User manual

Hillstar Boards – Hardware Description
 2013 Microchip Technology Inc. DS40001721A-page 27
FIGURE 3-5: PCB LAYER STACK
In a target system design the GND layer is not required. It is added for the Hillstar sens-
ing electrode as a shielding layer and shall simulate the presence of static components
which are placed in a target device underneath the sensing electrodes.
3.4 I
2
C TO USB BRIDGE
Connecting the MGC3130 Unit to a PC requires an I
2
C to USB Bridge. The Hillstar
Bridge works as a Composite Device Class (CDC). It controls the USB transfer towards
the host PC and handles the I
2
C communication with the MGC3130 Unit. Moreover, it
provides 3.3V power supply and the MCLR
signal to the MGC3130 Unit.
The bridge function is handled by Microchip’s PIC18F14K50 USB microcontroller.
The board is equipped with a mini USB connector (Type A) and a 2 mm 6-pin female
board-to-board connector for the I
2
C interface. The interface to the MGC3130 Unit
includes the following signals: EIO0, 3.3V, GND, SDA0, SCL0, and MCLR
. Please refer
to Figure 3-6.
FIGURE 3-6: I
2
C™ TO USB BRIDGE
Tx: 35 µm
Tx
Rx : 18 µm
GND: 18 µm
Not Used: 35 µm
0.25 mm
0.15 mm
935 µm
540 µm
1.546 mm
Top layer
Bottom
layer
2
nd
layer
3
rd
layer
Rx feeding line
Note: Please refer to the “MGC3130 GestIC
®
Design Guide” for the electrodes
equivalent circuitry, capacitances (C
RxTx
, C
RxG
, Tx
RxG
) and their typical
values.
™