LM556 - Dual Timer 4.5-16V | Texas Instruments
MPN: LM556 ✓ Hoạt độngLM556 Tóm tắt
A dual timer is an integrated timing circuit that combines threshold sensing, trigger control, discharge switching, and an output stage in each timer section. In the broader semiconductor hierarchy, the LM556 is a timer and oscillator within clock and timing integrated circuits. Its two independent sections can generate delayed pulses, control switching waveforms, flash lamps, pace sequential events, or provide two related timing functions without requiring two separate single-timer packages.
Each LM556 timing function uses an external timing resistor and timing capacitor. The trigger input can initiate a one-shot pulse, while the threshold input provides feedback for astable oscillation. A control-voltage input permits the timing reference to be adjusted within the limits defined by the manufacturer datasheet. The two timer sections operate independently, so one circuit can perform timing while the other handles a related but separate delay or pulse-generation function.
The LM556 operates across a 4.5 V to 16 V supply range. Many operating characteristics apply from 0 °C to 70 °C, while the Electrical Characteristics section identifies parameters that vary with voltage or temperature. The cited temperature-stability figure is 0.005% per °C, indicating how the timing characteristic can change across temperature. The output stage is TTL compatible, which supports interfacing with standard digital logic when the operating and load conditions are appropriate.
Typical uses include two-stage sequential timers, LED and lamp flashers, pulse-width control, delayed-action circuits, simple audio pulsation, industrial control timing, and laboratory pulse generators. Because each section can be configured independently, the LM556 is especially useful when a design needs two timing functions but does not justify two separate timer packages. The shared supply and ground pins also simplify the power architecture.
The principal design consideration is ensuring that timing-component values, discharge-device limits, control-voltage behavior, and output loading remain within the datasheet limits. Because both sections share VCC and ground, bypassing and return-current paths should support both timer sections operating simultaneously. Pin assignments should be checked against the exact SOIC footprint before PCB release.
This page consolidates the LM556 timing functions, operating limits, package details, application guidance, and verified replacement information into an engineering-focused reference. It also identifies where pin-compatible substitution requires additional datasheet and qualification review rather than treating package similarity alone as sufficient approval.
Bộ thay thế dễ dàng lắp đặt cho LM556 — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
Không có bộ thay thế dễ dàng lắp đặt sẵn có cho sản phẩm này.
Yêu cầu các bộ thay thếLM556 Thông số kỹ thuật
| Timer Configuration | 2 independent timer sections |
| Operating Modes | Astable and monostable |
| Supply Voltage Range | 4.5 V to 16 V |
| Specified Temperature Range | 0 °C to 70 °C |
| Timing Range | Microseconds to hours |
| Timing Elements | 1 external resistor and 1 external capacitor per timing function |
| Output Compatibility | TTL compatible |
| Temperature Stability | 0.005% per °C |
| Adjustable Duty Cycle | Yes |
| Reset Function | Shared reset input |
| Control Voltage Input | 1 timing-control input |
| Supply Architecture | Both timer sections share VCC and ground |
| Hộp | 14-pin narrow SOIC |
| Kiểu lắp đặt | Surface mount |
| Số chân | 14 pins |
Cấu hình chân LM556
| Chân 1 | DISCHARGE 1 — Open-collector discharge node for timer 1 |
| Chân 2 | THRESHOLD 1 — Threshold input for timer 1 |
| Chân 3 | TRIGGER 1 — Trigger input for timer 1 |
| Chân 4 | RESET — Common reset input for both timer sections |
| Chân 5 | CONTROL VOLTAGE — Timing reference control input |
| Chân 6 | TRIGGER 2 — Trigger input for timer 2 |
| Chân 7 | THRESHOLD 2 — Threshold input for timer 2 |
| Chân 8 | DISCHARGE 2 — Open-collector discharge node for timer 2 |
| Chân 9 | OUTPUT 2 — Timer 2 output |
| Chân 10 | NC — Not connected |
| Chân 11 | OUTPUT 1 — Timer 1 output |
| Chân 12 | VCC — Common positive supply input |
| Chân 13 | GND — Common ground connection |
| Chân 14 | NC — Not connected |
Ứng dụng tiêu biểu
LM556 phù hợp cho 6 Áp dụngs: Two-Stage Sequential Control, LED and Lamp Flashing, Pulse-Width Control, Delay and Retrigger Circuits, Simple Audio Pulsation, Test and Measurement Pulse Generator.
Two-Stage Sequential Control
The LM556 fits two-stage sequential control because its two timer sections operate independently while sharing only VCC and ground. One section can establish the first delay and the other can initiate a subsequent event, allowing a 14-pin package to replace two separate timer packages. Both sections support monostable operation, with timing determined by external resistors and capacitors across a microsecond-to-hour range. The 4.5 V to 16 V operating range accommodates conventional industrial logic supplies, while TTL-compatible outputs simplify interfacing with compatible digital stages. Because the sections share supply connections, PCB planning should provide low-impedance decoupling and a common return path that serves both timing channels.
