LTC1799CS5_技术文档

LTC1799

1kHz to 33MHz

Resistor Set SOT-23 Oscillator

U

FEATURES

DESCRIPTIO

■

One External Resistor Sets the Frequency

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). TheLTC1799hasbeendesignedforhighaccuracy

operation (≤1.5% frequency error) without the need for

external trim components.

■

Fast Start-Up Time: <1ms

■

1kHz to 33MHz Frequency Range

Low Profile (1mm) ThinSOT^TMPackage

■

Frequency Error ≤1.5% 5kHz to 20MHz

(T_A= 25°C)

■

Frequency Error ≤2% 5kHz to 20MHz

The LTC1799 operates with a single 2.7V to 5.5V power

supply and provides a rail-to-rail, 50% duty cycle square

waveoutput.TheCMOSoutputdriverensuresfastrise/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). Thethree-stateDIVinputdetermineswhetherthe

master clock is divided by 1, 10 or 100 before driving the

output, providing three frequency ranges spanning 1kHz

to33MHz(5Vsupply).TheLTC1799featuresaproprietary

feedback loop that linearizes the relationship between

R_SETand frequency, eliminating the need for tables to

calculate frequency. The oscillator can be easily pro-

grammed using the simple formula outlined below:

(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}U^{Single 2.7V to 5.5V Supply}

APPLICATIO S

■

Low Cost Precision Oscillator

Charge Pump Driver

■

Switching Power Supply Clock Reference

■

Clocking Switched Capacitor Filters

100,DIV Pin = V⁺

■

Fixed Crystal Oscillator Replacement

10k

N• R_SET

■

Ceramic Oscillator Replacement

f_OSC= 10MHz•

, N = 10, DIV Pin = Open

1, DIV Pin = GND

■

Small Footprint Replacement for Econ Oscillators

, LTC and LT are registered trademarks of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation.

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Typical Distribution of Frequency Error,

TYPICAL APPLICATIO

T_A= 25°C (5kHz ≤ f_OSC≤ 20MHz, V⁺= 5V)

25

20

15

10

5

Basic Connection

1kHz ≤ f

5

≤ 33MHz

OSC

5V

1

2

3

+

V

OUT

LTC1799

0.1µF

3k ≤ R

≤ 1M

SET

GND

SET

÷100

÷10

4

DIV

OPEN

÷1

1799 TA01

0

SOT-23 Actual Size

–1.25 –0.75

–0.25 0 0.25

0.75

1.25

FREQUENCY ERROR (%)

1799 TA02

1

LTC1799

W W

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ABSOLUTE AXI U RATI GS

PACKAGE/ORDER I FOR ATIO

(Note 1)

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

ORDER PART NUMBER

TOP VIEW

LTC1799CS5

LTC1799IS5

+

V

1

2

3

5

4

OUT

DIV

GND

SET

LTC1799C ............................................... 0°C to 70°C

LTC1799I............................................ –40°C to 85°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

S5 PART MARKING

S5 PACKAGE

5-LEAD PLASTIC SOT-23

LTND

LTNE

T_JMAX= 125°C, θ_JA= 256°C/W

Consult LTC Marketing for parts specified with wider operating temperature

ranges.

ELECTRICAL CHARACTERISTICS

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.

SYMBOL PARAMETER

∆f Frequency Accuracy

CONDITIONS

MIN

TYP

MAX

UNITS

+

V = 5V

5kHz ≤ f ≤ 20MHz

±0.5

±1.5

±2

±2.5

%

5kHz ≤ f ≤ 20MHz, LTC1799C

5kHz ≤ f ≤ 20MHz, LTC1799I

1kHz ≤ f ≤ 5kHz

●

(Notes 2, 3)

