Datasheet LTC1799CS5, LTC1799IS5 Datasheet (Linear Technology)

Download

Page 1

FEATURES

UNITS (%)

0 –1.25 –0.75 –0.25 0 0.25 0.75 1.25

FREQUENCY ERROR (%)

1799 TA02

■

One External Resistor Sets the Frequency

■

Fast Start-Up Time: <1ms

■

1kHz to 33MHz Frequency Range

■

Low Profile (1mm) ThinSOTTM Package

■

Frequency Error ≤1.5% 5kHz to 20MHz (TA = 25°C)

■

Frequency Error ≤2% 5kHz to 20MHz (TA = 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

APPLICATIO S

■

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.

ThinSOT is a trademark of Linear Technology Corporation.

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

). The LTC1799 has been designed for high accuracy

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 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

and frequency, eliminating the need for tables to

SET

calculate frequency. The oscillator can be easily programmed using the simple formula outlined below:

= = =



fMHz

=•

OSC





•

100

DIV Pin V

 

N Open

DIV Pin

 

DIV Pin GND



SET

 



TYPICAL APPLICATIO

3k ≤ R

SET

≤ 1M

0.1µF

SOT-23 Actual Size

Basic Connection

OUT

LTC1799

GND

SET

DIV

1799 TA01

1kHz ≤ f

÷100

OSC

÷1

≤ 33MHz

÷10

OPEN

Typical Distribution of Frequency Error,

TA = 25°C (5kHz ≤ f

≤ 20MHz, V+ = 5V)

OSC

Page 2

LTC1799

TOP VIEW

S5 PACKAGE

5-LEAD PLASTIC SOT-23

1 2 3

GND

SET

54OUT

DIV

PACKAGE/ORDER I FOR ATIO

WWWU

ABSOLUTE AXI U RATI GS

(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

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

ORDER PART NUMBER

LTC1799CS5 LTC1799IS5

S5 PART MARKING

= 125°C, θJA = 256°C/W

JMAX

Consult LTC Marketing for parts specified with wider operating temperature ranges.

LTND LTNE

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. V+ = 2.7V to 5.5V, RL=5k, CL = 5pF, unless otherwise noted. All voltages are with respect to GND.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

∆f Frequency Accuracy V+ = 5V 5kHz ≤ f ≤ 20MHz ±0.5 ±1.5 %

(Notes 2, 3) 1kHz ≤ f ≤ 5kHz ±2.5 %

SET

MAX

MIN

∆f/∆T Freq Drift Over Temp (Note 3) R ∆f/∆V Freq Drift Over Supply (Note 3) V+ = 3V to 5V, R

V I

DIV

Frequency-Setting Resistor Range ∆f < 1.5% V+ = 5V 5 200 kΩ

Maximum Frequency ∆f < 2.5%, Pin 4= 0V V+ = 5V 33 MHz

Minimum Frequency ∆f < 2.5%, Pin 4= V

Timing Jitter Pin 4 = V (Note 4) Pin 4 = Open 0.13 %

Long-Term Stability of Output Frequency 300 ppm/√kHr Duty Cycle (Note 7) Pin 4 = V+ or Open (DIV Either by 100 or 10) ● 49 50 51 %

Operating Supply Range ● 2.7 5.5 V Power Supply Current R

High Level DIV Input Voltage ● V+ – 0.4 V Low Level DIV Input Voltage ● 0.5 V DIV Input Current (Note 5) Pin 4 = V

The ● denotes the specifications which apply over the full operating

5kHz ≤ f ≤ 20MHz, LTC1799C 5kHz ≤ f ≤ 20MHz, LTC1799I

20MHz ≤ f ≤ 33MHz ±2.5 %

V+ = 3V 5kHz ≤ f ≤ 10MHz ±0.5 ±1.5 %

5kHz ≤ f ≤ 10MHz, LTC1799C 5kHz ≤ f ≤ 10MHz, LTC1799I 1kHz ≤ f ≤ 5kHz ±2.5 % 10MHz ≤ f ≤ 20MHz ±2.5 %

