LM5171-Q1: Boost mode output current regulation

Hi Yuto,

1. The output current monitor is achieved by monitoring the high side FET current. High side FET current is (1-D)* I_Lm. A chopper is used to convert inductor current signal to high side FET. You may refer to the diagram below.

2. LM5171 cannot regulate the output current directly. It can only monitor the output current. You need to add an external loop to regulate the output current.

3.This is a known issue. The address is 0x20, ...

Best Regards,

Feng

Hi Feng,

Thanks for your comments!

1.I understood that LM5171-Q1 can only monitor output current when boost and cannot regulate the load current directly. 

2. You mentioned we need external loop. Can you share the recommended way to do that? Do we have apps note or something? 
2-2. If we use external MCU to monitor output current and adjust ISETx to control output current, do we have required loop delay about the insight of stability?
2-3. And can we know the output current settling time of 

2-4. Do we have similar device to LM5171 which can directly regulate in both buck and boost operation?

3. Understood that D/S p10 is correct information - Am I understanding right?
 -> Additional query, the customer tried communicate with EVM. They use 2 boards and a board is operate as SYNC host and other operates as SYNC slave for multi phase operation. In this case, master can communicate via I2C only with using 0x00~0x07 address, but slave device can with 0x20~0x27. Does it what you expect? Is it decided by SYNCO/I? Please check it and make sure that.

Best regards,
Yuto

Hi Yuto,

2. You may refer to TIDA-01040 where an external current loop is used.

2-2. You also need to check the stablity of the loop when using MCU

2-3. ?

2-4. What is "directly regulate in both buck and boost operation"?

3. We were using 0x00~0x07 before RTM. So, for old EVMs, you may have 0x00~0x07. But you will only have 0x20~0x27 in the future.

Best Regards,
Feng

Hi Feng,

2. Clear

2-2. Do you have like indicator to estimate the stability or the target we have to meet?

2-3. Sorry, let me retype here. Can we know the output current settling time when we change ISET?

2-4. Directly regulate meant, either buck and boost operation, measure the "output current" and regulate it without external circuit. LM5171/70 only "measure" and regulate output current in buck mode, and input current is regulated in boost mode.

2-5. If analog switch can be used to switch the current to measure. Can we use integrated CS amp and external MUX to measure output current in both mode? Please look at my image below and tell me if it is acceptable.

3. Clear.

Thank you.
Yuto Kitamura