ADS5407: Use case of combination with LMH6553

Shinya Sawamoto

Expert 5285 points

Part Number: ADS5407
Other Parts Discussed in Thread: LMH6553

Hello team,

I'd like to check if there is any concern or design notice for ADS5407 analog input when it is combined with LMH6553?

Thanks in advance.
S.Sawamoto

over 5 years ago

0 jim s over 5 years ago

TI__Guru* 91947 points

Shinya,

We will check with the our amplifier team regarding this.

Regards,

Jim

0 Rob Reeder over 5 years ago in reply to jim s

TI__Mastermind 38330 points

Hi Shinya,

Is there a requirement to be DC coupled at the input and therefore the output of the amplifier to the ADC?

Can you AC couple instead?

Regards,

Rob

0 Shinya Sawamoto over 5 years ago in reply to Rob Reeder

TI__Expert 5285 points

Hi Rob,

DC coupled is considered but AC coupled can be also acceptable depends on the benefits.

Thanks.
S.Sawamoto

0 Rob Reeder over 5 years ago in reply to Shinya Sawamoto

TI__Mastermind 38330 points

Hi Sawanmoto,

If planning to AC couple this configuration, then simple put a series 0.1uF cap in-between the outputs of the amplifier and inputs of the ADC. You can also add a cap in series before the 59ohms to ground on the amplifier's input as well.

Few things to note:

I will recommend split supply operation on the LMH6553 such as +5V/-1V on the supplies.
The VCM of the LMH6553 should be tied same as the ADS5407.
The clamp voltage (Vclamp) should be tied to 2.4V as that will result in 2V_PP(Diff) operation at the LMH6553 output.
I will recommend using an anti-aliasing filter at the LMH6553 output and ADS5407 input, probably a 3^rd or 5^th order. The filter is matched on both the output and input which allows the differential swing of 2V_PP(Diff) to be divided down into 1V_PP(Diff), which is also the full scale level to the ADC.

Regards,

Rob

0 Shinya Sawamoto over 5 years ago in reply to Rob Reeder

TI__Expert 5285 points

Hi Rob,

Thanks a lot for your clear advice in detail!

Regards,
S.Sawamoto

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ADS5407: Use case of combination with LMH6553