74LS244N - Octal Buffer/Line Driver 3-State 20-PDIP | TI
料号： 74LS244N ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $1.25 | $1.25 |
| 10 | $1.05 | $10.50 |
| 100 | $0.85 | $85.00 |
| 500 | $0.72 | $360.00 |
| 1,000 | $0.62 | $620.00 |
74LS244N 概述
An octal buffer/line driver is a type of bus-interface logic IC used to isolate, boost, and directionally drive parallel data, address, or control signals between a controller and a bus. The 74LS244 is the de-facto industry standard 'bus driver' in the 74LS logic family and is widely second-sourced. It is commonly employed as a memory-address driver, clock driver, or bus-oriented transmitter/receiver, sitting one tier below the system CPU in the digital logic hierarchy and one tier above discrete bus traces.
Key features of the 74LS244N include symmetric active-low output-enable (1G, 2G) inputs that allow grouping into two 4-bit banks, 3-state outputs that present a high-impedance state when disabled, input hysteresis for improved noise margin, and ESD protection that exceeds typical 74LS ratings. The 'N' suffix denotes the through-hole 20-pin PDIP package, while 'M' would denote SOIC and 'NS' denotes SOP.
Architecturally, the 74LS244N uses bipolar Low-power Schottky technology with a Schottky-clamped transistor design that delivers low propagation delay (typically around 10-12 ns) at modest power consumption compared to standard 74-series TTL. The two independent enable lines let designers disable half the bus while the other half remains active, which is useful in mixed-voltage or partial-power-down designs.
Typical applications include memory-address bus buffering in 8-bit microcomputer and retrocomputing designs (Z80, 6502, 8080), clock-driver fan-out, peripheral-interface buffering, and bus isolation in educational or industrial PLC systems. It is also used to drive long PCB traces or backplane lines where the source drive of a typical microcontroller output would be insufficient.
When designing with this part, ensure that both 1G and 2G are tied LOW during normal operation to enable outputs, and that the high-impedance state is used to isolate two devices sharing a bus. Decoupling VCC with a 0.1 uF ceramic capacitor placed close to the supply pin is recommended to suppress switching transients.
This page synthesizes distributor pricing, same-package drop-in alternatives, and practical design notes that are not found in the bare manufacturer datasheet, helping engineers compare second-source options and design a robust bus-buffer stage.
直接替换替代料： 74LS244N ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
快速对比工具——选择替代料号进行并排对比：
SN74LS244N
✅ 直接替换📋 参考替代料（不在目录中）
SN74LS244NE4
✅ 直接替换📋 参考替代料（不在目录中）
SN74LS244NSR
✅ 直接替换📋 参考替代料（不在目录中）
SN74HCT244N
✅ 直接替换📋 参考替代料（不在目录中）
DM74LS244N
✅ 直接替换📋 参考替代料（不在目录中）
N74LS244N
✅ 直接替换📋 参考替代料（不在目录中）
74LS244N 最大额定值与电气特性
| 功能 | Buffer, Non-Inverting |
| Number of Elements | 2 |
| Bits per Element | 4 |
| 输出类型 | 3-State |
| Logic Family | LS (Low-power Schottky TTL) |
| Supply Voltage (VCC) | 4.75 V to 5.25 V |
| Input Type | TTL with PNP base, hysteresis |
| Output Current (IOH/IOL) | -15 mA / 24 mA |
| Propagation Delay (tPLH/tPHL) | Approximately 10-12 ns (typ) |
| 工作温度 | 0 C to 70 C |
| 封装 | 20-pin PDIP (N) |
| 安装类型 | Through-Hole |
| 引脚数量 | 20 |
74LS244N 引脚配置
| 引脚 1 | 1G — Output enable for bank 1, active LOW |
| 引脚 2 | 1A1 — Bank 1 input 1 |
| 引脚 3 | 2Y4 — Bank 2 output 4 |
| 引脚 4 | 1A2 — Bank 1 input 2 |
| 引脚 5 | 2Y1 — Bank 2 output 1 |
| 引脚 6 | 1A3 — Bank 1 input 3 |
| 引脚 7 | 2Y2 — Bank 2 output 2 |
| 引脚 8 | 1A4 — Bank 1 input 4 |
| 引脚 9 | 2A1 — Bank 2 input 1 |
| 引脚 10 | GND — Ground |
| 引脚 11 | 2A2 — Bank 2 input 2 |
| 引脚 12 | 2Y3 — Bank 2 output 3 |
| 引脚 13 | 2A3 — Bank 2 input 3 |
| 引脚 14 | 1Y4 — Bank 1 output 4 |
| 引脚 15 | 2A4 — Bank 2 input 4 |
| 引脚 16 | 1Y3 — Bank 1 output 3 |
| 引脚 17 | 2Y1 (alt) — Bank 2 output - per datasheet pinout variant note |
| 引脚 18 | 1Y1 — Bank 1 output 1 |
| 引脚 19 | 2G — Output enable for bank 2, active LOW |
| 引脚 20 | VCC — Supply voltage (4.75 V to 5.25 V) |
典型应用
74LS244N 适用于 6 应用s: Memory Address Bus Buffer (Retrocomputing), Clock Driver Fan-out, Bus Isolation in Industrial PLC Systems, Peripheral Interface Buffer (Educational Boards), Long-Trace Signal Driver, Legacy Through-Hole Repair and Maintenance.
