SN74LS90N - 4-Bit Decade Counter | Texas Instruments
MPN: SN74LS90N ✓ Hoạt độngSN74LS90N Tóm tắt
A decade counter is a synchronous-state counter built from flip-flops and logic gates. In the broader electronics hierarchy, a decade counter belongs to counter logic, digital logic ICs, logic ICs, and ultimately semiconductor devices. It is commonly used to divide one input frequency into lower, predictable frequencies or to produce a modulo-10 counting sequence for timing and control functions.
The SN74LS90N provides a 4-bit counter element, negative-edge triggering, and upward counting. Its TTL-compatible interface allows it to operate with other 74LS-family digital logic in established industrial control, instrumentation, and legacy computer systems. Because its counting architecture includes independently controlled sections, designers can also use it in divide-by-five, divide-by-six, divide-by-eight, and related applications depending on the selected output connections.
Technically, the monolithic counter combines four master-slave flip-flops with additional gating logic. The master-slave arrangement helps prevent race-through conditions when the clock changes state, while negative-edge triggering defines exactly when the stored count advances. Designers should still account for propagation delay, setup and hold requirements, and output transition behavior when operating near the device’s maximum clock frequency.
Typical uses include digital timing references, industrial sequence counters, frequency-divider circuits, test equipment, and embedded legacy control systems. The SN74LS90N is especially appropriate when an existing board requires a standard 14-pin TTL counter rather than a programmable modern counter. Availability and lifecycle decisions should be based on current distributor inventory because legacy through-hole logic sourcing can vary.
The primary design consideration is timing margin. Confirm the selected output’s transition timing against the load and the next device’s setup requirement, and route the clock to minimize ringing. Decoupling close to the supply pins and careful grounding remain necessary because every counter edge can propagate supply and ground disturbance into adjacent logic.
This page combines verified manufacturer and distributor information, package details, pricing context, sourcing guidance, and verified drop-in alternatives. It also distinguishes documented facts from parameters that still require confirmation from the manufacturer datasheet, helping engineers avoid unsupported assumptions during legacy-logic maintenance and redesign.
Bộ thay thế dễ dàng lắp đặt cho SN74LS90N — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
SN74LS90AP
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
SN74LS90BP
✅ Drop-In ⚠️ Thông số chưa được xác minh📋 Tham chiếu thay thế (không có trong danh mục)
SN74HCT90N
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
SN74LS90N
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →SN74LS90N Tỷ lệ tối đa & tính chất điện
| Counter Type | Decade counter |
| Number of Counter Elements | 1 element |
| Counter Width | 4 bit |
| Counting Direction | Up |
| Counting Mode | Asynchronous |
| Triggering Edge | Negative edge |
| Logic Family | LS-series TTL |
| Internal Count Sequence | Divide-by-five for the 74LS90 |
| Internal Architecture | Four master-slave flip-flops with additional gating |
| Package Type | 14-pin PDIP |
| Kiểu lắp đặt | Through-hole |
Hướng dẫn cấu hình chân SN74LS90N 14-pin pdip
Cấu hình chân cho SN74LS90N (14-pin pdip gói). IC số này bao gồm chân GPIO, giao diện truyền thông (UART, SPI, I2C) và chân nguồn. Tham khảo tài liệu thông số kỹ thuật của nhà sản xuất để biết các chức năng chân thay thế và tùy chọn cấu hình. Cực kỳ quan trọng cho thiết kế hệ thống tích hợp và lập trình PCB.
Không có dữ liệu chân cụ thể sẵn có cho SN74LS90N.
Tham khảo: tài liệu kỹ thuật cho cấu hình chân đầy đủ.
Ứng dụng tiêu biểu
SN74LS90N phù hợp cho 6 Áp dụngs: Digital Frequency Divider, Industrial Sequence Control, Test and Measurement Timing, Legacy Computer Control, Pulse and Event Counting, Teaching and Logic Prototyping.
Digital Frequency Divider
The SN74LS90N fits fixed frequency-divider and clock-generation circuits because it is a 4-bit asynchronous decade counter with negative-edge triggering. The manufacturer describes four master-slave flip-flops with additional gating and a divide-by-five count cycle for the 74LS90 family, allowing selectable outputs to establish different division relationships. In a legacy timing circuit, the counter can reduce a repetitive input clock while preserving the established 14-pin PDIP footprint. The primary design check is timing margin: propagation delay from the clock edge to the selected output must remain below the period available before the next active edge and must satisfy the receiving device’s setup requirement.
Được đề xuất
Industrial Sequence Control
The SN74LS90N is suitable for legacy industrial sequence control where a simple modulo-10 count is preferable to a programmable counter. Its 4-bit, upward-counting, asynchronous architecture provides predictable state advancement on each negative clock edge, while the TTL interface supports integration with established 74LS-family control logic. A maintenance engineer can use it for repeatable machine-event indexing, actuator sequencing, or discrete timing stages without redesigning the board footprint. Because timing behavior depends on propagation and transition delays, the design should verify the selected counter outputs against actuator relay-driver timing and prevent switch bounce or contact noise from propagating into the clock input.