= 3V 10 200 kΩ

= 3V 20 MHz

= 31.6k ● ±0.004 %/°C

SET

= 31.6k ● 0.05 0.1 %/V

SET

Pin 4 = 0V 0.4 %

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

= 200k, Pin 4 = V+, RL = ∞ V+ = 5V ● 0.7 1.1 mA

SET

= 10k, Pin 4 = 0V, RL = ∞ V+ = 5V ● 2.4 mA

SET

Pin 4 = 0V V

= 5k to 200k ● 45 50 55 %

SET

= 3V ● 2mA

V+ = 5V ● 5 8 µA

= 5V ● –8 –5 µA

● ±2%

● ±2.5 %

● ±2%

● ±2.5 %

1 kHz

0.06 %

Page 3

LTC1799

ELECTRICAL CHARACTERISTICS

The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V+ = 2.7V to 5.5V, RL=5k, CL = 5pF, Pin 4 = V+ unless otherwise noted. All voltages are with respect to GND.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

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 section). For these frequencies, the error is specified under the following assumption: 10k < R is guaranteed by design and test correlation.

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

OSC

High Level Output Voltage (Note 5) V+ = 5V IOH = –1mA ● 4.8 4.95 V

= –4mA ● 4.5 4.8 V

V+ = 3V IOH = –1mA ● 2.7 2.9 V

= –4mA ● 2.2 2.6 V

Low Level Output Voltage (Note 5) V+ = 5V IOL = 1mA ● 0.05 0.15 V

= 4mA ● 0.2 0.4 V

V+ = 3V IOL = 1mA ● 0.1 0.3 V

= 4mA ● 0.4 0.7 V

OUT Rise Time V+ = 5V Pin 4 = V+ or Floating, RL = ∞ 14 ns (Note 6) Pin 4 = 0V, R

V+ = 3V Pin 4 = V+ or Floating, RL = ∞ 19 ns

Pin 4 = 0V, R

OUT Fall Time V+ = 5V Pin 4 = V+ or Floating, RL = ∞ 13 ns (Note 6) Pin 4 = 0V, R

V+ = 3V Pin 4 = V+ or Floating, RL = ∞ 19 ns

Pin 4 = 0V, R

(see the Table 1 in the Applications Information

SET

equation.

≤ 100k. The frequency accuracy for f

SET

= 20MHz

OSC

= ∞ 7ns

= ∞ 11 ns

= ∞ 6ns

= ∞ 10 ns

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.

Page 4

LTC1799

TYPICAL PERFOR A CE CHARACTERISTICS

Frequency Variation vs R

SET

TA = 25°C

GUARANTEED LIMITS APPLY

OVER 5k TO 200k RANGE

–1

VARIATION (%)

–2

–3

–4

1 10 100 1000

TYPICAL

HIGH

TYPICAL

LOW

(kΩ)

SET

Peak-to-Peak Jitter vs Frequency

0.7

0.6

0.5

0.4

0.3

JITTER (%)

0.2

0.1

1k 100k 1M 10M

÷10

÷100

10k OUTPUT FREQUENCY, f

÷1

OUT

(Hz)

1799 G01

100M

1799 G03

Frequency Variation Over Temperature

1.00 R

= 31.6k

SET

÷1 OR ÷10 OR ÷100

0.75

0.50

0.25

–0.25

VARIATION (%)

–0.50

–0.75

–1.00

–40

TYPICAL

HIGH

TYPICAL

LOW

–20 0

TEMPERATURE (°C)

40 80

20 60

Supply Current vs Output Frequency

4.5 TA = 25°C

= 5pF

4.0

= 1M

3.5

3.0

2.5

2.0

1.5

SUPPLY CURRENT (mA)

1.0

0.5

÷100 (5V)

÷100 (3V)

1k 100k 1M 100M

÷10 (3V)

10k OUTPUT FREQUENCY, f

÷1 (5V)

÷10 (5V)

÷1 (3V)

OUT

1799 G02

10M

(Hz)

1799 G04

Output Resistance vs Supply Voltage

140

120

100

OUTPUT RESISTANCE (Ω)

OUTPUT SINKING CURRENT

2.5 3.0

= 25°C

OUTPUT SOURCING CURRENT

4.5

4.0

3.5 SUPPLY VOLTAGE (V)

5.0

5.5

1799 G05

6.0

LTC1799 Output Operating at 20MHz, VS = 5V

V+ = 5V, R

1V/DIV

= 5k, CL = 10pF V+ = 3V, R

SET

12.5ns/DIV

1799 G06

LTC1799 Output Operating at 10MHz, VS = 3V

= 10k, CL = 10pF

SET

1V/DIV

25ns/DIV

1799 G07

Page 5

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+ determines 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

SET

RES

SET

BIAS

–

GND

–

RES

GAIN = 1

= 1.13V ±25%

RES

– V

SET

)

MASTER OSCILLATOR

= 100MHz • kΩ •

(V+ – V

PROGRAMMABLE

DIVIDER

(÷1, 10 OR 100)

RES

)

SET

DIVIDER

SELECT

THREE-STATE

INPUT DETECT

GND

OUT

DIV

5µA

1799 BD

Page 6

LTC1799

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

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

RES

mately 1.13V below V+ by the PMOS transistor and its gate bias voltage. This voltage is accurate to ±7% at a particular input current and supply voltage (see Figure 1). The effective input resistance is approximately 2k.

A resistor R “locks together” the voltage (V+ – V

, connected between the V+ and SET pins,

SET

) and current, I

SET

RES

, variation. This provides the LTC1799’s high precision. The master oscillation frequency reduces to:

ƒ=

MHz



•





SET

Ω

 



The LTC1799 is optimized for use with resistors between 10k and 200k, corresponding to master oscillator frequencies between 0.5MHz and 10MHz. Accurate frequencies up to 20MHz (R

= 5k) are attainable if the supply

SET

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

OUT (Pin 5). The divide-by value is determined by the state 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 frequency range, ÷100, is selected by tying DIV to V+ or driving it to within 0.4V of V+. Figure 2 shows the relationship between R

, divider setting and output frequency,

SET

including the overlapping frequency ranges near 100kHz and 1MHz.

The CMOS output driver has an on resistance that is typically less than 100Ω. In the ÷1 (high frequency) mode, the rise and fall times are typically 7ns with a 5V supply and 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.

1.4

1.3

1.2

SET

– V

1.1

= V

RES

1.0

0.9

0.8 1

Figure 1. V+ – V

TA = 25°C

V+ = 5V

V+ = 3V

10 100 1000

(µA)

RES

Variation with I

SET

1799 F01

RES

1000

100

(kΩ)

SET

1k 100k 1M 10M

Figure 2. R

÷100 ÷10 ÷1

10k

DESIRED OUTPUT FREQUENCY (Hz)

vs Desired Output Frequency

SET

MOST

ACCURATE

OPERATION

100M

1799 F02

Page 7

WUUU

APPLICATIO S I FOR ATIO

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 programmable divider extends the frequency range to greater than three decades. Table 1 describes the recommended frequencies for each divider setting. Note that the ranges overlap; at some frequencies there are two divider/resistor combinations that result in the desired frequency.

In general, any given oscillator frequency (f

) should be

OSC

obtained using the lowest master oscillator frequency. Lower master oscillator frequencies use less power and are more accurate. For instance, f obtained by either R = 10MHz or R The R

= 100k is preferred for lower power and better

SET

= 100k, N = 10, master oscillator = 1MHz.

SET

= 10k, N = 100, master oscillator

SET

= 100kHz can be

OSC

accuracy.

Table 1. Frequency Range vs Divider Setting

DIVIDER SETTING FREQUENCY RANGE

< 100kHz

< 10kΩ), the

SET

÷1 ⇒ DIV (Pin 4) = GND >500kHz ÷10 ⇒ DIV (Pin 4) = Floating 50kHz to 1MHz ÷100 ⇒ DIV (Pin 4) = V

At 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 resistance, a simple equation relates resistance with frequency.

