LTC6909
1 to 8 Output, Multiphase
Silicon Oscillator with Spread
Spectrum Modulation
Features
Description
1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-Phase Outputs
n One External Resistor Sets the Output Frequency
from 12.5kHz to 6.67MHz
n Optional Spread Spectrum Frequency for Improved
EMI Performance
n ±10% Frequency Spreading
n Outputs Can Be Held Low or Floated (Hi-Z)
n Three Spread Spectrum Modulation Rates
fOUT/16, fOUT/32 and fOUT/64
n 400µA Supply Current
n Operates from a Single 2.7V to 5.5V Supply
n Fast Start-Up Time
n First Cycle Accurate
n Outputs Are High Impedance Until Frequency Settles
n MS16 Package
The LTC®6909 is an easy to use precision oscillator that
can provide 1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-phase synchronized outputs. The LTC6909 also offers spread spectrum
frequency modulation (SSFM), which can be enabled to improve electromagnetic compatibility (EMC) performance.
n
Applications
Synchronizing Multiple Switching Power Supplies
n
L, LT, LTC, LTM, Linear Technology, the Linear logo and µModule are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 6342817, 6614313,
7417509.
Eight separate outputs provide up to eight rail-to-rail,
50% duty cycle clock signals. Using three logic inputs, the
outputs are configured for phase separation, ranging from
45° to 120° (three to eight phases). The clock outputs can
also be held low or configured for Hi-Z. A single resistor,
combined with the phase configuration, sets the output
frequency, based on the following formula:
fOUT = 20MHz • 10k/(RSET • PH)
where PH = 3, 4, 5, 6, 7 or 8
The LTC6909 can be used in applications requiring only
one or two output phases. Alternatively, the LTC6908
family of parts provides the same two output signals but
in a smaller SOT-23 or 2mm × 3mm DFN package. The
LTC6908-1 provides complimentary (180°) outputs while
the LTC6908-2 provides quadrature (90°) outputs.
Typical Application
150kHz to 30MHz Output
Frequency Spectrum
(9kHz Res BW)
Providing a 4-Phase Synchronizing Clock to LTM Modules
0
INTVCC
0.1µF
LTC6909
OUT1
V+D
71.5k
GND
OUT2
V+A
OUT3
SET
OUT4
PH0
OUT5
PH1
OUT6
PH2
OUT7
MOD
OUT8
LTM4601
S0FT-START
TRACKING
1.5V
48A
0.01µF
DISABLE SSFM
–20
–30
–40
0
TRACKING
LTM4601-1
TRACKING
LTM4601-1
ENABLE SSFM
SSFM DISABLED
–10
–50
LTM4601-1
OUTPUT (dBc)
0.1µF
OUTPUT (dBc)
10V TO 14V
6909 TA01
SSFM ENABLED
SSFM = fOUT/32
–10
–20
–30
–40
–50
150kHz
30MHz
FREQUENCY
(FUNDAMENTAL AND HARMONICS SHOWN)
6909 TA01b
6909fa
1
LTC6909
Absolute Maximum Ratings
Pin Configuration
(Note 1)
Supply Voltage (V+A) to GND.......................................6V
Supply Voltage (V+D) to GND.......................................6V
Maximum Voltage
on Any Pin................. (GND – 0.3V) ≤ VPIN ≤ (V+ + 0.3V)
Operating Temperature Range (Note 2)
LTC6909C.............................................–40°C to 85°C
LTC6909I..............................................–40°C to 85°C
LTC6909H........................................... –40°C to 125°C
Specified Temperature Range (Note 3)
LTC6909C................................................. 0°C to 70°C
LTC6909I..............................................–40°C to 85°C
LTC6909H........................................... –40°C to 125°C
Junction Temperature............................................ 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................... 300°C
TOP VIEW
V+A
GND
PH0
PH1
OUT1
OUT2
OUT3
OUT4
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SET
PH2
MOD
V+D
OUT8
OUT7
OUT6
OUT5
MS PACKAGE
16-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 125°C/W
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LTC6909CMS#PBF
LTC6909CMS#TRPBF
6909
16-Lead Plastic MSOP
0°C to 70°C
LTC6909IMS#PBF
LTC6909IMS#TRPBF
6909
16-Lead Plastic MSOP
–40°C to 85°C
LTC6909HMS#PBF
LTC6909HMS#TRPBF
6909
16-Lead Plastic MSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C or as noted. Test conditions are V+ = V+A = V+D = 2.7V to 5.5V, RL = 5k,
CL = 5pF unless otherwise noted. The modulation is turned off (MOD is connected to OUT1) and PH = 8 unless otherwise specified.
