LP3936 Datasheet, PDF (6/20 Pages) National Semiconductor (TI) – Lighting Management System for Six White LEDs and One RGB or FLASH LED

Modes of Operation
RESET:
In the RESET mode all the internal registers are reset to the default values. Boost output register is set to
4.55V (register 0Dh = 07h), ext_pwm is enabled for color outputs (register 2Bh = 1Ch), EN_BOOST bit is
high (register 0Bh bit 5) and all other registers are set to 00h. Reset is entered always if input NRST is LOW
or internal Power On Reset is active.
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:
INTERNAL STARTUP SEQUENCE powers up all the needed internal blocks (V_REF, Bias, Oscillator, etc.).
To ensure the correct oscillator initialization, a 10 ms delay is generated by the internal state-machine.
Thermal shutdown (THSD) 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. In this mode the boost output is
raised in PFM 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
20081406
6