33905 datasheet(39/104 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33903/4/5

FUNCTIONAL DEVICE OPERATION

LP MODES

Debug can be left by removing 8 to 10 V from the DEBUG

pin, or by the SPI command (Ref. to MODE register).

The 5 V-CAN regulator is ON by default in Debug Mode.

LP MODES

The device has two main LP modes: LP Mode with VDD

OFF, and LP Mode with VDD ON.

Prior to entering into LP Mode, I/O and CAN Wake-Up

flags must be cleared (Ref. to mode register). If the Wake-Up

flags are not cleared, the device will not enter into LP Mode.

In addition, the CAN failure flags (i.e. CAN_F and CAN_UF)

must be cleared, in order to meet the LP current consumption

specification.

LP - VDD OFF

In this mode, VDD is turned OFF and the MCU connected

to VDD is unsupplied. This mode is entered using SPI. It can

also be entered by an automatic transition due to fail safe

management. 5 V-CAN and VAUX regulators are also turned

OFF.

When the device is in LP VDD OFF Mode, it monitors

external events to Wake-Up and leave the LP Mode. The

Wake-Up events can occur from:

•CAN

• LIN interface, depending upon device part number

• Expiration of an internal timer

• I/O-0, and I/O-1 inputs, and depending upon device part

number and configuration, I/O-2 and/or -3 input

• Cyclic sense of I/O-1 input, associated by I/O-0

activation, and depending upon device part number and

configuration, cyclic sense of I/O-2 and -3 input,

associated by I/O-0 activation

When a Wake-Up event is detected, the device enters into

Reset Mode and then into Normal Request Mode. The Wake-

Up sources are reported to the device SPI registers. In

summary, a Wake-Up event from LP VDD OFF leads to the

VDD regulator turned ON, and the MCU operation restart.

LP - VDD ON

In this mode, the voltage at the VDD pin remains at 5.0 V

(or 3.3 V, depending upon device part number). The

objective is to maintain the MCU powered, with reduced

consumption. In such mode, the DC output current is

expected to be limited to 100

μA or a few mA, as the ECU is

in reduced power operation mode.

During this mode, the 5 V-CAN and VAUX regulators are

OFF. The optional external PNP at VDD will also be

automatically disabled when entering this mode.

The same Wake-Up events as in LP VDD OFF Mode (CAN,

LIN, I/O, timer, cyclic sense) are available in LP VDD on

Mode.

In addition, two additional Wake-Up conditions are

available.

• Dedicated SPI command. When device is in LP VDD ON

Mode, the Wake-Up by SPI command uses a write to

“Normal Request Mode”, 0x5C10.

• Output current from VDD exceeding LP-ITH threshold.

In LP VDD ON Mode, the device is able to source several

tenths of mA DC. The current source capability can be time

limited, by a selectable internal timer. Timer duration is up to

32 ms, and is triggered when the output current exceed the

output current threshold typically 1.5 mA.

This allows for instance, a periodic activation of the MCU,

while the device remains in LP VDD on Mode. If the duration

exceed the selected time (ex 32 ms), the device will detect a

Wake-Up.

Wake-up events are reported to the MCU via a low level

pulse at INT pulse. The MCU will detect the INT pulse and

resume operation.

Watchdog Function in LP VDD ON Mode

It is possible to enable the watchdog function in LP VDD

ON Mode. In this case, the principle is timeout.

Refresh of the watchdog is done either by:

• a dedicated SPI command (different from any other SPI

command or simple CS activation which would Wake-

Up - Ref. to the previous paragraph)

• or by a temporary (less than 32 ms max) VDD over

current Wake-Up (IDD > 1.5 mA typically).

As long as the watchdog refresh occurs, the device

remains in LP VDD on Mode.

Mode Transitions

Mode transitions are either done automatically (i.e. after a

timeout expired or voltage conditions), or via a SPI command,

or by an external event such as a Wake-Up. Some mode

changes are performed using the Secured SPI commands.

33905 Datasheet(PDF) 39 Page - Freescale Semiconductor, Inc

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