RSET is defined as the resistor connected from the SET pin to the V+A pin.
SYMBOL
PARAMETER
CONDITIONS
ΔfMASTER
Frequency Accuracy (Notes 4, 5)
V+ = 5V
PH = 3
500kHz ≤ fMASTER ≤ 10MHz
500kHz ≤ fMASTER ≤ 10MHz
100kHz ≤ fMASTER < 500kHz
10MHz ≤ fMASTER ≤ 20MHz
V+ = 2.7V
PH = 3
500kHz ≤ fMASTER ≤ 10MHz
500kHz ≤ fMASTER ≤ 10MHz
100kHz ≤ fMASTER < 500kHz
ΔfOUT/ΔT
ΔfOUT/ΔV+
MIN
TYP
MAX
UNITS
l
l
l
±1
±2.5
±3
±2.7
±2.5
±3
±4.5
±3.5
%
%
%
%
l
l
±0.5
±2
±2.5
±2.5
±3
±4.5
%
%
%
Frequency Drift Over Temperature
RSET = 100k
l
±0.004
Frequency Drift Over Supply
V+ = 4.5V to 5.5V, RSET = 100k
V+ = 2.7V to 3.6V, RSET = 100k
l
l
0.4
0.04
%/°C
0.9
0.35
%/V
%/V
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LTC6909
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C or as noted. Test conditions are V+ = V+A = V+D = 2.7V to 5.5V, RL = 5k,
CL = 5pF unless otherwise noted. The modulation is turned off (MOD is connected to OUT1) and PH = 8 unless otherwise specified.
RSET is defined as the resistor connected from the SET pin to the V+A pin.
SYMBOL
RSET
PARAMETER
CONDITIONS
Range of the RSET Resistor
Connected Between the V+A Pin and
the SET Pin
4.5V ≤ V+ ≤ 5.5V
2.7V ≤ V+ ≤ 4.5V
MIN
Frequency Spread with SSFM
Enabled
RSET = 100k
MOD Pin = V+, GND or Open
10
20
l
±7
Long-Term Stability of the Output
Frequency (Note 9)
Duty Cycle (Note 6)
V+A, V+D
Operating Supply Voltage Range
IS
V+ Combined Supply Current
TYP
±10
MAX
UNITS
2000
2000
kΩ
kΩ
±13
%
300
SSFM Disabled
l
45
l
2.7
50
ppm/√kHr
55
%
5.5
V
RSET = 2M, RL = ∞, PH = 8, MOD = V+,
(fOUT = 12.5kHz), SSFM = fOUT/64
V+ = 5V
V+ = 2.7V
l
l
0.6
0.55
0.85
0.8
mA
mA
RSET = 20k, RL = ∞, PH = 3, MOD = GND,
(fOUT = 3.33MHz), SSFM = fOUT/16
V+ = 5V
V+ = 2.7V
l
l
2.4
1.55
2.7
1.8
mA
mA
RSET = 2M, RL = ∞, PH = 8, MOD = OUT1,
(fOUT = 12.5kHz), SSFM Off
V+ = 5V
V+ = 2.7V
l
l
0.4
0.37
0.65
0.6
mA
mA
VIH_MOD
High Level MOD Input Voltage
l
VIL_MOD
Low Level MOD Input Voltage
l
V+ – 0.4
V
0.4
V
4
µA
µA
IMOD
MOD Input Current (Note 7)
MOD Pin = V+, V+ = 5V
MOD Pin = GND, V+ = 5V
VIH_PH
High Level PHx Input Voltage
PHx Refers to PH0, PH1 and PH2
l
VIL_PH
Low Level PHx Input Voltage
PHx Refers to PH0, PH1 and PH2
l
0.4
V
l
±1
µA
IIN_PHX
VOH
Digital Input Current, PH0, PH1, PH2
0V < VIN
High Level Output Voltage
(OUT1 Through OUT8)(Note 7)
V+ = 5V
< V+
V+ = 2.7V
VOL
Low Level Output Voltage
(OUT1 Through OUT8)(Note 7)
V+ = 5V
V+ = 2.7V
l
l
–4
V+ – 0.4
2
–2
V
No Load
5mA Load to GND
l
4.35
4.92
4.65
V
V
No Load
3mA Load to GND
l
2.1
2.63
2.4
V
V
No Load
5mA Load to V+
l
0.07
0.25
0.55
V
V
No Load
3mA Load to V+
l
0.07
0.25
0.55
V
V
tr
Output Rise Time (Note 8)
V+ = 5V
V+ = 2.7V
1.6
2.5
ns
ns
tf
Output Fall Time (Note 8)
V+ = 5V
V+ = 2.7V
1.6
2
ns
ns
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: LTC6909C and the LTC6909I are guaranteed functional over the
operating temperature range of –40°C to 85°C.
