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Datasheet of MCIMX53SMD - TABLET SABRE PLATFORM MCIMX53
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Freescale Semiconductor
MCIMX53SMD Board Hardware User’s Guide, Rev. 0
33
Table 5-2.
MCIMX53SMD Board Power Supply Rails
5.2.2.
Backlight LED Driver
The Dialog PMIC provides a Boost circuit that controls an external MOSFET Q8. The PMIC is capable of driving
three independent strings of up to five white LEDs, each with approximately 24V and maximum of 50 mA. The
MCIMX53SMD board does not have a direct connection for white backlight LEDs; however, it supplies a
connection to the Expansion Port that can be used to support an attached LCD Daughter Card. The Expansion
Port uses the LED1_IN, LED2_IN, and LED3_IN ports of the PMIC.
When designing a circuit to use the Backlight LED driver, it is important to connect the cathode (negative) end
of the LED string directly to the LED_IN port of the PMIC. The PMIC controls the supply voltage to the Backlight
LEDs by ensuring that the voltage sensed on the LED_IN port is above a threshold voltage of 0.7V. If more than
one LED_IN ports are used, the lowest port must be above the threshold value. If the designer connects the
cathode end of the Backlight LED string to GROUND, the boost circuit will not work.
The MOSFET used in the boost circuit should have a low ON resistance value for best efficiency. The MOSTFET
chosen for the MCIMX53SMD board, on semiconductor NTLJF4156NT1G, also contains a necessary diode used
in the boost circuitry. This helps reduce the number of components.
5.2.3.
Touch-Screen Operation
The Dialog PMIC contains an autonomous Touch Screen Interface that measures the XY positions from a
standard four-WIRE resistive touch panel. An analog-to-digital converter (ADC) channel will detect the
presence of a pen touch on the panel, and that will trigger a series of voltage measurements on each of the
four touch panel wires (X+, X-, Y+, and Y-) by the ADC in a pre-selected sequence. The resulting voltage
readings are then reported to the i.MX53 processor for conversion to a panel X-Y position through the I2C
communications link.
To ensure the Touch Screen Interface wakes up autonomously with a pen stroke, it is necessary to supply a
1.8V reference voltage to the TSIREF_GPIO_7 pin of the PMIC. It is recommended that one of the high PSSR
Regulators of the PMIC be used to supply this voltage. VLDO6 – VLDO9 are possible sources for supplying this
reference voltage.
5.2.4.
Miscellaneous
It will automatically charge using the programmed charging settings whenever wall power is supplied to the
MCIMX53SMD board. When the battery voltage reaches the programmed level, charging will stop. Battery
discharge will not begin until wall power is removed from the board and, if a Li-ION battery is attached, the
main battery discharges to the battery cut off level.
There are two port ID traces connected from the Expansion Port header to two of the ADC pins of the PMIC.
Each unique Daughter Card designed by Freescale has a different resistor value attached to the two ID traces
on the Daughter Card. It is possible to use this voltage divider identification system to determine at boot time
if a daughter card is attached, and if so, which specific daughter card it is.
Over-Voltage protection is sensed by the DCIN (B4) pin of the PMIC. The voltage sensed by this pin must be
between 4.5V and 5.5V. If the voltage meets this threshold value, the voltage seen at DCIN is blocked from the
1V8_WiFi
EXPANSION PORT
CMOS Camera
WiFi
DCDC_15V
15V
DCDC_15V
VGA Dock
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