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 oscil-
lator 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 out-
put, 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 programmed 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
n
n
n
n
n
n
n
n
n
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)
applicaTions
n
n
n
n
n
n
n
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
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents including 6342817 and 6614313.
Typical applicaTion
Basic Connection
5V
0.1µF
3k ≤ R
SET
≤ 1M
1
2
3
V
+
OUT
LTC1799
GND
SET
DIV
1799 TA01
Typical Distribution of Frequency Error,
T
A
= 25°C (5kHz ≤ f
OSC
≤ 20MHz, V
+
= 5V)
25
20
15
10
5
0
–1.25
1kHz ≤ f
OSC
≤ 33MHz
5
5V
4
÷100
÷1
÷10
OPEN
UNITS (%)
TSOT-23 Actual Size
–0.75
–0.25 0 0.25
0.75
FREQUENCY ERROR (%)
1.25
1799 TA02
1799fd
For more information
www.linear.com/LTC1799
1
LTC1799
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
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
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 150°C,
θ
JA
= 256°C/W
orDer inForMaTion
LEAD FREE FINISH
LTC1799CS5#PBF
LTC1799IS5#PBF
LTC1799HS5#PBF
TAPE AND REEL
LTC1799CS5#TRPBF
LTC1799IS5#TRPBF
LTC1799HS5#TRPBF
http://www.linear.com/product/LTC1799#orderinfo
PART MARKING*
LTND
LTNE
LTND
PACKAGE DESCRIPTION
5-Lead Plastic TSOT-23
5-Lead Plastic TSOT-23
5-Lead Plastic TSOT-23
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
elecTrical characTerisTics
SYMBOL PARAMETER
∆f
Frequency Accuracy
(Notes 2, 3)
V
+
= 3V
V
+
= 5V
The
l
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
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
l
l
l
l
MIN
TYP
±0.5
±2.5
±2.5
±0.5
MAX
±1.5
±2
±2.5
UNITS
%
%
%
%
%
%
%
%
%
%
kΩ
kΩ
MHz
MHz
kHz
%/°C
l
l
±2.5
±2.5
5
10
33
20
1
±0.004
0.05
0.06
0.13
0.4
±1.5
±2
±2.5
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)
|∆f| < 1.5%
|∆f| < 2.5%, Pin 4 = 0V
|∆f| < 2.5%, Pin 4 = V
+
R
SET
= 31.6k
V
+
= 3V to 5V, R
SET
= 31.6k
Pin 4 = V
+
Pin 4 = Open
Pin 4 = 0V
200
200
0.1
%/V
%
%
%
1799fd
2
For more information
www.linear.com/LTC1799
LTC1799
elecTrical characTerisTics
SYMBOL PARAMETER
Long-Term Stability of Output Frequency
Duty Cycle (Note 7)
V
+
I
S
Operating Supply Range
Power Supply Current
R
SET
= 200k, Pin 4 = V
+
, R
L
= ∞
R
SET
= 10k, Pin 4 = 0V, R
L
= ∞
V
IH
V
IL
I
DIV
V
OH
High Level DIV Input Voltage
Low Level DIV Input Voltage
DIV Input Current (Note 5)
High Level Output Voltage (Note 5)
Pin 4 = V
+
Pin 4 = 0V
V
+
= 5V,
LTC1799C/I
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, RL = ∞
Pin 4 = 0V, RL = ∞
Pin 4 = V
+
or Floating, RL = ∞
Pin 4 = 0V, RL = ∞
Pin 4 = V
+
or Floating, RL = ∞
Pin 4 = 0V, RL = ∞
Pin 4 = V
+
or Floating, RL = ∞
Pin 4 = 0V, RL = ∞
V
+
= 5V
V
+
= 5V
V
+
= 5V
V
+
= 5V
V
+
= 3V
Pin 4 = V
+
or Open (DIV Either by 100 or 10)
Pin 4 = 0V (DIV by 1), R
SET
= 5k to 200k
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
The
l
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
MIN
49
45
2.7
0.7
TYP
300
50
50
51
55
5.5
1.1
2.4
2
V
+
– 0.4
0.5
–8
4.8
4.5
4.75
4.40
2.7
2.2
2.65
2.10
5
–5
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
0.15
0.4
0.20
0.50
0.3
0.7
0.35
0.80
8
MAX
UNITS
ppm/√kHr
%
%
V
mA
mA
mA
V
V
µA
µA
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
ns
ns
ns
ns
ns
ns
ns
ns
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
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
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.
1799fd
For more information
www.linear.com/LTC1799
3
LTC1799
Typical perForMance characTerisTics
4
3
2
VARIATION (%)
VARIATION (%)
1
0
–1
–2
–3
–4
1
10
R
SET
(k )
100
1000
1799 G01
Frequency Variation
vs R
SET
T
A
= 25°C
GUARANTEED LIMITS APPLY
OVER 5k TO 200k RANGE
TYPICAL
HIGH
1.00
0.75
0.50
0.25
0
–0.25
–0.50
–0.75
Frequency Variation
Over Temperature
R
SET
= 31.6k
÷1 OR ÷10 OR ÷100
TYPICAL
HIGH
TYPICAL
LOW
TYPICAL
LOW
–1.00
–40
–20
40
20
60
0
TEMPERATURE (°C)
80
1799 G02
0.7
0.6
0.5
JITTER (%)
0.4
0.3
0.2
Peak-to-Peak Jitter vs Frequency
4.5
4.0
÷1
SUPPLY CURRENT (mA)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
1k
10k
100k
1M
10M
OUTPUT FREQUENCY, f
OUT
(Hz)
100M
1799 G03
Supply Current
vs Output Frequency
T
A
= 25°C
C
L
= 5pF
R
L
= 1M
÷1 (5V)
÷10 (5V)
÷100 (5V)
÷10
÷100
0.1
0
÷100 (3V)
1k
÷10 (3V)
÷1 (3V)
100M
1799 G04
0
10k
100k
1M
10M
OUTPUT FREQUENCY, f
OUT
(Hz)
Output Resistance
vs Supply Voltage
140
T
A
= 25°C
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
OUTPUT RESISTANCE ( )
120
OUTPUT SOURCING CURRENT
100
1V/DIV
1V/DIV
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
12.5ns/DIV
1799 G06
25ns/DIV
1799 G07
1799 G05
4
1799fd
For more information
www.linear.com/LTC1799
LTC1799
pin FuncTions
V
+
(Pin 1):
Voltage Supply (2.7V ≤ V
+
≤ 5.5V). This sup-
ply 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 fre-
quency 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
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Embedded System
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