±2.5

20MHz ≤ f ≤ 33MHz

+

V = 3V

5kHz ≤ f ≤ 10MHz

±0.5

±1.5

±2

±2.5

%

5kHz ≤ f ≤ 10MHz, LTC1799C

5kHz ≤ f ≤ 10MHz, LTC1799I

1kHz ≤ f ≤ 5kHz

●

±2.5

10MHz ≤ f ≤ 20MHz

+

R

Frequency-Setting Resistor Range

Maximum Frequency

∆f < 1.5%

V = 5V

5

10

200

kΩ

SET

MAX

MIN

+

V = 3V

+

f

∆f < 2.5%, Pin 4= 0V

V = 5V

33

20

MHz

+

V = 3V

+

f

Minimum Frequency

∆f < 2.5%, Pin 4= V

1

kHz

%/°C

%/V

∆f/∆T

∆f/∆V

Freq Drift Over Temp (Note 3)

Freq Drift Over Supply (Note 3)

R

= 31.6k

●

±0.004

0.05

SET

+

V = 3V to 5V, R

= 31.6k

0.1

SET

+

Timing Jitter

(Note 4)

Pin 4 = V

0.06

0.13

0.4

%

Pin 4 = Open

Pin 4 = 0V

Long-Term Stability of Output Frequency

Duty Cycle (Note 7)

300

ppm/√kHr

+

Pin 4 = V or Open (DIV Either by 100 or 10)

●

49

45

50

51

55

%

Pin 4 = 0V (DIV by 1), R

= 5k to 200k

SET

+

V

Operating Supply Range

Power Supply Current

●

2.7

5.5

1.1

V

+

I

R

= 200k, Pin 4 = V , R = ∞

V = 5V

0.7

mA

S

SET

L

+

= 10k, Pin 4 = 0V, R = ∞

V = 5V

●

2.4

2

mA

L

+

V = 3V

+

V

High Level DIV Input Voltage

Low Level DIV Input Voltage

DIV Input Current (Note 5)

●

V – 0.4

V

IH

IL

0.5

8

+

I

Pin 4 = V

V = 5V

●

5

–5

µA

DIV

+

Pin 4 = 0V

V = 5V

–8

2

LTC1799

ELECTRICAL CHARACTERISTICS

All voltages are with respect to GND.

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.

SYMBOL PARAMETER

CONDITIONS

MIN

4.8

4.5

TYP

4.95

4.8

MAX

UNITS

+

V

High Level Output Voltage (Note 5)

Low Level Output Voltage (Note 5)

V = 5V

I

= –1mA

= –4mA

●

V

OH

+

V = 3V

I

= –1mA

= –4mA

●

2.7

2.2

2.9

2.6

V

OH

+

V = 5V

I

= 1mA

= 4mA

●

0.05

0.2

0.15

0.4

V

OL

+

V = 3V

I

= 1mA

= 4mA

+

●

0.1

0.4

0.3

0.7

V

OL

+

t

OUT Rise Time

(Note 6)

V = 5V

Pin 4 = V or Floating, R = ∞

Pin 4 = 0V, R = ∞

14

7

ns

r

f

L

+

V = 3V

Pin 4 = V or Floating, R = ∞

19

11

ns

L

Pin 4 = 0V, R = ∞

L

+

OUT Fall Time

(Note 6)

V = 5V

Pin 4 = V or Floating, R = ∞

13

6

ns

L

Pin 4 = 0V, R = ∞

L

+

V = 3V

Pin 4 = V or Floating, R = ∞

19

10

ns

L

Pin 4 = 0V, R = ∞

L

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

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.

different values of R

section). For these frequencies, the error is specified under the following

(see the Table 1 in the Applications Information

Note 5: To conform with the Logic IC Standard convention, current out of

a pin is arbitrarily given as a negative value.

SET

assumption: 10k < R ≤ 100k. The frequency accuracy for f

is guaranteed by design and test correlation.

= 20MHz

SET

OSC

Note 6: Output rise and fall times are measured between the 10% and

90% power supply levels. These specifications are based on

characterization.

