I'm using both the HMC980LP4E and the HMC981LP3E and would like to know if there are any ways to improve the device enable times?
Thanks and Best Regards.
EN pin response is pretty fast, but the rise time for the Vdd and Vgg loop is in the order of milliseconds.
The default value of shunt Vgate CAP on the EVB is 2.2 uF. Which will give couple of ms rise time typically. By reducing the value of this CAP you can reduce the rise time. 100 nF will give you something close to 100 uSec, a series 100 ohms is also need for stability. Reducing the CAP value further may provide even faster response but you may need to adjust the resistor value to stabilize the loop. We have not tested with below 100 nF.
Based on your answer the time period from the enable going high until the gate voltage settles is mostly governed by the Vgate CAP. I noticed that the enable plot in the HMC981LP3E data sheet is about 3 ms and the enable plot in the HMC980LP4E data sheet is about 1.5 ms. I assume they are different because they probably had different values of Vgate CAP when the plots for the data sheet were taken. Can I assume both parts are the similar and I should be able to have a 100us rise time in either of the two parts?
HMC980 and HMC981 are similar designs. The settling time is mostly effected by Vgate CAP. For both parts you should be able to get typical 10 uSec rise time.
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