data/text/DLP2/893179

LM5146-Q1: How to add over current protection for a particular current

Part Number: LM5146-Q1 Hi TI, i am using a Buck converter using LM546-Q1 .I have design for 8 amp out, for 13.5V Input 30-60V input . i am using RDSon for current limit sense . But in the datasheet it is not clear how ILIM pin save the circut for overcurrent protection please explain. . The issue i am facing with surge current.it is working fine while i am incresing the current from 0-1-2-3---8 up to 8 amp but while i am suddenly add load the circut went to hiccup mode as like short circuit. Please let me know how to resolve the issue, Is the anyway i can limit the current for 10 amp max? if i will use ILIM pin for 10amp limit the current, curcuit not able to take surge current. Please provide some suggestion .

Hi Dinesh, Unfortunately, I was not able to see the component values for the schematic that you have. You can check the component selection values with the calculator located at the bottom of this page <secret URL>/product/LM5146-Q1/toolssoftware Also the layout will play an important role in order to sense the current limit correctly. You can follow the layout guidelines here <secret URL>/lit/ds/symlink/lm5146-q1.pdf#page=48 Thanks -Arief

Hi Arif, Please explain How ILIM pin works? also please let me know how to switch off the converter if someone tries to take more current ? for example i have design the converter for 8 amp if somone tries to take 10 amp i wants to switch off at that moment so please let me know your suggestion. do i need to add another opamp or use another technique. Thanks Dinesh

Hello Arif, i am waiting for reply please explain . Best Regards, Dinesh Gread

Hi, I think the explanation of the current limit is located here <secret URL>/lit/ds/symlink/lm5146-q1.pdf#page=23 I dont think the device will shutdown if the current limit is achieved. If you want the part to shutdown then you have to use maybe an external current sense amplifier and set it such that it will disable the part when the desired current is reached. Thanks -Arief

Hi Dinesh, The LM5146-Q1 will enter hiccup mode if the current limit condition persists. Once the current limit is removed, normal operation resumes. Regards, Tim

Hi Arif, will you please suggest any circuit which i can use for current limit. Best Regards, DInesh Gread

Hi Dinesh, The inrush current is it due to charging to the output capacitor? If that is true then you can use a larger SS capacitor and slow down the rise time of the output such that the inrush current will not be too big and trigger the current limit Thanks -Arief

Hi Arif, i have made this circuit for 8 amp out. i want this circuit to limit the current at 9-10amp more than that it shoud not provide. the short circuit condition is fine it enter in hiccup mode but i want that if i design this circuit for 8 amp it should not provide more that that . can you please suggest any circuit by use of that i can limit the current . Also please let me know how to reduse the no load current currently the circut works on 400Khz and take 40ma and it is just waste can you please let me know how to minimize it. i dont have control on EN pin i.e this circuit will not off any time but load can be off so that i wants to reduse the no load current also. please suggest

Hicompany Team, i am waiting for your inputs . Best Regards, Dinesh Gread

HI Dinesh, You can use diode emulation mode (with SYNCIN tied low) to reduce the no-load input current. In terms of overcurrent protection (OCP). the setpoint is typically defined using the ILIM resistor at 130-150% of nominal full load current. This is because the inductor current overshoots during load transients and may inadvertently trip OCP. Please fill out the LM5146-Q1 quickstart file and send to us for review. Also, the schematic values above are unreadable, so please forward a higher res version if possible PS: Your design seems similar to the LM5146-Q1 EVM with 12V/8A output. Regards, Tim