DS1090U-2/V+ - Maxim Integrated

General Description

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, fac-

tory-programmed clock prescaler, and a pin-programmed

dither circuit. These features allow the DS1090 to be used

in applications where a spread-spectrum 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.

Applications

●Switched-Mode Power Supplies

●Servers

●Printers

●Embedded Microcontrollers

●Industrial Controls

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

Add “T” for Tape & Reel orders.

EconOscillator is a trademark of Maxim Integrated Products, Inc.

PART

OUTPUT

FREQUENCY

RANGE

PRESCALER PIN-

PACKAGE

DS1090U-1+ 4MHz to 8MHz 1 8 µSOP

DS1090U-2+ 2MHz to 4MHz 2 8 µSOP

DS1090U-4+ 1MHz to 2MHz 4 8 µSOP

DS1090U-8+ 500kHz to

1MHz 8 8 µSOP

DS1090U-16+ 250kHz to

500kHz 16 8 µSOP

DS1090U-32+ 125kHz to

250kHz 32 8 µSOP

J0GND

JC1

JC0RSET

VCC

OUT

µSOP

TOP VIEW

DS1090

VOUT

VIN

DC-DC

STEP-DOWN

CONVERTER

OUT

GND

VCC

RSET

JC0

JC1

45kΩ

TO 91kΩ

DS1090 Low-Frequency, Spread-Spectrum EconOscillator

19-7500; Rev 3; 9/16

Ordering Information

Pin Conguration

Typical Operating Circuit

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

(TA = -40°C to +85°C)

(VCC = +3.0V to +5.5V, TA = -40°C to +85°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage VCC (Note 1) 3.0 5.5 V

Input Logic 1 (J0, J1, JC0, JC1) VIH

0.7 x

VCC

VCC +

0.3 V

Input Logic 0 (J0, J1, JC0, JC1) VIL -0.3 +0.3 x

VCC

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Current ICC

CL = 15pF, VCC = 3.3V, RSET = 40kΩ 1.4 mA

CL = 15pF, VCC = 5.5V, RSET = 40kΩ 1.7 3

High-Level Output Voltage (OUT) VOH

IOH = -4mA 2.4 V

VCC = min

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 -1.0 µA

Resistor Current IRES VCC = max 150 µA

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

Absolute Maximum Ratings

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.

DC Electrical Characteristics

Recommended DC Operating Conditions

Note 1: All voltages referenced to ground.

Note 2: This is the change observed in output frequency due to changes in temperature or voltage.

Note 3: See the Typical Operating Characteristics section.

Note 4: Parameter is guaranteed by design and is not production tested.

Note 5: This is a percentage of the output period. Parameter is characterized but not production tested. This can be varied from 0%

to 8%.

Note 6: 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.

Note 7: Output voltage swings can be impaired at high frequencies combined with high output loading.

(VCC = +3.0V to +5.5V, TA = -40°C to +85°C, unless otherwise noted.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Internal Master Oscillator

Frequency fMOSC 4.0 8.0 MHz

Output Frequency Tolerance ∆fOUT

VCC = 3.3V,

TA = +25°C -3.0 +3.0 %

Voltage Frequency Variation ∆fOUT

TA = +25°C, RSET = 60kΩ,

VCC = 3.0V to 3.6V (Notes 2, 3) -0.5 +0.5

TA = +25°C, RSET = 60kΩ,

VCC = 4.5V to 5.5V (Notes 2, 3) -1.25 +1.25

Temperature Frequency Variation ∆fOUT

VCC = 3.3V

(Notes 2, 3, 4) -2.0 +2.0 %

Peak-to-Peak Dither (3σ)

(Note 5)

J0 = GND, J1 = GND 0

J0 = VCC, J1 = GND 2

J0 = GND, J1 = VCC 4

J0 = VCC, J1 = VCC 8

Power-Up Time tPOR +

tSTAB

(Note 6) 0.1 0.5 ms

Load Capacitance CL(Note 7) 30 pF

Output Duty Cycle 4MHz to 8MHz, TA = +25°C (Note 3) 45 55 %

<4MHz (Note 4) 50

Output Rise/Fall Time tR, tFCL = 15pF 20 ns

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

AC Electrical Characteristics

(VCC = +3.3V, TA = +25°C, unless otherwise noted.)

DS1090 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

5.04.54.03.5

0.95

1.20

1.45

1.70

0.70

3.0 5.5

NO LOAD, TA = +25°C

40kΩ

60kΩ

80kΩ

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

SUPPLY CURRENT

vs. TEMPERATURE

DS1090 toc02

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

0.70

0.90

1.10

1.30

1.50

0.50

-40 85

NO LOAD, VCC = 3.3V

40kΩ

60kΩ

80kΩ

SUPPLY CURRENT

vs. OUTPUT LOADING

DS1090 toc03

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

353025201510

5 40

TA = +25°C, RSET = 40kΩ

OUTPUT VOLTAGE HIGH

vs. OUTPUT CURRENT

DS1090 toc04

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE (V)

-1-2-3-4

2.8

2.9

3.0

3.1

2.7

-5 0

VCC = 3.0V

OUTPUT VOLTAGE LOW

vs. OUTPUT CURRENT

DS1090 toc05

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE (V)

4321

0.1

0.2

0.3

0.4

0 5

VCC = 3.0V

OUTPUT FREQUENCY

vs. SUPPLY VOLTAGE

DS1090 toc06

SUPPLY VOLTAGE (V)

FREQUENCY (MHz)

5.04.54.03.5

3.0 5.5

TA = +25°C

60kΩ

80kΩ

40kΩ

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

Typical Operating Characteristics

(VCC = +3.3V, TA = +25°C, unless otherwise noted.)

