STA2064

System features introduction

Doc ID 16057 Rev 1

15/19

3.5

System wakeup and power down

Typically the system using STA2064 will never be powered off, even when the user switches

the device off using the main power switch. The main power switch works in a way that puts

the device either in Backup or in DEEP-SLEEP mode. In this state, the only blocks within

STA2064 that are powered are the RTC, PMU, PWL, SRC and the backup RAM; at system

The following wakeup methods are possible:

●

The user presses a button on the unit that causes all of the main power supplies to

start. After an appropriate delay, the processor's reset line is lifted and allows the code

to start executing

●

The internal alarm feature triggers a dedicated signal that will cause all of the main

supplies to start. After an appropriate delay, the processor's reset line is lifted and

allows the code to start execution

Considering the above mentioned wakeup system, while in DEEP-SLEEP and in BACKUP

state also, some dedicated IO lines must be powered:

●

POR (input)

●

POWEREN (output)

●

VDDOK and BATOK (input)

●

WAKE (input)

●

32 kHz crystal (SXTALI and SXTALO)

●

OSC32KOUT (output)

In order to keep the external DRAM in self refresh while in DEEP-SLEEP, CKE of the DRAM

must be kept low. Since all the IOs are not powered in DEEP-SLEEP, in order to make the

self refresh working, an external pulldown resistor is needed.

DEEP-SLEEP

on

off

off

1.2V to 1.3V

(typically 1.25V)

off

Refer section

3.5

BACKUP

on

off

off

1.2V to 1.3V

(typically 1.25V)

off

Refer section

3.5

Table 3.

Power mode states (continued)

Power State

32 kHz

PLL1

PLL2

IOs

OFF

off

off

off

off

off

off

NORMAL

on

on

on

1.2V to 1.3V

1.7 to 3.6V