Note 3: Frequency accuracy is defined as the deviation from the

equation.

f

OSC

Note 7: Guaranteed by 5V test.

3

LTC1799

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TYPICAL PERFOR A CE CHARACTERISTICS

Frequency Variation

vs R_SET

Frequency Variation

Over Temperature

4

3

1.00

0.75

0.50

0.25

T

= 25°C

R

= 31.6k

A

SET

GUARANTEED LIMITS APPLY

OVER 5k TO 200k RANGE

÷1 OR ÷10 OR ÷100

2

TYPICAL

HIGH

TYPICAL

HIGH

1

0

–0.25

–0.50

–0.75

–1.00

TYPICAL

LOW

–1

–2

–3

–4

TYPICAL

LOW

1

10

100

1000

40

TEMPERATURE (°C)

80

–40 –20

0

20

60

R

(kΩ)

SET

1799 G01

1799 G02

Supply Current

vs Output Frequency

Peak-to-Peak Jitter vs Frequency

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

T

= 25°C

= 5pF

= 1M

A

L

C

R

÷1

÷1 (5V)

÷10 (5V)

÷100 (5V)

÷10

÷100

÷100 (3V) ÷10 (3V) ÷1 (3V)

1k

10k

100k

1M

10M

(Hz)

100M

1k

10k

100k

1M

10M

(Hz)

100M

OUTPUT FREQUENCY, f

OUT

1799 G03

1799 G04

Output Resistance

vs Supply Voltage

LTC1799 Output Operating at

20MHz, V_S= 5V

LTC1799 Output Operating at

10MHz, V_S= 3V

140

120

100

80

V⁺= 5V, R_SET= 5k, C_L= 10pF

V⁺= 3V, R_SET= 10k, C_L= 10pF

T

A

= 25°C

OUTPUT SOURCING CURRENT

1V/DIV

60

1799 G06

1799 G07

12.5ns/DIV

25ns/DIV

OUTPUT SINKING CURRENT

40

2.5 3.0 3.5 4.0 4.5

5.0 5.5 6.0

SUPPLY VOLTAGE (V)

1799 G05

4

LTC1799

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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

bypasseddirectlytoagroundplanewitha0.1µFcapacitor.

Floating Pin 4 divides the master oscillator by 10. Pin 4

should be tied to V⁺for the ÷100 setting, the lowest

frequencyrange. TodetectafloatingDIVpin, theLTC1799

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.

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.

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.

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.

W

BLOCK DIAGRA

V

= 1.13V ±25%

RES

+

PROGRAMMABLE

OUT

(V – V

)

V

SET

1

5

DIVIDER

(÷1, 10 OR 100)

+

R

SET

V

GAIN = 1

MASTER OSCILLATOR

I

RES

SET

DIVIDER

SELECT

5µA

3

2

–

I

RES

ƒ

MO

= 100MHz • kΩ •

+

(V – V

)

V

SET

BIAS

–

DIV

THREE-STATE

INPUT DETECT

GND

4

I

RES

5µA

GND

1799 BD

5

LTC1799

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THEORY OF OPERATIO

As shown in the Block Diagram, the LTC1799’s master

oscillator is controlled by the ratio of the voltage between

the V⁺and SET pins and the current entering the SET pin

(I_RES). The voltage on the SET pin is forced to approxi-

mately1.13VbelowV⁺bythePMOStransistoranditsgate

biasvoltage.Thisvoltageisaccurateto±7%ataparticular

input current and supply voltage (see Figure 1). The

effective input resistance is approximately 2k.

OUT(Pin5). Thedivide-byvalueisdeterminedbythestate

of the DIV input (Pin 4). Tie DIV to GND or drive it below

0.5V to select÷1. This is the highest frequency range, with

the master output frequency passed directly to OUT. The

DIV pin may be floated or driven to midsupply to select

÷10, the intermediate frequency range. The lowest fre-

quency range, ÷100, is selected by tying DIV to V⁺or

driving it to within 0.4V of V⁺. Figure 2 shows the relation-

ship between R_SET, divider setting and output frequency,

including the overlapping frequency ranges near 100kHz

and 1MHz.

