DS1090U-2/V+T - Maxim - Datasheet.Live

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-radi-

ated emissions from the power supply at its fundamen-

tal frequency, as well as harmonic frequencies. The

device consists of a resistor-programmed master oscil-

lator, factory-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 emis-

sions. 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

Automotive Applications

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

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

______________________________________________

Maxim Integrated Products

J0GND

JC1

JC0RSET

VCC

OUT

μSOP

TOP VIEW

DS1090

Pin Configuration

Ordering Information

DS1090

VOUT

VIN

DC-DC

STEP-DOWN

CONVERTER

OUT

GND

VCC

RSET

JC0

JC1

45kΩ

TO 91kΩ

Typical Operating Circuit

Rev 1; 2/07

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.

Add “T” for Tape & Reel orders.

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

EconOscillator is a trademark of Dallas Semiconductor.

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

2 _____________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

RECOMMENDED DC OPERATING CONDITIONS

(TA= -40°C to +85°C)

DC ELECTRICAL CHARACTERISTICS

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

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.

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

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 V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CL = 15pF, VCC = 3.3V, RSET = 40kΩ1.4

Supply Current ICC CL = 15pF, VCC = 5.5V, RSET = 40kΩ1.7 3 mA

IOH = -4mA

High-Level Output Voltage (OUT) VOH VCC = min 2.4 V

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

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

_____________________________________________________________________ 3

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 %

TA = +25°C, RSET = 60k,

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

Voltage Frequency Variation fOUT TA = +25°C, RSET = 60k,

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 %

J0 = GND, J1 = GND 0

J0 = VCC, J1 = GND 2

J0 = GND, J1 = VCC 4

Peak-to-Peak Dither (3)

(Note 5)

J0 = VCC, J1 = VCC 8

Power-Up Time tPOR +

tSTAB (Note 6) 0.1 0.5 ms

Load Capacitance CL (Note 7) 30 pF

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

Output Duty Cycle <4MHz (Note 4) 50 %

Output Rise/Fall Time tR, tF C

L = 15pF 20 ns

AC ELECTRICAL CHARACTERISTICS

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

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.

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

4 _____________________________________________________________________

Typical Operating Characteristics

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

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

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. 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

540

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

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

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

_____________________________________________________________________

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 (μA)

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

TA = +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

±2%

±4%

±8%

Typical Operating Characteristics (continued)

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

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

6 _____________________________________________________________________

Pin Description

Block Diagram

PIN NAME FUNCTION

1 OUT Oscillator Output

SET Frequency Control Resistor Input

CC Positive-Supply Terminal

4 GND Ground

5J0

6J1

Dither Amplitude (Percentage) Inputs

(see Table 2)

7 JC0

8 JC1 Dither Rate Divisor Inputs (see Table 1)

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

∑

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

_____________________________________________________________________ 7

Detailed Description

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

con 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 ampli-

tude with discrete inputs J0, J1, JC0, and JC1.

The DS1090 contains four basic circuit blocks: master

oscillator, factory-programmed prescaler, dither gener-

ator, and the voltage-bias circuit that provides the feed-

back path to the master oscillator for frequency control

and dithering functions.

Master Oscillator

The master oscillator is programmable in the applica-

tion by the use of an external resistor (RSET) tied to

ground (GND). Resistor values of 45kΩto 91kΩvary

the square-wave output frequency of the voltage-con-

trolled master oscillator (fMOSC) from 8MHz down to

4MHz (see Figure 1).

The master oscillator (Hz) frequency can be stated as

Factory-Programmed Prescaler

The prescaler divides the frequency of the master oscil-

lator 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 cir-

cuit (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 setting.

The dithering frequency can be also expressed as the

result of

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

Divisor

MOD MOSC

=×128

sistor

MOSC ≅+3 6461 11.

MASTER OSCILLATOR FREQUENCY vs.

EXTERNAL RESISTOR SELECTION

DS1090 fig01

RSET RESISTANCE (kΩ)

fMOSC (MHz)

7060

Figure 1. Master Oscillator Frequency

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

Figure 2. Center Frequency Dither Diagram

JC1 JC0 DITHERING PERCENTAGE

(fMOSC/n)

DIVISOR

SETTING

00 F

MOSC / 512 4

01 F

MOSC / 1024 8

10 f

MOSC / 2048 16

11 f

MOSC / 4096 32

Table 1. Dither Rate Divisor Settings

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

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.

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

is a registered trademark of Dallas Semiconductor Corporation.

Dither Percentage Settings

Dither amplitude (measured in percent ± from the mas-

ter 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 modu-

lates the master oscillator to a percentage of its resis-

tor-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 fre-

quency 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 compo-

nent with a temperature coefficient that satisfies the over-

all 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

capacitor, and mount it as close as possible to the VCC

and GND pins of the IC to minimize lead inductance.

J1 J0 DITHER PERCENT (%)

00 0

01 2

10 4

11 8

Table 2. Dither Percentage Setting

Package Information

For the latest package outline information, go to

www.maxim-ic.com/DallasPackInfo.

Chip Information

TRANSISTOR COUNT: 1883

SUBSTRATE CONNECTED TO GROUND