.5–5.5V with TTL-compatible inputs - requiring careful system-level voltage validation before substitution.
CD74HC4538M Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- Monostable
- Independent Circuits:
- 2
- Schmitt Trigger Input:
- Yes
- Propagation Delay:
- 21 ns
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage - Supply:
- 2 V ~ 6 V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
CD74HC4538M FAQ
1.How can I place an order for CD74HC4538M through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HC4538M 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 CD74HC4538M reliable?
The price and inventory of CD74HC4538M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HC4538M is usually 5 days.
3.What payment methods are accepted for CD74HC4538M?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HC4538M transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HC4538M?
CD74HC4538M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HC4538M 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 CD74HC4538M?
For technical support, including CD74HC4538M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HC4538M requirements.
6.How does Aetrix verify that CD74HC4538M is sourced from the original manufacturer or authorized distributors?
All CD74HC4538M 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 CD74HC4538M meets industry standards.
7.What is the process for return or replacement of CD74HC4538M?
All CD74HC4538M units undergo pre-shipment inspection (PSI). If there is an issue with CD74HC4538M, 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 CD74HC4538M part is unused and in its original packaging.
Return procedure for CD74HC4538M:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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