74HCT154BQ - 4-to-16 Line Decoder/Demultiplexer DHVQFN-24 | Nexperia
MPN: 74HCT154BQ ✓ Aktif74HCT154BQ Genel Bakış
Background knowledge: A decoder/demultiplexer is a combinational logic device that converts a small binary address into one of many mutually exclusive outputs. It belongs to the broader category of digital logic ICs, and within that category to the encoder/decoder/multiplexer/demultiplexer sub-family. In a typical digital system hierarchy, decoders sit between the processor/control logic and the peripheral devices they enable, providing one-hot selection signals such as memory chip-select, peripheral enables, or display-row selects. The 4-to-16 decoder is one of the most commonly used building blocks for memory and I/O expansion on legacy buses.
Key features of the 74HCT154BQ include two active-LOW enable inputs (E1 and E2) that can be used together as a strobe to eliminate normal address-decoding glitches on the outputs, a wide 4.5 V to 5.5 V supply range (HCT logic level, TTL-compatible inputs), CMOS output drive capability, and standardized input hysteresis for improved noise immunity in industrial environments. The two enable gates can also be cascaded to form a 5-to-32 decoder using two 74HCT154 devices, an important pattern for memory expansion beyond 16 devices.
Typical applications include memory chip-select decoding for systems with up to 16 memory or peripheral devices, address demultiplexing for legacy microprocessor address buses (such as 8085, Z80, 6800), LED matrix row/column driving, relay and solenoid driver expansion, and general-purpose one-of-N selection in industrial control logic. The enable-strobe feature is particularly valuable when the device feeds asynchronous logic that would otherwise propagate decoding glitches.
When designing with this part, pay attention to the active-LOW output polarity (Y outputs sink current when selected) and unused enable pins must be tied to their active state. The DHVQFN-24 package provides a low thermal resistance path and requires thermal vias under the exposed pad for reliable operation; ensure the pad is soldered to a sufficient copper area on the PCB. All inputs include clamp diodes so input voltages should be constrained within the supply range.
Drop-in alternatifler için 74HCT154BQ — aynı paket, pin-başına uyumlu. PCB yeniden montajı gerektiren farklı paket bileşenleri dışlanmıştır.
74HCT154BQ,118
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74HCT154D
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74HCT154DB,118
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SN74HCT154DWR
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MC74HCT154ADTR2G
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74HCT154BQ Maksimum Değerlendirmeler & Elektriksel Özellikler
| Fonksiyon | 4-to-16 line decoder/demultiplexer |
| Logic Family | 74HCT (high-speed Si-gate CMOS, TTL-compatible inputs) |
| Number of Address Inputs | 4 (A0, A1, A2, A3) - active HIGH |
| Çıkış Sayısı | 16 (Y0 to Y15) - active LOW, mutually exclusive |
| Enable Inputs | 2 (E1, E2) - active LOW, can be used as strobe |
| Supply Voltage (VCC) | 4.5 V to 5.5 V |
| Giriş电压范围 | 0 V to VCC |
| İşletim Sıcaklığı | -40 C to +125 C |
| Paket | DHVQFN-24 (SOT815-1), 5.5 mm x 3.5 mm |
| Montaj Türü | Surface Mount |
| MSL Seviyesi | 1 |
| Pin Sayısı | 24 |
| JEDEC Standard | No. 7A compliant |
| LSTTL Compatibility | Pin-compatible with Low-power Schottky TTL |
| Process Technology | High-speed Si-gate CMOS |
74HCT154BQ Pin Yapısı
| Pin 1 | A0 — Address input 0 (active HIGH) |
| Pin 2 | A1 — Address input 1 (active HIGH) |
| Pin 3 | A2 — Address input 2 (active HIGH) |
| Pin 4 | A3 — Address input 3 (active HIGH) |
| Pin 5 | E1 — Enable input 1 (active LOW) |
| Pin 6 | E2 — Enable input 2 (active LOW) |
| Pin 7 | Y0 — Output 0 (active LOW) |
| Pin 8 | Y1 — Output 1 (active LOW) |
| Pin 9 | Y2 — Output 2 (active LOW) |
| Pin 10 | Y3 — Output 3 (active LOW) |
| Pin 11 | Y4 — Output 4 (active LOW) |
| Pin 12 | Y5 — Output 5 (active LOW) |
| Pin 13 | Y6 — Output 6 (active LOW) |
| Pin 14 | Y7 — Output 7 (active LOW) |
| Pin 15 | Y8 — Output 8 (active LOW) |
| Pin 16 | Y9 — Output 9 (active LOW) |
| Pin 17 | Y10 — Output 10 (active LOW) |
| Pin 18 | Y11 — Output 11 (active LOW) |
| Pin 19 | Y12 — Output 12 (active LOW) |
| Pin 20 | Y13 — Output 13 (active LOW) |
| Pin 21 | Y14 — Output 14 (active LOW) |
| Pin 22 | Y15 — Output 15 (active LOW) |
| Pin 23 | GND — Ground (0 V) |
| Pin 24 | VCC — Positive supply voltage (4.5 V to 5.5 V) |
Tipik Uygulamalar
74HCT154BQ için uygundur 6 uygulamas: Memory Chip-Select Decoding, Address Demultiplexing for Legacy Microprocessors, LED Matrix Row/Column Driving, Relay and Solenoid Driver Expansion, Industrial Control Logic One-of-N Selection, 5-to-32 Decoder Cascade.
