KIT34825EPEVME Evaluation Board
, Rev. 2.0
8
Freescale Semiconductor
Hardware Description
4.1.5
On-Board LDO and VDD_5V
The evaluation board has a 3.3V LDO on the board. This LDO generates the VDDIO voltage as well as
to generate a reference voltage (3.3V) for the USB charger simulator (see section 4.2 for more
information). Unless powered by a different source, the JP13 should always be connected for the VDDIO
supply.
The 3.3V LDO is powered by a 5V supply (VDD_5V) from the standard type-B USB connector. The
VDD_5V supply are also used to supply the 34825 via jumper J12 to the VDD pin during the evaluation.
In addition, the VDD_5V can also be used to generate the 5V supply to the VBUS pin in the mini-USB
connector to simulate various power supplies, together with the D+/D- connection and the ID connection.
Jumper J9 is for this purpose. More details are given in the section 4.2.
4.2
Remote Control and Accessory Simulator
The remote control simulator contains 13 resistors (R3 to R15) that are corresponding to the 13 supported
keys (see datasheet for more details) and a push button (SW1) to simulate the action of the remote
control. The left side of
shows the detailed schematic. To simulate a key press, the user needs
to select one ID resistor value by shorting the corresponding jumper in J1 and then to press the push
button SW1. Shorting pin1 and pin2 of the jumper header J1 represents the S0 key. Shorting pin3 and
pin4 of the J1 represents S1 key, and so on.
shows the schematic of the accessory simulator. Resistor R16 to R34 represent
all supported ID resistors. R16 and R17 are in series with the remote control key resistors to form the
correct ID resistors. Shorting one pair of the headers in J2 is equivalent to connecting one ID resistor to
the ID pin.
The headers of 39 and 40 in J2 are connected to the DP and DM pins of the 34825. Shorting these two
headers is equivalent to short the DP and DM pins. To simulate the attachment of a dedicated charger,
the users can short the 39 and 40 headers first and then short jumper J9 to connect the VDD_5V to the
VBUS pin of the mini-USB connector. Once the J9 are shorted, the 34825 sees a 5V at the VBUS pin and
starts the power supply type identification. The identification result will be a dedicated charger.
Resistors R1 and R2 and jumper J3 are for simulating the USB charger. The USB charger requires the
power supply to offer a 0.6V to the DM pin when the DP pin is sourced with a 0.6V. Shorting J3 first and
then J9 creates and equivalent attachment of a USB charger to the mini-USB connector.
The headers in J2 should be left open unless an accessory is being simulated.
4.3
USB-to-I2C Interface
The USB-to-I2C interface consisting of the MCU block and the standard type-B connector enables users
to use the PC as the host controller of the I2C bus. Users can access the I2C register map with the GUI
in the PC and receive the interrupt signal from the 34825. The schematic of the USB-to-I2C interface is
given in
. The MCU in the schematic is powered by the USB bus voltage. A standard type-B
connector is given to connect the evaluation board to the PC. The USB bus voltage is the supply of the
VDD_5V discussed earlier.
