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DS1086L Schematic ( PDF Datasheet ) - Dallas Semiconductor

Teilenummer DS1086L
Beschreibung Spread-Spectrum EconOscillator
Hersteller Dallas Semiconductor
Logo Dallas Semiconductor Logo 




Gesamt 16 Seiten
DS1086L Datasheet, Funktion
Rev 0; 11/03
3.3V Spread-Spectrum EconOscillator
General Description
The DS1086L EconOscillator™ is a 3.3V programmable
clock generator that produces a spread-spectrum
(dithered) square-wave output of frequencies from
130kHz to 66.6MHz. The selectable dithered output
reduces radiated-emission peaks by dithering the fre-
quency 0.5%,1%, 2%, 4%, or 8% below the pro-
grammed frequency. The DS1086L has a power-down
mode and an output-enable control for power-sensitive
applications. All the device settings are stored in non-
volatile (NV) EEPROM memory allowing it to operate in
stand-alone applications.
Applications
Printers
Copiers
PCs
Computer Peripherals
Cell Phones
Cable Modems
www.DataSheet4U.com
Features
User-Programmable Square-Wave Generator
Frequencies Programmable from 130kHz to
66.6MHz
0.5%, 1%, 2%, 4%, or 8% Selectable Dithered
Output
Adjustable Dither Rate
Glitchless Output-Enable Control
2-Wire Serial Interface
Nonvolatile Settings
2.7V to 3.6V Supply
No External Timing Components Required
Power-Down Mode
5kHz Master Frequency Step Size
EMI Reduction
Industrial Temperature Range: -40°C to +85°C
Ordering Information
PART
DS1086LU
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
8 µSOP (118 mil)
Typical Operating Circuit
DITHERED 130kHz TO
µP 66.6MHz OUTPUT
VCC
XTL1/OSC1
XTL2/OSC2
VCC OUT
N.C. SPRD
VCC
GND
DS1086L
SCL*
SDA*
PDN
OE
DECOUPLING CAPACITORS
(0.1µF and 0.01µF)
*SDA AND SCL CAN BE CONNECTED DIRECTLY HIGH IF THE DS1086L NEVER NEEDS
TO BE PROGRAMMED IN-CIRCUIT, INCLUDING DURING PRODUCTION TESTING.
TOP VIEW
Pin Configuration
OUT 1
SPRD 2
VCC 3
GND 4
DS1086L
8 SCL
7 SDA
6 PDN
5 OE
µSOP
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.






DS1086L Datasheet, Funktion
3.3V Spread-Spectrum EconOscillator
Typical Operating Characteristics
(VCC = 3.3V, TA = 25°C, unless otherwise noted.)
SUPPLY CURRENT vs.
MASTER OSCILLATOR FREQUENCY
9
8
7 15pF LOAD
6
5
4 4.7pF LOAD
3
2
PRESCALER = 1
1
33 36 39 42 45 48 51 54 57 60 63 66
MASTER FREQUENCY (MHz)
SUPPLY CURRENT vs. TEMPERATURE
10
9 fO = 66MHz
8
7 fO = 50MHz
6
fO = 33.3MHz
5
4
3
-40
PRESCALER = 1
15pF LOAD
-15 10 35 60
TEMPERATURE (°C)
85
SUPPLY CURRENT vs. PRESCALER
7
6
5
4
3
2
1 fO = 50MHz
15pF LOAD
0
1 10 100 1000
PRESCALER
MASTER OSCILLATOR FREQUENCY PERCENT
CHANGE vs. SUPPLY VOLTAGE
0.5
0.4
0.3
0.2 fO = 66MHz
0.1
0
-0.1 fO = 50MHz
-0.2 fO = 33.3MHz
-0.3
-0.4 PRESCALER = 1
-0.5
2.7
3.0 3.3
SUPPLY VOLTAGE (V)
3.6
MASTER OSCILLATOR FREQUENCY PERCENT
CHANGE vs. TEMPERATURE
0.50
0.25 fO = 33.3MHz
0
-0.25
-0.50
-0.75
-1.00
-1.25
-1.50
-40
fO = 50MHz
fO = 66MHz
PRESCALER = 1
15pF LOAD
-15 10 35 60
TEMPERATURE (°C)
85
DUTY CYCLE vs. TEMPERATURE
55
54
fO = 66MHz
53
52
51
50
-40
fO = 50MHz
fO = 33.3MHz
PRESCALER = 1
-15 10 35 60
TEMPERATURE (°C)
85
DUTY CYCLE vs. SUPPLY VOLTAGE
55
54
fO = 66MHz
53
52 fO = 50MHz
51
2.7
fO = 33.3MHz
PRESCALER = 1
3.0 3.3
SUPPLY VOLTAGE (V)
3.6
6 _____________________________________________________________________

