I am reviewing the HMC856 eval board schematic on page 12 of the HMC856 data sheet. I am trying to figure out how to interface the control (B0-B4) to LVTTL (1.8, 2.5 or 3.3V) control system. Is it possible?
HMC856
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The HMC856 is a wideband time delay device with a 5-bit
digital control designed for timing compensation or clock skew
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Datasheet
HMC856 on Analog.com
I am reviewing the HMC856 eval board schematic on page 12 of the HMC856 data sheet. I am trying to figure out how to interface the control (B0-B4) to LVTTL (1.8, 2.5 or 3.3V) control system. Is it possible?
Hi,
One way to do is connect positive ports B0-B4 to a fixed voltage with a resistance, say 1.2k to GND and connect transistor switches to negative ports(B0~B4) with 2.7kohms each. Transistor switches can either be open or short to Vee. This way (B0-B4) change state. LVTTLs can drive switch transistors.
If you supply shift the part between 3.3V and GND, and if LVTTLs can supply enough current, you wouldnt need interfacing transistors/level shifters. The RF signal though should be AC couple in that case.
Sinan
Hi,
I saw the HMC856 Eval board schematic (page 12 of the datasheet) and the B0-B4 ports are connected differently.
The positive ports B0-B4 are connected singularly to a test point with a 2.7KOhm resistor while the negative ports B0-B4 are connected together with 1.2KOhm to a test point. Your suggestion is not applicable to HMC856 Eval board. Is it correct?
Could you help me to understand the right way to management the B0-B4 ports of the HMC856 Eval board?
Could you help me to understand the right way to management the B0-B4 ports of the HMC856 with LVTTL signals?
Best Regards,
Daniele
Control pins have internal 600ohms and there is a voltage division with externally connected resistors which are pulled down to -3.3V.
Hi,
in the eval board, the 600 Ohm internal pull ups are connected to VT. The VT-J8 pin is floating (I didn't see a specific interconnection) while you supposed that this pin is connected to GND. It is correct?
Best Regards,
Daniele
Hi,
in the eval board, the 600 Ohm internal pull ups are connected to VT. The VT-J8 pin is floating (I didn't see a specific interconnection) while you supposed that this pin is connected to GND. It is correct?
Best Regards,
Daniele
VT should be tied to GND, you are correct.