ADS4245 VCM output

srikanth adkewar

I am using ADS4245EP Analog to Digital converter in my design with differential input signal and single ended clock. I am operating only one channel(channel B) in 2's complement parallel CMOS mode.At the initial power up of the ADC ,Clkout signal from ADC remains high and VCM shows 200mV instead of 0.95V.I have followed design from the datasheet for my schematic. Please suggest a suitable solution to my problem.Pins sel include(SDATA,SEN,SDOUT:ground and RESET,SCLK:high and cntrl1,cntrl2,cntrl3:101 respectively).

over 9 years ago

0 jim s over 9 years ago

TI__Guru* 91947 points

Srikanth,

What is the clock sample rate and amplitude?

Regards,

Jim

0 srikanth adkewar over 9 years ago in reply to jim s

Prodigy 190 points

Dear jim,

Sampling rate:14MHz and amplitude:1.8V from LVCMOS xtal oscillator(Qtech).

Regards,

srikanth

0 jim s over 9 years ago in reply to srikanth adkewar

TI__Guru* 91947 points

Srikanth,

Is your CMOS clock connected as shown below? Do you have pins 38,39,58, and 59 floating? Are all power inputs at 1.8VDC?

Regards,

Jim

0 srikanth adkewar over 9 years ago in reply to jim s

Prodigy 190 points

yes jim,

pins 38,39,58 and 59 are floating and power input is at 1.8V driven by LDO TPS7A4501 (5v to 1.8v).I have checked all power inputs for the device and found out to be 1.8V. Could you please attach the clock connection again?I am not able to see the circuit. Also, I have a doubt, Does VCM generation requires the clock?It should be 0.95v to 1V immediately after power up.

I have used the same circuit for clock in single ended mode as given in datasheet with same capacitor values.

Regards,

Sreekanth

0 jim s over 9 years ago in reply to srikanth adkewar

TI__Guru* 91947 points

Sreekanth,

The CMOS clock diagram is shown in the data sheet. I do not know your answer regarding the VCM.

Regards,

Jim

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ADS4245 VCM output