THS7376: Asking for the THS7376 schematic review

Hi SHH,

What is the purpose of the capacitors QC245, QC245, and QC245, and also QC184, QC185, and QC186? They will affect the impedance matching of the 75 ohm transmission line and might cause reflections or even instability. Also, I do not see any 1 to 2 path.

Best regards,

Sean

Hi Sean,

the cap design was refer to d/s figure 123.

The signal from BMC VGA to PI type filter, then connect to VGA1 and THS7376.

THS7376 will connect to VGA_HDR1's pin header. pin header connect to VGA connector.

BR,

SHH

Hi SHH,

The d/s figure 123 is a test circuit. 5pF is added to simulate a worst case parasitic capacitance.
Is VGA1 an output? You should follow the circuit in d/s Figure 134. both outputs should be driven by the THS7376.

Best regards,

Sean

Hi Sean,

VGA1 is output.

could you please confirm the following block diagram is as your suggested?

for the figure 134 setting.

1. Should cusotmer place 75ohm on the red circle highlighted?

2. what is the resistor value is blue circle highlighted?

3. what is the layout trach impedance? keep 75ohm? Do we have layout guide for customer?

BR,

SHH

I confirm this block diagram.

1. Yes

2.This depends on the Pi attenuator. At the BMC (BNC?) input, you must have 75 ohms to ground. If your Pi attenuator has an input of 75 ohms, this resistor is not needed.

3. If you keep layout tight, you need not worry about making your traces 75Ω.Here are some guidelines.

Best regards,

Sean

TI high-speed PCB guidelines.pdf

Hi Shh,

unless the signal traces are very short, I would strongly recommend to use microstrip line techniques to provide 75R signal traces. Each individual line needs its own 75R series termination resistor which should be mounted very close to the driver output.

Kai

Hi Kai,
thanks for comment.
for the figure 134, if customer only connect one signal and leave the other connector disconnection. Will that impact the connected one?

BR,
SHH

Hi Shh,

is the circuit working?

Kai