Memory Chip-Select Decoding
The 74HCT154BQ decodes four binary address bits into sixteen mutually exclusive active-LOW chip-select lines, making it ideal for selecting up to 16 memory or peripheral devices on a shared bus. Its 4.5 V to 5.5 V supply and TTL-compatible inputs interface directly with 5 V microprocessors such as the 8085, Z80, or 6800. The two active-LOW enable inputs (E1, E2) can be tied together as a master strobe to gate decoding during bus cycles, eliminating address-decode glitches that would otherwise propagate to peripheral enable lines.
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Address Demultiplexing for Legacy Microprocessors
In 8085-, Z80-, and 6800-family designs, the 74HCT154BQ demultiplexes high-order address lines into individual device enables, allowing the address bus to select one of sixteen peripheral or memory chips per access. With 5 V TTL-compatible inputs and CMOS output drive, it slots directly onto these legacy buses without level shifting. The active-LOW output polarity matches the chip-select convention of most 5 V SRAM, EEPROM, and peripheral ICs, reducing external inverter stages.
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LED Matrix Row/Column Driving
The 74HCT154BQ sinks current on one of sixteen active-LOW outputs per address combination, enabling direct row or column selection in 4x4 to 16x1 LED matrix displays. With CMOS output drive and TTL input thresholds, it can be controlled by 5 V microcontrollers via just four GPIO lines plus a strobe. The two enable inputs support PWM brightness modulation by strobing the decoder at duty-cycle rates, while the active-LOW outputs can directly sink LED cathodes through appropriate current-limiting resistors.
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Relay and Solenoid Driver Expansion
The 74HCT154BQ expands a 4-bit microcontroller port to control up to sixteen relays or solenoids, each output selecting one device when the corresponding address is presented. Its active-LOW outputs can directly drive the gate of a logic-level MOSFET or the input of an optocoupler/relay driver, enabling one-of-N switching in industrial automation panels. The two enable inputs allow safety interlock gating, disabling all outputs by default until a valid strobe combination is presented.
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Industrial Control Logic One-of-N Selection
In PLC and industrial control designs, the 74HCT154BQ selects exactly one of sixteen mutually exclusive outputs based on a 4-bit command word, simplifying front-panel switch multiplexing, fault-code routing, and test-point selection. Its industrial -40 C to +125 C temperature range and JEDEC-compliant specification suit harsh environments. The HCT sub-family's TTL-compatible inputs allow direct connection to 5 V optocouplers or 5 V tolerant GPIO from older PLC CPUs.
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5-to-32 Decoder Cascade
Two 74HCT154BQ devices can be cascaded via their enable inputs to form a 5-to-32 decoder, expanding the addressable space to 32 mutually exclusive outputs for larger memory or peripheral arrays. By using one device's Y0-Y15 outputs as enables for the second stage, the top decoder passes through E1/E2 gating to select which of 16 sub-decoders is active. This pattern doubles the chip count but avoids more expensive programmable logic for simple decode trees.