A resistor R_SET, connected between the V⁺and SET pins,

“locks together” the voltage (V⁺– V_SET) and current, I_RES

,

variation.ThisprovidestheLTC1799’shighprecision.The

master oscillation frequency reduces to:

The CMOS output driver has an on resistance that is

typicallylessthan100Ω. Inthe ÷1(highfrequency)mode,

theriseandfalltimesaretypically7nswitha5Vsupplyand

11ns with a 3V supply. These times maintain a clean

square wave at 10MHz (20MHz at 5V supply). In the ÷10

and ÷100 modes, where the output frequency is much

lower, slew rate control circuitry in the output driver

increases the rise/fall times to typically 14ns for a 5V

supply and 19ns for a 3V supply. The reduced slew rate

lowers EMI (electromagnetic interference) and supply

bounce.

10kΩ

ƒ_MO= 10MHz •

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_SET= 5k) are attainable if the supply

voltage is greater than 4V.

To extend the output frequency range, the master oscilla-

tor signal may be divided by 1, 10 or 100 before driving

1000

1.4

T

= 25°C

A

1.3

1.2

1.1

1.0

0.9

0.8

+

V

= 5V

MOST

ACCURATE

OPERATION

÷100

÷10

÷1

100

10

1

+

V

= 3V

1

10

100

1000

1k

10k

100k

1M

10M

100M

I

(µA)

DESIRED OUTPUT FREQUENCY (Hz)

RES

1799 F02

1799 F01

Figure 1. V⁺– V_SETVariation with I_RES

Figure 2. R_SETvs Desired Output Frequency

6

LTC1799

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APPLICATIO S I FOR ATIO

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ALTERNATIVE METHODS OF SETTING THE OUTPUT

FREQUENCY OF THE LTC1799

SELECTING THE DIVIDER SETTING AND RESISTOR

The LTC1799’s master oscillator has a frequency range

spanning 0.1MHz to 33MHz. However, accuracy may

suffer if the master oscillator is operated at greater than

10MHz with a supply voltage lower than 4V. A program-

mable divider extends the frequency range to greater than

three decades. Table 1 describes the recommended fre-

quencies for each divider setting. Note that the ranges

overlap;atsomefrequenciestherearetwodivider/resistor

combinations that result in the desired frequency.

The oscillator may be programmed by any method that

sources a current into the SET pin (Pin 3). The circuit in

Figure 3 sets the oscillator frequency using a program-

mable current source and in the expression for f_OSC, the

resistorR_SETisreplacedbytheratioof1.13V/I_CONTROL.As

already explained in the “Theory of Operation,” the voltage

difference between V⁺and SET is approximately 1.13V,

therefore, the Figure 3 circuit is less accurate than if a

resistor controls the oscillator frequency.

In general, any given oscillator frequency (f_OSC) should be

obtained using the lowest master oscillator frequency.

Lower master oscillator frequencies use less power and

are more accurate. For instance, f_OSC= 100kHz can be

obtained by either R_SET= 10k, N = 100, master oscillator

=10MHzorR_SET=100k, N=10, masteroscillator=1MHz.

The R_SET= 100k is preferred for lower power and better

accuracy.

Figure 4 shows the LTC1799 configured as a VCO. A

voltage source is connected in series with an external 10k

resistor. The output frequency, f_OSC, will vary with

V_CONTROL, that is the voltage source connected between

V⁺and the SET pin. Again, this circuit decouples the

relationship between the input current and the voltage

between V⁺and SET; the frequency accuracy will be

degraded. The oscillator frequency, however, will mono-

Table 1. Frequency Range vs Divider Setting

tonically increase with decreasing V_CONTROL

.

