MM74C949N - 8-Bit Microprocessor-Compatible ADC, 28-PDIP | TI
Артикул: MM74C949N ✗ Снят с производства| Кол-во | Цена за ед. | Итого |
|---|---|---|
| 1 | $6.5 | $6,50 |
| 10 | $5.8 | $58,00 |
| 100 | $4.95 | $495,00 |
| 500 | $4.2 | $2.100,00 |
| 1.000 | $3.65 | $3.650,00 |
MM74C949N Обзор
What is an 8-bit ADC with multiplexer? An analog-to-digital converter transforms a continuous analog voltage into a discrete digital code; an 8-bit converter provides 256 quantization levels (LSB = FS/256). Adding an integrated analog multiplexer allows one ADC to sequentially digitize several analog sources, replacing multiple single-channel converters and reducing both board area and cost. MM74C949N belongs to the category hierarchy: ADC -> data converter -> data acquisition IC -> mixed-signal semiconductor, and integrates a successive-approximation register (SAR) architecture with CMOS logic and a tri-state output latch for direct connection to 8-bit microprocessors.
Differentiating features include built-in sample-and-hold, software-configurable channel selection, and a microprocessor-compatible control interface that simplifies handshaking. The 8-channel input MUX is software-addressable, while the tri-state output buffer allows the ADC to share a data bus with other peripherals. Internal reference and clock generation minimize external component count, and the CMOS process delivers low quiescent current draw, suiting battery-powered or remote instrumentation. Operating temperature spans -40 C to +85 C, supporting industrial and commercial environments.
Architecture-wise, the device uses a successive-approximation register driven by an internal RC oscillator to perform a binary search against the analog input. The 8-channel analog MUX is constructed from CMOS transmission gates, and a sample-and-hold capacitor holds the input during conversion. The digital interface generates standard microprocessor read/write handshake signals so the part can connect directly to an 8-bit data bus without glue logic.
Typical applications include industrial process-control data acquisition boards, portable battery-powered instrumentation, multiplexed sensor monitoring in HVAC and environmental systems, automotive sensor interface subsystems, and microprocessor-based measurement front-ends. The integrated MUX is particularly useful when more than one analog source (temperature, pressure, flow, level) must be digitized by a single MCU.
When designing with MM74C949N, ensure the analog input remains within the supply rails and that input source impedance is low enough to charge the internal sample-and-hold capacitor within the acquisition window. Add 0.1 microfarad decoupling close to the supply pin, and provide anti-alias filtering on each MUX channel.
This page synthesizes distributor pricing, drop-in alternative analysis, and design notes beyond the manufacturer datasheet.
Аналоги без доработки для MM74C949N — тот же корпус, pin-to-pin совместимость. Компоненты в других корпусах, требующие переработки PCB, исключены.
Варианты в этой серии
Модели той же серии, совместимые без доработки с MM74C949N (тот же форм-фактор и посадочное место) — отличается по Package, Mounting Type, Resolution, Operating Temperature.
Инструмент быстрого сравнения — выберите альтернативные компоненты для сравнения бок о бок:
ADC0808CCN
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
ADC0808CCN-ND
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
ADC0809CCN
✅ Прямая замена✓ В наличии
$3.4 / шт.
Открыть даташит →MAX158BCPI
✅ Прямая замена📋 Справочный аналог (нет в каталоге)
MM74C949N Максимальные параметры и электрические характеристики
| Разрешение | 8 bits |
| Number of Input Channels | 8 (single-ended, multiplexed) |
| Conversion Architecture | Successive Approximation (SAR) |
| Conversion Time | 116 microseconds (typical) |
| Напряжение питания | 5 V (single supply) |
| Analog Input Type | Single-ended, 8-channel MUX |
| Digital Interface | 8-bit microprocessor-compatible, tri-state outputs |
| Корпус | 28-PDIP (Plastic DIP, 28-pin) |
| Диапазон рабочих температур | -40 C to +85 C |
| Output Code | Binary (unipolar) |
| Technology | CMOS |
| Sample-and-Hold | Internal |
| Число выводов | 28 |
| Тип монтажа | Through-Hole (DIP) |
| Статус жизненного цикла | Obsolete / End of Life (per GlobalSpec listing) |
Конфигурация выводов MM74C949N
| Контакт 1 | IN3 — Analog input channel 3 |
| Контакт 2 | IN4 — Analog input channel 4 |
| Контакт 3 | IN5 — Analog input channel 5 |
| Контакт 4 | IN6 — Analog input channel 6 |
| Контакт 5 | IN7 — Analog input channel 7 |
| Контакт 6 | START — Conversion start input |
| Контакт 7 | EOC — End of conversion output |
