LTC6905 Linear Technology, LTC6905 Datasheet - Page 4

• Manufacturer Part Number: LTC6905
• Description: 17MHz to 170MHz Resistor Set SOT-23 Oscillator
• Manufacturer: Linear Technology

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PI FU CTIO S
LTC6905
V
must be kept free from noise and ripple. It should be
bypassed directly to the GND (Pin 2) with a 0.1µF capacitor
or higher.
GND (Pin 2): Ground. Should be tied to a ground plane for
best performance.
SET (Pin 3): Frequency-Setting Resistor Input. The value
of the resistor connected between this pin and V
mines the oscillator frequency. The voltage on this pin is
held by the LTC6905 to approximately 1V below the V
voltage. For best performance, use a precision metal film
resistor with a value between 10k and 25k and limit the
capacitance on this pin to less than 10pF.
DIV (Pin 4): Divider-Setting Input. This three-state input
selects among three divider settings, determining the value
TYPICAL PERFOR A CE CHARACTERISTICS
4
+
45
40
35
30
25
20
10
15
(Pin 1): Voltage Supply (2.7V ≤ V
U
5
0
2.5
R
OUT
3
U
vs V
SUPPLY VOLTAGE (V)
+
3.5
1V/DIV
LTC6905 Output Operating at
17.5MHz, V
4
U
4.5
W
S
5
6905 G04
= 3V
12.5ns/DIV
U
5.5
+
≤ 5.5V). This supply
1.20
1.00
0.80
0.60
0.40
0.20
0
6905 G06
Jitter vs Frequency
0
+
20
÷4
deter-
40
÷2
FREQUENCY (MHz)
60
+
80 100
of N in the frequency equation. Pin 4 should be tied to V
for the ÷1 setting, the highest frequency range. Floating Pin
4 divides the master oscillator by 2. Pin 4 should be tied to
GND for the ÷4 setting, the lowest frequency range. To detect
a floating DIV pin, the LTC6905 attempts to pull the pin
toward midsupply. This is realized with two internal current
sources, one tied to V
ground and Pin 4. Therefore, driving the DIV pin high re-
quires sourcing approximately 15µA. Likewise, driving DIV
low requires sinking 15µA. When Pin 4 is floated, it should
be bypassed by a 1nF capacitor to ground or it should be
surrounded by a ground shield to prevent excessive cou-
pling from other PCB traces.
OUT (Pin 5): Oscillator Output. This pin can drive 5kΩ
and/or 5pF loads. For larger loads, refer to the Applications
Information section.
120 140 160
1V/DIV
÷1
LTC6905 Output Operating at
170MHz, V
6905 G05
180
S
+
= 3V
–0.2
–0.4
–0.6
–0.8
–1.0
and Pin 4 and the other one tied to
1.0
0.8
0.6
0.4
0.2
1ns/DIV
0
–40
Frequency vs Temperature
–20
0
TEMPERATURE (°C)
20
6905 G07
40
60
80 100 120
6905 G08
6905fa
+