System features introduction STA2065
16/20 Doc ID 16050 Rev 5
3.5 System wakeup and power down
Typically the system using STA2065 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 in DEEP-SLEEP mode. In this state, the only blocks within STA2065 that are
powered are the RTC, PMU, PWL, SRC and the backup RAM; at system level, only the
V
DD_ON
is powered.
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, some dedicated
IO lines must be powered:
● POR (input)
● POWEREN (output)
● VDDOK and BATOK (input)
● WAKE (input)
● 32KHz xtal (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.
SLEEP on off
off (SW can take
it on)
= V
DD
1.2V to 1.3V
(1.25V typ)
1.7 to 3.6V
DEEP-SLEEP on off off
1.2 to 1.3V
(1.25V typ)
off Refer section 3.5
Table 3. Power mode states (continued)
Power State 32kHz PLL1 PLL2 V
DD_ON
V
DD
IOs
