VSP5610: in one channel not getting 3 count

VISHAL KALWANI

Part Number: VSP5610

Hi,

I have conifigured Afe in cds mode and i have ground my input signal.In 2 channels i am able to see 3 counts. while in other in one channel i am able to 150 counts why?

My AFE Configuration settings are

I have configured Mclk of 1 Mhz.

Clamp mode is pixel clamp

Reference and clamp level selection is internal Reference 2.2v.

channel polarity-CCD

And counts set in SHP AND SHD ARE

SHP_CH 1&2_Rising edge-6

SHP_CH 1&2_Falling Edge-14

SHD_CH1&2_Rising Edge-31

SHD_CH1&2_FALLING-38

SHP_CH 3&4_Rising edge-7

SHP_CH 3&4_Falling Edge-14

SHD_CH3&4_Rising Edge-32

SHD_CH3&4_FALLING-38

Gain=1

I have attached the schematic picture of Afe.

over 6 years ago

0 Praveen Aroul over 6 years ago

TI__Mastermind 49956 points

Hi Vishal,

Can you provide a high-res image of your schematics?

0 VISHAL KALWANI over 6 years ago in reply to Praveen Aroul

Intellectual 705 points

i have divided the image in 2 parts.

And sending you 2 images you can look in to it.

0 Praveen Aroul over 6 years ago in reply to VISHAL KALWANI

TI__Mastermind 49956 points

Hi Vishal,

Based on the timing you had listed, the min pulse widths (tpw, tdw) for both SHP and SHD are being violated.

Please refer to the datasheet (section 7) for the CDS timing specification.

0 VISHAL KALWANI over 6 years ago in reply to Praveen Aroul

Intellectual 705 points

Hi Praveen,

I have calculated tpw and tdw and there are in range.

I have used x2 sampling.

In datasheet

Tpw= 17ns to 250ns

Tdw = 17ns to 250ns

and our tpw and tdw are

channel1 &2

Tpw=166ns

tdw=146ns

and for channel 3 and 4

tpw=146ns

tdw=125ns

so both tpw and tdw are in range.

How you are saying they are violating?can u explain?

0 Praveen Aroul over 6 years ago in reply to VISHAL KALWANI

TI__Mastermind 49956 points

Hello Vishal,

Your timing configuration seems correct. It was my bad.

We reviewed your schematics and did not notice anything out of the ordinary.

Regarding your original question, can you please clarify what you mean by 3 counts / 150 counts? Are you referring to LSBs (ADC codes)?

If so, 150 LSBs seem high for the idle channel noise.

Here are some debug tips:

1. increase the channel gain and check the noise. If the noise codes are higher, then it seems like the noise is getting coupled at the input.

2. look at the FFT of the data for the possible noise source.

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VSP5610: in one channel not getting 3 count