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Önerilen Ürünler Özeti
Mühendislik referans verileri: 74HCT154BQ — karşılaştırma, tasarım rehberi ve uyumluluk bilgileri.
Seçim Kılavuzu
Alternatiflerle Karşılaştırma
| Parametre | Bu Ürün | 74HCT154BQ,118 | 74HC154BQ | SN74HCT154DWR | MC74HCT154ADTR2G |
|---|---|---|---|---|---|
| Package | DHVQFN-24 (SOT815-1) 5.5x3.5 mm | DHVQFN-24 - same | DHVQFN-24 - same | SOIC-24 wide-body - different footprint | TSSOP-24 - different footprint |
| Brand | Nexperia | Nexperia (same brand) | Nexperia (same brand) | Texas Instruments | onsemi |
| Logic Family | 74HCT (TTL-compatible inputs, CMOS outputs) | 74HCT (same) | 74HC (full CMOS thresholds) | 74HCT (same) | 74HCT (same) |
| Supply Voltage Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 2.0 V to 6.0 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Address Inputs | 4 (A0-A3, active HIGH) | 4 (same) | 4 (same) | 4 (same) | 4 (same) |
| Number of Outputs | 16 (active LOW) | 16 | 16 | 16 | 16 |
| Enable Inputs | 2 (E1, E2, active LOW) | 2 (same) | 2 (same) | 2 (same) | 2 (same) |
| Operating Temperature | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C | -40 C to +85 C | -40 C to +85 C |
| Lifecycle Status | Active | Active | Active | Active | Active |
Ana Farklılayıcılar
- Compact DHVQFN-24 (SOT815-1) saves PCB area versus SOIC-24 alternatives (karşılaştırma:SN74HCT154DWR)
- Industrial -40 C to +125 C operating temperature range (karşılaştırma:SN74HCT154DWR)
- Dual active-LOW enable inputs function as decode strobe (karşılaştırma:MC74HCT154ADTR2G)
Tasarım Notları
The DHVQFN-24 package has an exposed thermal pad on its underside that must be soldered to a sufficiently large PCB copper area (typically a ground plane) to meet the datasheet's thermal resistance specification. Without this pad soldered, the junction-to-ambient thermal resistance increases dramatically, potentially limiting operation in high-temperature environments. Per Nexperia layout guidelines, use an array of thermal vias under the pad to conduct heat into inner ground planes, and ensure the pad footprint follows the SOT815-1 land pattern exactly.
All unused inputs of the 74HCT154BQ must be tied to their inactive state to prevent floating-input oscillations that can draw excessive supply current and inject noise into the logic. Specifically, the two enable inputs (E1, E2) are active-LOW, so they must be tied to VCC (logic HIGH) when not in use; floating enables can cause unpredictable output patterns. Address inputs (A0-A3) should also be tied HIGH or LOW rather than left floating, even though some unused outputs may be tolerable. Per the JEDEC 7A specification, the device includes input clamp diodes - never drive inputs above VCC or below GND.
When using the 74HCT154BQ's two enable inputs as a strobe to eliminate decoding glitches, drive both E1 and E2 from clean logic sources synchronous with the address bus. Asynchronous enable gating can introduce its own glitches if the enable transitions during address changes. For high-speed designs, add small RC snubbers (10-100 ohm series, 10-47 pF to ground) on the address inputs if the source impedance is high, or buffer the address bus to the decoder with a fast HC/HCT gate to ensure clean edges and avoid propagation-delay-induced decoding errors.
The 74HCT154BQ draws very low quiescent current (typically a few microamps) but switching many outputs simultaneously can produce brief VCC current spikes proportional to load capacitance. Decouple VCC with a 100 nF ceramic capacitor placed within 5 mm of the VCC pin, and add a 1-10 uF bulk capacitor if multiple 74HCT154 devices share the same supply rail. The DHVQFN-24 package provides excellent low-inductance VCC/GND distribution when the exposed pad is properly soldered.
Uyumluluk Bilgisi
RoHS compliant and halogen-free per Nexperia product page. JEDEC standard no. 7A compliant. Not AEC-Q100 qualified - this is a commercial/industrial logic IC, not an automotive-grade part.
