SN65LVDS31: SN65LVDS31 connect to SNL65LVDT33 over 2.5 meters

Poh Kok Keng

Part Number: SN65LVDS31

Dear Sir/Madam,

I want to design a SPI to LVDS connection over 2.5 meters using SN65LVDS31 (Transmit) and SNL65LVDT33 (Receive with internal terminating resistor).

i'm considering fews methods of doing the 2.5 meters inter connection in order to make sure i get the best signal performance and also the smallest connector size.

If I chose to use IDC Flat ribbon cable, can I use 0.635/0.64mm cable pitch? Do Iyou suggest to separate each signal with a Ground or can I separate them as a pair with ground? The idea is to use the smallest connector that I can use?

Do I need to use a Twisted pair IDC Ribbon Cable of either 0.64mm or 1.27mm cable pitch and do direct solder between the 2 boards.

Hope to get some advice. thx

Best Regards,
kpk

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 316900 points

For differential transmission, the two signals should be near each other (you can insert ground between the pair and other signals). Small pitch is no problem.

Twisted pair is better than a straight ribbon cable, but whether it makes a difference depends on your environment; you'll have to test.

0 Ivan Teo over 3 years ago in reply to Clemens Ladisch

Prodigy 60 points

For a SPI Master device to communicate with a SPI Slave device across 2.5meters long cable at speed of about 15~20Mbits/sec, can we use 0.634mm pitch flat ribbon cable with ground between different pair and other signals?

Cable / Connector configuration as below:

Signal Name	Pin No	Pin No	Signal Name
VCC	1	2	VCC
VCC	3	4	VCC
GND	5	6	P_MOSI
N_MOSI	7	8	GND
P_SCLK	9	10	N_SCLK
GND	11	12	P_CS
N_CS	13	14	GND
P_MISO	15	16	N_MISO
GND	17	18	P_IRQ
N_IRQ	19	20	GND
P_BUSY	21	22	N_BUSY
GND	23	24	I2C_SDA
GND	25	26	I2C_SCL
GND	27	28	GPIO
GPIO	29	30	GND

Please help to advise.

Thanks and Best Regards,

Ivan

0 Clemens Ladisch over 3 years ago in reply to Ivan Teo

Guru 316900 points

This looks OK.

0 Ivan Teo over 3 years ago in reply to Clemens Ladisch

Prodigy 60 points

Thanks for the review and advise.

0 Ivan Teo over 3 years ago

Prodigy 60 points

Hi,

Notice that SN65LVDS33PW is out of stock. Can we use SN65LVDS32PW instead of SN65LVDS33PW if the speed is about 15~20 Mbits/sec?

Thanks and Best Regards,

Ivan

0 Clemens Ladisch over 3 years ago in reply to Ivan Teo

Guru 316900 points

The difference between SN65LVDS and SN65LVDT is that only the latter has integrated termination resitstors. The difference between 32 and 33 is that the latter has wider common-mode range to allow other protocols. All these devices will work.

0 JMMN over 3 years ago in reply to Clemens Ladisch

TI__Guru 60870 points

Thanks Clemens!

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SN65LVDS31: SN65LVDS31 connect to SNL65LVDT33 over 2.5 meters