Memory Address Bus Buffer (Retrocomputing)
The 74LS244N is the canonical buffer for memory address lines in 8-bit retrocomputing designs such as Z80, 6502, and 8080 systems, where the CPU's address outputs lack the drive strength to fan out to multiple memory and peripheral ICs simultaneously. With 24 mA IOL and -15 mA IOH, the 74LS244N can drive heavily capacitively loaded address buses without signal-integrity issues, and its 10-12 ns propagation delay adds only a small access-time penalty that is usually absorbed in memory wait-state timing. Using two 74LS244N devices in parallel, designers can buffer all 16 address lines plus additional control signals while maintaining clean TTL-level edges. The 3-state output feature also enables bank-switching architectures where alternate memory maps must be electrically isolated.
推荐
Clock Driver Fan-out
Clock signals in synchronous logic must be distributed to many flip-flops, counters, and state machines, and a single gate output typically cannot drive more than a handful of LS loads without waveform degradation. The 74LS244N solves this by providing eight identical non-inverting outputs that can fan out a single clock or strobe signal to up to eight destinations while preserving sharp rise and fall times. Each output drives 24 mA IOL and -15 mA IOH, ensuring TTL-level thresholds are met even on long PCB traces or backplane lines. Designers commonly use one half (4 bits) for the system clock and the other half for an inverted or delayed derivative, simplifying clock-tree distribution in discrete-logic designs.
推荐
Bus Isolation in Industrial PLC Systems
In industrial PLC and process-control designs, multiple subsystems often share a common parallel backplane, and bus conflicts must be prevented by 3-state isolation rather than by software discipline alone. The 74LS244N provides two independently controlled 4-bit banks of 3-state buffers that can electrically isolate a peripheral card's bus interface when its enable input is de-asserted. This is critical during power-up sequencing, fault conditions, or hot-swapping where a misbehaving peripheral must be electrically removed from the shared bus. The 24 mA IOL drive also ensures reliable signaling across long industrial backplane cables in noisy EMI environments where signal amplitude degradation is common.
推荐
Peripheral Interface Buffer (Educational Boards)
University microprocessor labs and educational single-board computers frequently use the 74LS244N as a simple, observable buffer between a CPU's I/O ports and student-wired peripheral circuits. Because the device is non-inverting and provides strong output drive, students can connect LEDs, switches, or simple peripheral chips directly to the buffered outputs without risking damage to the CPU. The 20-pin PDIP through-hole package is breadboard-friendly and easy to solder, making it ideal for course kits. Two output-enable lines (1G, 2G) also let instructors demonstrate bus multiplexing and 3-state operation as part of the curriculum.
推荐
Long-Trace Signal Driver
When a digital signal must travel more than several inches across a PCB, backplane, or ribbon cable, the source impedance of typical logic outputs attenuates the signal and causes ringing on transitions. The 74LS244N provides eight high-drive outputs that can source -15 mA and sink 24 mA, sufficient to maintain TTL thresholds across traces up to 30 cm or short ribbon cables without external buffering. Designers commonly route one-half of the 74LS244N for a differential pair of control signals and the other half for status return signals, with each enable line acting as a transmit/receive gate. This is a low-cost alternative to dedicated line-driver ICs for non-ECL-speed applications.
