Texas Instruments LM329CZ

Overview

LM329CZ from National Semiconductor is a precision 6.9 V temperature-compensated zener reference diode in TO-92 plastic package, rated for 0°C to +70°C operation, with 30–50 ppm/°C tempco, 0.6–2 Ω dynamic impedance, and 7–100 µV RMS noise (10 Hz–10 kHz). It serves as a stable voltage reference in analog instrumentation and power supply feedback loops.

For engineers reviewing the LM329CZ datasheet, LM329CZ pinout, LM329CZ application, or LM329CZ equivalent, key selection considerations include its 6.9 V nominal breakdown voltage, low dynamic impedance across 0.6–15 mA operating current, ±0.3 V initial tolerance at 25°C, and TO-92 thermal derating profile (180°C/W junction-to-ambient).

Technical Context

The LM329CZ uses a subsurface zener structure fabricated via planar process, integrating temperature-compensating transistors on the same die to minimize voltage drift from thermal cycling and mechanical stress. Its buffered output enables stable regulation without external buffering circuitry.

It operates as a two-terminal shunt reference: reverse-biased with cathode grounded or floating, anode connected to regulated node. Performance is specified over 0.6–15 mA current range, with dynamic impedance maintained below 1 Ω at 1 mA and under 2 Ω across full range.

Key Specifications

Pinout & Package

LM329CZ is housed in a 3-lead TO-92 plastic package (NS Package Z03A), with Pin 1 = Anode, Pin 2 = Cathode, Pin 3 = Case (internally connected to Cathode). The case is electrically tied to the cathode terminal, requiring isolation from ground planes when used in floating configurations.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt reference applications.

Compared with TL431ACZ and LM385BZ-6.8, the LM329CZ delivers superior low-noise performance and fixed 6.9 V output without external components, making it optimal for cost-sensitive, medium-current analog references where precision and simplicity are prioritized over adjustability or micropower operation.

Availability

LM329CZ is available at Aetrix Electronics and suitable for analog instrumentation, linear power supply feedback, bipolar supply referencing, and sensor signal conditioning requiring stable component supply and consistent parametric performance across production lots.

Supply support for LM329CZ 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

National Semiconductor was a U.S.-based semiconductor company specializing in analog and mixed-signal ICs, acquired by Texas Instruments in 2011. Its legacy precision reference portfolio remains widely deployed in industrial and test equipment.

The LM329CZ belongs to the LM129/LM329 family of shunt voltage references designed specifically for applications demanding low noise, low tempco, and high long-term stability without external compensation circuitry.

FAQ

What is the nominal reverse breakdown voltage of the LM329CZ?

The LM329CZ has a nominal reverse breakdown voltage of 6.9 V, with a guaranteed range of 6.6 V to 7.25 V at 25°C and operating current between 0.6 mA and 15 mA. This value is specified in the Electrical Characteristics table of the official National Semiconductor datasheet DS005714, and applies directly to the LM329CZ variant within the LM329 family.

Does the LM329CZ require an external current-limiting resistor?

Yes, the LM329CZ is a two-terminal shunt reference and must be used with an external series current-setting resistor to establish its operating current between 0.6 mA and 15 mA. The resistor value is calculated as (V_IN − 6.9 V) / I_REF, where V_IN is the unregulated input voltage and I_REF is the chosen reference current. This is inherent to all shunt reference topologies, including the LM329CZ.

What is the temperature coefficient specification for the LM329CZ?

The LM329CZ is specified with a temperature coefficient of 30–50 ppm/°C, corresponding to the "C" grade in the LM329 family. This is confirmed in the Electrical Characteristics table of DS005714, where LM329C entries list 30 ppm/°C (min) and 50 ppm/°C (max) under Temperature Coefficient at I_R = 1 mA.

Can the LM329CZ be used in place of a standard 1N4370 zener diode?

Yes, the LM329CZ can replace discrete zeners like the 1N4370 in most applications, offering significantly lower dynamic impedance (≤2 Ω vs. ~100 Ω), better tempco (30–50 ppm/°C vs. ~100 ppm/°C), and lower noise (7–100 µV vs. >200 µV). However, the LM329CZ requires proper thermal management in TO-92 package and is not rated for the same peak pulse currents as ruggedized discrete zeners.

Is the metal case of the LM329CZ electrically isolated?

No, the metal case of the LM329CZ is not electrically isolated-it is internally connected to Pin 2 (Cathode) and Pin 3 (Case) as confirmed in the Connection Diagrams section of DS005714. When mounting on a heatsink or metal chassis, ensure electrical isolation unless the cathode node is intentionally tied to that surface. This configuration is consistent across all TO-92 variants including the LM329CZ.