Rev 0; 4/04
Low-Frequency, Spread-Spectrum
EconOscillator
General Description
Features
♦ Low-Cost, 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-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.
♦ Simple User Programming
♦ Output Frequency Programmable from 125kHz
to 8MHz
♦ Dither Percentage Programmable from 0% to 8%
♦ Dither Rate Programmable (f
/ 512, 1024,
MOSC
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
OUTPUT
PIN-
FREQUENCY
RANGE
PART
PRESCALER
PACKAGE
Applications
Switched-Mode Power Supplies
DS1090U-1
DS1090U-2*
DS1090U-4*
DS1090U-8*
4MHz to 8MHz
2MHz to 4MHz
1MHz to 2MHz
500kHz to 1MHz
1
2
4
8
8 µSOP
8 µSOP
8 µSOP
8 µSOP
Servers
Printers
250kHz to
500kHz
Embedded Microcontrollers
Industrial Controls
Automotive Applications
DS1090U-16
DS1090U-32*
16
32
8 µSOP
8 µSOP
125kHz to
250kHz
Add “/T” for Tape & Reel orders.
*Contact factory for availability.
Pin Configuration
Typical Operating Circuit
V
V
OUT
IN
TOP VIEW
V
V
CC
CC
OUT
1
2
3
4
8
7
6
5
JC1
JC0
J1
DC-DC
STEP-DOWN
CONVERTER
R
SET
OUT
JC0
DS1090
V
CC
GND
J0
JC1
J0
DS1090
R
SET
µSOP
45kΩ
TO 91kΩ
J1
GND
EconOscillator is a trademark of Dallas Semiconductor.
______________________________________________ Maxim Integrated Products
1
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.