Note 3: The LTC6909C is guaranteed to meet specified performance from
0°C to 70°C. The LTC6909C is designed, characterized and expected to
meet specified performance from –40°C to 85°C but is not tested or QA
sampled at these temperatures. The LTC6909I is guaranteed to meet
specified performance from –40°C to 85°C. The LTC6909H is guaranteed
to meet specified performance from –40°C to 125°C.
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LTC6909
Electrical Characteristics
Note 4: fMASTER is the internal master oscillator frequency. The output
frequency is fMASTER/PH. The PH value is determined by the connections
of the PH0, PH1 and PH2 pins as described in the Applications Information
section.
Note 5: Frequency accuracy is defined as the deviation from the fOUT
equation. fMASTER = 20MHz • 10k/RSET, fOUT = 20MHz • 10k/(RSET • PH),
PH = 3, 4, 5, 6, 7 or 8.
Note 6: Guaranteed by 5V test.
Note 7: To conform to the Logic IC Standard, current out of a pin is
defined as a negative value.
Note 8: Output rise and fall times are measured between the 10% and the
90% power supply levels with no output loading. These specifications are
based on characterization.
Note 9: Long term drift on silicon oscillators is primarily due to the
movement of ions and impurities within the silicon and is tested at 30°C
under otherwise nominal operating conditions. Long term drift is specified
as ppm/√kHr due to the typically nonlinear nature of the drift. To calculate
drift for a set time period, translate that time into thousands of hours, take
the square root and multiply by the typical drift number. For instance, a
year is 8.77kHr and would yield a drift of 888ppm at 300ppm/√kHr. Drift
without power applied to the device (aging) may be approximated as
1/10th of the drift with power, or 30ppm/√kHr for a 300ppm/√kHr device.
Typical Performance Characteristics
FREQUENCY ERROR (%)
TYPICAL MAX
0
TYPICAL MIN
–2
–3
GUARANTEED MIN
OVER TEMPERATURE
–4
–5
10k
100k
0.75
GUARANTEED MAX
OVER TEMPERATURE
2
1 TYPICAL MAX
0
–1
GUARANTEED MIN
OVER TEMPERATURE
–2 TYPICAL MIN
–3
–5
10k
10M
100k
RSET (Ω)
1M
3000
PH = 3, SSFM ENABLED
CLOAD = 5pF
RLOAD = 5k
2500
1500
RSET = 100k
400
RSET = 2M
200
2.7
3.2
–1.00
–40
–20
0
40
20
TEMPERATURE (°C)
60
CLOAD = 5pF
V+ = 5V, PH = 3
80
6909 G03
Supply Current
vs RSET (SSFM Disabled)
3000
2500
2000
V+ = 2.7V, PH = 3
1500
1000
600
0
10M
2000
RSET = 400k
800
TYPICAL MIN
ISUPPLY (µA)
1000
–0.50
CLOAD = 5pF
RLOAD = 5k
V+ = 5V, PH = 3
V+ = 5V, PH = 8
RSET = 20k
1200
–0.25
Supply Current
vs RSET (SSFM Enabled)
ISUPPLY (µA)
SUPPLY CURRENT (µA)
1400
TYPICAL MAX
0
6909 G02
Supply Current vs Supply Voltage
1600
0.25
RSET (Ω)
6909 G01
1800
0.50
–0.75
–4
1M
Frequency Error vs Temperature
1.00
TA = 25°C
4
3
2
–1
Frequency Error vs RSET, V+ = 5V
FREQUENCY ERROR (%)
TA = 25°C
4 GUARANTEED MAX
OVER TEMPERATURE
3
1
5
FREQUENCY ERROR (%)
5
Frequency Error vs RSET, V+ = 2.7V
4.2
3.7
SUPPLY VOLTAGE (V)
500
4.7
6909 G04
0
10k
V+ = 5V, PH = 8
V+ = 2.7V, PH = 3
1000
500
V+ = 2.7V, PH = 8
100k
1M
10M
