My Inquiry
My Account
NXP Semiconductors 74HCT688DB,118
- Part No.:
- 74HCT688DB,118
- Manufacturer:
- NXP Semiconductors
- Category:
- Comparators
- Package:
- 20-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
74HCT688DB,118.pdf
- Description:
- IC COMPARATOR IDENTITY 8B 20SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,470
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
74HCT688DB,118 from Nexperia is an 8-bit magnitude comparator IC designed for digital logic systems requiring high-speed word equality detection. It compares two 8-bit binary or BCD words (P₀–P₇ and Q₀–Q₇), features active-low enable (E), delivers a single P = Q output, and operates at 4.5 V with 17 ns propagation delay (Pn/Qn to P = Q) at 25 °C.
For engineers reviewing the 74HCT688DB,118 datasheet, 74HCT688DB,118 pinout, 74HCT688DB,118 application, or 74HCT688DB,118 equivalent, this device is selected for precise 8-bit equality checking in TTL-compatible control logic, address decoding, and multi-chip comparison architectures where HCT-level input thresholds and standard-output drive are required.
Technical Context
The 74HCT688DB,118 implements combinational logic that evaluates bitwise equivalence across all eight input pairs only when E is LOW; the output P = Q goes HIGH exclusively when all eight Pn = Qn conditions hold simultaneously. Its HCT family design ensures TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max at VCC = 4.5 V) and CMOS-level output swing.
It supports cascading via the E input - the P = Q output of a higher-order stage can drive E of a lower-order stage to build wider comparators (e.g., 16-bit). No internal latching or clocking is present; operation is fully asynchronous and level-sensitive.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - compatible with standard 5 V TTL/CMOS logic rails |
| Pn/Qn to P = Q tPHL/tPLH | 17 ns typ. at VCC = 5 V, CL = 15 pF - enables sub-60 MHz comparison throughput |
| E to P = Q tPHL/tPLH | 12 ns typ. at VCC = 5 V, CL = 15 pF - fast enable-response critical for pipelined compare chains |
| Input Capacitance (CI) | 3.5 pF - low loading preserves signal integrity on shared bus lines |
| Power Dissipation Cap. (CPD) | 30 pF - used to calculate dynamic power: PD = CPD × VCC² × fi + Σ(CL × VCC² × fo) |
| Output Drive | Standard CMOS - IOH/ IOL = ±4 mA at VCC = 4.5 V - drives multiple LSTTL inputs directly |
Pinout & Package
74HCT688DB,118 is supplied in a 20-pin SOIC (Small Outline Integrated Circuit) package, 7.5 mm wide, with 0.65 mm pitch and gull-wing leads. Pin 1 is marked by a bevelled corner or notch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (E) | Active-low enable input | Asserts comparison logic only when LOW; HIGH forces P = Q output LOW regardless of inputs |
| 2,4,6,8,11,13,15,17 (P0–P7) | First 8-bit word input | Bit-parallel data input A; P0 = LSB, P7 = MSB |
| 3,5,7,9,12,14,16,18 (Q0–Q7) | Second 8-bit word input | Bit-parallel data input B; Q0 = LSB, Q7 = MSB |
| 10 (GND) | Ground reference | 0 V return path for all internal logic and output drivers |
| 19 (P = Q) | Equality output | Open-drain compatible HIGH-active signal indicating full 8-bit match (P₀–P₇ ≡ Q₀–Q₇) |
| 20 (VCC) | Positive supply | Primary power rail (4.5–5.5 V); powers all internal gates and output stage |
Key Features
| Feature | Design Value |
|---|---|
| 8-bit parallel magnitude comparison | Detects exact bitwise equality between two independent 8-bit words in a single cycle |
| TTL-compatible input thresholds | Accepts standard 5 V TTL logic levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V), eliminating level-shifting in mixed-logic systems |
| Cascadable architecture | Enables multi-word comparisons (e.g., 16-bit) using P = Q output to drive E of adjacent 74HCT688DB,118 devices |
| Standard-output drive capability | Delivers ±4 mA at VCC = 4.5 V - sufficient to drive up to 10 LSTTL loads without buffering |
Applications
| Memory Address Decoding | Microprocessor Bus Arbitration |
|---|---|
Use Scenario: Detecting exact match between CPU address bus and peripheral chip-select range. IC Role / Device Role / Timing Role: 74HCT688DB,118 acts as a synchronous, level-sensitive address comparator generating chip-enable pulses. Use Value: Enables zero-wait-state peripheral selection with deterministic timing due to fixed 17 ns Pn→P=Q propagation. | Use Scenario: Resolving bus master priority among multiple DMA controllers sharing one data bus. IC Role / Device Role / Timing Role: 74HCT688DB,118 compares unique ID registers to assert arbitration grant signals. Use Value: Guarantees glitch-free grant assertion with TTL-compatible inputs, avoiding metastability in multi-master handshake protocols. |
| Industrial PLC Input Validation | Digital Test Equipment Pattern Matching |
Use Scenario: Verifying correct configuration word entry into programmable logic controller I/O modules. IC Role / Device Role / Timing Role: 74HCT688DB,118 compares user-entered setup code against stored factory defaults. Use Value: Provides fail-safe validation with no external clock dependency - functional even during power-up sequencing. | Use Scenario: Real-time detection of specific 8-bit test vectors in automated circuit board testers. IC Role / Device Role / Timing Role: 74HCT688DB,118 serves as a hardware pattern matcher feeding pass/fail flags to test sequencer logic. Use Value: Reduces FPGA resource usage by offloading deterministic pattern checks to dedicated, low-latency logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-bit magnitude comparator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS688N | Bipolar TTL technology; 5 V only; higher ICC (25 mA typical); slower (tPLH = 25 ns) | Higher power consumption and heat generation; less noise-immune inputs | Select when legacy TTL system compatibility outweighs power and speed requirements |
| 74HC688D,653 | CMOS variant; identical pinout; wider VCC range (2–6 V); VIH/VIL referenced to VCC | Not TTL-input-compatible; requires level translation in mixed 5 V TTL environments | Select for battery-powered or multi-rail systems where input threshold flexibility is prioritized over direct TTL interface |
Compared with SN74LS688N and 74HC688D,653, the 74HCT688DB,118 uniquely balances TTL-level input compatibility, 5 V CMOS efficiency, and 17 ns propagation-making it optimal for upgrading legacy LSTTL designs without layout changes or voltage rail modifications.
