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Final Electrical Specifications
LTC1799 1kHz to 30MHz Resistor Set SOT-23 Oscillator
FEATURES
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DESCRIPTIO
January 2001
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One External Resistor Sets the Frequency 1kHz to 30MHz Frequency Range SOT-23 Miniature Package Frequency Error 1.5% 5kHz to 20MHz (TA = 25C) Frequency Error 2% 5kHz to 20MHz (TA = 0C to 70C) 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 100 CMOS Output Driver Operates from a Single 2.7V to 5.5V Supply
The LTC(R)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 (RSET). 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 3.32k to 1M to select a master oscillator frequency between 100kHz and 30MHz (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 30MHz (5V supply). The LTC1799 features a proprietary feedback loop that linearizes the relationship between RSET and frequency, eliminating the need for tables to calculate frequency. The oscillator can be easily programmed using the simple formula outlined below:
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
fOSC
100, DIV PIN = V + 10k = 10MHz * , N = 10, DIV PIN = Hi - Z N * RSET 1 DIV PIN = GND ,
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Basic Connection
V+ 0.1F 5k RSET 200k 1 2 3 V+ OUT LTC1799 GND SET DIV
1799 TA01
Typical Distribution of Frequency Error, TA = 25C
25
5kHz fOSC 20MHz 5 V+ 4 /100 /10 GND /10 UNITS (%)
20
15
Hi-Z
10
5
SOT-23 Actual Size
0 -1.25
-0.75 -0.25 0 0.25 0.75 FREQUENCY ERROR (%)
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.
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1.25
1799 TA02
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LTC1799
ABSOLUTE
(Note 1)
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PACKAGE/ORDER I FOR ATIO
TOP VIEW V+ 1 5 OUT GND 2 SET 3 4 DIV
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) OUT to GND ................................... - 0.3V to (V + + 0.3V) Operating Temperature Range LTC1799C ............................................... 0C to 70C LTC1799I ............................................ - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC1799CS5 LTC1799IS5 S5 PART MARKING LTND LTNE
S5 PACKAGE 5-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 256C/W
Consult factory for parts specified with wider operating temperature ranges.
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V+ = 2.7V to 5.5V, RL=5k, CL = 5pF, Pin 4 = V+ unless otherwise noted. All voltages are with respect to GND.
SYMBOL f PARAMETER Frequency Accuracy CONDITIONS V+ = 5V 5kHz < f < 20MHz 5kHz < f < 20MHz, LTC1799C 5kHz < f < 20MHz, LTC1799I 1kHz < f < 5kHz 20MHz < f < 30MHz 5kHz < f < 10MHz 5kHz < f < 10MHz, LTC1799C 5kHz < f < 10MHz, LTC1799I 1kHz < f < 5kHz 10MHz < f < 20MHz V + = 5V V + = 3V V + = 5V V + = 3V
q q q q
ELECTRICAL CHARACTERISTICS
MIN
TYP 0.5 2.5 2.5 0.5
MAX 1.5 2 2.5
UNITS % % % % % % % % % % k k MHz MHz kHz %/C
(Notes 2, 3) V+ = 3V
q q
2.5 2.5 5 10 30 20 1 0.004 0.05 0.06 0.13 0.4 300
q q q
1.5 2 2.5
RSET fMAX fMIN 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
f < 1.5% f < 2.5%, Pin 4= 0V f < 2.5%, Pin 4= V +
200 200
RSET = 31.6k V+ = 2.7V to 5.5V, RSET = 31.6k Pin 4 = V + Pin 4 = Floating Pin 4 = 0V or Floating (DIV Either by 100 or 10) Pin 4 = 0V (DIV by 1) RSET = 200k, Pin 4 = V +, RL =0 V+ V+ = 5V Pin 4 = V +
0.1
ppm/kHr 51 55 5.5 1.1 2.4 2 0.5 % % V mA mA mA V V A A
49 45 2.7
50 50 0.7
V+ IS
Operating Supply Range Power Supply Current RSET = 10k, Pin 4 = 0V, No Load = 5V V + = 3V
q q q q V+ - 0.4 q
VIH VIL IDIV
High Level DIV Input Voltage Low Level DIV Input Voltage DIV Input Current Pin 4 = V + Pin 4 = 0V
q q
5 -5
8 8
2
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%/V % % %
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LTC1799
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. V+ = 2.7V to 5.5V, RL=5k, CL = 5pF, Pin 4 = V+ unless otherwise noted. All voltages are with respect to GND.