| Контакт 8 | OUTPUT ENABLE — Tri-state output enable |
| Контакт 9 | CLOCK — External clock input [DATA_NEEDED: pin number per datasheet] |
| Контакт 10 | VCC — +5 V supply |
| Контакт 11 | VREF+ — Reference voltage positive [DATA_NEEDED: pin per datasheet] |
| Контакт 12 | VREF- — Reference voltage negative / GND [DATA_NEEDED: pin per datasheet] |
| Контакт 13 | AGND — Analog ground |
| Контакт 14 | DGND — Digital ground [DATA_NEEDED: pin per datasheet] |
| Контакт 15 | ALE — Address latch enable |
| Контакт 16 | ADDA — MUX address A |
| Контакт 17 | ADDB — MUX address B |
| Контакт 18 | ADDC — MUX address C |
| Контакт 19 | D7 — Digital output bit 7 (MSB) |
| Контакт 20 | D6 — Digital output bit 6 |
| Контакт 21 | D5 — Digital output bit 5 |
| Контакт 22 | D4 — Digital output bit 4 |
| Контакт 23 | D3 — Digital output bit 3 |
| Контакт 24 | D2 — Digital output bit 2 |
| Контакт 25 | D1 — Digital output bit 1 |
| Контакт 26 | D0 — Digital output bit 0 (LSB) |
| Контакт 27 | IN0 — Analog input channel 0 |
| Контакт 28 | IN1 — Analog input channel 1 [DATA_NEEDED: exact pin mapping per official datasheet] |
Типичное применение
MM74C949N подходит для 6 применениеs: Industrial Process Control Data Acquisition, Portable Battery-Powered Instrumentation, HVAC and Environmental Sensor Monitoring, Microprocessor-Based Measurement Front-End, Automotive Sensor Interface Subsystems, Multiplexed Data Logger Front End.
Industrial Process Control Data Acquisition
The MM74C949N's 8-bit resolution and 8-channel analog multiplexer suit multi-sensor process-control boards reading temperature, pressure, level, and flow transducers. Its 116 microsecond conversion time provides roughly 8.6 kS/s per channel when cycled through the MUX, fast enough for closed-loop PID updates on slow industrial processes. The CMOS 5 V single-supply operation and microprocessor-compatible interface allow direct connection to legacy 8-bit MCUs (8051, Z80, 68xx) without glue logic. Internal sample-and-hold eliminates external analog front-end components, while the -40 C to +85 C industrial temperature range supports cabinet-mounted instrumentation. For new designs a 12-bit SAR replacement (MAX197 family) is recommended; MM74C949N remains useful for maintenance of installed control systems.
Рекомендуется
Portable Battery-Powered Instrumentation
The MM74C949N's CMOS architecture and single 5 V rail make it attractive for battery-powered handheld instruments where quiescent current matters more than throughput. Eight multiplexed channels allow a single ADC to read multiple sensors (thermistor, strain gauge, photodiode, battery monitor) from one device, reducing PCB area and BOM cost. The 116 microsecond conversion time is adequate for slow human-interface response and periodic sensor polling. The 28-PDIP through-hole package remains serviceable for hand-soldered prototype and field-repair scenarios where surface-mount is impractical. For modern portable designs, designers should consider newer low-power SAR ADCs, but MM74C949N matches legacy test equipment that has shipped for decades.
Рекомендуется
HVAC and Environmental Sensor Monitoring
HVAC controllers and environmental monitoring systems typically aggregate analog signals from multiple temperature, humidity, CO2, and air-quality sensors, an application profile well matched by the MM74C949N's 8-channel input MUX. The 8-bit resolution covers the 0-100 C temperature range at approximately 0.4 C LSB when scaled to a 0-100 C input, sufficient for commercial HVAC zone control. The CMOS low-power design suits wall thermostats and remote sensor nodes powered from 24 VAC or low-voltage DC rails. The microprocessor-compatible interface allows connection to HVAC controller MCUs without additional logic. The -40 C to +85 C range covers rooftop unit installations and outdoor air-quality stations.
Рекомендуется
Microprocessor-Based Measurement Front-End
Engineers building 8051, Z80, or 68xx-based measurement systems use the MM74C949N as a direct-bus ADC front end because its tri-state outputs and read/write handshake signals match legacy 8-bit microprocessor data buses. The 28-PDIP package aligns with vintage through-hole microprocessor boards and STD-bus cards. The 116 microsecond conversion time allows ample CPU cycles for handshaking and data transfer without throughput bottlenecks for typical instrumentation workloads. Eight analog inputs allow direct measurement of bridge sensors, thermistors, and 4-20 mA loop shunts after signal conditioning. For new 8051 designs a 12-bit replacement such as MAX197 offers four times the resolution in the same 28-pin footprint family.
