LP3942YQ NSC [National Semiconductor], LP3942YQ Datasheet - Page 8

• Manufacturer Part Number: LP3942YQ
• Description: The Dual RGB LED Controller with 1.5x/2x Charge Pump and SPI Interface
• Manufacturer: NSC [National Semiconductor]

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Start-Up Sequence of LP3942
The LP3942 start-up sequence can be triggered in the following way: V
(or floating) and NSTBY is set to ‘1’ via SPI.
The LP3942 activates first internal oscillator and waits for appr. 0.8 ms. Then, if CP_ON bit is set to ‘1’, LP3942 enables internal
soft-start circuitry to start-up the charge pump smoothly. Soft-start sequence takes appr. 200 µs. After this start-up sequence,
P
Modes of Operation
RESET:
STANDBY:
STARTUP:
NORMAL/CP OFF During NORMAL MODE WITH CHARGE PUMP OFF all LED controls can be used but the charge pump is
NORMAL/CP ON
Internal Start-Up Sequence
OUT
is settled to correct value and RGB outputs can be enabled via SPI.
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 is active.
The STANDBY mode is entered if the register bit NSTBY is HIGH 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 power up.
INTERNAL STARTUP SEQUENCE powers up all the needed internal blocks. To ensure the correct oscillator
initialization, a 0.8 ms delay is generated by the internal state-machine. Thermal shutdown (T
chip operation and Startup mode is entered. Normal mode is entered after the device has cooled down.
not active.
In NORMAL MODE WITH CHARGE PUMP ON all the chip functions are active.
8
DD
power is connected to the device and NRST pin is ‘0’
20129207
SHD
) stops the