LP55231 datasheet(14/53 Pages) TI

14 / 53 page

STANDBY

RESET

INTERNAL

STARTUP

SEQUENCE

Reset Register = FF

POR=H

TSD = H

NORMAL MODE

EN=H (pin) and

CHIP_EN=H (bit)

EN=L (pin) or

CHIP_EN=L (bit)

POR

TSD = L

POWER SAVE

Enter power save

Exit power save

LP55231

SNOSCR5 – MARCH 2013

www.ti.com

Modes of Operation

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

Reset Register (3DH) is written FFH or internal Power-On Reset is active. Power-On Reset (POR) will

activate during the chip startup or when the supply voltage VDD fall below 1.5V (typ.). Once VDD rises

above 1.5V (typ.), POR will deactivate, and the chip will continue to the STANDBY mode. CHIP_EN

control bit is low after POR by default.

STANDBY: The STANDBY mode is entered if the register bit CHIP_EN or EN pin is LOW and Reset is not

active. This is the low-power consumption mode, when all circuit functions are disabled. Most registers

can be written in this mode if EN pin is risen to high so that control bits will be effective right after the

startup (see Control Register Details).

STARTUP: When CHIP_EN bit is written high and EN pin is high, the INTERNAL STARTUP SEQUENCE

powers up all the needed internal blocks (VREF, Bias, Oscillator etc.). Startup delay is 500

μs. If the chip

temperature rises too high, the Thermal Shutdown (TSD) disables the chip operation, and the chip waits in

STARTUP mode until no thermal shutdown event is present.

NORMAL: During NORMAL mode the user controls the chip using the Control Registers.

POWER SAVE: In POWER-SAVE mode analog blocks are disabled to minimize power consumption. See

chapter Automatic Power Save Mode for further information.

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