MCIMX286CVM4B Freescale Semiconductor, MCIMX286CVM4B Datasheet - Page 2264

• 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

Operation
are taken first with the HW_LRADC_CTRL2_TEMP_ISRC current source set at 300
μA, then another voltage measurement with the current source set at 20 μA. The temperature
will be roughly:
or, from the LRADC conversion (LSB=0.45mV):
Freescale recommends taking 5–10 samples for the min and max and then averaging them
to get a good reading.
The temperature reading error will likely be dominated by part-to-part matching of the
diodes. Some manufacturers' diodes show substantially less variation than others. Freescale
has shown three-sigma accuracy of +/-7.5C using Fairchild MMBD914 (from multiple
batches of diodes).
If better accuracy is required, Freescale recommends using a thermistor for external
temperature sensing. The thermistor will be more accurate, but over a smaller temperature
range than the diode method.
Any routing impedance to the diode will cause a shift in the temperature reading. This can
be measured and corrected in software for each design.
Two ohms of routing impedance would cause (2 * (300μA – 20μA) error of 0.56 mV or
1.25 degrees C error.
38.2.2 Internal Die Temperature Sensing
The i.MX28 has a new internal die temperature sensor that uses two of the sixteen physical
LRADC channels. To use the internal die temperature sensor,
HW_LRADC_CTRL2_TEMPSENSE_PWD should be cleared. (This bit can be left cleared
after power up. There is no need to toggle it on and off.) Two of the eight virtual LRADC
channels need to be mapped to the temperature sensing channels 8 and 9 using
HW_LRADC_CTRL4. Then, these virtual LRADC channels should BOTH be converted
using the LRADC conversion scheduler described below. The temperature in degrees Kelvin
will be equal to:
2264
degrees Kelvin = (Vmax – Vmin) / 0.409 mV
degrees Kelvin = (Codemax – Codemin) * 1.104
(Channel9 – Channel8) * Gain_correction/4
i.MX28 Applications Processor Reference Manual, Rev. 1, 2010
Freescale Semiconductor, Inc.