nb3n502 ON Semiconductor, nb3n502 Datasheet - Page 4

• Manufacturer Part Number: nb3n502
• Description: 14 Mhz To 190 Mhz Pll Clock Multiplier
• Manufacturer: ON Semiconductor

High Frequency CMOS/TTL Oscillators
mode crystal, can build a high frequency CMOS/TTL output
oscillator. For example, a 20 MHz crystal connected to the
NB3N502 with the 5X output selected (S1 = L, S0 = H)
produces a 100 MHz CMOS/TTL output clock.
External Components
Decoupling Instructions
supply, noise de−coupling is required. The 0.01 mF
decoupling capacitor has to be connected between V
GND on pins 2 and 3. It is recommended to place
de−coupling capacitors as close as possible to the NB3N502
device to minimize lead inductance. Control input pins can
be connected to device pins V
GND planes on the board.
The NB3N502, along with a low frequency fundamental
In order to isolate the NB3N502 from system power
Figure 3. Using a Crystal as Reference Clock
Internal
to Device
12 pF
C
IN1
X1/CLK
C
C
S1
L1
Crystal
R
G
DD
C
C
or GND, or to the V
S2
L2
X2
APPLICATIONS INFORMATION
C
12 pF
IN2
DD
DD
http://onsemi.com
and
and
NB3N502
Example 1: Equal stray capacitance on PCB
Example 2: Different stray capacitance on PCB trace X1/CLK vs. X2
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
LOAD1
LOAD2
IN1
S1
LOAD1,2
L2
L1
LOAD
LOAD1
IN1
S1
L1
L2
LOAD
LOAD1
IN1
S1
L1
L2
4
= C
= C
= 36 − 12 − 6 = 18 pF
= 36 − 12 − 6 = 18 pF
= 36 − 12 − 4 = 20 pF
= 36 − 12 − 8 = 16 pF
[ C
= C
= 4 pF & C
[ C
= C
= C
Series Termination Resistor Recommendation
CLKOUT pin.
Crystal Load Capacitors Selection Guide
pin (C
crystal should be used.
small capacitors from X1/CLK to ground and from X2 to
ground. These capacitors, C
stray capacitance of the board to match the nominally
required crystal load capacitance (C
Because load capacitance can only be increased in this
trimming process, it is important to keep stray capacitance
to a minimum by using very short PCB traces (and no vias)
between the crystal and device. Crystal load capacitors, if
needed, must be connected from each of the pins X1 and X2
to ground. The load capacitance of the crystal (C
(crystal)) must be matched by total load capacitance of the
oscillator circuitry network, C
the crystal (see Figure 3 and equations below).
(Crystal) = 18 pF (Specified by the crystal manufacturer)
(Crystal) = 18 pF
LOAD2
LOAD1
= C
= C
S2
= C
= C
IN2
IN2
A 33 W series terminating resistor can be used on the
The total on−chip capacitance is approximately 12 pF per
The device crystal connections should include pads for
S2
IN2
= 2 S C
= 6 pF
IN1
IN2
[ 5 pF (Typ) [External PCB stray capacitance]
LOAD2
LOAD2
= 12 pF
= 12 pF
[ 12 pF (Typ) [Internal capacitance]
IN1
− C
− C
+ C
+ C
S2
LOAD
and C
IN2
IN1
= 8 pF
= 36 pF
= 36 pF
S1
S2
− C
− C
+ C
+ C
(Crystal)
IN2
S2
S1
L1
L2
). A parallel resonant, fundamental mode
[Total capacitance on X2]
[External load capacitance on X2]
[External load capacitance on X1/CLK]
[Total capacitance on X1/CLK]
L1
INX
and C
, C
L2
SX
, are used to adjust the
and C
LOAD
LX
, as seen by
(crystal)).
LOAD