MCIMX286CVM4B Freescale Semiconductor, MCIMX286CVM4B Datasheet - Page 902

• Manufacturer Part Number: MCIMX286CVM4B
• Description: IC MPU I.MX286 289MAPBGA
• Manufacturer: Freescale Semiconductor
• Series: i.MX28r

Specifications of MCIMX286CVM4B

• Core Processor: ARM9
• Core Size: 32-Bit
• Speed: 454MHz
• Connectivity: CAN, EBI/EMI, Ethernet, I²C, MMC, SmartCard, SPI, SSI, UART/USART, USB OTG
• Peripherals: DMA, I²S, LCD, POR, PWM, WDT
• Program Memory Size: 128KB (32K x 32)
• Program Memory Type: Mask ROM
• Ram Size: 32K x 32
• Voltage - Supply (vcc/vdd): 1.25 V ~ 5.25 V
• Data Converters: A/D 17x12b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 289-LFBGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Number Of I /o: -
• Eeprom Size: -
• Lead Free Status / Rohs Status: Compliant

Linear Regulators
11.3.2 5V to Battery Power Interaction
The i.MX28 supports several different options related to the interaction of the switching
converters with the linear regulators. The two primary options are a reset on 5V
insertion/removal or a handoff to the DC-DC converters that is invisible to the end-user of
the application.
Figure 11-3
includes these two options as the two system architecture
decision boxes.
11.3.2.1 Battery Power to 5-V Power
By default, the DC-DC converter turns off when VDD5V becomes valid and the system
does not reset. If the system is operating from the DC-DC converter and is using more
current than the linear regulators can supply, then the VDDD, VDDA, and VDDIO rails
will droop when 5V is attached and the system may brownout and shut down. To avoid this
issue, set the ENABLE_DCDC bit and set the LINREG_OFFSET fields to 0b2 in anticipation
of VDD5V becoming present. The ENABLE_DCDC bit will cause the DC-DC converter
to remain on even after 5V is connected and, thus, guarantee a stable supply voltage until
the system is configured for removal of 5V. The LINREG_OFFSET fields = 0b2 cause the
linear regulators to regulate to a lower target voltage than the switching converter and
prevent unwanted interaction between the two power supplies. After the system is configured
for removal of 5V, ENABLE_DCDC can be set low and ENABLE_ILIMIT set low in
register HW_POWER_5VCTRL to allow the linear regulators to supply the system power,
if desired.
11.3.2.2 5-V Power to Battery Power
Configuring the system for a 5-V-to-battery power handoff requires setup code to monitor
the battery voltage as well as detect the removal of 5V.
Monitoring the battery voltage is performed by LRADC. Typically, this involves
programming the LRADC registers to periodically monitor the battery voltage as described
in
LRADC
Overview. The measured battery voltage should be written into the
HW_POWER_BATTMONITOR register field BATT_VAL using the AUTOMATIC field
in the HW_LRADC_CONVERSION register. Also, configuring battery brownout should
be performed so that the system behaves as desired when 5V is no longer present and the
battery is low.
The recommended method to detect removal of 5V requires setting
VBUSVALID_5VDETECT and programming the detection threshold VBUSVALID_TRSH
to 0x1 in HW_POWER_5VCTRL. Next, in order to minimize linear regulator and DC-DC
converter interaction, it is necessary to set the LINREG_OFFSET = 0b2 in the
i.MX28 Applications Processor Reference Manual, Rev. 1, 2010
902
Freescale Semiconductor, Inc.