Được đề xuất
Test and Measurement Timing
The SN74LS90N can serve as a fixed timing and counting element in test equipment where a stable, hardware-driven decade sequence is required. Its four master-slave flip-flops and additional gating implement the documented divide-by-five count cycle, making it useful when a test system needs repeatable intervals or numbered measurement stages. The negative-edge trigger defines when the count advances and allows the circuit to be synchronized with other legacy timing logic. When using the device in instrumentation, keep the clock distribution short, provide local supply bypassing, and compare the selected output’s delay with the measurement system’s acquisition and settling requirements.
Được đề xuất
Legacy Computer Control
The SN74LS90N is appropriate for maintaining a legacy computer or control system that requires a through-hole decade counter rather than a modern programmable or surface-mount device. Its 14-pin PDIP package supports repair and board-level substitution workflows, and the asynchronous negative-edge count behavior fits established TTL control schemes. The part can index recurring operations, divide a system clock, or generate a modulo-10 state sequence for peripheral control. Retrofitting requires more than package compatibility: confirm supply voltage, input thresholds, output levels, timing margins, and environmental requirements against the original system documentation before approving the replacement.
Được đề xuất
Pulse and Event Counting
The SN74LS90N can be used for pulse counting in low-speed event-counting, batch, or indexing systems because it provides a 4-bit up counter with negative-edge triggering. Multiple output taps provide visibility into internal count states, allowing external control logic to decode selected stages or use the counter as a repeatable event divider. This is useful when the input events are already conditioned and the required count range is fixed. Practical implementation should include input conditioning for noisy mechanical contacts, account for clock pulse width and setup time, and ensure that the selected output remains stable for the acquisition or decoding circuit.
Được đề xuất
Teaching and Logic Prototyping
The SN74LS90N is useful in electronics education and logic-prototyping benches because its through-hole package is easy to install and its internal counter states can be observed at accessible outputs. Students or engineers can demonstrate decade counting, negative-edge triggering, gated divisions, and interactions between 74LS-family logic on a common 5 V TTL-style board. The Texas Instruments datasheet describes the four master-slave flip-flops and extra gating that create the counter’s internal behavior, making the device a practical platform for tracing causality between clock transitions and output states. Projects should still follow safe assembly practices and use the manufacturer pinout and electrical limits rather than inferring connections from a generic 74LS90 drawing.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho SN74LS90N — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | SN74LS90AP | SN74LS90BP | SN74HCT90N | SN74LS90N |
|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | onsemi |
| Package | 14-pin PDIP | PDIP-14 | PDIP-14 | PDIP-14 | PDIP-14 |
| Counter Type | Decade counter | Decade counter | Decade counter | Decade counter | Decade counter |
| Logic Family | LS-series TTL | LS-series TTL | LS-series TTL | HCT TTL-compatible CMOS | LS-series TTL |
Bảo phân biệt quan trọng
- Original Texas Instruments 74LS90 sourcing (vsonsemi SN74LS90N)
- Mixed-logic input compatibility (vsSN74HCT90N)
- Standard 14-pin through-hole integration (vsSN74LS90AP)
- Negative-edge-triggered fixed counting (vsSN74LS90BP)
Ghi chú thiết kế
Do not infer pin assignments from a generic 74LS90 drawing. The supplied evidence confirms the SN74LS90N uses a 14-pin PDIP, but it does not reproduce the individual pin names. Download the official Texas Instruments PDF and verify clock, clear, enable, supply, ground, and output connections against the actual PCB footprint. Also confirm the negative-edge trigger and the selected output's timing before exchanging the device.
Treat the clock net as a potentially high-speed edge even when the counter operates at a low repetition rate. Keep the clock route short, minimize stub branches, and place any required damping close to the driver. Because the device advances on the negative edge, a ringing or double transition at that edge can cause an unintended count increment. Confirm the received waveform at the IC pin rather than relying only on a source-side measurement.
Provide local supply bypassing at the IC and route the return current through a low-impedance ground path. Counter outputs transition simultaneously with internal clock activity, so inadequate decoupling can couple supply disturbance into adjacent 74LS logic. The supplied snippets do not include the device's supply range or current consumption, so obtain those limits from the manufacturer datasheet before selecting capacitors or planning power-budget headroom.
A same-function counter is not automatically a drop-in replacement. For the SN74HCT90N and onsemi SN74LS90N, verify pinout, input thresholds, output levels, propagation delay, maximum clock frequency, temperature range, and power limits in the relevant manufacturer datasheet. In mixed TTL/CMOS systems, HCT input compatibility can be advantageous, but it may also alter noise margins and should be reviewed against the complete interface.
Thông tin tuân thủ
The supplied verified results do not provide explicit RoHS, REACH, lead-free, halogen-free, or conflict-minerals declarations. No AEC-Q100 qualification is identified in the supplied evidence.