Được đề xuất
LED and Lamp Flashing
The LM556 can implement repeatable LED or lamp flashing circuits because each section supports astable operation and adjustable duty cycle. External resistor-capacitor timing networks determine the repetition rate, allowing one channel to flash one indicator while the other handles a different timing pattern. Its 4.5 V to 16 V supply range supports common control-rail environments, and the 0.005% per °C temperature-stability figure provides a defined basis for comparing timing drift. The designer should include suitable drive transistors rather than driving current-limited lamps directly unless the output and dissipation limits permit it. Verify the resistor values against the manufacturer timing equations before laying out the board.
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Pulse-Width Control
The LM556 is suitable for pulse-width control because each timer section can combine monostable timing with an external trigger and discharge path. A trigger pulse starts the interval, the timing network establishes the delay, and the associated output produces the timed waveform. Two sections can create separate pulse windows or coordinate complementary events. The 4.5 V to 16 V operating range and TTL-compatible output provide useful compatibility with conventional logic, but the load current and output timing must remain within the Electrical Characteristics table. Use local timing-component grounding and short trigger routes to reduce sensitivity to switching-node interference.
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Delay and Retrigger Circuits
The LM556 supports delay and retrigger functions through its two independent monostable sections. One channel can generate a delayed response to a trigger, while the other provides a complementary or follow-up interval. Timing remains external and scalable from microseconds to hours, making the device useful in laboratory controls, automated test sequences, and industrial delay panels. Its shared VCC and ground simplify power routing, although both sections should be checked for simultaneous switching. Pay particular attention to reset, trigger, threshold, and discharge behavior, and test worst-case timing over the intended temperature range rather than relying only on nominal component tolerances.
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Simple Audio Pulsation
The LM556 can generate simple audio pulsation using one or both astable sections. A resistor-capacitor network establishes the repetition rate, while the timer output drives a suitable amplifier or transducer stage. This makes the device appropriate for low-cost alarms, metronome-style signals, and basic audible alert circuits. The 4.5 V to 16 V supply range supports common control voltages, while TTL-compatible outputs facilitate coupling into compatible driver logic. For clearer results, keep timing components away from loudspeaker and amplifier return currents, and account for the temperature coefficient of the timing components. Verify that the output waveform remains suitable for the connected audio stage.
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Test and Measurement Pulse Generator
The LM556 can serve as the timing element in a basic bench pulse generator or trigger source because its two sections provide independent astable and monostable options. One channel may produce a continuous reference waveform while the other creates a delayed trigger, creating useful relationships for simple measurements. External resistors and capacitors define the intervals, and the 0.005% per °C temperature-stability figure provides a reference for evaluating timing repeatability. Place the timing network close to the relevant pins, provide solid bypassing, and avoid routing outputs near sensitive measurement inputs. Confirm output rise and fall behavior in the intended load configuration before using the pulses as precision timing references.
Được đề xuất
Dữ liệu tham khảo kỹ thuật cho LM556 — 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 |
|---|---|
| Package | 14-pin narrow SOIC |
| Brand | Texas Instruments |
| Timer Sections | 2 |
| Operating Modes | Astable and monostable |
| Supply Voltage Range | 4.5 V to 16 V |
| Specified Temperature Range | 0 °C to 70 °C |
| Timing Range | Microseconds to hours |
| Output Compatibility | TTL compatible |
| Temperature Stability | 0.005% per °C |
Bảo phân biệt quan trọng
- Two independent timing sections in one package (vsLM555)
- Broad timing range (vsNE556)
- Independent astable or monostable configuration (vsSingle-section LM555)
Ghi chú thiết kế
Place each timing resistor and capacitor close to the threshold, trigger, and discharge pins of the timer section they serve. Keep the two timing networks physically separate to reduce coupling between channels. Provide a short ground return from the timing components to the LM556 ground pin, and place supply bypassing close to pin 12 rather than relying on a distant general-purpose capacitor.
Do not confuse the shared reset and control-voltage architecture with separate controls for the two timer sections. Reset can affect both channels, while the control-voltage input sets the timing reference and must not be left without the intended bias or stabilization network. Use the manufacturer timing equations to select resistor and capacitor values, and verify component tolerances over the intended temperature range.
Route trigger and threshold nets away from discharge outputs and switching-node connections to prevent false triggering or premature threshold crossing. If an output drives a higher-current load, use an appropriate buffer or transistor stage and preserve the LM556 output loading limits. Validate timing edges with the intended load rather than relying on an unloaded waveform.
Thông tin tuân thủ
Compliance status was not identified in the manufacturer product information or datasheet excerpts cited for this part. Verify the exact orderable MPN and package suffix with the manufacturer before making a compliance declaration.