Availability
74HCT688DB,118 is available at Aetrix Electronics and suitable for memory address decoding, microprocessor bus arbitration, industrial PLC input validation, and digital test equipment pattern matching requiring stable component supply and long-term industrial lifecycle support.
Supply support for 74HCT688DB,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 discrete, logic, and PowerMOS semiconductors, formed in 2017 from the former NXP Standard Products business, with deep expertise in automotive, industrial, computing, and consumer applications.
The 74HCT688DB,118 belongs to Nexperia's 74HCT logic family - engineered specifically to provide pin- and function-compatible CMOS alternatives to legacy 74LS TTL devices while maintaining identical input thresholds and drive strength.
FAQ
What is the operating voltage range for the 74HCT688DB,118?
The 74HCT688DB,118 operates over a supply voltage range of 4.5 V to 5.5 V. This narrow window ensures strict TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and stable CMOS output performance. Operation outside this range may cause incorrect logic states or increased quiescent current. Always verify VCC stability within ±5 % in production designs using the 74HCT688DB,118.
Does the 74HCT688DB,118 support cascading for comparing more than 8 bits?
Yes, the 74HCT688DB,118 supports cascading via its active-low enable (E) input. The P = Q output of a higher-order comparator can drive the E input of a lower-order 74HCT688DB,118 to construct 16-bit or wider magnitude comparisons. This is explicitly documented in the application information section of the original Philips/Nexperia datasheet and verified in Fig.8 of the December 1990 specification.
What is the maximum propagation delay from input to output for the 74HCT688DB,118?
The maximum propagation delay for the 74HCT688DB,118 is 43 ns (Pn/Qn to P = Q) and 36 ns (E to P = Q) under worst-case industrial temperature (−40 °C to +85 °C) and VCC = 4.5 V, per AC characteristics tables in the Nexperia datasheet. These values include process, voltage, and temperature extremes - not typical-only figures.
Is the 74HCT688DB,118 pin-compatible with the 74LS688?
Yes, the 74HCT688DB,118 is pin-compatible and functionally equivalent to the 74LS688, including identical pin numbering, terminal functions, and logic behavior. This allows direct replacement in existing LSTTL designs without PCB modification, provided VCC remains at 5 V and system timing margins accommodate the slightly faster 74HCT688DB,118 propagation delays.
What package type is used for the 74HCT688DB,118?
The 74HCT688DB,118 uses a 20-pin SOIC (Small Outline Integrated Circuit) package, 7.5 mm wide, with 0.65 mm lead pitch and gull-wing surface-mount leads. This package is defined in Nexperia's "74HC/HCT/HCU/HCMOS Logic Package Outlines" document and matches JEDEC MS-013AC standards for mechanical compatibility and reflow soldering profiles.
74HCT688DB,118 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- 74HCT
- Package/Case:
- 20-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Identity Comparator
- Number of Bits:
- 8
- Output:
- Active Low
- Output Function:
- A=B
- Voltage - Supply:
- 4.5V ~ 5.5V
- Current - Output High, Low:
- 4mA, 4mA
- Max Propagation Delay @ V, Max CL:
- 34ns @ 4.5V, 50pF
- Current - Quiescent (Iq):
- 8 µA
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 20-SSOP
- Mounting Type:
- Surface Mount
74HCT688DB,118 FAQ
1.How can I place an order for 74HCT688DB,118 through Aetrix?
Please submit a Request for Quotation (RFQ) for 74HCT688DB,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 74HCT688DB,118 reliable?
The price and inventory of 74HCT688DB,118 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74HCT688DB,118 is usually 5 days.
3.What payment methods are accepted for 74HCT688DB,118?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74HCT688DB,118 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74HCT688DB,118?
74HCT688DB,118 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74HCT688DB,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 74HCT688DB,118?
For technical support, including 74HCT688DB,118 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74HCT688DB,118 requirements.
6.How does Aetrix verify that 74HCT688DB,118 is sourced from the original manufacturer or authorized distributors?
All 74HCT688DB,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 74HCT688DB,118 meets industry standards.
7.What is the process for return or replacement of 74HCT688DB,118?
All 74HCT688DB,118 units undergo pre-shipment inspection (PSI). If there is an issue with 74HCT688DB,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 74HCT688DB,118 part is unused and in its original packaging.
Return procedure for 74HCT688DB,118:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
74HCT688DB,118 Tags
-
SN74HC688PWR
Texas Instruments
-
74HC85PW,118
Nexperia USA Inc.
-
74HC688D,653
Nexperia USA Inc.
-
SN74F521DWR
Texas Instruments
-
CD74HCT688M96
Texas Instruments
-
SN74F521N
Texas Instruments
-
CD4585BE
Texas Instruments
-
SN74HC688DWR
Texas Instruments
-
SN74LS85DR
Texas Instruments
-
CD74HC85E
Texas Instruments
-
MC14585BDR2G
onsemi
-
SN74HC688N
Texas Instruments
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…
