MCIMX281AVM4B Freescale Semiconductor, MCIMX281AVM4B Datasheet - Page 909

• Manufacturer Part Number: MCIMX281AVM4B
• Description: IC MPU I.MX28 1.2 289MAPBGA
• Manufacturer: Freescale Semiconductor
• Series: i.MX28r

Specifications of MCIMX281AVM4B

• 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: Supplier Unconfirmed

Chapter 11 Power Supply
The battery charger is capable of generating a large amount of heat within the i.MX28,
especially at currents above 400 mA. The dissipated power can be estimated as: (5V –
battery_volt) * current. At max current (785 mA) and a 3-V battery, the charger can dissipate
1.57 W, raising the die temp as much as 80 C°. To ensure that the system operates correctly,
the die temperature sensor should be monitored every 100 ms. If the die temperature exceeds
115 C° (the max value for the chip temp sensor), then the battery charge current must be
reduced. The LRADC can also be used to monitor the battery temperature or chip
temperature. There is an integrated current source for the external temperature sensor that
can be configured and enabled through HW_LRADC_CTRL2 register.
11.7 11.5.1 Battery Detection
The battery is detected by checking the battery brownout status or measuring the battery
pin voltage. If either indicates the battery voltage is below an application-defined low-voltage
threshold, the battery is not attached. When the battery voltage is measured in the expected
operational range, the FASTSETTLING bitfield in the HW_POWER_REFCTRL register
should be set to enable an internal load on the battery. If no battery is connected, the internal
load will discharge the capacitor on the battery pin to bring the voltage below the
application-defined low-voltage threshold. If a battery is connected, the voltage should
remain in the expected operational range. After battery detection is complete, the
FASTSETTLING bitfield should be cleared to disable the internal load.
The internal load is automatically disabled when a battery brownout is detected. In this
case, the FASTSETTLING bitfield must be cycled to re-enabled the load. This is important
for situations where the load is enabled at a battery voltage just above the battery brownout
threshold and then the battery voltage drops below the threshold causing the brownout status
to change. Software must account for this situation by re-enabling the load when the battery
voltage is below the brownout threshold. The length of time for the battery capacitor to
discharge is variable between designs and is dependent on the amount of capacitance on
the board.
11.8 Silicon Speed Sensor
The i.MX28 integrates three silicon speed sensors to measure the performance characteristics
of an individual die at its ambient temperature and process parametrics. One is inside ARM9
to measure ARM9 performance, one is in core logic which including system bus and
peripherals to measure core logic performance and another one is inside DC-DC block. A
silicon speed sensor consists of a ring oscillator and a frequency counter. The ring oscillator
runs on the VDDD power rail. Therefore, its frequency tracks the silicon performance as it
changes in response to changes in operating voltage and temperature. The crystal oscillator
i.MX28 Applications Processor Reference Manual, Rev. 1, 2010
Freescale Semiconductor, Inc.
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