RSET (Ω)
0
10k
V+ = 2.7V, PH = 8
100k
1M
10M
RSET (Ω)
6909 G05
6909 G06
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LTC6909
Typical Performance Characteristics
Typical Output Resistance
vs Supply Voltage
Supply Current vs Temperature
110
700
600
550
V+ = 2.7V
500
RSET = 100k
PH = 3
CLOAD = 5pF
SSFM DISABLED
450
20 40 60 80
TEMPERATURE (°C)
90
80
70
60
50
40
20
3.0
RISE TIME
2.5
2.0
1.5
FALL TIME
1.0
0.5
30
100 120
CLOAD = 5pF
4.0 TA = 25°C
RLOAD = 5k
3.5
0
2.7
2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5
SUPPLY VOLTAGE (V)
3.2
3.7
4.2
4.7
SUPPLY VOLTAGE (V)
5.2
6909 G09
6909 G08
6909 G07
Jitter vs RSET
Output Operating at 3.33MHz
1.2
CLOAD = 5pF
1.0
V+ = 5V, DIV = 3
0.8
500mV/DIV
V+ = 2.7V, DIV = 3
0.6
0.4
50ns/DIV
V+ = 3.3V
CLOAD = 15pF
RLOAD = 5k
V+ = 5V, DIV = 8
0.2
0
10k
V+ = 2.7V, DIV = 8
100k
1M
6909 G11
10M
RSET (Ω)
6909 G10
Output Frequency Spectrum
SSFM Enable and Disabled
Output Operating at 6.66MHz
0 RES BW = 9kHz
SSFM ENABLED
(N = 16)
10dB/DIV
0
OUTPUT RISE/FALL TIME (ns)
OUTPUT RESISTANCE (Ω)
V+ = 5V
JITTER (% P-P)
SUPPLY CURRENT (µA)
4.5
100
650
400
–40 –20
Output Rise/Fall Time
vs Supply Voltage
1V/DIV
SSFM DISABLED
–100
50ns/DIV
V+ = 5V
CLOAD = 15pF
RLOAD = 5k
6909 G12
2.5 MHz
FREQUENCY (200kHz/DIV)
6909 G13
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LTC6909
Pin Functions
V+A (Pin 1): Analog Voltage Supply (2.7V ≤ V+A ≤ 5.5V).
This supply should be kept free of noise and ripple. It
should be bypassed directly to GND with a 0.1µF or greater
low ESR capacitor. V+A and V+D must be connected to the
same supply voltage.
GND (Pin 2): Ground Connections. Should be tied to a
ground plane for best performance.
PH0, PH1, PH2 (Pins 3, 4, 15): Output Phasing Selection Pins. These are standard CMOS logic input pins and
they do not have an internal pull-up or pull-down. These
pins must be connected to a valid logic input 0 or 1 voltage. Connect the pins to GND for a logic 0 and to the V+D
pin for a logic 1. These pins configure the output phase
relationships as follows:
PH2
PH1
PH0
0
0
0
All Outputs Are Floating (Hi-Z)
MODE
0
0
1
All Outputs Are Held Low
0
1
0
3-Phase Mode (PH = 3)
0
1
1
4-Phase Mode (PH = 4)
1
0
0
5-Phase Mode (PH = 5)
1
0
1
6-Phase Mode (PH = 6)
1
1
0
7-Phase Mode (PH = 7)
1
1
1
8-Phase Mode (PH = 8)
The PH0, PH1, PH2 pin connections not only determine
the phase relationship of the output signals but also divide
the master oscillator frequency by the value PH.
OUT1 Through OUT8 (Pins 5 Through 12): Oscillator
Outputs. These are CMOS rail-to-rail logic outputs with
a series resistance of approximately 40Ω, capable of
driving 1k and/or 50pF loads. Larger loads may cause
minor frequency inaccuracies due to supply bounce at
high frequencies. When any output pin is not in use, it is
in a floating, high impedance state. The outputs are also
held in a high impedance state during start-up. After the
part’s internal frequency setting loop has settled, the outputs are active, clean and operating at the set frequency
(first cycle accurate).
