FEATURES
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LTC1799
1kHz to 33MHz
Resistor Set SOT-23 Oscillator
DESCRIPTIO
The LTC
®
1799 is a precision oscillator that is easy to use
and occupies very little PC board space. The oscillator
frequency is programmed by a single external resistor
(R
SET
). The LTC1799 has been designed for high accuracy
operation (≤1.5% frequency error) without the need for
external trim components.
The LTC1799 operates with a single 2.7V to 5.5V power
supply and provides a rail-to-rail, 50% duty cycle square
wave output. The CMOS output driver ensures fast rise/fall
times and rail-to-rail switching. The frequency-setting
resistor can vary from 3k to 1M to select a master
oscillator frequency between 100kHz and 33MHz (5V
supply). The three-state DIV input determines whether the
master clock is divided by 1, 10 or 100 before driving the
output, providing three frequency ranges spanning 1kHz
to 33MHz (5V supply). The LTC1799 features a proprietary
feedback loop that linearizes the relationship between
R
SET
and frequency, eliminating the need for tables to
calculate frequency. The oscillator can be easily pro-
grammed using the simple formula outlined below:
⎧
100, DIV Pin
=
V
+
⎛
10k
⎞
⎪
f
OSC
=
10MHz
•
⎜
⎟
, N
=
⎨
10, DIV Pin
=
Open
⎝
N
•
R
SET
⎠
⎪
1, DIV Pin
=
GND
⎩
One External Resistor Sets the Frequency
Fast Start-Up Time: < 1ms
1kHz to 33MHz Frequency Range
Frequency Error
≤1.5%
5kHz to 20MHz
(T
A
= 25°C)
Frequency Error
≤
2% 5kHz to 20MHz
(T
A
= 0°C to 70°C)
±40ppm/°C
Temperature Stability
0.05%/V Supply Stability
50%
±1%
Duty Cycle 1kHz to 2MHz
50%
±5%
Duty Cycle 2MHz to 20MHz
1mA Typical Supply Current
100Ω CMOS Output Driver
Operates from a Single 2.7V to 5.5V Supply
Low Profile (1mm) SOT-23 (ThinSOT™ Package)
APPLICATIO S
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Low Cost Precision Oscillator
Charge Pump Driver
Switching Power Supply Clock Reference
Clocking Switched Capacitor Filters
Fixed Crystal Oscillator Replacement
Ceramic Oscillator Replacement
Small Footprint Replacement for Econ Oscillators
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
ThinSOT is a trademark of Linear Technology Corporation.
Protected by U.S. Patents including 6342817 and 6614313.
TYPICAL APPLICATIO
Typical Distribution of Frequency Error,
T
A
= 25°C (5kHz
≤
f
OSC
≤
20MHz, V
+
= 5V)
25
Basic Connection
20
5V
0.1µF
3k
≤
R
SET
≤
1M
1
2
3
1kHz
≤
f
OSC
≤
33MHz
5
5V
4
÷100
÷10
GND
SET
DIV
1799 TA01
UNITS (%)
V
+
OUT
LTC1799
15
10
OPEN
÷1
5
TSOT-23 Actual Size
0
–1.25
–0.75
–0.25 0 0.25
0.75
FREQUENCY ERROR (%)
U
U
U
1.25
1799 TA02
sn1799 1799fbs
1
LTC1799
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
+
1
GND 2
SET 3
4 DIV
5 OUT
Supply Voltage (V
+
) to GND ........................– 0.3V to 6V
DIV to GND .................................... – 0.3V to (V
+
+ 0.3V)
SET to GND ................................... – 0.3V to (V
+
+ 0.3V)
Operating Temperature Range
LTC1799C ............................................... 0°C to 70°C
LTC1799I ............................................ – 40°C to 85°C
LTC1799H ........................................ – 40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART NUMBER
LTC1799CS5
LTC1799IS5
LTC1799HS5
S5 PART MARKING
LTND
LTNE
LTND
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 256°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
∆f
PARAMETER
Frequency Accuracy
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 2.7V to 5.5V, R
L
=5k, C
L
= 5pF, unless otherwise noted.
All voltages are with respect to GND.
CONDITIONS
V
+
= 5V
5kHz
≤
f
≤
20MHz
5kHz
≤
f
≤
20MHz, LTC1799C
5kHz
≤
f
≤
20MHz, LTC1799I/H
1kHz
≤
f
≤
5kHz
20MHz
≤
f
≤
33MHz
5kHz
≤
f
≤
10MHz
5kHz
≤
f
≤
10MHz, LTC1799C
5kHz
≤
f
≤
10MHz, LTC1799I/H
1kHz
≤
f
≤
5kHz
10MHz
≤
f
≤
20MHz
V
+
= 5V
V
+
= 3V
V
+
= 5V
V
+
= 3V
●
●
●
●
MIN
TYP
±0.5
MAX
±1.5
±2
±2.5
UNITS
%
%
%
%
%
%
%
%
%
%
kΩ
kΩ
MHz
MHz
kHz
%/°C
(Notes 2, 3)
V
+
= 3V
±2.5
±2.5
±0.5
●
●
±1.5
±2
±2.5
±2.5
±2.5
5
10
33
20
1
±0.004
0.05
0.06
0.13
0.4
300
●
●
●
●
●
●
●
V
+
– 0.4
●
R
SET
f
MAX
f
MIN
∆f/∆T
∆f/∆V
Frequency-Setting Resistor Range
Maximum Frequency
Minimum Frequency
Freq Drift Over Temp (Note 3)
Freq Drift Over Supply (Note 3)
Timing Jitter
(Note 4)
Long-Term Stability of Output Frequency
Duty Cycle (Note 7)
⏐
∆f
⏐
< 1.5%
⏐
∆f
⏐
< 2.5%, Pin 4= 0V
⏐
∆f
⏐
< 2.5%, Pin 4= V
+
200
200
R
SET
= 31.6k
V
+
= 3V to 5V, R
SET
= 31.6k
Pin 4 = V
+
Pin 4 = Open
Pin 4 = 0V
Pin 4 = V
+
or Open (DIV Either by 100 or 10)
Pin 4 = 0V (DIV by 1), R
SET
= 5k to 200k
R
SET
= 200k, Pin 4 = V
+
, R
L
=
∞
R
SET
= 10k, Pin 4 = 0V, R
L
=
∞
V
+
= 5V
V
+
= 5V
V
+
= 3V
0.1
ppm/√kHr
51
55
5.5
1.1
2.4
2
0.5
%
%
V
mA
mA
mA
V
V
µA
µA
sn1799 1799fbs
49
45
2.7
50
50
0.7
V
+
I
S
Operating Supply Range
Power Supply Current
V
IH
V
IL
I
DIV
High Level DIV Input Voltage
Low Level DIV Input Voltage
DIV Input Current (Note 5)
Pin 4 = V
+
Pin 4 = 0V
V
+
= 5V
V
+
= 5V
●
●
–8
5
–5
8
2
U
%/V
%
%
%
W
U
U
W W
W
LTC1799
ELECTRICAL CHARACTERISTICS
SYMBOL
V
OH
PARAMETER
High Level Output Voltage (Note 5)
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 2.7V to 5.5V, R
L
=5k, C
L
= 5pF, Pin 4 = V
+
unless otherwise noted.
All voltages are with respect to GND.
CONDITIONS
V
+
= 5V,
LTC1799C/I
V
+
= 5V,
LTC1799H
V
+
= 3V,
LTC1799C/I
V
+
= 3V,
LTC1799H
V
OL
Low Level Output Voltage (Note 5)
V
+
= 5V,
LTC1799C/I
V
+
= 5V,
LTC1799H
V
+
= 3V,
LTC1799C/I
V
+
= 3V,
LTC1799H
t
r
OUT Rise Time
(Note 6)
V
+
= 5V
V
+
= 3V
t
f
OUT Fall Time
(Note 6)
V
+
= 5V
V
+
= 3V
I
OH
= – 1mA
I
OH
= – 4mA
I
OH
= – 1mA
I
OH
= – 4mA
I
OH
= – 1mA
I
OH
= – 4mA
I
OH
= – 1mA
I
OH
= – 4mA
I
OL
= 1mA
I
OL
= 4mA
I
OL
= 1mA
I
OL
= 4mA
I
OL
= 1mA
I
OL
= 4mA
I
OL
= 1mA
I
OL
= 4mA
Pin 4 = V
+
or Floating, R
L
=
∞
Pin 4 = 0V, R
L
=
∞
Pin 4 = V
+
or Floating, R
L
=
∞
Pin 4 = 0V, R
L
=
∞
Pin 4 = V
+
or Floating, R
L
=
∞
Pin 4 = 0V, R
L
=
∞
Pin 4 = V
+
or Floating, R
L
=
∞
Pin 4 = 0V, R
L
=
∞
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
MIN
4.8
4.5
4.75
4.40
2.7
2.2
2.65
2.10
TYP
4.95
4.8
4.95
4.75
2.9
2.6
2.90
2.55
0.05
0.2
0.05
0.25
0.1
0.4
0.10
0.45
14
7
19
11
13
6
19
10
MAX
UNITS
V
V
V
V
V
V
V
V
0.15
0.4
0.20
0.50
0.3
0.7
0.35
0.80
V
V
V
V
V
V
V
V
ns
ns
ns
ns
ns
ns
ns
ns
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
Frequencies near 100kHz and 1MHz may be generated using two
different values of R
SET
(see the Table 1 in the Applications Information
section). For these frequencies, the error is specified under the following
assumption: 10k < R
SET
≤
100k. The frequency accuracy for f
OSC
= 20MHz
is guaranteed by design and test correlation.
Note 3:
Frequency accuracy is defined as the deviation from the
f
OSC
equation.
Note 4:
Jitter is the ratio of the peak-to-peak distribution of the period to
the mean of the period. This specification is based on characterization and
is not 100% tested.
Note 5:
To conform with the Logic IC Standard convention, current out of
a pin is arbitrarily given as a negative value.
Note 6:
Output rise and fall times are measured between the 10% and
90% power supply levels. These specifications are based on
characterization.
Note 7:
Guaranteed by 5V test.
sn1799 1799fbs
3
LTC1799
TYPICAL PERFOR A CE CHARACTERISTICS
Frequency Variation
vs R
SET
4
3
2
VARIATION (%)
T
A
= 25°C
GUARANTEED LIMITS APPLY
OVER 5k TO 200k RANGE
TYPICAL
HIGH
1
0
–1
–2
–3
–4
1
10
VARIATION (%)
Peak-to-Peak Jitter vs Frequency
0.7
0.6
÷1
0.5
SUPPLY CURRENT (mA)
JITTER (%)
0.4
0.3
÷10
0.2
÷100
0.1
0
1k
100k
1M
10M
10k
OUTPUT FREQUENCY, f
OUT
(Hz)
100M
1799 G03
Output Resistance
vs Supply Voltage
140
T
A
= 25°C
OUTPUT RESISTANCE (Ω)
120
OUTPUT SOURCING CURRENT
100
80
60
OUTPUT SINKING CURRENT
40
2.5
3.0
3.5 4.0 4.5
5.0
SUPPLY VOLTAGE (V)
5.5
6.0
4
U W
1799 G05
Frequency Variation
Over Temperature
1.00
0.75
0.50
0.25
0
–0.25
–0.50
–0.75
TYPICAL
LOW
TYPICAL
HIGH
R
SET
= 31.6k
÷1
OR
÷10
OR
÷100
TYPICAL
LOW
100
R
SET
(kΩ)
1000
1799 G01
–1.00
–40
–20
40
20
60
0
TEMPERATURE (°C)
80
1799 G02
Supply Current
vs Output Frequency
4.5
4.0
3.5
3.0
2.5
÷10
(5V)
2.0
1.5
1.0
0.5
0
1k
10k
100k
1M
10M
OUTPUT FREQUENCY, f
OUT
(Hz)
100M
1799 G04
T
A
= 25°C
C
L
= 5pF
R
L
= 1M
÷1
(5V)
÷100
(5V)
÷100
(3V)
÷10
(3V)
÷1
(3V)
LTC1799 Output Operating at
20MHz, V
S
= 5V
V
+
= 5V, R
SET
= 5k, C
L
= 10pF
LTC1799 Output Operating at
10MHz, V
S
= 3V
V
+
= 3V, R
SET
= 10k, C
L
= 10pF
1V/DIV
1V/DIV
12.5ns/DIV
1799 G06
25ns/DIV
1799 G07
sn1799 1799fbs
LTC1799
PI FU CTIO S
V
+
(Pin 1):
Voltage Supply (2.7V
≤
V
+
≤
5.5V). This supply
must be kept free from noise and ripple. It should be
bypassed directly to a ground plane with a 0.1µF capacitor.
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
+
deter-
mines the oscillator frequency. The voltage on this pin is
held by the LTC1799 to approximately 1.13V below the V
+
voltage. For best performance, use a precision metal film
resistor with a value between 10k and 200k 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 of N in the frequency equation. Pin 4 should be tied
to GND for the
÷1
setting, the highest frequency range.
Floating Pin 4 divides the master oscillator by 10. Pin 4
should be tied to V
+
for the
÷100
setting, the lowest
frequency range. To detect a floating DIV pin, the LTC1799
attempts to pull the pin toward midsupply. This is realized
with two internal current sources, one tied to V
+
and Pin
4 and the other one tied to ground and Pin 4. Therefore,
driving the DIV pin high requires sourcing approximately
5µA. Likewise, driving DIV low requires sinking 5µA.
When Pin 4 is floated, preferably it should be bypassed by
a 1nF capacitor to ground or it should be surrounded by a
ground shield to prevent excessive coupling from other
PCB traces.
OUT (Pin 5):
Oscillator Output. This pin can drive 5kΩ
and/or 10pF loads. Larger loads may cause inaccuracies
due to supply bounce at high frequencies. Transients will
not cause latchup if the current into/out of the OUT pin is
limited to 50mA.
BLOCK DIAGRA
1
R
SET
I
RES
3
V
+
SET
+
–
2
GND
W
U
U
U
V
RES
= 1.13V
±25%
(V
+
– V
SET
)
+
GAIN = 1
MASTER OSCILLATOR
ƒ
MO
= 100MHz • kΩ •
I
RES
+
(V – V
SET
)
PROGRAMMABLE
DIVIDER
(÷1, 10 OR 100)
V
+
DIVIDER
SELECT
OUT
5
–
V
BIAS
5µA
I
RES
THREE-STATE
INPUT DETECT
DIV
4
5µA
GND
1799 BD
sn1799 1799fbs
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