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Texas Instruments CAHCT138QPWRG4Q1
- Part No.:
- CAHCT138QPWRG4Q1
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
CAHCT138QPWRG4Q1.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:5,850
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Product details
Overview
CAHCT138QPWRG4Q1 from Texas Instruments is an automotive-grade 3-line to 8-line decoder/demultiplexer in TSSOP-16 package, featuring TTL-compatible inputs, 5.5 V absolute max supply rating, 12 ns max propagation delay at 15 pF load, and operation across −40°C to +125°C. It serves as a high-speed memory address decoder in engine control units and ADAS domain controllers.
For engineers reviewing the CAHCT138QPWRG4Q1 datasheet, CAHCT138QPWRG4Q1 pinout, CAHCT138QPWRG4Q1 application, or CAHCT138QPWRG4Q1 equivalent, key selection criteria include automotive AEC-Q100 qualification, enable-input architecture for cascading, output drive capability (±8 mA), thermal performance (RθJA = 135.9°C/W), and compatibility with 5 V logic systems.
Technical Context
This device implements positive-logic decoding with three binary select inputs (A, B, C) and three enable terminals (G1 active-high; G2A/G2B active-low), enabling precise selection of one of eight active-low outputs. Its EPIC CMOS process ensures TTL-level input thresholds while maintaining CMOS power efficiency.
Propagation delays are asymmetrically optimized: tPLH/tPHL from G1 to any Y is 6.6–10.5 ns (CL = 15 pF), faster than delays from select inputs (7.6–12 ns), supporting tight timing budgets in memory decode paths where enable gating precedes address settling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures stable operation across automotive battery rail variations including cold-crank conditions. |
| Propagation Delay | 6.6 ns (min) / 10.5 ns (max) from G1 to Y - Enables sub-100 MHz system clock domain synchronization in memory subsystems. |
| Output Drive | ±8 mA - Sufficient to directly drive multiple 74AHCT inputs or small LED indicators without external buffers. |
| Input Compatibility | TTL-voltage compatible (VIL ≤ 0.8 V, VIH ≥ 2 V) - Interoperates seamlessly with legacy 5 V microcontrollers and FPGAs. |
| Operating Temperature | −40°C to +125°C - Validated for under-hood and transmission-control module environments per AEC-Q100 Grade 1. |
| ESD Rating | ±2000 V HBM - Meets automotive ESD robustness requirements for assembly and field reliability. |
| Power Dissipation Cap. | 14 pF - Low dynamic power consumption supports high-density PCB layouts with minimal thermal impact. |
Pinout & Package
TSSOP-16 (PW) package: 5.00 mm × 6.4 mm body, 1.2 mm max height, lead pitch 0.65 mm, RoHS-compliant NiPdAu finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A (Pin 1) | Select input A (LSB) | Binary address bit 0; must be tied to VCC or GND if unused to prevent floating CMOS input instability. |
| B (Pin 2) | Select input B | Binary address bit 1; part of 3-bit address bus interface for memory or peripheral selection. |
| C (Pin 3) | Select input C (MSB) | Binary address bit 2; completes 3-bit decode range (0–7) for 8-channel demux or chip-enable generation. |
| G2A (Pin 4) | Active-low enable A | First cascade enable; low enables decoding only when G2B and G1 are also asserted per function table. |
| G2B (Pin 5) | Active-low enable B | Second cascade enable; used with G2A to form dual-active-low gating for hierarchical decoding schemes. |
| G1 (Pin 6) | Active-high enable | Primary system-level enable; high permits output activation when G2A/G2B are low - critical for power-gated subsystems. |
| Y0 (Pin 15) | Active-low output 0 | Low-true decoded output; sinks current when selected - interfaces directly with enable pins of memory ICs or logic gates. |
| Y7 (Pin 7) | Active-low output 7 (MSB) | Most significant decoded channel; identical electrical specs to Y0–Y6 but assigned highest address value. |
| GND (Pin 8) | Ground reference | Primary return path for all internal logic and output currents; requires low-inductance connection to PCB ground plane. |