ALTERNATIVE METHODS OF SETTING THE OUTPUT FREQUENCY OF THE LTC1799

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 programmable current source and in the expression for f resistor R

is replaced by the ratio of 1.13V/I

SET

CONTROL

OSC

, the

. 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.

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 V

CONTROL

, that is the voltage source connected between

, will vary with

OSC

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 monotonically increase with decreasing V

CONTROL

5µA TO 200µA

0.1µF

≅

OSC

CONTROL

OUT

LTC1799

GND

SET

1799 F03

10MHz

10kΩ

••I

1.13V

EXPRESSED IN (A)

CONTROL

400kHz TO 21MHz

(APPROXIMATE, SEE TEXT)

N = 1

DIV

CONTROL

SET

SETMIN

SETMAX

Any resistor, R oscillator, f

•

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

= 1M)

SET

OSC

100







MHz

•

OSC



, N =















, tolerance adds to the inaccuracy of the

CONTROL

0V TO 1.13V

Figure 3. Current Controlled Oscillator

0.1µF

+ –

SET

10k

LTC1799

GND

SET

10MHz

≅

OSC

• • 1 –

OUT

N = 1

DIV

1799 F04

10k

CONTROL

()

SET

1.13V

Figure 4. Voltage Controlled Oscillator

Page 8

LTC1799

WUUU

APPLICATIO S I FOR ATIO

POWER SUPPLY REJECTION

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 coefficient of 0.1%/V but, as Figure 5 shows, the typical supply sensitivity is lower.

0.15 R

= 31.6k

SET

PIN 4 = FLOATING (÷10)

0.10

25°C

0.05

FREQUENCY DEVIATION (%)

–0.05

2.5

3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V)

–40°C

85°C

5.0 5.5

1799 F05

START-UP TIME

The start-up time and settling time to within 1% of the final value can be estimated by t 20µs. Note the start-up time depends on R

START

≅ R

(2.8µs/kΩ) +

SET

and it is

SET

independent from the setting of the divider pin. For instance with R

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

SET

its 200kHz final value (N = 10) in approximately 160µs. Figure 6 shows start-up times for various R

resistors.

SET

Figure 7 shows an application where a second set resistor R

is connected in parallel with set resistor R

SET2

SET1

via switch S1. When switch S1 is open, the output frequency of the LTC1799 depends on the value of the resistor R

SET1

. When switch S1 is closed, the output frequency of the LTC1799 depends on the value of the parallel combination of R

SET1

and R

SET2

The start-up time and settling time of the LTC1799 with switch S1 open (or closed) is described by t

START

shown above. Once the LTC1799 starts and settles, and switch S1 closes (or opens), the LTC1799 will settle to its new output frequency within approximately 25µs.

Figure 5. Supply Sensitivity

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, 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. Otherwise, the oscillator may show an additional 0.1% to 0.2% of frequency error.

If the LTC1799 is powered by a switching regulator and the switching frequency or its harmonics coincide with the output frequency of the LTC1799, the jitter of the oscillator output may be affected. This phenomenon will become noticeable if the switching regulator exhibits ripples beyond 30mV.

FREQUENCY ERROR (%)

3V OR 5V

SET1

SET2

–10

200k

10k

31.6k

100 200

TIME AFTER POWER APPLIED (µs)

Figure 6. Start-Up Time

OUT

LTC1799

GND

SET

DIV

400 600

300 500

÷100

÷10

÷1

1799 F07

TA = 25°C V

OSC

OR f

OSC

= 5V

1799 F06

= 10MHz •

10k

()

N • R

SET1

10k

()

N • R

//R

SET1

SET2

Figure 7

Page 9

WUUU

APPLICATIO S I FOR ATIO

LTC1799

Jitter

The typical jitter is listed in the Electrical Characteristics and shown in the Typical Performance Characteristics. These specifications assume that the capacitance on SET

