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# HMC401 VCO Temperature Range

Will HMC401 operate beyond the specified datasheet limits of -40 degC to _85 degC? Ideally, I would like to run it at temperatures up to 105 degC ambient.

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• Operating the HMC401 at 105°C ambient isn't recommended. The HMC401 is an older device and unfortunately doesn't have power dissipation or thermal information listed on the datasheet. However, it's similar to the HMC533LP4 except for the package and output amplifier. The power dissipation is 1.1W with a maximum junction temperature of 135°C. Using the thermal resistance of the HMC533LP4 of 36°C/W (which is typical of many Hittite GaAs parts) we arrive at a 144.6°C junction temperature when operating at 105°C ambient. When the HMC401 package style with its less than ideal thermal conductivity is considered it makes the decision easy.