|
|
PDF AN2633 Data sheet ( Hoja de datos )
| Número de pieza | AN2633 | |
| Descripción | STR91xFA low power management and power consumption Application note | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de AN2633 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
|
No Preview Available !
AN2633
Application note
STR91xFA low power management
and power consumption
Introduction
Power consumption is a significant issue for developers of embedded systems today.
Whether the target application is a cellphone, MP3 player, remote control, bio-medical
device or one of a whole new generation of electronic products, it is very likely that efficient
power management and low current consumption are on top of the list of design goals. In
terms of low power design techniques, more and more embedded designers use dynamic
control of clocks and frequencies. For this reason, this application note focuses on this in the
context of the STR91xFA microcontroller family.
This application note is intended for system designers who require a hardware
implementation overview of the STR91xFA low power modes. It includes details on the
power supply circuitry and components, clock systems, register settings and power
management. This guideline document is intended to show how to make the best use of the
extensive low power features of the STR91xFA microcontroller family,
Software source files can be downloaded with this application note for testing the STR91xFA
power modes.
January 2008
Rev 1
1/48
www.st.com
Free Datasheet http://www.Datasheet4U.com
1 page  
AN2633
Power supply and clocks
1.1.2
1.1.3
Note:
1.1.4
Note:
Independent A/D converter supply and reference voltage
The ADC has an isolated power supply which you can separately filter and shield from noise
in the PCB.
On 128-pin and 144-ball packages, the ADC unit has an independent analog voltage supply
input at pin AVDD (the ADC current consumption is detailed in Section 3.3: Measurements
and typical values on page 41) to accept a very clean voltage source. Additionally, an
independent supply ground connection is provided on pin AVSS. You can connect a separate
external reference voltage input for ADC on the AVREF pin for better accuracy on low
voltages inputs. The voltage on AVREF can range from 1.0 V to VDDQ.
On 80-pin/ball packages, the ADC voltage supply is tied internally to the ADC reference
voltage pin AVCC_AVREF and the analog ground is shared with the digital ground at a single
point, on pin AVSS_VSSQ.
Battery supply
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 main digital supplies (VDD and
VDDQ). The SRAM will automatically switch its supply from the internal VDD source to the
VBATT pin when the VDD and VDDQ voltage drops below the LVD threshold (and VBAT
remains above the threshold).
In order to use the battery supply, the LVD must be enabled.
The VBATT pin also supplies power to the RTC unit, allowing the RTC to function even when
the main digital supplies (VDD and VDDQ) are switched off. By programming the device
configuration via JTAG, you can select to power only the RTC (by configuring the RTC) or
both the SRAM (by enabling the PWR bit in the RTC_CR register) and the RTC from VBATT.
Low voltage detector (LVD)
Voltage dropout: The LVD circuit monitors VDD, and VDDQ supplies and generates a global
reset whenever either voltage drops below the configured VDD_LVD and VDDQ_LVD levels. If
the MCU was reset by the LVD, this is flagged in the System status register
(SCU_SYSSTATUS) and an interrupt request to the VIC is generated if enabled.
Voltage brownout: You can also program the LVD to generate an Early Warning interrupt
when either voltage drops below the VDD_BRN and VDDQ_BRN thresholds. The Early Warning
event signal is connected to the VIC1.7 interrupt channel. Software can manage the Early
Warning interrupt using the VIC1.7 channel bits in the VIC registers.
When the LVD is turned off, the VBAT feature is not supported.
The LVD logic consists of a lower power voltage band gap that provide an accurate voltage
reference. This voltage reference is used to create the voltage threshold levels that are
compared with the supply voltages.
When either voltage supply falls below the threshold for that supply, the LVD generates a
global reset.
1.2 Power down mode
In STR91xFA low power modes, the Flash automatically reduces its power consumption and
can be read immediately after wake-up.
5/48
Free Datasheet http://www.Datasheet4U.com
5 Page 
AN2633
Power supply and clocks
1.3.8
1.3.9
1.3.10
1.3.11
1.3.12
1.3.13
Baud rate clock (BRCLK)
The baud rate clock is an internal clock derived from fMSTR that is used by the three on-chip
UART peripherals for baudrate generation. You can optionally divide the frequency by 2 by
setting the BR_SEL bit in the Clock control register (SCU_CLKCNTR). BRCLK can be gated
through the Peripheral Clock Gating Registers (see Section 1.3.13).
External memory interface (BCLK)
You can select the frequency of the EMI bus clock (BCLK) to be HCLK or HCLK/2 using the
EMIRATIO bit in the Clock control register (SCU_CLKCNTR). By default the frequency is
HCLK/2. The BCLK clock is available on the LFBGA package as an output pin. You can
disable the BCLK output by setting the BCLK_EN bit in the EMI register (SCU_GPIOEMI).
USB clock (USBCLK)
The USB clock can be derived from fMSTR when the frequency is 48 MHz or 96 MHz. If you
use another fMSTR frequency, the 48 MHz USBCLK must be sourced from the external pin
(GPIO pin). You select this using the USB_SEL [1:0] bits in the Clock control register
(SCU_CLKCNTR). USBCLK can be gated through the Peripheral Clock Gating Registers
(see Section 1.3.13).
Ethernet MAC clock
Special consideration regarding the Ethernet MAC: The external Ethernet PHY interface
device requires it’s own 25 MHz clock source. This clock can come from one of two sources:
● A 25 MHz clock signal coming from a dedicated output pin (P5.2) of the STR91xFA. In
this case, the STR91xFA must use a 25 MHz signal on its main oscillator input in order
to pass this 25 MHz clock back out to the PHY device through pin P5.2. The advantage
here is that an inexpensive 25 MHz crystal may be used to source a clock to both the
STR91xFA and the external PHY device.
● An external 25 MHz oscillator connected directly to the external PHY interface device.
In this case, the fOSC input clock doesn't have to be a 25 MHz crystal (from 4 MHz to
25 MHz).
You enable the output clock using the MAC_SEL bit in the Clock control register
(SCU_CLKCNTR).
External RTC calibration clock
The RTC_CLK can be enabled as an output on the JRTCK pin by setting the Calibration
Clock Output Enable bit in the RTC_CR register. The RTC_CLK is used for RTC oscillator
calibration. The RTC_CLK is active in Sleep mode and can be used as a system wake-up
control clock.
Peripheral clock gating
After reset, only the CPU, the Flash memory, the SRAM and a small subset of Peripheral
clock gating register 0 (SCU_PCGR0) and Peripheral clock gating register 1 (SCU_PCGR1)
registers) of the peripherals start operating. The other parts of the system remain stopped.
because the related PCGR bits are reset. To start them, you have to write 1 to the related
register bit. You can stop the peripheral again, by writing 0 to the related bit.
11/48
Free Datasheet http://www.Datasheet4U.com
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AN2633.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| AN2633 | LIN Drivers Application Note |  Motorola Semiconductors |
| AN2633 | STR91xFA low power management and power consumption Application note | STMicroelectronics |
| AN2635 | On-Chip FLASH Programming Routines |  Freescale Semiconductor |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |