Rev 1; 2/07 Low-Frequency, Spread-Spectrum EconOscillator The DS1090 is a low-cost, dithered oscillator intended to be used as an external clock for switched-mode power supplies and other low-frequency applications. The dithering or sweeping function reduces peak-radiated emissions from the power supply at its fundamental frequency, as well as harmonic frequencies. The device consists of a resistor-programmed master oscillator, factory-programmed clock prescaler, and a pinprogrammed dither circuit. These features allow the DS1090 to be used in applications where a spreadspectrum clock is desired to reduce radiated emissions. A combination of factory-set prescalers and external resistor allows for output frequencies ranging from 125kHz to 8MHz. Both dither frequency and dither percentage are set using control pins. Features ♦ Low-Cost, Spread-Spectrum EconOscillator™ ♦ Simple User Programming ♦ Output Frequency Programmable from 125kHz to 8MHz ♦ Dither Percentage Programmable from 0% to 8% ♦ Dither Rate Programmable (fMOSC / 512, 1024, 2048, or 4096 ) ♦ 3.0V to 5.5V Single-Supply Operation ♦ CMOS/TTL-Compatible Output ♦ Operating Temperature Range: -40°C to +85°C Ordering Information PART Applications OUTPUT FREQUENCY RANGE PRESCALER PINPACKAGE DS1090U-1+ 4MHz to 8MHz 1 8 μSOP Switched-Mode Power Supplies DS1090U-2+ 2MHz to 4MHz 2 8 μSOP Servers DS1090U-4+ 1MHz to 2MHz 4 8 μSOP Printers DS1090U-8+ 500kHz to 1MHz 8 8 μSOP DS1090U-16+ 250kHz to 500kHz 16 8 μSOP DS1090U-32+ 125kHz to 250kHz 32 8 μSOP Embedded Microcontrollers Industrial Controls Automotive Applications Add “T” for Tape & Reel orders. Pin Configuration Typical Operating Circuit VOUT VIN TOP VIEW VCC VCC DS1090 OUT 1 8 JC1 7 JC0 OUT RSET 2 JC0 VCC 3 6 J1 JC1 GND 4 5 J0 DS1090 J0 RSET 45kΩ TO 91kΩ DC-DC STEP-DOWN CONVERTER GND μSOP J1 EconOscillator is a trademark of Dallas Semiconductor. ______________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 DS1090 General Description DS1090 Low-Frequency, Spread-Spectrum EconOscillator ABSOLUTE MAXIMUM RATINGS Voltage Range on VCC Relative to Ground ...........-0.5V to +6.0V Voltage Range on Input Pins Relative to Ground.................................-0.5V to (VCC + 0.5V), not to exceed 6.0V Operating Temperature Range ...........................-40°C to +85°C Storage Temperature Range .............................-55°C to +125°C Soldering Temperature .......................................See IPC/JEDEC J-STD-020A Specification Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. RECOMMENDED DC OPERATING CONDITIONS (TA = -40°C to +85°C) PARAMETER Supply Voltage SYMBOL VCC CONDITIONS (Note 1) MIN TYP MAX UNITS 3.0 5.5 V VCC + 0.3 V +0.3 x VCC V MAX UNITS Input Logic 1 (J0, J1, JC0, JC1) VIH 0.7 x VCC Input Logic 0 (J0, J1, JC0, JC1) VIL -0.3 DC ELECTRICAL CHARACTERISTICS (VCC = +3.0V to +5.5V, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP CL = 15pF, VCC = 3.3V, RSET = 40kΩ 1.4 CL = 15pF, VCC = 5.5V, RSET = 40kΩ 1.7 Supply Current ICC High-Level Output Voltage (OUT) VOH Low-Level Output Voltage (OUT) VOL IOL = 4mA 0.4 V High-Level Input Current (J0, J1, JC0, JC1) IIH VIH = VCC +1.0 µA Low-Level Input Current (J0, J1, JC0, JC1) IIL VIL = 0V Resistor Current 2 IRES IOH = -4mA VCC = min VCC = max _____________________________________________________________________ 3 2.4 mA V -1.0 µA 150 µA Low-Frequency, Spread-Spectrum EconOscillator DS1090 AC ELECTRICAL CHARACTERISTICS (VCC = +3.0V to +5.5V, TA = -40°C to +85°C, unless otherwise noted.) PARAMETER SYMBOL Internal Master Oscillator Frequency fMOSC Output Frequency Tolerance f OUT Voltage Frequency Variation Temperature Frequency Variation f OUT f OUT Peak-to-Peak Dither (3) (Note 5) Power-Up Time Load Capacitance Note 1: Note 2: Note 3: Note 4: Note 5: Note 6: Note 7: MAX UNITS 4.0 8.0 MHz VCC = 3.3V, TA = +25°C -3.0 +3.0 % TA = +25°C, RSET = 60k, VCC = 3.0V to 3.6V (Notes 2, 3) -0.5 +0.5 TA = +25°C, RSET = 60k, VCC = 4.5V to 5.5V (Notes 2, 3) -1.25 +1.25 VCC = 3.3V (Notes 2, 3, 4) -2.0 +2.0 TYP % 0 J0 = VCC, J1 = GND J0 = GND, J1 = VCC 2 J0 = VCC, J1 = VCC 8 (Note 6) CL (Note 7) 4MHz to 8MHz, TA = +25°C (Note 3) <4MHz (Note 4) tR, tF MIN J0 = GND, J1 = GND t POR + t STAB Output Duty Cycle Output Rise/Fall Time CONDITIONS CL = 15pF % 4 0.1 45 % 0.5 ms 30 pF 55 50 20 % ns All voltages referenced to ground. This is the change observed in output frequency due to changes in temperature or voltage. See the Typical Operating Characteristics section. Parameter is guaranteed by design and is not production tested. This is a percentage of the output period. Parameter is characterized but not production tested. This can be varied from 0% to 8%. This indicates the time between power-up and the outputs becoming active. An on-chip delay is intentionally introduced to allow the oscillator to stabilize. tSTAB is equivalent to ~500 clock cycles and is dependent upon the programmed output frequency. Output voltage swings can be impaired at high frequencies combined with high output loading. _____________________________________________________________________ 3 Typical Operating Characteristics (VCC = +3.3V, TA = +25°C, unless otherwise noted.) 40kΩ 60kΩ 0.95 40kΩ 1.10 60kΩ 0.90 DS1090 toc03 TA = +25°C, RSET = 40kΩ SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 1.45 NO LOAD, VCC = 3.3V 1.30 4 DS1090 toc02 NO LOAD, TA = +25°C SUPPLY CURRENT (mA) 1.50 DS1090 toc01 1.70 1.20 SUPPLY CURRENT vs. OUTPUT LOADING SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT vs. SUPPLY VOLTAGE 0.70 5V 3 4V 2 3V 1 80kΩ 80kΩ 0 3.5 4.0 4.5 5.0 -40 5.5 -15 10 35 60 5 85 10 15 20 25 30 35 SUPPLY VOLTAGE (V) TEMPERATURE (°C) LOAD CAPACITANCE (pF) OUTPUT VOLTAGE HIGH vs. OUTPUT CURRENT OUTPUT VOLTAGE LOW vs. OUTPUT CURRENT OUTPUT FREQUENCY vs. SUPPLY VOLTAGE 0.4 DS1090 toc04 VCC = 3.0V OUTPUT VOLTAGE (V) 3.0 VCC = 3.0V 2.9 2.8 10 TA = +25°C 9 40 0.3 FREQUENCY (MHz) 3.1 DS1090 toc05 3.0 DS1090 toc06 0.50 0.70 OUTPUT VOLTAGE (V) DS1090 Low-Frequency, Spread-Spectrum EconOscillator 0.2 40kΩ 8 7 60kΩ 80kΩ 6 0.1 5 2.7 -4 -3 -2 OUTPUT CURRENT (mA) 4 4 0 -5 -1 0 0 1 2 3 4 5 OUTPUT CURRENT (mA) _____________________________________________________________________ 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 Low-Frequency, Spread-Spectrum EconOscillator RESISTOR CURRENT vs. RESISTOR VALUE DUTY CYCLE vs. TEMPERATURE 9 RSET = 40kΩ 8 7 DUTY CYCLE (%) FREQUENCY (MHz) 51 40kΩ 60kΩ 80kΩ 6 VCC = 3.3V 50 VCC = 5V 49 18 VCC = 3.3V, TA = +25°C