LM199AH

Overview

The LM199AH is a precision, temperature-stabilized monolithic zener reference from Texas Instruments. It integrates a temperature stabilizer circuit and an active reference zener on a single chip. The device operates within a reverse breakdown voltage range of 6.8 V to 7.1 V at currents between 0.5 mA and 10 mA. It features a typical temperature coefficient of 0.00005 %/°C across the -55°C to +85°C range and 0.0010 %/°C from +85°C to +125°C. The unit provides low dynamic impedance (0.5 Ω typical) and RMS noise of 7 μV in the 10 Hz to 10 kHz band. It requires a heater supply voltage of 9 V to 40 V and draws up to 200 mA initial turn-on current.

Feature Summary

• Monolithic integration of a temperature stabilizer circuit with an active subsurface zener structure for high stability.
• Hermetic TO-46 metal can package equipped with a thermal shield to minimize heater power consumption.
• Low dynamic impedance achieved through active circuitry, allowing stable operation over a wide operating current range.
• Fast warm-up time and minimal hysteresis during thermal cycling due to temperature stabilization.

Applications

• Analog-to-digital converter references
• Calibration standards
• Precision voltage or current sources
• Standard cell replacements

Procurement Notes

Verify the specific suffix 'AH' against the manufacturer's latest documentation to confirm military-grade specifications and environmental ratings. Ensure the procurement includes the required polysulfone thermal shield, as it is integral to the device's thermal regulation performance. Confirm that the ordering information matches the exact part number variant intended for the application environment.

Selection Notes

Select the LM199AH when extreme long-term stability and ultra-low temperature coefficients are required compared to standard zeners. Consider the TO-46 hermetic package requirements and the necessity of a separate heater supply circuit capable of handling the initial surge current. Evaluate the need for the thermal shield to ensure proper temperature regulation and power efficiency in the final assembly.

Part Context

The LM199 series belongs to Texas Instruments' family of precision voltage references designed to replace ordinary zener diodes. Unlike standard zeners, these devices utilize a monolithic active circuit to stabilize the breakdown voltage against temperature variations. The LM199AH specifically denotes the enhanced version rated for extended temperature ranges and potentially stricter military specifications.

Replacement Considerations

LM299AH

FAQ

What is the purpose of the thermal shield included with the LM199AH?

The thermal shield minimizes heater power consumption and improves temperature regulation by reducing heat loss to the surrounding environment.

How does the LM199AH handle initial turn-on current?

The device draws an initial turn-on current of up to 200 mA; this surge can be reduced by adding appropriate resistors and capacitors to the heater circuit.