6 Page









DS1086L pdf, datenblatt
3.3V Spread-Spectrum EconOscillator
Example Frequency Calculations
Example #1: Calculate the register values needed to
generate a desired output frequency of 11.0592MHz.
Since the desired frequency is not within the valid mas-
ter oscillator range of 33.3MHz to 66.6MHz, the
prescaler must be used. Valid prescaler values are 2x
where x equals 0 to 8 (and x is the value that is pro-
grammed into the P3 to P0 bits of the PRESCALER reg-
ister). Equation 1 shows the relationship between the
desired frequency, the master oscillator frequency, and
the prescaler.
fDESIRED = fMASTER OSCILLATOR
prescaler
fMASTER OSCILLATOR
2X
=
(1)
By trial and error, x is incremented from 0 to 8 in
Equation 2, finding values of x that yield master oscillator
frequencies within the range of 33.3MHz to 66.6MHz.
Equation 2 shows that a prescaler of 4 (x = 2) and a
master oscillator frequency of 44.2368MHz generates
our desired frequency. Writing 0080h to the
PRESCALER register sets the PRESCALER to 4. Be
aware that other settings also reside in the PRESCALER
register.
fMASTER OSCILLATOR = fDESIRED x prescaler = fDESIRED x 2X
fMASTER OSCILLATOR = 11.0592MHz x 22 = 44.2368MHz (2)
Once the target master oscillator frequency has been
calculated, the value of offset can be determined.
Using Table 2, 44.2368MHz falls within both OS - 1 and
OS - 2. However, choosing OS - 1 would be a poor
choice since 44.2368MHz is so close to OS - 1’s mini-
mum frequency. On the other hand, OS - 2 is ideal
since 44.2368MHz is close to the center of
OS - 2’s frequency span. Before the OFFSET register
can be programmed, the default value of offset (OS)
must be read from the RANGE register (last five bits). In
this example, 12h (18 decimal) was read from the
RANGE register. OS - 2 for this case is 10h (16 deci-
mal). This is the value that is written to the OFFSET reg-
ister.
Finally, the two-byte DAC value needs to be deter-
mined. Since OS - 2 only sets the range of frequencies,
the DAC selects one frequency within that range as
shown in Equation 3.
fMASTER OSCILLATOR = (MIN FREQUENCY OF SELECTED OFFSET
RANGE) + (DAC value x 5kHz)
(3)
Valid values of DAC are 0 to 1023 (decimal) and 5kHz
is the step size. Equation 4 is derived from rearranging
Equation 3 and solving for the DAC value.
(fMASTER OSCILLATOR
MIN FREQUENCY OF SELECTED
DAC VALUE =
OFFSET RANGE)
5kHz STEP SIZE
DAC VALUE = (44.2368MHz 41.0MHz)
5kHz STEP SIZE
= 647.36 647 (decimal)
(4)
Since the two-byte DAC register is left justified, 647 is
converted to hex (0287h) and bit-wise shifted left six
places. The value to be programmed into the DAC reg-
ister is A1C0h.
In summary, the DS1086L is programmed as follows:
PRESCALER = 0080h
OFFSET = OS - 2 or 10h (if range was read as 12h)
DAC = A1C0h
Notice that the DAC value was rounded. Unfortunately,
this means that some error is introduced. To calculate
how much error, a combination of Equation 1 and
Equation 3 is used to calculate the expected output fre-
quency. See Equation 5.
(MIN FREQUENCY OF SELECTED OFFSET
fOUTPUT
=
RANGE) + (DAC
VALUE x 5kHz STEP SIZE)
prescaler
fOUTPUT
= (41.0MHz) + (647 x 5kHz) =
4
44.235MHz = 11.05875MHz
4
(5)
12 ____________________________________________________________________

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