BinKey

sn74hct573n-octal-transparent-latch

4 min read

Important Note

This entire repo was AI created - including all of the data within. The intent was to A) help me with my personal electronics inventory; and B) see how I could use AI to make that process a bit easier. DO NOT TRUST!

SN74HCT573N Octal Transparent D-Type Latch

Details

  • Location: Cabinet-3, Bin 33, Section E
  • Category: Logic Gates
  • Quantity: 1
  • Status: Available
  • Package: 20-pin DIP (Dual In-line Package)
  • Datasheet: SN74HCT573 Datasheet

Description

The SN74HCT573N is a CMOS Octal Transparent D-Type Latch with 3-State Outputs from Texas Instruments. This IC contains eight D-type transparent latches with tri-state outputs, designed specifically for driving highly capacitive or relatively low-impedance loads. It’s part of the 74HCT series, which provides TTL-compatible inputs with CMOS performance.

Key Features

  • Eight D-Type Latches: Independent transparent latches in one package
  • Tri-State Outputs: High-impedance state for bus applications
  • Transparent Operation: Data flows through when latch enable is high
  • TTL Compatible Inputs: Works with both TTL and CMOS logic levels
  • High Drive Capability: Can drive 15 LSTTL loads
  • Bus-Structured Pinout: Optimized for microprocessor bus interfacing
  • 74HCT Series: High-speed CMOS with TTL compatibility

Technical Specifications

  • Package: 20-pin DIP (0.6” width)
  • Technology: High-Speed CMOS (74HCT Series)
  • Supply Voltage: 4.5V - 5.5V (TTL compatible)
  • Logic Type: D-Type Transparent Latch
  • Number of Latches: 8 (Octal)
  • Output Type: Tri-State (3-State)
  • Propagation Delay: 25ns typical
  • Output Drive: 6mA source/sink current
  • Operating Temperature: -40°C to +85°C
  • Input Compatibility: TTL and CMOS

Typical Pinout (DIP-20)

    SN74HCT573N
    ┌─────────────┐
OE  │1          20│ VCC
D0  │2          19│ D7
Q0  │3          18│ Q7
D1  │4          17│ D6
Q1  │5          16│ Q6
D2  │6          15│ D5
Q2  │7          14│ Q5
D3  │8          13│ D4
Q3  │9          12│ Q4
GND │10         11│ LE
    └─────────────┘

Pin Descriptions

  • VCC (Pin 20): Positive supply voltage (+4.5V to +5.5V)
  • GND (Pin 10): Ground (0V)
  • D0-D7 (Pins 2,4,6,8,13,15,17,19): Data inputs
  • Q0-Q7 (Pins 3,5,7,9,12,14,16,18): Data outputs (tri-state)
  • LE (Pin 11): Latch Enable (active high)
  • OE (Pin 1): Output Enable (active low)

Operation

Latch Function

The SN74HCT573N operates as a transparent latch:

Truth Table

LEOEOperation
HLTransparent (Q follows D)
LLLatched (Q holds previous state)
XHHigh-impedance output

Control Signals

  • Latch Enable (LE):
    • HIGH: Transparent mode - outputs follow inputs
    • LOW: Latch mode - outputs hold current state
  • Output Enable (OE):
    • LOW: Outputs enabled (normal operation)
    • HIGH: Outputs in high-impedance state

Data Flow

  1. Transparent Mode: When LE is HIGH, data on D inputs appears at Q outputs
  2. Latch Mode: When LE goes LOW, current data is latched and held
  3. Tri-State: When OE is HIGH, outputs go to high-impedance regardless of other inputs

Applications

  • Microprocessor Bus Interface: Latching data from processor buses
  • Memory Address Latching: Holding address information in memory systems
  • Data Bus Buffering: Isolating and driving data buses
  • Register Implementation: Creating temporary data storage
  • Bus Multiplexing: Time-division multiplexing of bus signals
  • I/O Port Expansion: Expanding microcontroller I/O capabilities
  • State Machine Design: Storing state information
  • Pipeline Registers: Buffering data in pipelined systems

Circuit Examples

Basic Data Latch

  • Connect data sources to D0-D7
  • Connect outputs Q0-Q7 to destination circuits
  • Use LE to control when data is latched
  • Use OE to enable/disable outputs

Bus Interface

  • Connect to microprocessor data bus
  • Use address decoding to control LE
  • Use bus control signals for OE
  • Provides isolated, latched data output

Address Latch

  • Common in microprocessor systems
  • Latches multiplexed address/data bus
  • Separates address from data portions
  • Essential for memory interfacing

Design Considerations

  • Setup and Hold Times: Ensure data is stable around LE transitions
  • Output Loading: Can drive up to 15 LSTTL loads
  • Power Supply: Requires stable 5V supply for TTL compatibility
  • Decoupling: Use bypass capacitors near VCC/GND pins
  • Signal Integrity: Consider transmission line effects at high speeds
  • Tri-State Bus: Ensure only one driver enabled at a time

Advantages

  • High Integration: Eight latches in single package
  • Tri-State Outputs: Ideal for bus-oriented systems
  • TTL Compatible: Works with existing TTL systems
  • Low Power: CMOS technology reduces power consumption
  • High Speed: Fast propagation delays for real-time applications
  • Robust Design: Industrial temperature range operation

Comparison with Similar ICs

SN74HCT573N vs SN74HC573N

  • SN74HCT573N: TTL-compatible inputs (4.5V-5.5V supply)
  • SN74HC573N: CMOS inputs (2V-6V supply range)

SN74HCT573N vs SN74HCT574N

  • SN74HCT573N: Transparent latch (level-triggered)
  • SN74HCT574N: D-type flip-flop (edge-triggered)

SN74HCT573N vs SN74HCT373N

  • SN74HCT573N: Bus-structured pinout
  • SN74HCT373N: Standard pinout arrangement

Tags

logic-gate, latch, transparent-latch, octal, d-type, tri-state, 74hct-series, texas-instruments, dip-20 cabinet-3 bin-33 section-e status-available

Notes

The SN74HCT573N is part of the 74HCT high-speed CMOS logic family and is widely used for:

  • Microprocessor and microcontroller interfacing
  • Memory system address latching
  • Bus buffering and isolation
  • Digital system design
  • Educational electronics projects

Modern alternatives and related parts:

  • SN74AHCT573: Advanced high-speed CMOS version
  • SN74LVC573A: Low-voltage CMOS version (1.65V-3.6V)
  • SN74ALS573C: Advanced low-power Schottky version
  • CD74HCT573E: Pin-compatible alternative

The SN74HCT573N is particularly valued in legacy system maintenance and educational applications where TTL compatibility is required. Its transparent latch operation makes it ideal for applications requiring level-triggered data storage, as opposed to edge-triggered flip-flops.

Timing Characteristics

  • Propagation Delay (tpd): 25ns typical
  • Setup Time (tsu): 20ns typical
  • Hold Time (th): 5ns typical
  • Output Enable Time (ten): 23ns typical
  • Output Disable Time (tdis): 18ns typical

These timing specifications make it suitable for most microprocessor applications operating at moderate clock speeds.

Graph View

Backlinks