Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Help !!! How can I connect Spartan II with A/D

Status
Not open for further replies.
J

jonatan

Member level 1
Joined
Jun 10, 2002
Messages
39
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
227
lvttl to ttl

I have Digilent-2E with SpartanII FPGA and A/D TI-ADS2807 with 2 single-ended input.

I want to know what is the better I/O Signal Type to choose (LVCMOS,HSTL,SSTL,LVTTL) in the Input FPGA I/O pin to connect with that A/D.

Thanks in advance
 

ttl to lvttl

The spartan data sheet clearly mentions the voltage levels for different I/O standards. Have alook at it along with the data sheet of ADC.
 

ttl lvttl

hi!

may i ask u a question? we have a spartanXC2S200-D2 digilent board. i am beginner for using this board. i want to use this board for external TTL inputs and outputs.but you knew, this boards outputs are LVTTL (3.3 V) . how can i use this device to TTL?

my second question is ; "Can i program this board for using VHDL?

Please note that I am new to FPGA and a beginner of VHDL, so whatever information you give will be valuable to me.


Thanks in advance.
Regards
 

ttl to lvttl converter

Hi bekirhakan,
For your first question about the conversion to/from LVTTL from/to TTL
first : to convert from TTL to LVTTL use a 5V Tolerable buffer just like LVTH16245A , it's a BUS TRANSCEIVERS designed
for low-voltage (3.3-V) VCC operation, but with the capability to provide a TTL interface to a 5-V system environment.
second : you don't need a converter from LVTTL to TTL because the input 3.3v is considered level 1 to the chip
Also you can use the previous chip for both because it's a transceiver..
here is a good URL if you want to know more about the differences between the TTL families
https://www.xs4all.nl/~ganswijk/chipdir/ttl.htm

For your second question Iam afraid I couldn't get it .. can you illustrate it a bit
 

interfacing spartan to ttl

Hi bekirhakan and Vonn,

Yes you can use VHDL to program the digilent board. Try ISE webpack (free) at xilinx website. With this soft and one paralel cable you will be able to program the board with vhdl code.

bekirhakan could you tell us more about conversion to/from LVTTL-->CMOS??
 

convert lvttl to ttl

Regarding to the conversion from/to different levels ; there are chips from a company called Semtech provides solutions for this conversion , you can visit the URL :
http://www.semtech.com/products/products_line_familydisplay.asp_Q_FamilyID_E_29_A_LineID_E_5
to know more about their solutions ..

I have seen also a pdf from ti that is useful to know different levels and they called it LOGIC REFERENCE GUIDE
you can get it from this URL :

http://www.ti.com.tw/pdf/scyb004a.pdf
 

convert ttl to lvttl

I am trying to interface an 8-bit microcontroller to a spartan III development board (digilent) which is similar to one of the posts above. The Spartan III also only supports LVTTL. Someone said earlier that 3.3V on the chip would be considered logic 1(high)... What chip are you referring to? Are you generalizing all TTL standard i/o chips? Xilinx seems to think otherwise. They say you need a voltage level shifting chip, such as the QuickSwitch IDT QS3861. Looking at my C501 8-bit uc, the datasheet says that VIH is at a minimum of 3.5.

Any reply is greatly appreciated.

Thanks!
 

lvttl ttl

This is snipped directly from usenet today , from a xilinx design engineer

(Ansver first , question in bottom)

/Bingo



Eric Smith wrote:
> Austin Lesea <austin@xilinx.com> writes:
>
>>Spartan 3 has clamp diodes that always prevent the voltage on the pin
>>from being more than a diode drop above Vcco (or below ground).
>>
>>So, if Vcco is 3.3V, and the diode drop is ~ 0.5V at the current thru
>>the 270 ohms, then the max V is 3.8V, well below the abs max limit of
>>4.05V in the data sheet.
>>
>>But, take care, as if you have Vcco = 3.45V, then you are getting
>>uncomfortably close to the 4.05V abs max limit.
>
>
> If I want to drive a Spartan 3 input from 5V TTL (not CMOS), such as
> an SN74LS14, do I need a series resistor, and if so, what value? The
> data sheet gives a typical output voltage of 3.4V at -0.4 mA (which is
> the recommended maximum Ioh). They don't give a maximum Voh. Since
> it's bipolar, it's obviously less than the supply rail. I suppose I
> could size the series resistor as if it were a 5.5V CMOS output, but
> I'd prefer to use a lower value if it can be guaranteed not to exceed
> the maximum current of the S3 clamp diode
Click to expand...
.
 

lvttl & ttl

Thanks for the reply. I am actually not so much concerned with the 5V to 3.3V shift. As stated in the previous post there is the clamping diode and I can use a series resistor to reduce the voltage amount. I am actually more concerned with the 3.3V to 5V. This will be evident when I set up a port on the fpga to be an output, and try to connect this port pin to an input on my 8051.

Hopefully I am clear in my description.

Thanks again!
 

ttl to lvttl lvcmos converter

This level conversion method has a serious flaw, since the voltage regulator on the low side has to have some current sink capability, since the current that flows through the clamp diodes has to be sunk by the regulator, a resistor load might be used but in large number of 5->3.3 this is not feasable...
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top