str912fa STMicroelectronics, str912fa Datasheet - Page 18

• Manufacturer Part Number: str912fa
• Description: Arm966e-s? 16/32-bit Flash Mcu With Ethernet, Usb, Can, Ac Motor Control, 4 Timers, Adc, Rtc, Dma
• Manufacturer: STMicroelectronics

Functional overview
2.11.3 Sleep mode
2.12
2.12.1 Independent A/D converter supply and reference voltage
2.12.2 Battery supply
18/78
In this mode all clock circuits except the RTC are turned off and main oscillator input pins
X1_CPU and X2_CPU are disabled. The RTC clock is required for the CPU to exit Sleep Mode.
The entire chip is quiescent (except for RTC and wake-up circuitry). There are three means to
exit Sleep Mode and re-start the system:
●
●
●
Voltage supplies
The STR91xFA requires two separate operating voltage supplies. The CPU and memories
operate from a 1.65V to 2.0V on the VDD pins, and the I/O ring operates at 2.7V to 3.6V on the
VDDQ pins.
The ADC unit on 128-pin and 144-ball packages has an isolated analog voltage supply input at
pin AVDD to accept a very clean voltage source, independent of the digital voltage supplies.
Additionally, an isolated analog supply ground connection is provided on pin AVSS only on 128-
pin and 144-ball packages for further ADC supply isolation. On 80-pin packages, the analog
voltage supply is shared with the ADC reference voltage pin (as described next), and the
analog ground is shared with the digital ground at a single point in the STR91xFA device on pin
AVSS_VSSQ.
A separate external analog reference voltage input for the ADC unit is available on 128-pin and
144-ball packages at the AVREF pin for better accuracy on low voltage inputs. For 80-pin
packages, the ADC reference voltage is tied internally to the ADC unit supply voltage at pin
AVREF_AVDD, meaning the ADC reference voltage is fixed to the ADC unit supply voltage.
See
AVREF, and AVREF_AVDD.
An optional stand-by voltage from a battery or other source may be connected to pin VBATT to
retain the contents of SRAM in the event of a loss of the V
automatically switch its supply from the internal V
of V
The VBATT pin also supplies power to the RTC unit, allowing the RTC to function even when
the main digital supplies (V
possible to select whether or not to power from VBATT only the RTC unit, or power the RTC unit
and the SRAM when the STR91xFA device is powered off.
DD
Table 7: Operating
Some resets (external reset pin, low-voltage, power-up, JTAG debug command)
RTC alarm
Input from wake-up unit
drops below that of VBATT.
conditions, for restrictions to the relative voltage levels of VDDQ, AVDD,
DD
and V
DDQ
) are switched off. By configuring the RTC register, it is
DD
source to the VBATT pin when the voltage
DD
supply. The SRAM will
STR91xFA