Analog Devices Inc. LTZ1000ACH

Overview

LTZ1000ACH from Analog Devices (formerly Linear Technology) is an ultra-precision, temperature-stabilized 7V zener-based voltage reference IC. It delivers 0.05ppm/°C temperature drift, 1.2µV_P-P low-frequency noise (0.1Hz–10Hz), 2µV/√kHr long-term stability, and 400°C/W junction-to-ambient thermal resistance. It is used in metrology-grade calibrators and primary standard cells where sub-ppm stability is mandatory.

For engineers reviewing the LTZ1000ACH datasheet, LTZ1000ACH pinout, LTZ1000ACH application, or LTZ1000ACH equivalent, key selection criteria include verified thermal resistance (θ_JA = 400°C/W), subsurface zener + dual transistor architecture, TO-5 metal-can package pin functions, and heater-controlled die temperature stabilization at ~60°C.

Technical Context

The LTZ1000ACH integrates a subsurface zener diode, heater resistor, and two matched transistors (Q1 for compensation, Q2 for sensing) on a single die. Its precision relies on external circuitry to regulate heater current and maintain constant die temperature-typically 60°C-minimizing zener voltage drift via thermal stabilization.

Unlike conventional references, it requires Kelvin-sensing of the zener and strict thermal management: thermocouple effects from kovar-to-copper leads must be nullified, air currents suppressed, and heater/ground return paths isolated to prevent current-induced voltage errors. The LTZ1000ACH's proprietary die attach yields higher θ_JA (400°C/W vs. 80°C/W for LTZ1000CH), reducing external insulation demands.

Key Specifications

Pinout & Package

LTZ1000ACH is housed in an 8-lead TO-5 metal can (H8 package, 0.200" pin circle diameter) with kovar leads. The hermetic metal enclosure ensures long-term stability and EMI immunity in metrology environments.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-precision voltage reference applications.

Compared with LTC6655-7, LTZ1000ACH offers 40× lower drift and 2× lower noise but demands complex heater control and thermal isolation; compared with LTZ1000CH, LTZ1000ACH reduces insulation burden by 5× due to its 400°C/W θ_JA, enabling simpler mechanical packaging.

Availability

LTZ1000ACH is available at Aetrix Electronics and suitable for calibration standards, high-resolution DMMs, and standard cell replacements requiring stable component supply across extended product lifecycles.

Supply support for LTZ1000ACH 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

Analog Devices (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and precision ICs, serving test & measurement, aerospace, and industrial markets.

The LTZ1000A family was designed specifically for metrology-grade voltage references-prioritizing long-term stability, ultra-low noise, and thermal insensitivity over integration or ease of use.

FAQ

What is the primary function of the LTZ1000ACH in precision measurement systems?

The LTZ1000ACH serves as an ultra-stable 7V voltage reference with 0.05ppm/°C drift and 1.2µV_P-P noise, enabling calibration-grade accuracy in instruments like 8½-digit DMMs and primary standard cells. Its subsurface zener and dual-transistor thermal control allow LTZ1000ACH to maintain sub-ppm stability over years-far exceeding commercial references.

How does the LTZ1000ACH differ from the LTZ1000CH in thermal performance?

The LTZ1000ACH has a specified θ_JA of 400°C/W, versus 80°C/W for the LTZ1000CH, due to a proprietary die attach method that increases thermal resistance between die and ambient. This means LTZ1000ACH requires significantly less external thermal insulation to stabilize its die temperature at 60°C-reducing mechanical design complexity.

Why must Pin 4 (Substrate & Zener Negative) never be forward-biased in the LTZ1000ACH?

Forward-biasing Pin 4 permanently degrades the beta of transistor Q1, causing irreversible long-term drift and noise increase in the LTZ1000ACH. The substrate diode formed at this node is not intended for conduction; keeping Pin 4 at the highest potential in the circuit avoids zenering and preserves LTZ1000ACH's metrology-grade stability.

Can the LTZ1000ACH be used without external heater control circuitry?

No-the LTZ1000ACH requires external circuitry to regulate heater current and maintain constant die temperature (~60°C). Without proper heater control, its 0.05ppm/°C drift and 2µV/√kHr stability cannot be achieved. The LTZ1000ACH datasheet provides reference schematics using op-amps and transistors to implement closed-loop thermal regulation.

What package type and lead material does the LTZ1000ACH use, and why does it matter?

The LTZ1000ACH uses an 8-lead TO-5 metal can (H8 package) with kovar leads. Kovar's matched thermal expansion coefficient minimizes thermomechanical stress, but forms thermocouples with copper PCBs-generating up to 35µV/°C error. This necessitates symmetric trace routing and thermal shielding, making LTZ1000ACH layout critically dependent on managing thermocouple EMFs.