V+D (Pin 13): Digital Voltage Supply (2.7V ≤ V+D ≤ 5.5V).
This pin should be bypassed directly to GND with a 0.1µF
or greater low ESR capacitor. V+D and V+A must be connected to the same supply voltage.
MOD (Pin 14): Spread Spectrum Frequency Modulation
Setting Input. This input selects among four modulation
rate settings. The MOD pin should be tied to ground for
an fOUT/16 modulation rate. Floating the MOD pin selects
an fOUT/32 modulation rate. The MOD pin should be tied
to V+D for the fOUT/64 modulation rate. Tying one of the
active outputs to the MOD pin turns the modulation off.
To detect a floating MOD pin, the LTC6909 attempts to
pull the pin to the midsupply point. This is realized with
two internal current sources, one tied to V+D and MOD
and the other one tied to GND and MOD. Therefore, driving the MOD pin high requires sourcing approximately
2µA. Likewise, driving the MOD pin low requires sinking
approximately 2µA. When the MOD pin is floated for the
fOUT/32 modulation rate, it must be bypassed using a
1nF or larger, capacitor to GND. Any AC signal coupling
to the MOD pin could potentially be detected and stop the
frequency modulation.
SET (Pin 16): Frequency Setting Resistor Input. The value
of the resistor connected between this pin and V+A determines the frequency of the master oscillator. The output
frequency, fOUT, is the master oscillator frequency divided
by PH as set by the PH0, PH1 and PH2 pin connections.
The voltage on this pin is held approximately 1.1V below
V+A. For best performance, use a precision metal film
resistor with a value between 20k and 400k, and limit the
capacitance on the pin to less than 10pF. Resistor values
outside of this range will have some loss of accuracy as
noted in the Electrical Characteristics table.
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LTC6909
Block Diagram
PH0 PH1 PH2
3
4 15
V+A
I
fMASTER = 20MHz • 10k • +MASTER = 20MHz • 10k/RSET
V – VSET
(SSFM = OFF)
MASTER
OSCILLATOR
DRIVER
5 OUT1
DRIVER
6 OUT2
DRIVER
7 OUT3
DRIVER
8 OUT4
DRIVER
9 OUT5
IREF
DRIVER
10 OUT6
MDAC
DRIVER
11 OUT7
DRIVER
12 OUT8
+
1
RSET
SET
V+D
13
VSET
16
VBIAS
V
OUT
–
ISET =
V+ – VSET
RSET
V+
DETECT
CLOCK INPUT
+
–
POR
OUTPUT
Hi-Z
UNTIL
STABLE
DIVIDE BY
16/32/64
3-STATE
INPUT DECODER
MOD 14
OUTPUT
PHASING
DRIVERS
IMASTER
PSEUDORANDOM
CODE GENERATOR
+
–
GND 2
1 POLE
LPF
WHEN A CLOCK SIGNAL IS PRESENT AT THE
MOD PIN INPUT, THE MODULATION IS DISABLED
GND
6909 BD
6909fa
7
LTC6909
Operation
As shown in the Block Diagram, the LTC6909’s master
oscillator is controlled by the ratio of the voltage between
the V+A and SET pins and the current entering the SET pin
(IMASTER). When the spread spectrum frequency modulation (SSFM) is disabled, IMASTER is strictly determined by
the (V+A – VSET) voltage and the RSET resistor. When SSFM
is enabled, IMASTER is modulated by a filtered pseudorandom noise (PRN) signal. Here the IMASTER current is a
random value uniformly distributed between (ISET – 10%)
and (ISET + 10%). In this way, the frequency is modulated
to produce an approximately flat frequency spectrum,
centered about the set frequency with a bandwidth equal
to approximately 20% of the center frequency.
