I wonder Control Voltage using HMC346AMS8GE?

Question

Hi! 
 I`m using HMC346AMS8GE attenuator? 
 V1 and V2 Control Pin same Voltage or a different Voltage supply? and I Pin open or GND Short? 
 
 Single-Line Control Driver is it possible application only? 
 input power for 0.25dB Compression +8dBm ~ +4dBm : is there a problem When Out of Range?

salemdar · Accepted Answer

The opamp needs to take the input from I pin, and reflect to V2 pin always. The voltage of I pin changes with respect to V1 voltage. You should follow the external opamp configuration exacly the same. 
 
 The opamp supply voltage should be at least -5V, so that it's rail can cover -5V.)

salemdar · Answer

Hi AGU, 
 
 I would recommend including an LDO because any ripple on the V1 or V2 will modulate the attenuation and reflect to the output as additional spurs. 
 
 Thanks

salemdar · Answer

Hi, 
 
 V1 voltage controls the series devices and V2 voltage controls the parallel device. To set the attenuation, V1 is adjusted between 0 to -4V. However, to ensure 50ohm impedance for all V1 voltage, V2 needs to be adjusted. Otherwise RF ports will not show good return loss. 
 
 There is also a reference attenuator inside the part. The transistor sizing and resistors are 10x scaled and they are also connected to V1 and V2. Thus the external loop reads the input impedance from pin I, and tries to adjust the input impedance to 500ohm via an external opamp loop and drive V2 voltage. 
 
 Thus, V1 is driven only as single drive but V2-I pins are needed to be connected to an external opamp loop. 
 
 Best Regards

salemdar · Answer

Hi Sang, 
 
 HMC346A is a GaAs based VVA and we would expect part to part variance on the gate pinch-off of series and shunt devices on the attenuator. Therefore, it is not meaningful to create a look-up table and apply to every part. 
 
 The external I-V2 loops ensures the reference attenuator's input impedance to be 500ohm and main attenuator's input impedance to be 50ohms. If this is not set, mismatch losses would add on the attenuation, and this creates uncertainties on the end-to-end attenuation. 
 
 For experimenting purposes, if you still want to drive V1 and V2 separately, I suggest you monitor input impedance of I pin. You may use an SMU or fixed current source to apply 10uA and monitor the voltage on it to calculate the input impedance. 
 
 Thanks 
 Sinan

Electronic Design Services - PartnerZone

Products Mentioned

I wonder Control Voltage using HMC346AMS8GE?