SPSB081 datasheet(18/135 Pages) STMICROELECTRONICS

18 / 135 page

Figure 9. Cyclic monitoring: the external contacts are supplied periodically by the internal timer

In standby modes, the inputs are configurable with an internal pull-up or pull-down current source according to

the setup of the external contact. Moreover, in case of cyclic sensing, an internal pull-down resistor (RWU_act) is

periodically activated on each rising edge of the TIMER_ON. RWU_act is activated also for static wake-up, but in

this case it occurs just after WU request (see the figure above), keeping this condition for at least the filter time

tWU_stat (or more, if the WU is valid and the device enters in active mode).

In active mode, the inputs have in fact only the internal pull-down resistor and the input status can be read by SPI.

Static sense should be configured before the read operation is started to reflect the actual input level.

Being DIR/WU2_EN enable bit, in config register (0x3F), set to 0 by default, the DIR/WU2 pin is configured

as wake-up function. If DIR/WU2_EN enable bit is set to 1 the DIR/WU2 pin is a low voltage direct driving of

OUT1..4. Threshold is set in this case at 1.5 V.

3.5

Functional overview (truth table)

Table 8. Functional overview

Version

Function

Comments

Operating modes

Active mode

V1_standby static

mode (cyclic

sense)

VBAT_standby

static mode

(cyclic sense)

3.4.1

Voltage regulator

VOUT=5V/3V3

On (1)

Off

3.4.2

Voltage regulator

VOUT=5V/3V3

On/Off

On (2)/Off

On (2)/ Off

3.4.3

Reset generator

Off

3.4.4

Window watchdog

V1 monitor

Off (On if IV1 >

Icmp and ICMP =

Off

SPSB081

Functional overview (truth table)

DS14048 - Rev 1

page 18/135

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