The voltage on the SET pin is forced to approximately 1.1V
below V+A by the PMOS transistor and its gate bias voltage. This voltage is accurate to ±5% at a particular input
current and supply voltage (see Figure 1). The LTC6909
is optimized for use with resistors between 20k and 400k
corresponding to master oscillator frequencies between
500kHz and 10MHz. Accurate master oscillator frequencies up to 20MHz (RSET = 10k) are attainable if the supply
voltage is greater than 4V. The RSET resistor, connected
between the V+A and SET pins, locks together the (V+A –
VSET) voltage and the current ISET. This allows the parts
to attain excellent frequency accuracy regardless of the
precision of the SET pin. The master oscillation frequency is:
fMASTER = 20MHz • 10k/RSET
1.4
TA = 25°C
VRES = V+ – VSET
1.3
1.2
V+ = 5V
V+ = 3V
1.0
0.9
1
10
IRES (µA)
Output Frequency and Configurations
The output frequency of the LTC6909 is set by the RSET
resistor value and the connections of the PH0, PH1 and
PH2 logic input pins. The following formula defines the
relationship:
fOUT = 20MHz • 10k/(RSET • PH)
where PH = 3, 4, 5, 6, 7 or 8 and is defined as follows:
PH2
PH1
PH0
0
0
0
MODE
All Outputs Are Floating (Hi-Z)
0
0
1
All Outputs Are Held Low
0
1
0
3-Phase Mode (PH = 3)
0
1
1
4-Phase Mode (PH = 4)
1
0
0
5-Phase Mode (PH = 5)
1
0
1
6-Phase Mode (PH = 6)
1
1
0
7-Phase Mode (PH = 7)
1
1
1
8-Phase Mode (PH = 8)
The PH0, PH1 and PH2 pins are standard logic input pins.
These pins do not have any active pull-up or pull-down
circuitry. As such, they cannot be left floating and must be
connected to a valid logic high or low voltage. The PH0,
PH1 and PH2 pin connections not only divide the master
oscillator frequency by the value PH but also determine
the phase relationship between the output signals. Figure
2 shows the output waveforms for each of the eight possible output configurations.
Note that 2-phase, complementary (180° phase shifted)
outputs are available in the 4-, 6- and 8-phase modes
by choosing the correct pair of signals. For example, in
4-phase mode, OUT1 and OUT3 (or OUT2 and OUT4) are
complementary.
1.1
0.8
0.1
When the spread spectrum frequency modulation (SSFM)
is disabled, the master oscillator frequency is stationary.
When SSFM is enabled, the master oscillator frequency
varies from 0.9 • fMASTER to 1.1 • fMASTER.
100
1000
6909 F01
Figure 1. V+ – VSET Variation with IRES
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8
LTC6909
Operation
MASTER OSCILLATOR
PH2 - PH1 - PH0 = 000
PH2 - PH1 - PH0 = 001
PH2 - PH1 - PH0 = 010
ALL OUTPUTS ARE Hi-Z
ALL OUTPUTS ARE LOW
PH = 3, fOUTPUT = fMASTER/3
ADJACENT OUTPUTS ARE PHASE SHIFTED BY 120°
PH = 4, fOUTPUT = fMASTER/4
ADJACENT OUTPUTS ARE PHASE SHIFTED BY 90°
PH = 5, fOUTPUT = fMASTER/5
ADJACENT OUTPUTS ARE PHASE SHIFTED BY 72°
PH = 6, fOUTPUT = fMASTER/6
ADJACENT OUTPUTS ARE PHASE SHIFTED BY 60°
OUT1
OUT2
OUT3
OUT4 Hi-Z
OUT5 Hi-Z
OUT6 Hi-Z
OUT7 Hi-Z
OUT8 Hi-Z
PH2 - PH1 - PH0 = 011
OUT1
OUT2
OUT3
OUT4
OUT5 Hi-Z
OUT6 Hi-Z
OUT7 Hi-Z
OUT8 Hi-Z
PH2 - PH1 - PH0 = 100
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6 Hi-Z
OUT7 Hi-Z
OUT8 Hi-Z
PH2 - PH1 - PH0 = 101
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7 Hi-Z
OUT8 Hi-Z
6909 F02a
Figure 2a. Output Waveforms for Different PH Settings
6909fa
9
LTC6909
Operation
MASTER OSCILLATOR
PH2 - PH1 - PH0 = 110
PH = 7, fOUTPUT = fMASTER/7
ADJACENT OUTPUTS ARE PHASE SHIFTED BY 51.43°
PH = 8, fOUTPUT = fMASTER/8
ADJACENT OUTPUTS ARE PHASE SHIFTED BY 45°
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8 Hi-Z
PH2 - PH1 - PH0 = 111
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8
6909 F02b
Figure 2b. Output Waveforms for Different PH Settings
6909fa
10
LTC6909
Operation
is generated by a linear feedback shift register that is 15
bits long. The pseudorandom sequence will repeat every
(215 – 1) • N clock cycles. This guarantees a repetition
rate below 13Hz for output frequencies up to 6.67MHz.
