Cypress CY4603, User Manual, Page: 63 / 94

HX3 Kits User Guide, Doc. #: 001-91203 Rev. *D 63
Hardware
5.1.3.2 Clock and Reset
This section describes the hardware circuit implemented for clock and reset aspects as shown in
Figure 5-4 .
Figure 5-4. Clock Design
HX3 requires an external crystal with a frequency of 26 MHz and an accuracy of ±150 ppm in parallel
resonant, fundamental mode. The crystal drive circuit is capable of a low-drive level (<200 µW). The
crystal circuit implemented using the NX3225SA-26.000000MHZ-G4 part meets these requirements.
HX3 undergoes a hardware reset when the RESETN pin is pulled LOW. The RESETN pin is tied to
the power supply (V3p3) through an external resistor and to ground (GND) through an external
capacitor as shown in
Figure 5-5 . This RC circuit implements a 15-ms reset timing at power on,
which guarantees the stable operation for HX3. There is also an external reset button to reset the
HX3 hub controller manually whenever needed.
Figure 5-5. Reset Design
26MHz
54
55
XTL_OUT
XTL_IN
xtalout
xtalin
Y1
NX3225SA-26.000000MHZ-G4
1
3
2
4
C15
12pF_50V
C16 12pF_50V
V3p3
R11
10K
C11
1.5uF_16V
SW1
B3U1000P
1 2
RESETN
31
RESETN