RESISTOR CURRENT (μA) VCC = 3.3V DS1090 toc08 52 DS1090 toc07 10 DS1090 toc09 OUTPUT FREQUENCY vs. TEMPERATURE 16 14 12 10 5 DS1090U-1 -15 10 35 60 85 -15 10 35 FREQUENCY ERROR vs. SUPPLY VOLTAGE (FROM 3.3V) FREQUENCY ERROR vs. TEMPERATURE (FROM +25°C) 0 40kΩ 60kΩ -20 0 80kΩ 3.5 4.0 4.5 40kΩ SUPPLY VOLTAGE (V) 5.0 5.5 -40 ±2% ±4% ±8% -50 -60 -1.0 -70 -80 -2.0 3.0 -30 VCC = 3.3V, TA = +25°C, JC0 = JC1 = 1 OFF -10 1.0 60kΩ -5.0 80 POWER SPECTRUM vs. SPREAD POWER (dBm) FREQUENCY ERROR (%) 80kΩ 70 0 DS1090 toc11 DS1090 toc10 2.5 60 RSET (kΩ) 2.0 VCC = 3.3V 50 40 85 60 TEMPERATURE (°C) TA = +25°C -2.5 -40 TEMPERATURE (°C) 5.0 FREQUENCY ERROR (%) 8 48 -40 DS1090 toc12 4 -40 -15 10 35 TEMPERATURE (°C) 60 85 4.80 5.35 5.90 FREQUENCY (MHz) _____________________________________________________________________ 5 DS1090 Typical Operating Characteristics (continued) (VCC = +3.3V, TA = +25°C, unless otherwise noted.) Low-Frequency, Spread-Spectrum EconOscillator DS1090 Pin Description PIN NAME FUNCTION 1 OUT Oscillator Output 2 RSET Frequency Control Resistor Input 3 VCC Positive-Supply Terminal 4 GND Ground 5 J0 6 J1 7 JC0 8 JC1 Dither Amplitude (Percentage) Inputs (see Table 2) Dither Rate Divisor Inputs (see Table 1) Block Diagram RSET DS1090 VOLTAGEBIAS CIRCUIT MASTER OSCILLATOR (VCO) + ∑ fMOSC + FACTORY PROGRAMMED PRESCALER (÷ 1, 2, 4, 8, 16, OR 32) 4MHz–8MHz VCC VCC DITHER GENERATOR GND + - DITHER AMPLITUDE (0, 2, 4, OR 8%) f MOD TRIANGLE GENERATOR DITHER RATE (÷ 128) (÷ 4, 8, 16, OR 32) J0 J1 JC0 JC1 6 _____________________________________________________________________ fOUT fOSC BUFFER OUT Low-Frequency, Spread-Spectrum EconOscillator (+ 1, 2, or 4% of fMOSC) Programmed fMOSC DITHER AMOUNT (2, 4, OR 8%) (- 1, 2, or 4% of fMOSC) 1 fMOD fMOSC 8 fMOSC (MHz) IF DITHER AMOUNT = 0% DS1090 fig01 9 DS1090 MASTER OSCILLATOR FREQUENCY vs. EXTERNAL RESISTOR SELECTION 7 6 TIME 5 Figure 2. Center Frequency Dither Diagram 4 Factory-Programmed Prescaler 3 40 50 60 80 70 90 RSET RESISTANCE (kΩ) Figure 1. Master Oscillator Frequency The prescaler divides the frequency of the master oscillator by 1, 2, 4, 8, 16, or 32 to generate the squarewave output clock (fOSC). This divisor is factory-set and is an ordering option. Dither Generator Detailed Description The DS1090 is a center-dithered, spread-spectrum silicon oscillator for use as an external clock in reducedEMI applications. With a combination of factoryprogrammed prescalers and a user-selected external resistor, output frequencies from 125kHz to 8MHz can be achieved. The output center frequency can be dithered by selecting the desired dither rate and amplitude with discrete inputs J0, J1, JC0, and JC1. The DS1090 contains four basic circuit blocks: master oscillator, factory-programmed prescaler, dither generator, and the voltage-bias circuit that provides the feedback path to the master oscillator for frequency control and dithering functions. Master Oscillator The master oscillator is programmable in the application by the use of an external resistor (RSET) tied to ground (GND). Resistor values of 45kΩ to 91kΩ vary the square-wave output frequency of the voltage-controlled master oscillator (fMOSC) from 8MHz down to 4MHz (see Figure 1). The master