| VCC (Pin 16) | Supply voltage | 5 V nominal power rail; requires local 0.1 µF ceramic bypass capacitor placed within 3 mm of pin per layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q100 qualified | Grade 1 (−40°C to +125°C) qualification confirmed - suitable for safety-critical automotive ECUs without additional qualification effort. |
| Three enable inputs | G1 (active-high) + G2A/G2B (active-low) allow 24-line decoding without external inverters and 32-line with only one inverter - reduces component count and board area. |
| EPIC CMOS process | Delivers TTL-compatible input thresholds with CMOS-level static power (ICC ≤ 40 µA) - ideal for always-on vehicle networks with strict quiescent current limits. |
| Latch-up immunity | Exceeds 250 mA per JESD17 - prevents destructive latch-up during transient overvoltage events common in 12 V automotive systems. |
| Thermal pad option | WQFN variant includes exposed thermal pad (not present in TSSOP); this PW package relies on leadframe conduction - RθJA = 135.9°C/W reflects that limitation. |
Applications
| Engine Control Unit (ECU) Memory Decode | ADAS Camera Sensor Interface |
|---|---|
Use Scenario: Decoding 3-bit address lines from MCU to select among eight flash memory banks or EEPROM configuration zones in real-time calibration systems. IC Role / Device Role / Timing Role: Address decoder providing sub-11 ns propagation delay to meet tight memory access timing windows under 5 V supply. Use Value: Eliminates need for discrete gate logic or larger CPLDs, reducing BOM cost and PCB footprint while maintaining AEC-Q100 compliance. | Use Scenario: Routing parallel camera sensor data streams (e.g., from four 2-lane MIPI CSI-2 receivers) to designated image processing channels. IC Role / Device Role / Timing Role: Demultiplexer using G1 as frame-sync enable and A/B/C as channel ID selector - outputs drive enable lines of downstream serializer ICs. Use Value: Enables deterministic, low-jitter signal routing with no added setup/hold timing constraints beyond MCU GPIO timing. |
| Body Control Module (BCM) I/O Expansion | Electric Power Steering (EPS) Fault Monitoring |
Use Scenario: Expanding limited MCU GPIO count to manage 8 independent LED status indicators, relay drivers, or diagnostic test points. IC Role / Device Role / Timing Role: Logic-level demux converting serial control bits into parallel active-low enable signals for discrete driver ICs. Use Value: Provides ±8 mA sink capability per output - sufficient to drive LEDs directly without current-limiting resistors in many configurations. | Use Scenario: Monitoring eight independent motor phase fault signals (overcurrent, overtemperature, open-load) and asserting a single aggregated fault line to the EPS MCU. IC Role / Device Role / Timing Role: OR-ing function implemented via wired-AND of active-low outputs feeding a pull-up resistor - any fault pulls line low. Use Value: Leverages inherent active-low outputs to implement fail-safe fault aggregation without external diodes or logic gates. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AHCT138QPWRQ1 | Same silicon, identical specs, different TI internal marking (AHT138Q vs HB138Q); same TSSOP-16 packaging and reel configuration. | No functional or application difference - both qualified for automotive use and share identical thermal, timing, and electrical behavior. | Select based on distributor stock availability or preferred TI internal part number convention. |
| MC74VHC138DTG | Non-automotive grade; operates from 2 V to 5.5 V; higher max propagation delay (16 ns @ 50 pF); no AEC-Q100 qualification. | Suitable for industrial or consumer boards where extended temperature range and automotive qualification are not required. | Use only in non-safety-critical designs lacking AEC-Q100 mandates; verify timing margins due to slower switching. |
Compared with SN74AHCT138QPWRQ1, CAHCT138QPWRG4Q1 offers identical performance but distinct TI internal traceability; versus MC74VHC138DTG, it delivers guaranteed automotive reliability, tighter timing, and lower dynamic power - essential for ECU and ADAS deployments.
Availability
CAHCT138QPWRG4Q1 is available at Aetrix Electronics and suitable for engine control units, ADAS camera interfaces, and body control modules requiring stable component supply across automotive production lifecycles.
