LM5156-Q1: LM5156QDSSRQ1 queries

Siburaj D S

Part Number: LM5156-Q1
Other Parts Discussed in Thread: LM5155-Q1, LM5158, LM5157, LM3481, LM5155, LM5156

Hi Team,

For the part number LM5156QDSSRQ1 below things are missing in the datasheet. Please reply to below queries ASAP.

1. Overload and short circuit circuit current limit value. Is it possible to configure the values of overload and short circuit current limit ?

2. Is it possible to run this regulator in BOOST mode without using external MOSFETs ?

3. Inside the datasheet its mentioned like regulator is having internal softstart ? Can you share the value of softstart time ?

4. Whether this part will support continuous/discontinuous mode of operation. If possible Application circuit for the same.

5. Is it possible to share the emission report for this component to check about the EMC aspects ?

6. Advantage/disadvantages of LM5156-Q1 compared with LM5155-Q1. While checking the datasheet I observed the below things. Please add if anything missing below

Advantages of LM5156-Q1 - Spread spectrum support, Higher Input voltage range.

Disadvantages of LM5156-Q1 - Non-availability of short circuit protection

Regards,

Siburaj D.S.

over 1 year ago

0 Stefan Schauer over 1 year ago

TI__Mastermind 42161 points

Hi Siburaj,

thank you for using the E2E forum.

See my answers/comments mapped to your questions:

1. overcurrent is detected once the voltage at the sense resistor reaches the value of V_sense
see: Current Sense and Slope Compensation (CS Pin)

2.No, this device requires an external MOSFET - but you can use the LM5157 or LM5158 - this have the power MOSFET integrated

3. see datasheet: Soft Start (SS Pin)

4. Please have a look at this report, it explains in details the difference of CCM and DCM and how to dimension the system for that:
Under the Hood of a DC/DC Boost Converter (ti.com)

5. EMC heavily depends on the layout and components around that. So EMC reports for a component/device does not give any valuable information.

6. see: Achieve Low EMI with Dual Random Spread Spectrum | TI.com Video

Best regards,

Stefan

0 Stefan Schauer over 1 year ago in reply to Stefan Schauer

TI__Mastermind 42161 points

Hi Siburaj,

I have not seen an update on this thread for the last 8 days.

If the issue is solved it would be great to press the is solved button.

If there is still something open, just let me know with the new details.

Best regards,

Stefan

0 Siburaj D S over 1 year ago in reply to Stefan Schauer

Prodigy 75 points

For Part LM3481 ripple current value is Delta iL= DVIN / 2LfS. For the LM5155 and LM5156 Delta iL= DVIN / LfS. So the ripple in LM5155/Lm5156 will be double compared to LM3481 right ? Is my understanding correct ?

0 Stefan Schauer over 1 year ago in reply to Siburaj D S

TI__Mastermind 42161 points

Hi Siburaj,

no, for both the ripple is equal, just the

LM3481 uses delta iL as average to peak

LM515x uses delta iL a peak to peak.

(This also described in the text discussing the formula. So you should find this when searching for this information if you would like to check.)

Best regards,

Stefan

0 Siburaj D S over 1 year ago in reply to Stefan Schauer

Prodigy 75 points

In webench simulation ripple voltage observed as 62.58 mV for the LM3481 and 189.62 mV for LM515x. For LM515x series observed ripple around 3 times when compared with 62.58 mV. Is it correct ?

0 Stefan Schauer over 1 year ago in reply to Siburaj D S

TI__Mastermind 42161 points

Hi Siburaj,

when you compare this do you have all settings equal for the both devices you compare, esp. to check:

- switching frequency

- inductor

- input and output cap

- input voltage range

- output voltage and load

Best regards,

Stefan

0 Brigitte over 1 year ago in reply to Stefan Schauer

TI__Guru 58215 points

Hello Siburaj,

As we did not hear back from you, I expect the answer was sufficient or you have been able to solve your issue yourself. If my assumption is wrong, please post below or create a new thread if this one is already locked.

Best regards,
Brigitte

Power management

Power management forum

LM5156-Q1: LM5156QDSSRQ1 queries