UM0529
Evaluation board components
9/29
3 Evaluation
board
components
3.1 Microcontroller
U1
The microcontroller used for the STUSB02E/STUSB03E transceiver evaluation board is
ST72F63B. It is programmed with firmware to support the USB HID functionality for
demonstration purposes.
3.1.1 Oscillator
A 12 MHz crystal is used for providing the necessary clock to the microcontroller. C3 and C4
capacitors are used along with a quartz crystal.
3.2 STUSB02E/STUSB03E transceiver U5
The STUSB02E and STUSB03 are single chip USB transceivers that support both USB full-
speed and USB low
-
speed operations. Both have an integrated 5 V to 3.3 V regulator which
allows direct powering from the VBUS. The transceivers also support sharing mode when
VBUS is not present which allows the D+/D- lines to be shared with other serial protocols.
They are also designed to operate down to 1.6 V so that they are compatible with lower
system voltages of most portable systems, which include PDAs, MP3 players and cell
phones.
3.3
74LCX139MTR low voltage dual 2-to-4 decoder/demultiplexer
U2,U3
The 74LCX139MTR is a low
-
voltage CMOS dual 2-to-4 line decoder/ demultiplexer. It is
ideal for low-power and high-speed 3.3 V applications. It can be interfaced to 5 V signal
environment for inputs. The active low enable input can be used for gating or as a data input
for demultiplexing applications. While the enable input is held high, all four outputs are high
independently of the other inputs.
It has the same speed performance at 3.3 V as well as the
5 V, combined with lower power
consumption. All inputs and outputs are equipped with protection circuits against static
discharge, giving them 2 KV ESD immunity and transient excess voltage.
As explained above this device is used for interfacing between the microcontroller and
STUSB02/STUSB03E for 5 V to 3.3 V signals. The 74LVX139MTR device can also be used
as it also has 5 V tolerant inputs.
Note:
The 74LCX139MTR is used for interfacing
the
ST72F63B microcontroller with an operating
voltage ranging from 4 V to 5.5 V in the evaluation board to transceiver. In
the
final
Table 1.
Microcontroller details
Feature
Description
Sales type
ST72F63BK4B1
Package
PSDIP32
Operating voltage
4.0 V to 5.5 V
www.BDTIC.com/ST