Supply support for CAHCT138QPWRG4Q1 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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for automotive, industrial, personal electronics, and communications markets.
The SN74AHCT automotive logic family - including CAHCT138QPWRG4Q1 - was designed specifically for high-reliability, high-speed memory decoding and data-routing in automotive electronic control units operating under harsh environmental conditions.
FAQ
What is the maximum operating temperature for CAHCT138QPWRG4Q1?
The CAHCT138QPWRG4Q1 is rated for continuous operation from −40°C to +125°C ambient temperature, meeting AEC-Q100 Grade 1 requirements. This specification is validated across the full supply voltage range (4.5 V to 5.5 V) and applies to the TSSOP-16 (PW) package variant supplied as CAHCT138QPWRG4Q1. Thermal derating is not required within this range.
Does CAHCT138QPWRG4Q1 support 3.3 V logic inputs?
No - CAHCT138QPWRG4Q1 features TTL-compatible inputs with VIL ≤ 0.8 V and VIH ≥ 2.0 V, optimized for 5 V systems. While it may function with 3.3 V logic under some conditions, TI does not guarantee operation below VIH = 2.0 V. For mixed-voltage designs, level-shifting or a 3.3 V–compatible alternative like SN74LVC138A should be used instead of relying on CAHCT138QPWRG4Q1.
How are unused inputs handled on CAHCT138QPWRG4Q1?
All unused inputs on CAHCT138QPWRG4Q1 - including A, B, C, G2A, G2B, and G1 - must be permanently tied to either VCC or GND to prevent floating CMOS nodes, which can cause increased ICC, erratic output behavior, or latch-up. TI's application report SCBA004 explicitly mandates this practice. Leaving inputs unconnected is not permitted in production designs using CAHCT138QPWRG4Q1.
Can CAHCT138QPWRG4Q1 be used as a demultiplexer?
Yes - CAHCT138QPWRG4Q1 functions as a 1-to-8 demultiplexer when G1 is used as the data input and A/B/C serve as select lines. In this mode, the selected output (Y0–Y7) mirrors the logic state of G1 (active-high), while all other outputs remain high. This configuration is explicitly supported in the device functional modes section of the CAHCT138QPWRG4Q1 datasheet and requires no external components.
What is the recommended bypass capacitor for CAHCT138QPWRG4Q1?
Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible (≤ 3 mm) to the VCC pin (Pin 16) of CAHCT138QPWRG4Q1, with low-inductance connection to the GND pin (Pin 8). For enhanced noise suppression, a parallel 1 µF capacitor may be added - but the 0.1 µF unit is mandatory per TI layout guidelines to ensure stable operation under fast-switching transients.
CAHCT138QPWRG4Q1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 8mA, 8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- Automotive
- Qualification:
- AEC-Q100
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
CAHCT138QPWRG4Q1 FAQ
1.How can I place an order for CAHCT138QPWRG4Q1 through Aetrix?
Please submit a Request for Quotation (RFQ) for CAHCT138QPWRG4Q1 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 CAHCT138QPWRG4Q1 reliable?
The price and inventory of CAHCT138QPWRG4Q1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CAHCT138QPWRG4Q1 is usually 5 days.
3.What payment methods are accepted for CAHCT138QPWRG4Q1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CAHCT138QPWRG4Q1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CAHCT138QPWRG4Q1?
CAHCT138QPWRG4Q1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CAHCT138QPWRG4Q1 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 CAHCT138QPWRG4Q1?
For technical support, including CAHCT138QPWRG4Q1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CAHCT138QPWRG4Q1 requirements.
6.How does Aetrix verify that CAHCT138QPWRG4Q1 is sourced from the original manufacturer or authorized distributors?
All CAHCT138QPWRG4Q1 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 CAHCT138QPWRG4Q1 meets industry standards.
7.What is the process for return or replacement of CAHCT138QPWRG4Q1?
All CAHCT138QPWRG4Q1 units undergo pre-shipment inspection (PSI). If there is an issue with CAHCT138QPWRG4Q1, 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 CAHCT138QPWRG4Q1 part is unused and in its original packaging.
Return procedure for CAHCT138QPWRG4Q1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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