SYMBOL VOH PARAMETER High Level Output Voltage CONDITIONS V + = 5V V + = 3V VOL Low Level Output Voltage V + = 5V V + = 3V tr OUT Rise Time (Note 5) V + = 5V V + = 3V tf OUT Fall Time (Note 5) V + = 5V V + = 3V 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 RSET (see the Table 1 in the Applications Information section). For these frequencies, the error is specified under the following assumption: 10k < RSET 100k. Note 3: Frequency error (defined as the deviation from the fOSC equation) includes drift over temperature and over supply. IOH = - 1mA IOH = - 4mA IOH = - 1mA IOH = - 4mA IOL = 1mA IOL = 4mA IOL = 1mA IOL = 4mA Pin 4 = V+ or Floating, RL = 0 Pin 4 = 0V, RL = 0 Pin 4 = V+ or Floating, RL = 0 Pin 4 = 0V, RL = 0 Pin 4 = V+ or Floating, RL = 0 Pin 4 = 0V, RL = 0 Pin 4 = V+ or Floating, RL = 0 Pin 4 = 0V, RL = 0
q q q q q q q q
ELECTRICAL CHARACTERISTICS
MIN 4.8 4.5 2.7 2.2
TYP 4.95 4.8 2.9 2.6 0.05 0.2 0.1 0.4 14 7 19 11 13 6 19 10
MAX
UNITS V V V V
0.15 0.4 0.3 0.7
V V V V ns ns ns ns ns ns ns 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: Output rise and fall times are measured between the 10% and 90% power supply levels. These specifications are based on characterization.
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. 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 1.1V 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 2pF. 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. Therefore, driving the DIV pin high requires sourcing approximately 5A. Likewise, driving DIV low requires sinking 5A. When floated, the DIV pin will be held near midsupply by these current sources. When it is floated, it is recommended that the DIV pin be bypassed by a 1nF capacitor or surrounded by a ground shield to prevent excessive coupling from other PCB traces. OUT (Pin 5): Oscillator Output. This pin can easily drive 5k or 10pF loads. Larger loads may cause inaccuracies due to supply bounce at high frequencies.
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LTC1799
APPLICATIO S I FOR ATIO
Selecting the Divider Setting and Resistor The LTC1799's master oscillator has a frequency range spanning 0.1MHz to 30MHz. 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 (fOSC) should be obtained using the lowest master oscillator frequency. Lower master oscillator frequencies use less power and are more accuate. For instance, fOSC = 100kHz can be obtained by either RSET = 10k, N = 100, master oscillator = 10MHz or RSET = 100k, N = 10, master oscillator = 1MHz. The RSET = 100k is preferred for lower power and better accuracy.
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted. S5 Package 5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
2.60 - 3.00 (0.102 - 0.118) 1.50 - 1.75 (0.059 - 0.069) 0.00 - 0.15 (0.00 - 0.006) 0.90 - 1.45 (0.035 - 0.057) 2.80 - 3.00 (0.110 - 0.118) (NOTE 3)
0.35 - 0.55 (0.014 - 0.022)
0.09 - 0.20 (0.004 - 0.008) (NOTE 2)
NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DIMENSIONS ARE INCLUSIVE OF PLATING 3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 4. MOLD FLASH SHALL NOT EXCEED 0.254mm 5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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Table 1. Frequency Range vs Divider Setting
DIVIDER SETTING /1 /10 DIV (Pin 4) = GND DIV (Pin 4) = Floating DIV (Pin 4) = V+ FREQUENCY RANGE > 500kHz* 50kHz to 1MHz < 100kHz /100 < 10k), the LTC1799 may suffer reduced accuracy with a supply voltage less than 4V.
*At master oscillator frequencies greater than 10MHz (R SET
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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. RSET = 10k * [10MHz/(N * fOSC)], N = 1, 10, 100 (RSETMIN = 3.32k (5V Supply), 5k (3V Supply), RSETMAX = 1M) Any resistor, RSET, tolerance adds to the inaccuracy of the oscillator, fOSC. Settling Time The settling time is proportional to RSET and is approximately tSETTLE RSET * (5s/k). This parameter is guaranteed by design and not 100% tested.
0.35 - 0.50 0.90 - 1.30 (0.014 - 0.020) (0.035 - 0.051) FIVE PLACES (NOTE 2)
1.90 (0.074) REF
0.95 (0.037) REF
S5 SOT-23 0599
1799i LT/TP 0101 2K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2001

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