L9300 datasheet(10/178 Pages) STMICROELECTRONICS

10 / 178 page

Power up and power down

7.1

Device configuration

The device can be configured to work in two different modes through a dedicated pin CONFIG.

As the protected battery is available and internal logic is out of reset (POR released), the device senses the

connection on the CONFIG pin: in case the pin is grounded the device is configured to work with reduced stby

current consumption (no CAN activity during stby) and with a subset of functions disabled in ON state. An external

1 kΩ resistor is highly recommended to implement the connection to limit the risk of parasitic effects in case of

ground shifts in the board. Once configured in reduced current consumption mode, the following features are kept

disabled:

•

CAN WAKE-UP

•

Q&A WATCHDOG

The status of CONFIG pin is latched at power-up and available as echo on bit15 (Asic Configuration) of

TRKFAULT SPI register; the latched configuration can be reset only by a switch-off of the device: in case CONFIG

pin connection is lost during the device activity the status of the device will not change until a new power-up

sequence. To avoid additional current consumption from protected battery line when the device is configured in

fully functional mode no internal pull-up/down structure is implemented on the pin itself; to latch properly the high

configuration on CONFIG pin, CONFIG has to be connected to a power supply available before the ASIC POR

release (example: battery line).

7.2

Power up

As the protected battery is available the device moves to a stand-by state (STBY): at that point a wake up signal

on the WAKE pin is required to turn on the device and to start the regulators power up sequence as in the figure

below.

The device first enables internal charge pump and VDD1 pre-regulator, the following regulator’s enable signals

are delayed until VDD1 reaches the VDD1_ST_en threshold to guarantee they have enough supply voltage to

perform slope control and minimize overshoot; this delay is applied independently of the chosen supply for

configurable regulators. Regulators enabling are delayed to distribute total in-rush current from supply lines: first

regulator enabled after VDD1 is VDD4, followed by VDD3 and finally from VDD2 and TRKn outputs. The latest

regulators wait for VDD3 and VDD4 to be out from under voltage conditions to ensure proper configuration latch

in case either VDD3 or VDD4 is used as tracking reference.

L9300

Power up and power down

DS12258 - Rev 5

page 10/178

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