MAXIM DS1090 User Manual

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, 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.

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 (f

MOSC

/ 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

1

Pin Configuration

Ordering Information

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.

EconOscillator is a trademark of Dallas Semiconductor.

OUTPUT

PART

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+

DS1090U-16+

DS1090U-32+

FREQUENCY
RANGE

500kHz to
1MHz

250kHz to
500kHz

125kHz to
250kHz

PRE SCALER

8 8 μSOP

16 8 μSOP

32 8 μSOP

PIN­PACKAGE

V

IN

V

CC

DC-DC

STEP-DOWN

V

CC

DS1090

R

SET

45kΩ

TO 91kΩ

GND

CONVERTER

OUT

JC0

JC1

J0

J1

V

OUT

TOP VIEW

1

OUT

2

SET

V

3

CC

4

87JC1

DS1090

μSOP

JC0R

J1

6

J0GND

5

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 VCCRelative to Ground ...........-0.5V to +6.0V

Voltage Range on Input Pins

Relative to Ground.................................-0.5V to (V

CC

+ 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 V

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

Input Logic 0 (J0, J1, JC0, JC1) V

CC

(Note 1) 3.0 5.5 V

IH

IL

0.7 x
V

-0.3

CC

V

CC

0.3

+0.3 x

V

CC

+

V

V

Supply Current I

High-Level Output Voltage (OUT) V

Low-Level Output Voltage (OUT) V

High-Level Input Current
(J0, J1, JC0, JC1)

Low-Level Input Current
(J0, J1, JC0, JC1)

Resistor Current I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CC

OH

OL

I

IH

I

RES

CL = 15pF, VCC = 3.3V, R

CL = 15pF, VCC = 5.5V, R

IOH = -4mA

VCC = min

IOL = 4mA 0.4 V

VIH = V

CC

VIL = 0V -1.0 µA

IL

VCC = max 150 µA

= 40kΩ 1.4

SET

= 40kΩ 1.7 3

SET

2.4 V

mA

+1.0 µA

DS1090

Low-Frequency, Spread-Spectrum

EconOscillator

_____________________________________________________________________ 3

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. t

STAB

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.

Internal Master Oscillator
Frequency

Output Frequency Tolerance f

Voltage Frequency Variation f

Temperature Frequency Variation f

Peak-to-Peak Dither (3)
(Note 5)

Power-Up Time

Load Capacitance CL (Note 7) 30 pF

Output Duty Cycle

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

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

f

MOSC

OUT

OUT

OUT

t

POR

t

STAB

4.0 8.0 MHz

VCC = 3.3V,
T

= +25°C

A

TA = +25°C, R

= 3.0V to 3.6V (Notes 2, 3)

V

CC

TA = +25°C, R
V

= 4.5V to 5.5V (Notes 2, 3)

CC

VCC = 3.3V
(Notes 2, 3, 4)

J0 = GND, J1 = GND 0

J0 = VCC, J1 = GND 2

J0 = GND, J1 = VCC 4

J0 = V

+

(Note 6) 0.1 0.5 ms

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

<4MH z (Note 4) 50

, J1 = VCC 8

CC

SET

SET

= 60k,

= 60k,

-3.0 +3.0 %

-0.5 +0.5

%

-1.25 +1.25

-2.0 +2.0 %

%

%