OUTPUT FREQUENCY

vs. TEMPERATURE

DS1090 toc07

TEMPERATURE (°C)

FREQUENCY (MHz)

603510-15

-40 85

VCC = 3.3V

60kΩ

80kΩ

40kΩ

DUTY CYCLE

vs. TEMPERATURE

DS1090 toc08

TEMPERATURE (°C)

DUTY CYCLE (%)

603510-15

-40 85

RSET = 40kΩ

VCC = 3.3V

VCC = 5V

DS1090U-1

RESISTOR CURRENT

vs. RESISTOR VALUE

DS1090 toc09

RSET (kΩ)

RESISTOR CURRENT (mA)

706050

40 80

VCC = 3.3V, TA = +25°C

FREQUENCY ERROR

vs. SUPPLY VOLTAGE (FROM 3.3V)

DS1090 toc10

SUPPLY VOLTAGE (V)

FREQUENCY ERROR (%)

5.04.54.03.5

-2.5

2.5

5.0

-5.0

3.0 5.5

= +25°C

40kΩ

60kΩ

80kΩ

FREQUENCY ERROR

vs. TEMPERATURE (FROM +25°C)

DS1090 toc11

TEMPERATURE (°C)

FREQUENCY ERROR (%)

603510-15

-1.0

1.0

2.0

-2.0

-40 85

VCC = 3.3V

40kΩ

60kΩ

80kΩ

POWER SPECTRUM vs. SPREAD

DS1090 toc12

FREQUENCY (MHz)

POWER (dBm)

5.35

-70

-60

-50

-40

-30

-20

-10

-80

4.80 5.90

VCC = 3.3V,

TA = +25°C,

JC0 = JC1 = 1

OFF

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

Typical Operating Characteristics (continued)

PIN NAME FUNCTION

1 OUT Oscillator Output

2 RSET Frequency Control Resistor Input

3 VCC Positive-Supply Terminal

4 GND Ground

5 J0 Dither Amplitude (Percentage) Inputs

(see Table 2)

6 J1

7 JC0 Dither Rate Divisor Inputs (see Table 1)

8 JC1

DS1090

∑

GND

MASTER

OSCILLATOR

(VCO)

4MHz–8MHz

FACTORY

PROGRAMMED

PRESCALER

( 1, 2, 4, 8, 16, OR 32)

TRIANGLE

GENERATOR

VCC

RSET VOLTAGE-

BIAS CIRCUIT

OUT

fMOSC fOSC

fMOD

fOUT

JC0

JC1

BUFFER

DITHER

AMPLITUDE

(0, 2, 4, OR 8%)

DITHER RATE

( 4, 8, 16, OR 32)

( 128)

DITHER GENERATOR

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

Block Diagram

Pin Description

Detailed Description

The DS1090 is a center-dithered, spread-spectrum silicon

oscillator for use as an external clock in reduced-EMI

applications. With a combination of factory-programmed

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

MOSC

3.6461 E 11

fResistor

≅

Factory-Programmed Prescaler

The prescaler divides the frequency of the master oscillator

by 1, 2, 4, 8, 16, or 32 to generate the square-wave output

clock (fOSC). This divisor is factory-set and is an ordering

option.

Dither Generator

Spread-spectrum functionality is achieved by a user-

configurable 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

user-configurable 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 triangle-wave signal of either

1/512th, 1/1024th, 1/2048th, or 1/4096th of the master

oscillator (fMOD), depending upon the user’s divisor set-

ting.

The dithering frequency can be also expressed as the

result of

where Divisor is 4, 8, 16, or 32.

MOSC

MOD

fDivisor 128

Figure 2. Center Frequency Dither Diagram

Figure 1. Master Oscillator Frequency

Table 1. Dither Rate Divisor Settings

JC1 JC0 DITHERING PERCENTAGE

(fMOSC/n)

DIVISOR

SETTING

0 0 fMOSC /512 4

0 1 fMOSC /1024 8

1 0 fMOSC /2048 16

1 1 fMOSC /4096 32

MASTER OSCILLATOR FREQUENCY vs.

EXTERNAL RESISTOR SELECTION

DS1090 fig01

RSET RESISTANCE (kΩ)

fMOSC (MHz)

7060

fMOSC

TIME

DITHER

AMOUNT

(2, 4, OR 8%)

IF DITHER AMOUNT = 0%

(- 1, 2, or 4% of fMOSC)

fMOD

(+ 1, 2, or 4% of fMOSC)

Programmed fMOSC

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

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 tri-

angle-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).

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 low-

frequency 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.

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.

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 capaci-

tor, and mount it as close as possible to the VCC and GND

pins of the IC to minimize lead inductance.

Table 2. Dither Percentage Setting

J1 J0 DITHER PERCENT (%)

0 0 0

0 1 2

1 0 4

1 1 8

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

Chip Information

SUBSTRATE CONNECTED TO GROUND

Package Information

For the latest package outline information and land patterns

(footprints), go to www.maximintegrated.com/packages. Note

that a “+”, “#”, or “-” in the package code indicates RoHS status

only. Package drawings may show a different suffix character, but

the drawing pertains to the package regardless of RoHS status.

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses

are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)

shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

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DS1090 Low-Frequency, Spread-Spectrum EconOscillator

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

1 2/07 — —

2 2/15 Remove automotive reference from data sheet 1

3 9/16 Corrected typo in Benets and Features section 1

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