The LTZ1000 and LTZ1000A are ultra stable temperature controllable references. They are designed to provide 7V outputs with temperature drifts of 0.05ppm/°C, about 1.2µVP-P of noise and long term stability of 2µV/√kHr. Included on the chip is a subsurface Zener reference, a heater resistor for temperature stabilization, and a temperature sensing transistor. External circuitry is used to set operating currents and to temperature stabilize the reference. This allows maximum ? exibility and best long term stability and noise. The LTZ1000 and LTZ1000A references can provide superior performance to older devices such as the LM199, provided that the user implements the heater control and properly manages the thermal layout. To simplify thermal insulation, the LTZ1000A uses a proprietary die attach method to provide signi? cantly higher thermal resistance than the LTZ1000.