Seven bits of the shift register are sent in parallel to the
MDAC which produces the modulating current waveform.
Being a digitally generated signal, the output of the MDAC
is not a perfectly smooth waveform, but consists of (27)
discrete steps that change every shift register clock cycle.
Note that the shift register clock is the output frequency,
fOUT, divided by N, where N is the modulation rate divider
setting, which is determined by the state of the MOD pin.
The MOD pin should be tied to ground for the N = 16 setting. Floating the MOD pin selects N = 32. The MOD pin
should be tied to V+ for the N = 64 setting.
Spread Spectrum Frequency Modulation
The LTC6909 can operate with spread spectrum frequency
modulation (SSFM). In this mode, the oscillator’s frequency
is modulated by a pseudorandom noise (PRN) signal
to spread the oscillator’s energy over a wide frequency
band. This spreading decreases the peak electromagnetic
radiation levels and improves electromanetic compatibility
(EMC) performance.
The amount of frequency spreading is fixed at 20% (±10%),
where frequency spreading is defined as:
Frequency Spreading (in %) = 100 • (fMAX – fMIN)/fOUT
The IMASTER current is a dynamic signal generated by
a multiplying digital-to-analog converter (MDAC) referenced to ISET and lowpass filtered. IMASTER varies in a
psuedorandom noise-like manner between 0.9 • ISET and
1.1 • ISET. This causes the output frequency to vary in a
pseudorandom noise-like manner between 0.9 • fOUT and
1.1 fOUT.
The output of the MDAC is then filtered by a lowpass filter
with a corner frequency set to the modulation rate (fOUT/N).
This limits the rate of frequency change and softens the
corners of the frequency control signal, but allows the
waveform to fully settle at each frequency step. The rise
and fall times of this single pole filter are approximately
0.35/fCORNER. This is beneficial for clocking switching
regulators, as discussed in the Applications Information
section. Figure 3 illustrates how the output frequency
varies over time.
To disable the SSFM, connect one of the active outputs
to the MOD pin. An AC detector circuit shuts down the
modulation circuitry if a frequency in the vicinity of the
output frequency is detected at the MOD pin.
As stated previously, the modulating waveform is a pseudorandom noise-like waveform. The pseudorandom signal
FREQUENCY
fOUT + 10%
128 STEPS
fOUT – 10%
tSTEP = N/fOUT
tSTEP
tREPEAT
TIME
tREPEAT = ((215 – 1) • N)/fOUT
6909 F03
Figure 3
6909fa
11
LTC6909
Applications Information
Selecting The Frequency-Setting Resistor
The LTC6909 has a master oscillator frequency range
spanning 100kHz to 20MHz depending on the RSET resistor value. However, accuracy may suffer if the oscillator
is operated at a master oscillator frequency greater than
10MHz with a supply voltage lower than 4V. With a linear
correspondence between the master oscillator period and
the RSET resistance, a simple equation relates resistance
with frequency.
RSET =10k • 20MHz/fMASTER
RSETMIN = 10k (5V supply), 20k (2.7V supply),
RSETMAX = 2M
Any RSET resistor tolerance will shift the output frequency
by the same amount.
Alternative Methods of Setting the Output
Frequency of the LTC6909
The oscillator may be programmed by any method that
sources a current into the SET pin. The circuit in Figure 4
sets the oscillator frequency using a programmable current
source and in the expression for fOUT, the resistor RSET is
replaced by the ratio of 1.1V/ICONTROL. As already explained
in the Operation section, the voltage difference between
V+ and SET is approximately 1.1V ±5%, therefore, the
Figure 4 circuit is less accurate than if a resistor controls
the output frequency.
V+
ICONTROL
CBYP
V+A
CBYP
V+
VCONTROL
+
–
V+A
GND
RSET
SET
6909 F05
fOUT = 10k • 20MHz/RSET(1 – VCONTROL/1.13V)
Figure 5. Voltage Controlled Oscillator
the relationship between the input current and the voltage between V+ and SET; the frequency accuracy will be
degraded. The oscillator frequency, however, will increase
monotonically with decreasing VCONTROL.
