Data Sheet

LT8641A

analog.com

Rev 0

18 of 35

several hundred μA. The SYNC/MODE pin may be tied high for pulse-skipping mode with spread spectrum

modulation.

To improve EMI, the LT8641A can operate in spread spectrum mode. This feature varies the clock with a triangular

frequency modulation of approximately +20%. For example, if the LT8641A’s frequency is programmed to switch at

2MHz, spread spectrum mode modulates the oscillator between 2MHz and 2.4MHz.

To improve efficiency across all loads, source the supply current to internal circuitry from the BIAS pin when biased

at 3.1V or above. Else, the internal circuitry draws current from VIN. Connect the BIAS pin to VOUT if the LT8641A output

is programmed at 3.3V to 25V.

Comparators monitoring the FB pin voltage pull the PG pin low if the output voltage varies more than ±8% (typical)

from the set point, or if a fault condition is present.

The oscillator reduces the LT8641A’s operating frequency when the voltage at the FB pin is low. This frequency

foldback helps to control the inductor current when the output voltage is lower than the programmed value that

occurs during start-up or overcurrent conditions. When a clock is applied to the SYNC/MODE pin, the SYNC/MODE pin

is floated, or held DC high, the frequency foldback is disabled, and the switching frequency slows down only during

overcurrent conditions.