LTC6990IDCB#TRPBF Linear Technology, LTC6990IDCB#TRPBF Datasheet - Page 19

• Manufacturer Part Number: LTC6990IDCB#TRPBF
• Description: IC MPU SUPERVISORY 6DFN
• Manufacturer: Linear Technology

Specifications of LTC6990IDCB#TRPBF

• Frequency: *
• Voltage - Supply: *
• Current - Supply: 235µA
• Operating Temperature: *
• Package / Case: 6-WFDFN Exposed Pad
• Count: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
Eliminating V
Control
Many DACs allow for the use of an external reference.
If such a DAC is used to provide the V
V
the DAC’s reference voltage, as shown in Figure 14. The
DAC’s output voltage now tracks any V
eliminates it as an error source. The SET pin cannot be
tied directly to the reference input of the DAC because
the current drawn by the DAC’s REF input would affect
the frequency.
I
Pushing I
range forces the master oscillator to operate outside of
the 62.5kHz to 1MHz range in which it is most accurate.
SET
SET
Extremes (Master Oscillator Frequency Extremes)
error is eliminated by buffering V
SET
outside of the recommended 1.25μA to 20μA
SET
Error Effects with DAC Frequency
μP
Figure 14. Digitally Controlled Oscillator with V
D
CLK
CS/LD
IN
V
LTC1659
V
CC
+
SET
CTRL
SET
GND
REF
and using it as
variation and
V
OUT
voltage, the
LTC6078
V
+
1/2
+
–
R
VCO
The oscillator will still function with reduced accuracy
in its extended range (see the Electrical Characteristics
section).
The LTC6990 is designed to function normally for I
as low as 1.25μA. At approximately 500nA, the oscillator
output will be frozen in its current state. For N
OUT will halt in a low state. But for larger divider ratios,
it could halt in a high or low state. This avoids introduc-
ing short pulses while modulating a very low frequency
output. Note that the output will not be disabled as when
OE is low (e.g. the output will not enter a high impedance
state if Hi-Z = 1).
At the other extreme, the master oscillator frequency can
reach 2MHz for I
mended to operate the master oscillator beyond 2MHz
because the accuracy of the DIV pin ADC will suffer.
R
SET
OE
GND
SET
D
f
OUT
IN
LTC6990
= 0 to 4095
SET
1MHz • 50k
N
DIV
6990 F14
Variation Eliminated
OUT
DIV
V
+
• R
VCO
SET
• 1
= 40μA (R
C1
0.1μF
R
R
VCO
SET
V
+
4096
R1
R2
D
IN
SET
= 25k). It is not recom-
LTC6990
DIV
= 1 or 2,
19
6990f
SET