DIVIDER SETTING

FREQUENCY RANGE

*

÷1

DIV (Pin 4) = GND

>500kHz

400kHz TO 21MHz

(APPROXIMATE, SEE TEXT)

÷10

DIV (Pin 4) = Floating

50kHz to 1MHz

< 100kHz

+

V

1

2

3

5

+

÷100

*

DIV (Pin 4) = V

V

OUT

LTC1799

0.1µF

I

At master oscillator frequencies greater than 10MHz (R < 10kΩ), the

LTC1799 may suffer reduced accuracy with a supply voltage less than 4V.

CONTROL

SET

GND

SET

5µA TO 200µA

4

N = 1

DIV

After choosing the proper divider setting, determine the

correct frequency-setting resistor. Because of the linear

correspondence between oscillation period and resis-

tance,asimpleequationrelatesresistancewithfrequency.

1799 F03

10MHz 10kΩ

ƒ

OSC

•

• I

CONTROL

N

1.13V

I

EXPRESSED IN (A)

CONTROL

Figure 3. Current Controlled Oscillator

100

10MHz

N • f_OSC

R_SET= 10k •

, N = 10

1

+

V

1

2

3

5

4

+

V

OUT

LTC1799

0.1µF

(R_SETMIN= 3k (5V Supply), 5k (3V Supply),

R_SETMAX= 1M)

V

CONTROL

+

GND

SET

–

0V TO 1.13V

R

SET

10k

N = 1

DIV

Any resistor, R_SET, tolerance adds to the inaccuracy of the

1799 F04

oscillator, f_OSC

.

V

10MHz 10k

N

CONTROL

1.13V

ƒ

OSC

•

• 1–

(

)

R

SET

Figure 4. Voltage Controlled Oscillator

7

LTC1799

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APPLICATIO S I FOR ATIO

POWER SUPPLY REJECTION

START-UP TIME

Thestart-uptimeandsettlingtimetowithin1%ofthefinal

value can be estimated by t_STARTR_SET(2.8µs/kΩ) +

20µs. Note the start-up time depends on R_SETand it is

independent from the setting of the divider pin. For in-

stance with R_SET= 50k, the LTC1799 will settle with 1% of

its 200kHz final value (N = 10) in approximately 160µs.

Figure 6 shows start-up times for various R_SETresistors.

Low Frequency Supply Rejection (Voltage Coefficient)

Figure 5 shows the output frequency sensitivity to power

supply voltage at several different temperatures. The

LTC1799 has a conservative guaranteed voltage coeffi-

cient of 0.1%/V but, as Figure 5 shows, the typical supply

sensitivity is lower.

Figure 7 shows an application where a second set resistor

R_SET2is connected in parallel with set resistor R_SET1via

switch S1. When switch S1 is open, the output frequency

0.15

R

= 31.6k

SET

PIN 4 = FLOATING (÷10)

0.10

0.05

0

oftheLTC1799dependsonthevalueoftheresistorR_SET1

.

25°C

When switch S1 is closed, the output frequency of the

LTC1799 depends on the value of the parallel combination

–40°C

85°C

of R_SET1and R_SET2

.

The start-up time and settling time of the LTC1799 with

switch S1 open (or closed) is described by t_STARTshown

above.OncetheLTC1799startsandsettles,andswitchS1

closes(oropens),theLTC1799willsettletoitsnewoutput

frequency within approximately 25µs.

–0.05

2.5

3.0

3.5

4.0

4.5

5.0

5.5

SUPPLY VOLTAGE (V)

1799 F05

60

Figure 5. Supply Sensitivity

T

= 25°C

= 5V

A

+

V

50

40

30

20

10

0

High Frequency Power Supply Rejection

The accuracy of the LTC1799 may be affected when its

power supply generates significant noise with frequency

contents in the vicinity of the programmed value of f_OSC

If a switching power supply is used to power up the

LTC1799,andiftherippleofthepowersupplyismorethan

afewtensofmillivolts, makesuretheswitchingfrequency

and its harmonics are not related to the output frequency

of the LTC1799. Otherwise, the oscillator may show an

additional 0.1% to 0.2% of frequency error.

