DS15BA101: DS15BA101

HungLin Hsu

Part Number: DS15BA101

Hi,

we use DS15BA101SDE to be our buffer. input is LVDS and output is also LVDS, than use this IC Rvo to adjust Vod that range is 100mV to 900mV.

I had a problem because I LVDS a port is 5 pairs differential signals. DS15BA101SDE is just support a pair for each. If data rate is 1Gbps, how many (UI) skew rate between IC and IC?

Could I know the maximum value or definition?

Best regards,

Hsu

over 7 years ago

0 Nasser Mohammadi over 7 years ago

TI__Guru* 93670 points

Hi Hsu,

Part to part skew in your block diagram is about 500ps.

Regards,,,nasser

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

Thanks a lot.

Regards, Hsu

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

I have a problem. Why did I make circuit no output which is always 20mV, I did the circuit as following

input amplitude is 400 mVp-p. where did I miss?

Regards, Hsu

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,

1). First of all, thanks very much for using DS15BA101 device.

2). It would be a good idea if you could please send us your complete schematic and test setup.

Here are some comments and questions that may help to see what is going on here:

a). When signal is attached to IN+/-, do you see current consumption increase?

b). I am assuming you have already checked and you have 3.3V on pin 5 and pin 3 & DAP are both attached to ground.

c). What is the data rate?

d). Are you using a high impedance scope probe? Also, is it AC coupled?

e). Please use your voltmeter to make sure pin 4 is connected to RVO 953 ohm Resistor. Also, the other side of this Resistor is attached to 3.3V.

f). What is current consumption of DS15BA101 when signal is applied?

g). What is current consumption of DS15BA101 when there is no signal on input of DS15BA101?

h). Finally, if you use a DC voltage on input do you see output move as you expect?

Hope these help to see what could be the root cause of no output on your DS15BA101 design.

Regards,,nasser

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

thank you,

1. as following is application circuit.

2. our data rate is 140Mbps ~ 800Mbps, if data rate below 140M, what happen on this device?

3. input is LVDS, output is also LVDS.

4. measurement equipment is agilent MSO9104A, and differential scope. I had tested input LVDS signal which is 400mVp-p, but output is 20mVp-p

5. 2 parts current is approximately 60mA

Regards, Hsu

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,

In this schematic you show RP148 as 100-Ohm Resistor. This should be 953-Ohm. Do you see any output if you change this to the recommended 953-ohm Resistor?
Please let us know your result.

Regards,,,nasser

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,
I have changed to 953-ohm. it is also the same.

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,

1). Please use your voltmeter to make sure RVO 953-ohm is indeed connected to pin 4 of the device in your pcb layout. Also, please use your voltmeter to make sure RP148 is connected to 3.3V VCC.

2). Please connect a DC voltage on IN+ and IN- and check to make sure output changes. For example, connect IN+ to 3.3V and IN- to GND and make sure you have constant high on OUT+ and OUT-. Next, connect IN+ to GND and IN- to 3.3V and make sure the output switches or follows the input.

3). Please send me your pcb layout or gerber.

I believe there is a mis-connection in your pcb layout and we need to find this. Please let me know.

Regards,,,nasser

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

Thank you, I am trying. and tell you result later.

Regards, Hsu

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

Thank you, Signal had output and I changed Rvo which can change Vp-p. problem is my test method wrong. Now I want to tape-out and do pcb.

Thanks a again

Regards, Hsu

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,

I am very glad that you solved this problem.

Regards,,,nasser

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,
DS15BA101 can accept LVDS input and output. Please make sure you AC couple on both input and output.
Regards,,,nasser

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

Can you show me a reference design?

Regards, Hsu

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

Because I did not understand, LVDS is DC couple. Why I need use AC couple on both input and output?

Regards, Hsu

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,
AC Coupling is used to isolate or make interface independent of the common mode voltages on driver and receiver sides. Please note figure 6 and 7 of the DS15BA101 data sheet.
Regards,,,nasser

0 HungLin Hsu over 7 years ago in reply to Nasser Mohammadi

Prodigy 220 points

Hi, Nasser,

But I had asked this circuit, LVDS directly in and LVDS directly out, as below. did I also could to do this?

Regard, Hsu

0 Nasser Mohammadi over 7 years ago in reply to HungLin Hsu

TI__Guru* 93670 points

Hi Hsu,

You can DC couple as you have shown in your schematic as long as electrical specifications for input and output common mode voltages are met. Please note DC Electrical Characteristic table in DS15BA101.

Regards,,,nasser

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DS15BA101: DS15BA101