oscillator (Hz) frequency can be stated as fMOSC ≅ 3.6461E +11 Re sistor Spread-spectrum functionality is achieved by a userconfigurable divider (determines dither rate), a triangle generator, and a user-configurable dither amplitude circuit (see Block Diagram). The input to the triangle-wave generator is derived from the internal master oscillator and is fed through a userconfigurable divider. The settings of control pins JC0 and JC1 determine this dither rate divisor setting (see Table 1), dividing the master clock by 4, 8, 16, or 32. The clock signal is further divided by 128 in the triangle-wave generator, which results in a trianglewave signal of either 1/512th, 1/1024th, 1/2048th, or 1/4096th of the master oscillator (fMOD), depending upon the user’s divisor setting. The dithering frequency can be also expressed as the result of fMOD = fMOSC Divisor ×128 where Divisor is 4, 8, 16, or 32. Table 1. Dither Rate Divisor Settings DITHERING PERCENTAGE (fMOSC/n) DIVISOR SETTING 0 FMOSC / 512 4 1 FMOSC / 1024 8 1 0 fMOSC / 2048 16 1 1 fMOSC / 4096 32 JC1 JC0 0 0 _____________________________________________________________________ 7 DS1090 Low-Frequency, Spread-Spectrum EconOscillator Table 2. Dither Percentage Setting J1 J0 DITHER PERCENT (%) 0 0 0 0 1 2 1 0 4 1 1 8 RSET Resistor Selection The value of the resistor used to select the desired frequency is calculated using the formula in the Master Oscillator section (see also Figure 1). It is recommended to use, at minimum, a 1%-tolerance, 1/16th-watt component with a temperature coefficient that satisfies the overall stability requirements desired of the end-equipment. Place the external RSET resistor as close as possible to minimize lead inductance. Dither Percentage Settings Dither amplitude (measured in percent ± from the master oscillator center frequency) is set using input pins J0 and J1. This circuit uses a sense current from the master oscillator bias circuit to adjust the amplitude of the triangle-wave signal to a voltage level that modulates the master oscillator to a percentage of its resistor-set center frequency. This percentage is set in the end application to be 0%, 2%, 4%, or 8% (see Table 2). Power-Supply Decoupling To achieve best results, it is highly recommended that a decoupling capacitor is used on the IC power-supply pins. Typical values of decoupling capacitors are 0.01µF and 0.1µF. Use a high-quality, ceramic, surface-mount capacitor, and mount it as close as possible to the VCC and GND pins of the IC to minimize lead inductance. Chip Information Application Information Pin Connection The DS1090 is intended to provide a fixed-frequency, dithered clock to be used as a clock driver for DC-DC converters and other applications requiring a lowfrequency EMI-reduced clock oscillator. All control pins must be biased per Tables 1 and 2 for proper operation for the individual application’s requirements. RSET must be tied to ground (GND) by a customer-supplied resistor. TRANSISTOR COUNT: 1883 SUBSTRATE CONNECTED TO GROUND Package Information For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products is a registered trademark of Dallas Semiconductor Corporation. is a registered trademark of Maxim Integrated Products.