Texas Instruments LMC567CN/NOPB

Overview

LMC567CN/NOPB from Texas Instruments is a low-power CMOS tone decoder IC implementing a phase-locked loop (PLL) with VCO, phase detector, and amplitude detector for frequency-selective signal detection. It operates from 2 V to 9 V, supports input frequencies up to 500 kHz, features 20-mA sink output current, ground-referenced input, and internal hysteresis for noise rejection - used in touch-tone decoding, ultrasonic controls, and carrier-current remote systems.

For engineers reviewing the LMC567CN/NOPB datasheet, LMC567CN/NOPB pinout, LMC567CN/NOPB application, or LMC567CN/NOPB equivalent, key selection criteria include its 500-kHz input frequency limit, 2–9-V supply range, SOIC-8 package compatibility, oscillator timing dependency on Rt/Ct, and absence of supply current increase during output activation.

Technical Context

The LMC567CN/NOPB integrates a voltage-controlled oscillator (VCO) running at twice the input tone frequency, quadrature dividers, a phase detector forming a closed-loop PLL, and an amplitude detector with hysteresis. Its lock-in behavior requires external timing components (Rt on Pin 6, Ct on Pin 5) to set center frequency and filter time constants (C1 on Pin 1, C2 on Pin 2).

Operation relies on two critical analog paths: the loop filter (Pin 2) governs PLL acquisition speed and largest detection bandwidth (LDBW), while the output filter (Pin 1) sets threshold response and noise immunity. The output (Pin 8) is an N-channel FET switch to ground, activated only when both PLL lock and sufficient input amplitude are simultaneously met.

Key Specifications

Pinout & Package

LMC567CN/NOPB is housed in an 8-pin SOIC (D package) with nominal body size 4.90 mm × 3.91 mm and maximum height 1.75 mm. Pin 1 is marked by a beveled corner or dot; the device uses standard JEDEC MS-012AA outline.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar tone decoder applications.

Compared with LM567CMX/NOPB and NE567DR, the LMC567CN/NOPB delivers superior power efficiency, extended frequency range, and integrated hysteresis - making it the preferred choice for modern battery-powered and noise-prone tone detection systems.

Availability

LMC567CN/NOPB is available at Aetrix Electronics and suitable for touch-tone decoding, ultrasonic controls, and carrier-current remote systems requiring stable component supply, long-term manufacturability, and RoHS-compliant packaging.

Supply support for LMC567CN/NOPB 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 company specializing in analog and embedded processing technologies, with leadership in precision analog, power management, and signal chain solutions.

The LMC567CN/NOPB belongs to TI's legacy precision analog timer and decoder product line, designed specifically for low-power, high-reliability tone detection in industrial, consumer, and communications equipment.

FAQ

What is the maximum input frequency supported by the LMC567CN/NOPB?

The LMC567CN/NOPB supports input frequencies up to 500 kHz, verified per its Electrical Characteristics table under Recommended Operating Conditions. This upper limit applies across the full 2–9 V supply range and –25°C to +125°C operating temperature. Operation beyond 500 kHz is not guaranteed and may result in degraded lock-in performance or failure to activate the output.

How does the LMC567CN/NOPB differ from the LM567 in oscillator configuration?

The LMC567CN/NOPB requires its external timing capacitor (Ct on Pin 5) to be halved relative to an equivalent LM567 design because its internal VCO runs at exactly twice the input frequency - whereas the LM567 VCO runs at the same frequency. This difference necessitates Ct reduction and corresponding Rt adjustment to maintain identical decode center frequency, as documented in the Device Functional Modes section.

Can the LMC567CN/NOPB drive an LED directly from its output pin?

Yes, the LMC567CN/NOPB output (Pin 8) is a 20-mA sink-capable N-channel FET switch to ground. With a 5-V supply and appropriate series resistor (e.g., 220 Ω), it can directly drive standard red/green LEDs. Output saturation voltage remains ≤0.15 V at 2 mA, ensuring efficient LED biasing without additional driver circuitry.

What is the purpose of the OF_CAP (Pin 1) and LF_CAP (Pin 2) terminals on the LMC567CN/NOPB?

OF_CAP (Pin 1) connects to the output filter capacitor (C1), setting the response time and noise immunity of the amplitude detector. LF_CAP (Pin 2) connects to the loop filter capacitor (C2), determining PLL acquisition speed and largest detection bandwidth. Both pins interface with internal resistors (40 kΩ and 80 kΩ respectively) to form first-order RC filters critical to tone discrimination performance.

Does the LMC567CN/NOPB require external components to operate?

Yes, the LMC567CN/NOPB requires four external passive components: timing resistor (Rt, Pin 6), timing capacitor (Ct, Pin 5), loop filter capacitor (C2, Pin 2), and output filter capacitor (C1, Pin 1). These define center frequency, PLL bandwidth, and output response - no internal oscillation or filtering occurs without them. A 0.1-µF VCC decoupling capacitor is also mandatory.