ISO1412DWEVM: ISO1412DWEVM: Output Amplitude

Hi Kai,

Thank you for reaching out to us!

From the first figure, the output X and Y swings to 5V.

This amplitude indicates that there is no termination between pin X and pin Y.

Please connect a jumper on J2 as described in the table 2 of the EVM user guide.

This jumper enables the 120ohm termination across pin X and pin Y.

The 400kHz ripple could be a result of the reflection or power noise since the

ISO1412 does not generate a 400kHz signal. Please plot the signals of pin X

and pin Y after enabling the termination. The waveforms should be similar to

the waveform depicted in the User guide.

If you still see the 400kHz ripple, please plot the Vcc2 with respect to Gnd2

with a good probe to validate whether the noise is coupled from the Vcc2.

Regards,

Alfred

Hi Alfred:

I have the Jumper ON for the above situations, without the jumper the ripple are worst.

The 400kHz ripple could be a result of the reflection or power noise<<<<<

I thought about the same thing and I have monitor the Vcc2, it was rock solid when idle, but once I inject signal into (D-GND1), the Vcc2 has that 400K ripple

I am using a

BK PRECISION 9130 TRIPLE OUTPUT PROGRAMMABLE DC POWER SUPPLY.

TEKTRONIX TDS 2012C

Looks to me the Primary side somehow causing the ripple coupled on the other side.

I am not in the office at least til next week, I will upload more pictures.

I am designing a product which using the other ISO series, ISO7341, ISO1042, and they do not have this issue and have been working perfect.

Hi Kai,

Thank you for the additional information you provided! I look forward for the data you will be collecting next week.

Could you please check the current limit of the DC power supply? Could you please set it at least 100mA?

Regards,

Alfred

Hi Alfred:

Please see below with more data captured. Looks like the ripple changed proportional to Input Frequency.

I have tested with 100K-500KHz, Vcc2, Y, with and without Termination Jumper.

BK Precision 9130 Power Supply is set to 5V, Max Current as 1A.

Same Result When I use a Din Rail Micron 5V 6A Power Supply.

Do you think my dev board is defective?

100K Hz, Vcc2, Y Termination Jumper ON

100K Hz, Vcc2, Y Termination Jumper OFF

200K Hz, Vcc2, Y Termination Jumper ON

200K Hz, Vcc2, Y Termination Jumper OFF

300K Hz, Vcc2, Y Termination Jumper ON

300K Hz, Vcc2, Y Termination Jumper OFF

400K Hz, Vcc2, Y Termination Jumper ON

400K Hz, Vcc2, Y Termination Jumper OFF

500K Hz, Vcc2, Y Termination Jumper ON

500K Hz, Vcc2, Y Termination Jumper OFF

For some Reason my Reply minutes ago was flagged as SPAM...

I guess I uploaded too many pictures at once.

Let me try again...

I tested the unit with 100kHz-500kHz, seems like the ripple changed directly proportion to Input Frequency.

I monitored the Y, Vcc2<< with respect to GND2, with and without Termination Jumper.

The BK Precision 9130 Power supply is set to 5V 1A Max current.

I used another DIN Rail Power supply Micron 5V 6A got the same result.

Do you think I got the defective Eval Board.

100kHz Vcc2 Y Jumper is ON.

200kHz Vcc2 Y Jumper is ON.

300kHz Vcc2 Y Jumper is ON.

400kHz Vcc2 Y Jumper is ON.

500kHz Vcc2 Y Jumper is ON.

100kHz Vcc2 Y Jumper is OFF

200kHz Vcc2 Y Jumper is OFF

300kHz Vcc2 Y Jumper is OFF

400kHz Vcc2 Y Jumper is OFF

500kHz Vcc2 Y Jumper is OFF

Hi Kai,

Thank you for capturing and sharing the plots!

The ripple frequency does not seem to directly scale with the input frequency proportionally.

The ripple frequency is 400kHz for input frequencies of 100kHz and 200kHz.

It goes up to about 600kHz when the input frequency is 300kHz,

and 1MHz when the input frequencies are 400kHz and 500KHz.

Hence, the ripple frequency is not proportionally scaled with the input frequency.

With a power supply that is capable of 1A connected to Vcc2,

it should be very stable given that ISO1412 consumes much lower than 1A.

Also, you probed at the connector that is connected to the power source.

The connector is a good conductor and the voltage should be very stable. 

Hence, we should not see high magnitude ripples on the Vcc2.

Could you please provide the following plots?

Connect Vcc1 to a supply with at least 1A.

1. Probe the Vcc1 with the input D set to high.
2. Probe the Vcc1 with an input D toggles from 100kHz to 500kHz with a frequency step of 100kHz.
3. Probe the Vcc2 with the input D set to high.

Regards,

Alfred

Hi Alfred:

Please see below:

1. Probe the Vcc1 with the input D set to high.

Vcc stays Solid ON.

2. Probe the Vcc1 with an input D toggles from 100kHz to 500kHz with a frequency step of 100kHz.

3. Probe the Vcc2 with the input D set to high.

I have GND1 and GND2 short together to get both readings.

Hi Kai,

Do you have another EVM board that you can repeat the measurement?

Can I connect with you through your email on ti.com to ship you another EVM if needed.

Regards,

Alfred