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How to exit LHM for ASL3417SHN Buck regulator? Facing issues even after following the suggested LHM exit steps to refresh the LHM timeout.

Question asked by Anupama TJ on Nov 17, 2018

We are calling BuckLHMExit() function before initializing the Buck regulator in the beginning and then calling the BuckLHMRefresh() for every timeout of 500 msec. Below is the code.

The duty cycle for Buck is given 100% to drive 100mA current. But the LED at the output of the Buck blinks for few times (4-5 times) and switches off. The Buck is supplied by 39v of input voltage. We are able to see the Buck voltage  at the output without connecting the LED as 4-5 pulses of 39V in CRO.

Below is the Buck configuration values:

config[0] = 0x0080;

config[1] = 0x000E;

config[2] = 0x0176;

config[3] = 0x0200;

config[4] = 0x0300;

config[5] = 0x0400;

config[6] = 0x0500;

config[7] = 0x0600;

config[8] = 0x0B00;

config[9] = 0x0C00;

config[10] = 0x0D00;

config[11] = 0x0F10;


Not sure if the Buck is able to exit from LHM mode continuously.

Please let us know how to get continuous current from Buck or how to glow the LED continuously.


void BuckLHMExit() //Three step deactivation procedure as per manual


uint8_t config[3];

uint8_t configResponse[3];

config[0] = 0x331E;

config[1] = 0x332E;

config[2] = 0x334E;




void BuckLHMRefresh() // Continuous LHM Timeout Refresh


uint8_t config[1];

uint8_t configResponse[1];

config[0] = 0x337E;





Thanks, your quick reply is most appreciated.