LTC6990CS6#TRPBF Linear Technology, LTC6990CS6#TRPBF Datasheet - Page 18

• Manufacturer Part Number: LTC6990CS6#TRPBF
• Description: IC MPU SUPERVISORY TSOT23-6
• Manufacturer: Linear Technology

Specifications of LTC6990CS6#TRPBF

• Frequency: *
• Voltage - Supply: *
• Current - Supply: 235µA
• Operating Temperature: *
• Package / Case: TSOT-23-6, TSOT-6
• Count: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
LTC6990
Depending on the application’s requirements, the non-
inverting VCO circuit in Figure 13 may be preferred for
this wide of a frequency variation as its maximum inac-
curacy due to V
to only ±3% with a small change to the voltage tuning
range specifi cation.
Reducing V
Figure 13 shows a VCO that reduces the effect of ΔV
by adding an op-amp to make V
This circuit also has a positive transfer function (the out-
put frequency increases as V
for positive V
absolute frequency error at the highest output frequency.
Compared to the simple VCO circuit of Figure 11, the
absolute frequency error is unchanged. However, with
18
SET
IN
SET
Error Effects in VCO Applications
voltages, this circuit places the greatest
error is only ±9% and can be reduced
0.4V TO 4V
V
IN
IN
100k
R3
increases). Furthermore,
CTRL
dependent on V
+
–
33pF
C4
Figure 13. VCO with Reduced ΔV
LTC6078
1/2
3V
30.1k
R4
V
V
CTRL
SET
R
SET
75k
SET
VCO
.
3V
R
249k
SET
the maximum absolute frequency error (in Hertz) now
occurring at the highest output frequency, the relative
frequency error (in percent) is greatly improved.
Additionally, by choosing the VCO’s specifi cations shrewdly,
the frequency error (in percent) due to V
reduced to ΔV
ment, the design must abide by three conditions. First,
the V
Second, choose V
R
Figure 13 shows a design similar to the previous design
example where the V
0.4V. This satisfi es the V
and the design assures that the output frequency error
due to V
OE
GND
SET
VCO
LTC6990
/R
IF
IN
f
f
OUT
OUT
SET
OUT
6990 F13
R4
R3
DIV
SET
V
voltage must be positive throughout the range.
SET
+
=
Sensitivity
1MHz • 50k
N
R
R
1MHz • 50k
10kHz TO 100kHz
N
DIV
≥ R4/R3.
VCO
SET
DIV
variation is only ±3%.
• R
, THE EQUATION REDUCES TO:
• R
SET
f
OUT
VCO
SET
C1
0.1μF
/V
•
MAX
•
R
R
SET
V
V
VCO
SET
SET
3V
IN
MIN
/V
R1
1M
DIVCODE = 3
(N
R2
280k
= ±3%. To realize this improve-
MAX
V
DIV
MIN
IN
voltage is now specifi ed to be
V
V
SET
IN
• 25kHz/V
= 8, Hi-Z = 0)
/V
≥ f
MIN
1 •
MAX
R4
R3
≥ f
/f
MAX
MIN
/f
SET
. Last, choose
MIN
variation is
condition
6990f