INCAA looked at it and wrote the text below.
Sundance will do an evaluation of the proposed alternative CTX101R.
Part

Parallel open circuit
inductance [uH]

Parallel full load
current
[A (dc)]

Parallel DC resistance
[Ohm (max)]

Series open circuit
inductance
[uH]

Series full load current
[A(dc)]

Series DC resistance [Ohm
(max)]

Height
[mm]

CTX101AR

10.58

2.5

0.046

42.30

1.25

0.183

4.19

CTX102R

10.58

2.5

0.031

42.30

1.25

0.125

5.97

CTX101R

10.00

1.9

0.044

40.00

0.95

0.176

4.19

CTX101PR

9.62

1.8

0.052

38.48

0.85

0.227

4.19

The big difference between the CTX101AR and the CTX102R, CTX101R or CTX101PR is the used core material. De CTX101AR is an OCTAPAC PLUS, the CTX102R and CTX101R are an OCTAPAC, and the CTX101PR is a ECONOPAC…
OCTAPAC’s are designed around high frequency, low loss core material.
ECONOPAC’s are a lower cost version of OCTAPAC’s offering high saturation flux density, Iron powder core material.
OCTAPAC PLUS’s offer higher current ratings and higher saturation flux densities than OCTAPAC and ECONOPAC, Amorphous metal core material.
The advantage of the ‘higher current ratings and higher saturation flux densities’ for the originally used CTX101AR in a lower size device can be replaced by the higher size CTX102R device which has about the same specifications. Het problem of the CTX102R is however its height. The FMC specification states that the height of the part located in component envelope (see ANSI/VITA 57.1 FPGA Mezzanine Card (FMC) Standard, Figure 3) can only be 4.7mm high (see Figure 9), so the CTX102R is not allowed, as it is situated on the EDA02063 Fmc Adc 100M 14b 4cha within that area.
The next best is the CTX101R which has a slightly lower inductance and a slightly lower full load current specification.
The power circuit of the EDA02063 Fmc Adc 100M 14b 4cha, using the inductor as L1 and the LT1931ES5 (IC21) as switching regulator, can only provide 350mA. The LT1931 datasheet states: “When using coupled inductors, choose one that can handle at least 1A of current without saturating, and ensure that the inductor has a low DCR (copperwire resistance) to minimize I2R power losses.” The datasheet even suggests the CTX101.
So you could ask yourself why in the original design the CTX101AR was chosen and not the CTX101R. This seems to have been a choice based on tests. The EDA02063 Fmc Adc 100M 14b 4cha V1.0 used a SDQ124R7R which is 4.7uH. If a 10uH equivalent should have been the better value, a SDQ12100R could have been a drop in replacement. As of the V2.0 version of the design the CTX101AR is used and not the CTX101R. There are no design review documents available on the ohwr site regarding this design change to V2.0, so it is unknown why this part is changed.
A change from the CTX101AR to the CTX101R for the V5.0 version could have some potential influence on the characteristics of the LT1931ES5 circuit, which could be shown in the form of a difference noise floor or a different amplitude of spurious frequencies in the measured signals. This can only be checked by an investigation by means of measurements.