TYPICAL APPLICATIO S

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

0.1µF

SET

LTC1799

GND

SET

800Hz ≤ f 80Hz ≤ f

OUT

SW1

DIV

0.1µF

≤ 8kHz, N = 10

SINE

≤ 800Hz, N = 100

SINE

OPEN, N = 10

3V, N = 100

OSC

1µF

÷2 ÷4

÷8 ÷16 ÷32 ÷64

÷128 ÷256

2 16 10

9 15

74HC4520

CLOCK A ENABLE A V

ENABLE B RESET A V

CLOCK B RESET B

Q1A Q2A Q3A Q4A Q1B Q2B Q3B Q4B

3 4 5 6 11 12 13 14

(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.

1 2 3 4 5 6 7 8

V NC V SA LPA BPA HPA/NA INV A

LTC1067-50

249k

51.1k

CLK

AGND

LPB BPB

HPB/NB

INV B

16 15

R62 14k

–

12 11 10 9

R32 51.1k

R22 20k

R52

5.11k SINEWAVE

OUT

SINE

1799 TA05

10MHz

= •

64R

100k

OSC

R11

R61 10k

0.1µF

R51 5.11k

R31 51.1k

R21 20k

10k

SET

CLOCK-TUNABLE LOWPASS FILTER WITH

A STOPBAND NOTCH AT THE 3rd HARMONIC

OSC

• 3

()

Page 10

LTC1799

TYPICAL APPLICATIO S

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

CLK

CS/LD

LTC1659

CLK

10k

CS/LD

OUT

R3 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

OUT

REF

GND

1/4 LT1491

–

10k

8 7 6 5

0.1µF

R5 10k

R6 10k

R7 10k

10k

1/4 LT1491

–

1/4 LT1491

0.1µF

5kHz TO 85kHz

10k

–

I =

(V+ – V

10k

SET

0.1µF

)

• 4096

LTC1799

GND

SET

C: DAC CODE 200 ≤ C ≤ 3480

OUT

DIV

OSC

1799 TA06

OUT

= 100kHz •

4096

Input Code vs Output Frequency

(N = 100, Pin 4 = V+)

100

(kHz)

OUT

0 1024 2048 3072 4096

DAC CODE

1799 TA07

Page 11

PACKAGE DESCRIPTIO

LTC1799

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)

.90 – 1.45

(.035 – .057)

.00 – .15

(.00 – .006)

.90 – 1.30

(.035 – .051)

.35 – .55

(.014 – .021)

.20

(.008)

DATUM ‘A’

NOTE:

1. CONTROLLING DIMENSION: MILLIMETERS

2. DIMENSIONS ARE IN

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

SOT-23

(ThinSOT)

1.00 MAX

(.039 MAX)

.01 – .10

(.0004 – .004)

.80 – .90

(.031 – .035) .30 – .50 REF

(.012 – .019 REF)

MILLIMETERS

(INCHES)

2.60 – 3.00

(.102 – .118)

.09 – .20

(.004 – .008)

(NOTE 2)

1.50 – 1.75

(.059 – .069)

(NOTE 3)

PIN ONE

.95

(.037)

REF

1.90

(.074)

REF

.25 – .50

(.010 – .020)

(5PLCS, NOTE 2)

S5 SOT-23 0401

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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Page 12

LTC1799

1799 TA04

1400

1200

1000

800

600

400

200

–20–100 102030405060708090

TEMPERATURE (°C)

FREQUENCY (kHz)

MAX TYP MIN

TYPICAL APPLICATIO S

ON/SHDN

Shutting Down the LTC1799

74AC04

10k

0.1µF

LTC1799

GND

SET

OUT

DIV

1799 TA08

OUT

100k

THERMISTOR

Temperature-to-Frequency Converter

0.1µF

: YSI 44011 800 765-4974

LTC1799

GND

SET

OUT

DIV

1799 TA03

OSC

10MHz

Output Frequency vs Temperature

10k

• R

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507

●

www.linear.com

1799f LT/TP 0801 2K • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2001