Modes of Operation

20202406

RESET:

In the reset mode all the internal registers are reset to the default values. Reset is entered always if input

NRST is LOW or internal Power On Reset (POR) is active. Power on reset will activate during the chip

startup or when the supply voltage V

and the chip will continue to the STANDBY mode. NSTBY control bit is low after POR by default.

STANDBY:

The standby mode is entered if the register bit NSTBY is LOW and reset is not active. This is the low power

consumption mode, when all circuit functions are disabled. Registers can be written in this mode and the

control bits are effective immediately after start up.

STARTUP:

When NSTBY bit is written high, the internal startup sequence powers up all the needed internal blocks

(V

internal state-machine. If the chip temperature rises too high, the thermal shutdown (TSD) disables the chip

operation and startup mode is entered until no thermal shutdown event is present.

BOOST STARTUP: Soft-start for boost output is generated in the boost startup mode. The boost output is raised in a low current

PWM mode during the 10 ms delay generated by the state-machine. The boost startup is entered from

internal startup sequence if EN_BOOST is HIGH or from normal mode when EN_BOOST is written HIGH.

NORMAL:

During normal mode the user controls the chip using the Control Registers. The registers can be written in

any sequence and any number of bits can be altered in a register in one write.

www.national.com

6