LTC6900CS5#TRMPBF Linear Technology, LTC6900CS5#TRMPBF Datasheet - Page 9

• Manufacturer Part Number: LTC6900CS5#TRMPBF
• Description: IC OSC PREC 1KHZ-20MHZ TSOT23-5
• Manufacturer: Linear Technology
• Type: Oscillator, Siliconr

Specifications of LTC6900CS5#TRMPBF

• Frequency: 20MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Current - Supply: 920µA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Count: -
• Other names: LTC6900CS5#TRMPBFTR

APPLICATIONS INFORMATION
A Ground Referenced Voltage Controlled Oscillator
The LTC6900 output frequency can also be programmed by
steering current in or out of the SET pin, as conceptually
shown in Figure 8. This technique can degrade accuracy
as the ratio of (V
dependent of the value of R
Block Diagram. This loss of accuracy will become noticeable
when the magnitude of I
frequency variation of the LTC6900 is still monotonic.
Figure 9 shows how to implement the concept shown in
Figure 8 by connecting a second resistor, R
SET pin and a ground referenced voltage source, V
For a given power supply voltage in Figure 9, the output
frequency of the LTC6900 is a function of V
and (V
S1
R
f
⎡
⎢
⎢
⎢
⎢
⎣
R
OSC
Figure 8. Concept for Programming via Current Steering
SET2
1+
SET1
3V OR 5V
+
V
(
=
– V
+
I
R
V
PR
SET
10MHz
IN
V
SET
RES
− V
N
0.1μF
1
2
3
) = V
+
I
V
GND
SET
RES
+
LTC6900
+
)
•
•
R
– V
RES
⎛
⎜
⎜
⎜
⎜
⎝
IN
OUT
6900 F07
DIV
1+
1
2
3
20k
:
SET
R
PROG
V
GND
SET
Figure 7
R
+
LTC6900
5
4
SET
1
R
) / I
SET
÷100
SET
IN
÷1
OUT
6900 F08
DIV
is comparable to I
•
, as shown in the LTC6900
RES
V
⎞
⎟
⎟
⎟
⎟
⎠
+
÷10
⎤
⎥
⎥
⎥
⎥
⎦
5
4
f
OR
f
is no longer uniquely
÷100
OSC
OSC
÷1
= 10MHz •
= 10MHz •
5V
÷10
IN
, between the
OPEN
IN
(
(
N • R
N • R
, R
20k
RES
SET1
SET1
IN
20k
, R
IN
)
//R
. The
.
SET2
SET
(1)
)
When V
sumes the highest value and it is set by the parallel com-
bination of R
f
the accuracy of f
When V
proaches the ground potential, the oscillator frequency,
f
by the change of V
by ±8%, assuming the variation of V
perature coeffi cient of V
By manipulating the algebraic relation for f
simple algorithm can be derived to set the values of external
resistors R
1. Choose the desired value of the maximum oscillator
2. Set the desired value of the minimum oscillator fre-
3. Choose V
R
(
OSC
OSC
R
V
SET
frequency, f
voltage V
quency, f
V
from the following:
IN(MAX)
IN
IN(MIN)
Figure 9. Implementation of Concept Shown in Figure 8
, is independent of the value of V
, assumes its lowest value and its accuracy is affected
=
+
–
IN
V
IN
IN
= V
R
− V
V
is less than V
SET
≥ 0.
IN
+
OSC(MIN)
V
IN(MAX)
RES
RES
IN
V
+
+
–
RES
+
, the output frequency of the LTC6900 as-
and R
and R
OSC(MAX)
)
= 1.1 and calculate the ratio of R
OSC
R
−
0.1μF
SET
⎡
⎢
⎢
⎣
RES
⎛
⎜
⎝
(
≤ V
, occurring at minimum input voltage
f
is within the data sheet limits.
IN
f
f
SET
OSC(MAX)
f
OSC(MAX)
OSC(MIN)
OSC(MIN)
= (V
, as shown in Figure 9.
+
. Also note, the output frequency,
, occurring at maximum input
RES
.
+
1
2
3
, and expecially when V
+
V
GND
SET
is 0.02%/°C.
– V
+
LTC6900
)
⎞
⎟ V
⎠
SET
− 1
(
OUT
6900 F09
DIV
IN(MIN)
). At 25°C V
⎤
⎥
⎥
⎦
5
4
RES
+
÷100
f
is ±5%. The tem-
OSC
LTC6900
÷1
= (V
5V
− V
÷10
OSC
+
+
– V
RES
OPEN
)
above, a
− 1
IN
SET
IN
varies
/R
6900fa
) so
9
ap-
SET
(2)