MAXIM DS1090U-8

Rev 0; 4/04
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.
*Contact factory for availability.
Pin Configuration
Typical Operating Circuit
VOUT
VIN
TOP VIEW
VCC
VCC
OUT 1
DC-DC
STEP-DOWN
CONVERTER
JC0
3
6
J1
GND 4
5
J0
DS1090
VCC
J0
GND
7
RSET 2
DS1090 JC1
RSET
JC1
OUT
JC0
45kΩ
TO 91kΩ
8
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
SYMBOL
CONDITIONS
(Note 1)
MIN
TYP
MAX
UNITS
3.0
5.5
V
Supply Voltage
VCC
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
MAX
UNITS
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
(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
∆fOUT
Voltage Frequency Variation
Temperature Frequency Variation
∆fOUT
∆fOUT
Peak-to-Peak Dither (3σ)
(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
-11.5
+11.5
%
TA = +25°C, RSET = 60kΩ,
VCC = 3.0V to 3.6V (Notes 2, 3)
-0.3
+0.3
TA = +25°C, RSET = 60kΩ,
VCC = 4.5V to 5.5V (Notes 2, 3)
-1.25
+1.25
VCC = 3.3V
(Notes 2, 3, 4)
-2.5
+2.5
TYP
%
0
J0 = VCC, J1 = GND
2
J0 = GND, J1 = VCC
4
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
tPOR +
tSTAB
Output Duty Cycle
Output Rise/Fall Time
CONDITIONS
CL = 15pF
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
DS1090
AC ELECTRICAL CHARACTERISTICS
Typical Operating Characteristics
(VCC = +3.3V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
40kΩ
60kΩ
DS1090 toc02
1.30
0.95
4
40kΩ
TA = +25°C, RSET = 40kΩ
SUPPLY CURRENT (mA)
1.45
NO LOAD, VCC = 3.3V
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
NO LOAD, TA = +25°C
1.20
1.50
DS1090 toc01
1.70
SUPPLY CURRENT
vs. OUTPUT LOADING
1.10
60kΩ
0.90
DS1090 toc03
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
0.70
5V
3
4V
2
3V
1
80kΩ
80kΩ
3.5
4.0
4.5
5.0
0
-40
5.5
-15
10
35
60
85
5
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
VCC = 3.0V
OUTPUT VOLTAGE (V)
3.0
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
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
RESISTOR CURRENT
vs. RESISTOR VALUE
DS1090 toc09
OUTPUT FREQUENCY
vs. TEMPERATURE
16
14
12
10
5
DS1090U-1
48
-15
10
35
60
-15
10
35
85
60
TEMPERATURE (°C)
FREQUENCY ERROR
vs. SUPPLY VOLTAGE (FROM 3.3V)
FREQUENCY ERROR
vs. TEMPERATURE (FROM +25°C)
80kΩ
0
40kΩ
60kΩ
3.5
4.0
4.5
0
80kΩ
SUPPLY VOLTAGE (V)
5.5
80
-30
-40
±2%
±4%
±8%
-50
-60
-1.0
40kΩ
5.0
70
VCC = 3.3V,
TA = +25°C,
JC0 = JC1 = 1
OFF
-10
-20
-70
-80
-2.0
3.0
60
POWER SPECTRUM vs. SPREAD
1.0
60kΩ
-5.0
50
0
POWER (dBm)
FREQUENCY ERROR (%)
2.5
VCC = 3.3V
40
RSET (kΩ)
2.0
DS1090 toc10
TA = +25°C
-2.5
8
-40
TEMPERATURE (°C)
5.0
FREQUENCY ERROR (%)
85
DS1090 toc11
-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
1
OUT
Oscillator Output
FUNCTION
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
fOSC
(÷ 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
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
70
80
90
RSET RESISTANCE (kΩ)
Figure 1. Master Oscillator Frequency
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
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
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 (f MOD), 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.
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.
Chip Information
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
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Dallas Semiconductor Corporation.
is a registered trademark of Maxim Integrated Products.