LM385Z: Micropower Adjustable Band-Gap Voltage Reference

Overview

The LM385Z is a precision micropower 3-terminal adjustable band-gap voltage reference diode, part of the LM185/LM285/LM385 family. Designed for operation across a wide voltage range (1.24V to 5.3V) and current range (10µA to 20mA), this component delivers exceptional performance with low dynamic impedance and excellent temperature stability. The device is trimmed during manufacturing to ensure tight voltage tolerance, making it ideal for precision applications where stable voltage references are critical.

Constructed using only transistors and resistors, the LM385Z achieves low noise and high reliability. Its band-gap architecture ensures consistent performance over a broad temperature range, making it suitable for both commercial and industrial applications.

Features

• Adjustable Output Voltage: Configurable from 1.24V to 5.30V using external resistors.
• Low Operating Current: Functional from 10µA to 20mA, making it ideal for battery-powered applications.
• Low Dynamic Impedance: Ensures stable voltage reference even under varying load conditions.
• Excellent Temperature Stability: Maintains consistent performance across a wide temperature range.
• On-Chip Trimming: Factory-trimmed for tight voltage tolerance and precision.
• Low Noise: Band-gap design minimizes output noise, critical for sensitive analog circuits.
• Wide Supply Range: Operates from 1.24V up to 5.3V, accommodating various system requirements.
• Robust Construction: Built with transistors and resistors for long-term reliability.

Applications

The LM385Z is widely used in applications requiring a stable and precise voltage reference. Its low power consumption and adjustable output make it versatile for both portable and fixed systems.

• Precision Voltage References: Used in analog-to-digital converters (ADCs), digital-to-analog converters (DACs), and sensor interfaces.
• Battery-Powered Devices: Ideal for portable electronics, medical devices, and energy-efficient systems due to its low current consumption.
• Voltage Regulation: Provides stable references for linear regulators and power management circuits.
• Industrial Control Systems: Ensures accuracy in process control, instrumentation, and measurement equipment.
• Consumer Electronics: Used in audio equipment, displays, and other precision analog circuits.
• Automotive Electronics: Suitable for sensors and control modules requiring reliable voltage references.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM385Z under typical operating conditions (unless otherwise noted):

• Output Voltage Range: 1.24V to 5.30V (adjustable)
• Operating Current Range: 10µA to 20mA
• Dynamic Impedance: Typically 0.5Ω at 100µA
• Temperature Coefficient: Typically 20ppm/°C (LM385B grade)
• Voltage Tolerance: ±1% (LM385B grade)
• Long-Term Stability: Typically 20ppm/1000 hours
• Operating Temperature Range: -40°C to +85°C (LM385)

Key Performance Graphs

The LM385Z exhibits stable performance across its operating range:

• Output Voltage vs. Current: Demonstrates minimal variation over the 10µA to 20mA range.
• Temperature Stability: Shows low drift across the full temperature range.
• Noise Characteristics: Band-gap design ensures low output noise, critical for high-precision applications.

Package Information

The LM385Z is available in a compact 3-pin TO-92 package, which is widely used for through-hole PCB mounting. The package dimensions and pinout are as follows:

• Package Type: TO-92 (3-pin)
• Pin Configuration:
  • Pin 1 (Adjust): Connected to external resistors for voltage adjustment.
  • Pin 2 (Anode): Ground or negative supply connection.
  • Pin 3 (Cathode): Output voltage reference.
• Dimensions: 4.95mm (length) x 3.94mm (width) x 4.95mm (height).
• Weight: Approximately 0.35 grams.

Handling and Mounting Guidelines

To ensure optimal performance and reliability, follow these guidelines when working with the LM385Z:

• ESD Precautions: Handle with appropriate electrostatic discharge (ESD) protection to prevent damage.
• Soldering: Use standard soldering techniques, avoiding excessive heat to prevent thermal stress.
• PCB Layout: Place decoupling capacitors close to the device to minimize noise and ensure stability.

Conclusion

The LM385Z is a highly versatile and reliable voltage reference diode, offering precision, low power consumption, and excellent temperature stability. Its adjustable output and robust design make it suitable for a wide range of applications, from portable electronics to industrial systems. With its compact TO-92 package and proven performance, the LM385Z is an excellent choice for engineers seeking a dependable voltage reference solution.