.

200k

200

10k

31.6k

–10

400

600

0

100

300

500

TIME AFTER POWER APPLIED (µs)

1799 F06

Figure 6. Start-Up Time

IftheLTC1799ispoweredbyaswitchingregulatorandthe

switching frequency or its harmonics coincide with the

outputfrequencyoftheLTC1799, thejitteroftheoscillator

output may be affected. This phenomenon will become

noticeable if the switching regulator exhibits ripples be-

yond 30mV.

3V OR 5V

10k

N • R

1

5

+

f

= 10MHz •

OSC

V

OUT

(

)

SET1

OR

LTC1799

S1

2

3

+

10k

V

R

SET1

GND

SET

f

OSC

)

N • R

//R

SET1 SET2

÷100

÷1

R

SET2

4

÷10

DIV

1799 F07

Figure 7

8

LTC1799

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APPLICATIO S I FOR ATIO

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Jitter

(Pin 3) is limited to less than 10pF, as suggested in the Pin

Functions description. If this requirement is not met, the

jitter will increase. For more information, contact Linear

Technology Applications group.

The typical jitter is listed in the Electrical Characteristics

and shown in the Typical Performance Characteristics.

These specifications assume that the capacitance on SET

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TYPICAL APPLICATIO S

Low Power 80Hz to 8kHz Sine Wave Generator (I_Q< 4mA)

3V

f

OSC

1

2

5

+

V

OUT

3V

LTC1799

C1

R

SET

3V, N = 100

0.1µF

GND

SET

LTC1067-50

3V

SW1

4

OPEN, N = 10

3

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

C4

1µF

C3

+

DIV

V

CLK

0.1µF

74HC4520

CLOCK A

NC

AGND

R62 14k

÷2

÷4

1

2

3

+

–

R61

10k

Q1A

Q2A

Q3A

Q4A

Q1B

Q2B

Q3B

Q4B

V

3V

4

R52

5.11k

ENABLE A

SA

SB

LPB

BPB

R51 5.11k

R31 51.1k

÷8

16

10

7

5

SINEWAVE

OUT

V

LPA

BPA

DD

R32 51.1k

÷16

÷32

÷64

÷128

÷256

6

C2

0.1µF

ENABLE B

RESET A

10MHz

•

10k

64R

f

=

SINE

11

12

13

14

R11

N

SET

HPA/NA HPB/NB

INV A INV B

100k

R21 20k

R22 20k

8

V

SS

800Hz ≤ f

≤ 8kHz, N = 10

SINE

≤ 800Hz, N = 100

9

80Hz ≤ f

CLOCK B

RESET B

SINE

R

249k

H1

15

f

OSC

64

R

L1

51.1k

1799 TA05

CLOCK-TUNABLE LOWPASS FILTER WITH

A STOPBAND NOTCH AT THE 3rd HARMONIC

f

OSC

64

• 3

(

)

9

LTC1799

U

TYPICAL APPLICATIO S

3V Digitally Controlled Oscillator with 5kHz to 85kHz Range (N = 100, Pin 4 = V⁺)

3V

LTC1659

C3

0.1µF

1

2

3

4

8

7

6

5

CLK

V

CC

CLK

3V

D

IN

V

OUT

D

IN

CS/LD

REF

CS/LD

C2

0.1µF

D

OUT

GND

R5

10k

4

3

2

+

1

R6

10k

1/4 LT1491

3V

–

R1

11

10k

10

9

+

5kHz TO 85kHz

OUT

R8

8

R2

10k

1/4 LT1491

1

2

3

5

4

–

+

3V

R

V

OUT

S

R7

10k

C1

R4

10k

LTC1799

0.1µF

C

4096

f

= 100kHz •

OSC

GND

SET

5

6

R3

10k

+

–

3V

1799 TA06

DIV

7

1/4 LT1491

+

(V – V

)