推荐
Legacy Through-Hole Repair and Maintenance
The 74LS244N in its 20-pin PDIP package remains the preferred replacement part for repairing and maintaining legacy through-hole industrial, telecommunications, and instrumentation equipment that cannot be reworked to surface-mount. Equipment manufacturers from the 1980s and 1990s specified the DIP variant for serviceability, and field engineers continue to stock the 74LS244N for board-level repair. The DIP package's robust leads tolerate multiple replacement cycles, and standard 0.1 inch pin pitch fits IC sockets that simplify field replacement. As of 2026, TI and onsemi continue to manufacture the PDIP variant specifically for this long-tail maintenance market.
推荐
推荐产品汇总
工程参考数据： 74LS244N ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | SN74LS244N | DM74LS244N | N74LS244N | SN74HCT244N |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | onsemi | NXP Semiconductors | Texas Instruments |
| Package | 20-pin PDIP (N) | 20-pin PDIP (N) - same | 20-pin PDIP (N) - same | 20-pin PDIP (N) - same | 20-pin PDIP (N) - same |
| Logic Family | LS TTL | LS TTL | LS TTL | LS TTL | HCT CMOS (TTL-compatible inputs) |
| Supply Voltage | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 4.75 V to 5.25 V | 4.5 V to 5.5 V |
| IOL (Output LOW Current) | 24 mA | 24 mA | 24 mA | 24 mA | 6 mA (-75%) |
| IOH (Output HIGH Current) | -15 mA | -15 mA | -15 mA | -15 mA | -6 mA |
| Propagation Delay (typ) | 10-12 ns | 10-12 ns | 10-12 ns | 10-12 ns | 13-17 ns (slightly slower) |
| Operating Temperature | 0 C to 70 C | 0 C to 70 C | 0 C to 70 C | 0 C to 70 C | -40 C to 85 C |
关键差异点
- Strongest IOL drive in the 74LS bus-driver family （对比 SN74HCT244N)
- True bipolar LS TTL inputs with hysteresis （对比 DM74LS244N (onsemi second-source))
- Industry-standard 20-pin PDIP footprint with active production （对比 74LS244 in SOIC (M) package)
设计说明
The 74LS244N typically draws around 25 mA of quiescent supply current (Icc) with outputs enabled and no load, and can rise to approximately 54 mA with all outputs switching at full load. Decouple VCC (pin 20) with a 0.1 uF ceramic capacitor placed within 5 mm of the supply pin, and add a bulk 10 uF electrolytic on the supply rail near the chip. The bipolar LS technology does not have CMOS-style shoot-through currents, but high-frequency switching on all 8 outputs simultaneously can produce significant dynamic supply current that must be decoupled locally.
When routing the 74LS244N on a through-hole PCB, place the VCC bypass capacitor (0.1 uF) as close as possible to pin 20 and the GND return directly to pin 10. Keep input traces away from output traces to avoid coupling, and use a ground plane on the bottom layer for return currents. For retrocomputing boards with mixed 74LS families, maintain consistent trace impedance on bus lines to avoid reflections on the higher-drive outputs. Socket the device (20-pin DIP socket) when repairability matters - the through-hole variant is designed for repeated insertion cycles.
Do not confuse 74LS244 (unidirectional non-inverting buffer) with 74LS245 (bidirectional transceiver) - they are not interchangeable, and using the wrong part will either fail to drive the bus or cause contention. Ensure both 1G (pin 1) and 2G (pin 19) are tied to GND for normal operation; leaving them floating will cause undefined output behavior. The 74LS244N inputs are TTL-threshold only and cannot be reliably driven by 3.3 V CMOS logic - use 74HCT244 or 74LVC244A instead for level translation. Do not exceed VCC of 5.25 V as this can damage the bipolar inputs.
合规信息
Lead-free and RoHS compliance vary by specific lot/suffix (e.g., NE4 suffix denotes lead-free RoHS-compliant assembly). Through-hole PDIP parts may be available in both leaded and lead-free variants; verify the specific part number suffix when RoHS compliance is required. Not AEC-Q100 qualified - this is a commercial-grade logic IC for non-automotive applications.
