ADP2323ACPZ ripples at output

Hi , 

Sorry for earlier mistake , we are generating 3.3V & 1.8V from 5V. Please comment on sch. Ripples are observed only on 1.8V & not on 3.3V . 

looking forward for your reply 

Gaurav 

The schematic looks fine. Looking at the waveform, the 1.8V channel seems to work under PFM mode. Would you also measure the SW waveform together with 1.8Vout waveform?

If adding some load on the 1.8V channel, such as 1A, does the output ripple become smaller?

Hi , 

In our case PICOZED 7015 is the load , we are giving 1.8V & 5V to its input. we have tired changing the input voltage for 5V to 6.7V . I am attaching waveform below please have look , i have checked on SW pin of 1.8V channel. 

We have previously used ADP2323 in one of our project where the input voltage to IC was 12V & system was running fine. however in our existing project we are using 5V input to ADP2323 we are facing ripple issue. 

Looking forward for ur reply. 

Gaurav 

Looking at the SW waveform of 1.8V rail, it seems to work under PFM. Can we double check the MODE pin voltage level to make sure it is HIGH?

How about increasing the load of 1.8V (using e-load to add 1A)? Is the 1.8V rail still under PFM or enters into PWM?

Thanks!

Is this the SW waveform of 1.8Vout rail with heavy load?

Hi issue is resolve .

Thanks for the support 

Hi Ryang , 

Just to be double sure , in the above schematic can i replace ADP2323 with ADP2325 without changing the peripheral components  ? 

Gaurav 

Yes, you can.

Dear Ryang , 

We are using ADP2323, the schematic remains the same as mentioned previously , However there are two capacitors connected at three connectors viz JX1,JX2 & JX3 on which PicoZed board will be connected  , please refer the image attached . when we remove C112,C117 & C120  the regulator generates proper voltage & no noise/ripples been observed. However when we solder those capacitor we find ripples at output . we initially thought if we go with ADP2325 it will resolve our issue. However similar pattern is observed with ADP2325 . Can you please guide me ? 

 Gaurav 

Dear Ryang , 

We are using ADP2323, the schematic remains the same as mentioned previously , However there are two capacitors connected at three connectors viz JX1,JX2 & JX3 on which PicoZed board will be connected  , please refer the image attached . when we remove C112,C117 & C120  the regulator generates proper voltage & no noise/ripples been observed. However when we solder those capacitor we find ripples at output . we initially thought if we go with ADP2325 it will resolve our issue. However similar pattern is observed with ADP2325 . Can you please guide me ? 

 Gaurav 

C112, C117 and C120 perform the large load for the output of the ADP2323. During soft start, it requires large input current to charge those capacitors to Vout within the soft start time. If the soft start time is too short, the charging current may trigger high-side OCP, which results in failure of the start up.

What does the input 5V come from? power supply? another regulator? Does this 5V have enough load capability?

If we increase soft start time of both power rails of the ADP2323, does this issue go away?

Thanks!

HPDFI we have 12 VDC input supply from that we generate 5VDC using ADP2384ACPZN-R7 . This 5VDC is then given to ADP2323. Let me increase the soft start time & check. 

Please find the Schematic(power section )   

Hi , by increasing soft start the issue resolved thanks