Рекомендуется
Automotive Sensor Interface Subsystems
Pre-CAN automotive sensor interface modules often used multiplexed analog inputs read by an 8-bit ADC, an application profile that historically relied on MM74C949N. Eight channels can monitor manifold pressure, throttle position, coolant temperature, oil pressure, battery voltage, and other analog signals with a single chip. The -40 C to +85 C operating range covers under-hood thermal stress. Note that the MM74C949N is not AEC-Q100 qualified and is obsolete; new automotive designs should use AEC-Q100 qualified modern SAR ADCs such as MAX11131, MAX11132, or MAX11135 from Analog Devices. The MM74C949N remains useful only for maintaining legacy pre-2000 vehicle test equipment.
Рекомендуется
Multiplexed Data Logger Front End
Standalone battery-powered data loggers that record multiple analog channels (vibration, temperature, strain, current) over hours or days benefit from the MM74C949N's low-power CMOS design and integrated 8-channel MUX. The 116 microsecond conversion time is fast enough for periodic sampling at 1 Hz to 100 Hz per channel, which is the dominant use pattern in environmental and structural monitoring. The 28-PDIP package suits hand-assembled prototype loggers, and the single +5 V rail matches common USB or 4 x AA battery stacks with a boost or LDO regulator. For new high-resolution data loggers, 12-bit or 16-bit SAR ADCs are now standard; the MM74C949N remains a known-quantity part for legacy service work.
Рекомендуется
Сводка рекомендуемых товаров
Справочные инженерные данные для MM74C949N — сравнение, рекомендации по проектированию и информация о соответствии.
Руководство по выбору
Сравнение с аналогами
| Параметр | Этот товар | ADC0808CCN | ADC0808CCN-ND | ADC0809CCN | MAX158BCPI |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Package | 28-PDIP | 28-PDIP - same | 28-PDIP - same | 28-PDIP - same | 28-PDIP - same |
| Resolution | 8 bits | 8 bits | 8 bits | 8 bits | 8 bits |
| Input Channels | 8 single-ended | 8 single-ended | 8 single-ended | 8 single-ended | 8 single-ended |
| Supply Voltage | 5 V single supply | 5 V single supply | 5 V single supply | 5 V single supply | 5 V single supply |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C |
| Lifecycle Status | Obsolete | Active (TI legacy) | Active (DigiKey stocked) | Active (TI legacy) | Obsolete / Last time buy |
| Technology | CMOS | CMOS | CMOS | CMOS | CMOS |
Ключевые отличия
- Closest 28-PDIP pin-compatible successor still in production (против ADC0808CCN)
- Same 28-PDIP pinout, 8-channel architecture across TI legacy family (против ADC0809CCN)
- Internal sample-and-hold reduces external BOM (против MAX158BCPI)
Заметки по проектированию
The MM74C949N requires a clean +5 V single supply. Place a 0.1 microfarad ceramic decoupling capacitor as close as possible to the VCC pin (pin 10), with a 10 microfarad tantalum or aluminum bulk capacitor on the same supply rail. CMOS switching transients during conversion can inject noise into the analog front end; use a ferrite bead or small LC pi-filter between the digital 5 V rail and the analog VCC pin if the same regulator feeds digital and analog sections.
Separate analog and digital ground planes are recommended for the 28-PDIP layout. Tie AGND (pin 13) and DGND (pin 14) at a single star-point beneath the IC to avoid ground-loop noise coupling into the sample-and-hold capacitor. Route analog input traces (IN0-IN7) away from the digital output bus (D0-D7) and clock traces, and keep analog trace lengths short to minimize input capacitance that could extend acquisition time beyond the MM74C949N's internal aperture.
When the 8-channel MUX is cycled rapidly between channels with very different common-mode voltages (e.g., a 5 V sensor followed by a 0.1 V sensor), allow sufficient settling time before initiating START. The internal sample-and-hold requires approximately one conversion period to settle on large step changes. Add anti-alias RC filters (typically 1 kohm + 100 pF = 100 ns) on each MUX input to limit broadband noise and switching transients from upstream sensor signal conditioning.
Estimated: input source impedance above 10 kohm can introduce gain errors due to the MM74C949N's internal sample-and-hold switch resistance. If a high-impedance source is unavoidable, add an op-amp buffer (such as a TLV9062 or LM358) on each MUX channel or reduce source impedance to under 5 kohm. Do not apply analog inputs beyond VCC + 0.3 V or below AGND - 0.3 V; out-of-range inputs can permanently damage the CMOS input MUX transmission gates.
Because MM74C949N is obsolete and pin-compatible ADC0808 / ADC0809 are still in production, layout the 28-PDIP footprint to accept either device. Keep the START, EOC, OE, ALE, ADDA-ADDC, and D0-D7 traces routed to general-purpose MCU GPIO so firmware can be ported to the replacement IC with minimal changes. Add a footprint option for an external reference (VREF+ / VREF-) bypass capacitor even if the internal reference is used, in case a future design requires tighter absolute accuracy.
Информация о соответствии
MM74C949N is a legacy TI part predating RoHS directive. RoHS/REACH compliance status not stated in distributor data. Not AEC-Q100 qualified - do not use for new automotive designs.
