Texas Instruments TLC556CDG4

Overview

TLC556CDG4 from Texas Instruments is a dual CMOS timer IC with rail-to-rail CMOS output, 2 mW typical power consumption at 5 V, 100 mA sink / 10 mA source output drive, and single-supply operation from 2 V to 15 V. It functions as a precision timing engine in monostable and astable configurations for pulse generation and time-delay circuits.

For engineers reviewing the TLC556CDG4 datasheet, TLC556CDG4 pinout, TLC556CDG4 application, or TLC556CDG4 equivalent, this page delivers verified electrical specs, SOIC-14 package mapping, functional mode behavior, real-world timing design constraints, and validated alternative options for industrial timing designs.

Technical Context

The TLC556CDG4 integrates two independent CMOS timers sharing a common VDD and GND. Each timer uses a precision resistor divider (R–R–R) to set internal trigger (≈1/3 VDD) and threshold (≈2/3 VDD) reference levels, both adjustable via the CONT pin. Its flip-flop-based state machine supports monostable and astable modes with active-low RESET overriding TRIG and THRES inputs.

Timing accuracy benefits from high input impedance (>10¹² Ω), enabling use of smaller timing capacitors than bipolar NE556. Output transitions generate minimal supply current spikes due to low dynamic current draw, reducing decoupling capacitor requirements versus legacy bipolar timers.

Key Specifications

Pinout & Package

Package: SOIC-14 (D), 14-pin small-outline integrated circuit with 1.27 mm pitch, gull-wing leads, and JEDEC MS-012AC compliance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-timer applications.

Compared with NE556N and LTC6992IMS-1#PBF, the TLC556CDG4 uniquely balances low-power CMOS operation, high-output drive, analog programmability via R/C/CONT, and pin compatibility with legacy designs-making it optimal for cost-sensitive, mixed-signal industrial timing where both precision and drive strength matter.

Availability

TLC556CDG4 is available at Aetrix Electronics and suitable for industrial sensor timing, LED flasher control, PWM motor speed regulation, and power supply sequencing requiring stable component supply across extended production lifecycles.

Supply support for TLC556CDG4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and digital signal technologies with over 90 years of innovation in precision timing and power management.

The TLC556 series was designed as a CMOS upgrade path for NE556-based systems-delivering lower power, improved accuracy, and enhanced noise immunity for industrial, instrumentation, and consumer timing applications.

FAQ

What is the maximum operating frequency of the TLC556CDG4 in astable mode?

The TLC556CDG4 achieves a maximum astable frequency of 2.1 MHz under specified conditions (RA = 470 Ω, CT = 200 pF, RB = 200 Ω, VDD = 5 V, TA = 25 °C). At higher frequencies, propagation delay and discharge switch on-resistance introduce timing errors; actual usable frequency depends on component tolerances and PCB parasitics. The TLC556CDG4 datasheet specifies fmax = 2.1 MHz as the upper limit for reliable operation.

Does the TLC556CDG4 support dual independent timers, and how are they isolated?

Yes, the TLC556CDG4 contains two fully independent CMOS timer circuits sharing only VDD and GND. Each timer has dedicated TRIG, THRES, CONT, RESET, DISCH, and OUT pins (pins 1–8 and 9–14). No internal coupling exists between stages-timing behavior, output drive, and reset control operate autonomously. This isolation enables cascaded timing, differential delay generation, or separate monostable/astable configurations on one die.

Can the TLC556CDG4 operate from a 3.3 V supply, and what are the implications?

Yes, the TLC556CDG4 operates from 2 V to 15 V, including 3.3 V nominal supplies. At 3.3 V, trigger and threshold voltages scale to ≈1.1 V and ≈2.2 V respectively, maintaining supply-independent timing. Output swing remains rail-to-rail (0 V to 3.3 V), ensuring compatibility with 3.3 V logic. Quiescent current drops to ~275 µA typical, enhancing efficiency. Ensure external timing resistors are sized to maintain adequate current into comparator inputs at reduced voltage.

How does the CONT pin affect timing accuracy and stability in the TLC556CDG4?

The CONT pin directly sets the internal voltage divider ratio, altering both trigger (≈1/2 × CONT) and threshold (≈CONT) reference levels. Bypassing CONT to GND with a 0.01 µF ceramic capacitor suppresses noise-induced jitter and stabilizes duty cycle in astable mode. Without bypassing, leakage or noise on CONT causes threshold drift, leading to timing variation >±5%. The TLC556CDG4's high-impedance CONT input (10¹² Ω) makes it sensitive to layout-short traces and guard rings are recommended for precision applications.

Is the TLC556CDG4 pin-compatible with the NE556, and what design changes are needed for replacement?

Yes, the TLC556CDG4 is functionally and pin-compatible with the NE556 in D (SOIC-14) and N (PDIP-14) packages. Direct substitution is possible, but design changes improve performance: replace 10 µF electrolytic VDD decoupling with 0.1 µF ceramic (due to lower supply spikes), reduce timing capacitor values by 3–5× (due to higher input impedance), and tie RESET to VDD via 10 kΩ pull-up (NE556 tolerates floating RESET; TLC556CDG4 does not). No PCB layout change is required for SOIC-14 footprints.