C

4096

SET

I =

•

C: DAC CODE 200 ≤ C ≤ 3480

10k

NOTES:

1. FOR N = 10 (PIN 4 OPEN) THE RANGE IS 50kHz TO 850kHz

2. FOR N = 1 (PIN 4 = GND) THE RANGE IS 500kHz TO 8.5MHz

3. DRIVING PIN 4 OF THE LTC1799 WITH A 3-STATE LOGIC DEVICE

GIVES A RANGE OF 5kHz TO 8.5MHz

Input Code vs Output Frequency

(N = 100, Pin 4 = V⁺)

100

75

50

25

0

1024

2048

3072

4096

DAC CODE

1799 TA07

10

LTC1799

U

PACKAGE DESCRIPTIO

S5 Package

5-Lead Plastic SOT-23

(Reference LTC DWG # 05-08-1633)

(Reference LTC DWG # 05-08-1635)

2.80 – 3.10

(.110 – .118)

(NOTE 3)

SOT-23

(Original)

SOT-23

(ThinSOT)

.90 – 1.45

1.00 MAX

A

A1

A2

L

(.035 – .057)

(.039 MAX)

.00 – .15

(.00 – .006)

.01 – .10

(.0004 – .004)

2.60 – 3.00

1.50 – 1.75

(.102 – .118) (.059 – .069)

(NOTE 3)

.90 – 1.30

(.035 – .051)

.80 – .90

(.031 – .035)

.35 – .55

(.014 – .021)

.30 – .50 REF

(.012 – .019 REF)

PIN ONE

.95

(.037)

REF

.25 – .50

(.010 – .020)

(5PLCS, NOTE 2)

.20

(.008)

A2

A

DATUM ‘A’

1.90

(.074)

REF

L

.09 – .20

(.004 – .008)

(NOTE 2)

A1

S5 SOT-23 0401

NOTE:

1. CONTROLLING DIMENSION: MILLIMETERS

MILLIMETERS

2. DIMENSIONS ARE IN

(INCHES)

3. DRAWING NOT TO SCALE

4. DIMENSIONS ARE INCLUSIVE OF PLATING

5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR

6. MOLD FLASH SHALL NOT EXCEED .254mm

7. PACKAGE EIAJ REFERENCE IS:

SC-74A (EIAJ) FOR ORIGINAL

JEDEL MO-193 FOR THIN

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.

11

LTC1799

U

TYPICAL APPLICATIO S

Shutting Down the LTC1799

5V

74AC04

1

+

5

4

ON/SHDN

OUT

V

OUT

C1

0.1µF

LTC1799

R1

10k

2

3

GND

SET

DIV

1799 TA08

Temperature-to-Frequency Converter

Output Frequency vs Temperature

1400

1200

1000

800

600

400

200

0

MAX

TYP

MIN

5V

1

2

3

5

10MHz 10k

+

f

=

V

OUT

•

OSC

10

R

T

C1

0.1µF

LTC1799

R

T

100k

GND

SET

THERMISTOR

4

DIV

1799 TA03

R : YSI 44011 800 765-4974

T

–20 –10

0

10 20 30 40 50 60 70 80 90

TEMPERATURE (°C)

1799 TA04

1799f LT/TP 0801 2K • PRINTED IN USA

12 ^{LinearTechnology Corporation}

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

(408) 432-1900 FAX: (408) 434-0507 www.linear.com

LINEAR TECHNOLOGY CORPORATION 2001


型号：	LTC1799CS5
厂家：	Linear Systems
描述：	可编程晶振芯片
文件：	总12页 (文件大小：235K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTC1799CS5 [Linear Systems]

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