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# HMC7043 Power supply regulator design with HMC7043 EVM board.

Dear Experts,

My customer is making the power supply regulator design for HMC7043. Could you please reply to the following questions?

Q1: The HMC7043 EVM board uses LT1963 for 3.3[V] power supplies of HMC7043. According to LT1963 datasheet, the maximum electrical current of LT1963 is 1.5[A].

On the other hand, the LT1963 in HMC7043 EVM board supplies the 3.3[V] voltage to some power supply pins such as VCC2_OUT, VCC3_OUT, VCC4_CLKIN, VCC5_SYSREF, VCC6_OUT and VCC7_OUT except VCC1_CLKDIST. The total electrical current value of the power supply pins connected to LT1963 is 1810[mA] = 250[mA] + 500[mA] + 25[mA] + 35[mA] + 500[mA] + 500[mA] for VCC2_OUT, VCC3_OUT, VCC4_CLKIN, VCC5_SYSREF, VCC6_OUT and VCC7_OUT, respectively.

So, the power supply regulator, LT1963 with maximum electrical current at 1.5[A] has been applied to the HMC7043 power supply pins with the maximum electrical current at 1.81[A] in the HMC7043 EVM board. Therefore, the LT1963 doesn't have electrical current capability enough for HMC7043.

Of course, LT1963 will be able to supply more than 1.5[A] in most of the conditions. Because the current limit is over 1.5[A] for most of the conditions. However, it will not be guaranteed by LTC probably.

The HMC7043 EVM board has been designed for:
1) Some and/or typical functional testing purposes.
Or
2) The full functional testings with all of the conditions including corner cases and the really full operations.

Which is correct, the above descriptions?

Q2: My customer should put the power supply regulator which can support the maximum electrical current value at 1935[mA].

Is it correct?

1935[mA] = 1810[mA] + 125[mA] (VCC1_CLKDIST).

Thanks and regards.

• Hi,

The currents that is used in calculation, includes all output drivers and all features when set to maximum current consuming condition and all PVT variations and also aging factor. For a typical configuration (some outputs are pulsed, analog delay is disabled for some outputs, some dividers are not used, etc.) the consumption will be about 800-900mA. The consumption of different blocks are given in Table 17 and 18. Even when all features are enabled the total consumption will be about 1.5A. Hence there won't be any problem for evaluating HMC7043 part.

In any case a 2A LDO can be used for a new design. Please check our new, lowest output noise LDOs: ADP7158 or ADP719 for your design.

Regards,
Kazim

I am so sorry to ask you about the following questions again.

Q3: I reviewed the HMC7043 EVM board circuit schematics again and then found my misunderstanding as shown below.

The LT1963 output has DC-coupled with the LT1963 input through ferrite bead in the HMC7043 EVM board circuit schematics. Originally, I had understood that only VCC1_CLKDIST pin of the HMC7043, not "all of the power supply pins" would be connected to both of the LT1963 output and input. So, even if the LT1963 cannot supply enough electrical current to the HMC7043, the power supply source as "VCC_IN" for the HMC7043 EVM board will be able to supply enough current to the HMC7043. It is the latest of my understanding.

My customer has a question. Why did ADI/Hittite make the LT1963 output DC-couple with the LT1963 input as shown in the HMC7043 EVM board? Could you please advise my customer about your reply to the above question?.

Q4: I found "ADP7158" proposed by you in the ADI webpage but could not find "ADP719". Did you intend to propose "ADP7159", not "ADP719"? Let me clarify it.

Thanks and regards.

• Hello,

A3: There is not any DC-coupled connection from input to output in the default configuration. Those ferrite beads are labeled as "DEPOP", which means depopulate - do not place. The purpose of these extra ferrite beads to have the chance of bypassing LDO. Just remove FB6, FB7, FB8, FB9; install those parts to FB2, FB3, F4, FB5 and apply 3.3V to VCC_IN so that LDO will be bypassed. As I said, in default configuration, LDO is active, there is no extra connection and 5V is used to supply power to LDO (and no need for rework).

A4: Sorry, you are right, it should be ADP7159.

A5: PVT stands for Process, Voltage, Temperature. What I mean is max current includes all variations.

Regards,
Kazim

• This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

Thank you,