Digi NS9750 Manual de usuario Pagina 15

  • Descarga
  • Añadir a mis manuales
  • Imprimir
  • Pagina
    / 88
  • Tabla de contenidos
  • MARCADORES
  • Valorado. / 5. Basado en revisión del cliente
Vista de pagina 14
USB clock
www.digi.com
       11
USB clock
USB is clocked by a separate PLL driven by an external 48 MHz crystal, or it can be driven directly
by an external 48 MHz oscillator. Figure 3 shows a USB circuit.
Figure 3: USB clock
C9
100nF
TANK_LC
X2_USB_OSC
**
L4
1uH_5%
R8
1.5M
R7
62 OHMS
Tank Circuit
R9
100 OHM
3
41
2
X1
48.0000MHz
R6
100 OHM
Crystal circuit
C16
100pF_5%
Y1_OUT
X2_USB
C17
10pF
Y1
SM_Oscillator_48M
4
2
1 3
VCC
GND
TEST OUT
3R3V
X1_USB
NS9750B-A1
**
C15
10pF
**
**
Y1_PWR
TB1
BEAD_0805_601
** = Optional 48.000MHz Oscillator
X1_IN
X1_USB_OSC
TANK_RC
X1 is a 48 MHz 3
rd
harmonic (OT) crystal. It
has the same physical characteristics as a 16
MHz crystal. The circuit may have a tendency
to oscillate at 16 MHz unless precautions are
taken. A LC-tank circuit is added to provide a
“low-impedance” for the 16 MHz oscillation to
ground.
Vista de pagina 14
1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 87 88

Comentarios a estos manuales

Sin comentarios