Please tell me the inside resistance of HMC997LC4.
The customer wants to know the inside resistance between Vctrl-pin and GND.
Because he will use the external resister to input the divided voltage into Vctrl.
Please see the attached file.
Their measurement method seems valid, they can assume the resistance to be 8.3 kOhms.
The resistance will change with lot to lot like everything. But the tolerances are smaller than 2 percent, so I believe it is safe to assume 8.3 kOhm.
However, it is best to use a current source to drive Vctrl pins of HMC997LC4, like a DAC or an opamp.
As it is given on the Pin Description section of the DS, the resistance on Pin 9 is series to the gate of the transistor inside, it is not shunt as shown on the drawing you shared.
Typical current on that pin will be -0.1 mA when Vctl is -1 V and -0.51 when Vctrl is -4.5 V.
Thank you for your answer.
I could check the inside structure through your answer.
The customer measured the resistance of Vctrl to GND of HMC997LC4.
According to result, the resistance of Vctrl to GND has 8.3kohm.
First, he was thinking to use 2.7kohm voltage deviding resistors.
But Vctrl voltage was -2.15V in above case.
At that time, they used 1kohm and 1.2kohm resistors.
That result, Vctrl was -2.5V.
Should he understand that the resistance of Vctrl to GND has typicaly around 8.3kohm resistance?
If this value will be often changed by Lot, he can't decide the value of voltage deviding resistor.
It was cleared.
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