LTC1799 Linear Technology Corporation, LTC1799 Datasheet

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LTC1799

Manufacturer Part Number
LTC1799
Description
Manufacturer
Linear Technology Corporation
Datasheet

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FEATURES
TYPICAL APPLICATIO
APPLICATIO S
ThinSOT is a trademark of Linear Technology Corporation.
Protected by U.S. Patents including 6342817 and 6614313.
All other trademarks are the property of their respective owners.
, LTC and LT are registered trademarks of Linear Technology Corporation.
One External Resistor Sets the Frequency
Fast Start-Up Time: < 1ms
1kHz to 33MHz Frequency Range
Frequency Error ≤1.5% 5kHz to 20MHz
(T
Frequency Error ≤ 2% 5kHz to 20MHz
(T
±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)
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
A
A
3k ≤ R
= 25°C)
= 0°C to 70°C)
SET
≤ 1M
5V
0.1µF
U
TSOT-23 Actual Size
Basic Connection
1
2
3
V
GND
SET
LTC1799
+
1799 TA01
OUT
U
DIV
5
4
1kHz ≤ f
÷100
÷1
OSC
5V
÷10
≤ 33MHz
OPEN
Resistor Set SOT-23 Oscillator
DESCRIPTIO
The LTC
and occupies very little PC board space. The oscillator
frequency is programmed by a single external resistor
(R
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
calculate frequency. The oscillator can be easily pro-
grammed using the simple formula outlined below:
f
OSC
SET
SET
). The LTC1799 has been designed for high accuracy
=
and frequency, eliminating the need for tables to
10
®
1799 is a precision oscillator that is easy to use
MHz
T
Typical Distribution of Frequency Error,
A
25
20
15
10
–1.25
= 25°C (5kHz ≤ f
5
0
–0.75
N R
U
10
FREQUENCY ERROR (%)
k
SET
–0.25 0 0.25
1kHz to 33MHz
OSC
,
N
≤ 20MHz, V
=
100
10
1
0.75
,
,
1799 TA02
,
LTC1799
DIV Pin V
DIV Pin Open
DIV Pin GND
+
1.25
= 5V)
sn1799 1799fbs
=
=
=
+
1

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LTC1799 Summary of contents

Page 1

... SET 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 ...

Page 2

... 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 + < 1. ∆ ...

Page 3

... I = – 1mA OH LTC1799H I = – 4mA 5V 1mA OL LTC1799C 4mA 5V 1mA OL LTC1799H I = 4mA 3V 1mA OL LTC1799C 4mA 3V 1mA OL LTC1799H I = 4mA Pin Floating ∞ L Pin ∞ Pin Floating ∞ L Pin ∞ ...

Page 4

... 5pF ÷1 (5V) ÷10 (5V) ÷100 (5V) ÷100 (3V) ÷10 (3V) ÷1 (3V) 1k 10k 100k 1M 10M 100M OUTPUT FREQUENCY, f (Hz) OUT 1799 G04 LTC1799 Output Operating at 10MHz 3V 10k 10pF SET L 1V/DIV 1799 G06 25ns/DIV 1799 G07 sn1799 1799fbs ...

Page 5

... SET (Pin 3): Frequency-Setting Resistor Input. The value of the resistor connected between this pin and V 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 ...

Page 6

... MO R ⎝ ⎠ SET The LTC1799 is optimized for use with resistors between 10k and 200k, corresponding to master oscillator fre- quencies between 0.5MHz and 10MHz. Accurate frequen- cies up to 20MHz (R = 5k) are attainable if the supply SET voltage is greater than 4V. ...

Page 7

... DIV (Pin ÷100 ⇒ master oscillator frequencies greater than 10MHz (R LTC1799 may suffer reduced accuracy with a supply voltage less than 4V. After choosing the proper divider setting, determine the correct frequency-setting resistor. Because of the linear correspondence between oscillation period and resis- tance, a simple equation relates resistance with frequency. ⎧ ...

Page 8

... If a switching power supply is used to power up the LTC1799, and if the ripple of the power supply is more than a few tens of millivolts, make sure the switching frequency and its harmonics are not related to the output frequency of the LTC1799 ...

Page 9

... SET Block Diagram. This loss of accuracy will become notice- able when the magnitude of I PROG The frequency variation of the LTC1799 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 ...

Page 10

... This lower limit U TYPICAL APPLICATIO S Low Power 80Hz to 8kHz Sine Wave Generator ( OSC OUT 3V LTC1799 SET 3V 100 0.1µF GND SW1 OPEN SET DIV ...

Page 11

... U S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 0.95 REF 1.22 REF 1.50 – 1.75 2.80 BSC 1.4 MIN (NOTE 4) PIN ONE 0.95 BSC 0.80 – 0.90 1.00 MAX 0.09 – 0.20 (NOTE 3) LTC1799 2.90 BSC (NOTE 4) 0.30 – 0.45 TYP 5 PLCS (NOTE 3) 0.01 – 0.10 1.90 BSC S5 TSOT-23 0302 sn1799 1799fbs 11 ...

Page 12

... GND THERMISTOR 3 4 SET DIV 1799 TA03 R : YSI 44011 800 765-4974 T Linear Technology Corporation 12 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● Shutting Down the LTC1799 5V 74AC04 1 + ON/SHDN V OUT C1 LTC1799 R1 0.1µF 2 GND 10k 3 SET 1799 TA08 ...

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