SETTING THE MODULATION RATE OF THE LTC6909
The modulation rate of the LTC6909 is equal to fOUT/N,
where N is the modulation rate divider setting, which is
determined by the state of the MOD pin. The MOD pin should
be tied to ground for the N = 16 setting. Floating the MOD
pin selects N = 32. The MOD pin should be tied to V+ for
the N = 64 setting. To disable the SSFM, connect one of
the active outputs to the MOD pin. An AC detector circuit
shuts down the modulation circuitry if a frequency that is
close to the output frequency is detected at the MOD pin.
When the MOD pin is floated, for the fOUT/32 modulation
rate, it must be bypassed by at least a 1nF capacitor
to GND. Any AC signal coupling to the MOD pin could
potentially be detected and stop the frequency modulation.
DRIVING LOGIC CIRCUITS
GND
SET
6909 F04
fMASTER = 10k • (20MHz/1.13V) • ICONTROL(A)
Figure 4. Current Controlled Oscillator
Figure 5 shows the LTC6909 configured as a VCO. A voltage source is connected in series with an external 10k
resistor. The master oscillator frequency, fMASTER, will
vary with VCONTROL, that is the voltage source connected
between V+ and the SET pin. Again, this circuit decouples
The outputs of the LTC6909 are suitable for driving general digital logic circuits. However, the form of frequency
spreading used in the LTC6909 may not be suitable for
many logic designs. Many logic designs have fairly tight
timing and cycle-to-cycle jitter requirements. These systems often benefit from a spread spectrum clocking system
where the frequency is slowly and linearly modulated by a
triangular waveform, not a pseudorandom waveform. This
type of frequency spreading maintains a minimal difference
in the timing from one clock edge to the next adjacent
clock edge (cycle-to-cycle jitter). The LTC6909 uses a
pseudorandom modulating signal where the frequency
6909fa
12
LTC6909
Applications Information
transitions have been slowed and the corners rounded
by a first order lowpass filter with a corner frequency set
to the modulation rate (fOUT/N), where N is the modulation rate divider setting, which is determined by the state
of the MOD pin. This filtered modulating signal may be
acceptable for many logic systems but the cycle-to-cycle
jitter issues must be considered carefully.
DRIVING SWITCHING REGULATORS
The LTC6909 is designed primarily to provide an accurate
and stable clock for switching regulator systems. The
CMOS logic outputs are suitable for directly driving most
switching regulators and switching controllers. Linear
Technology has a broad line of fully integrated switching
regulators and switching regulator controllers designed
for synchronization to an external clock. All of these
parts have one pin assigned for external clock input. The
nomenclature varies depending on the part’s family history. SYNC, PLLIN, SYNC/MODE, EXTCLK, FCB and S/S
(shorthand for SYNC/SHDN) are examples of clock input
pin names used with Linear Technology ICs.
For the best EMC performance, the LTC6909 should be run
with the MOD pin tied to ground (SSFM enabled, modulation rate set to fOUT/16). Regulatory testing is done with
strictly specified bandwidths and conditions. Modulating
faster than, or as close to, the test bandwidth as possible
gives the lowest readings. The optimal modulating rate is
not as straightforward when the goal is to lower radiated
signal levels interfering with other circuitry in the system.
The modulation rate will have to be evaluated with the
specific system conditions to determine the optimal rate.
Depending on the specific frequency synchronization
method a switching regulator employs, the modulation
rate must be within the synchronization capability of the
regulator. Many regulators use a phase-locked loop (PLL)
for synchronization. For these parts, the PLL loop filter
should be designed to have sufficient capture range and
bandwidth.
The frequency hopping transitions of the LTC6909 are
slowed by a lowpass filter. The corner frequency of this
filter is set to the modulation rate (fOUT/N), where N is
the modulation rate divider setting, which is determined
by the state of the MOD pin. The MOD pin should be tied
to ground for the N = 16 setting. Floating the MOD pin
selects N = 32. The MOD pin should be tied to V+ for the
N = 64 setting. This is an important feature when driving
a switching regulator. The switching regulator is itself
a servo loop with a bandwidth typically on the order of
1/10 to 1/20 of the operating frequency. When the clock
frequency’s transition is within the bandwidth of the switching regulator, the regulator’s output stays in regulation. If
the transition is too sharp, beyond the bandwidth of the
switching regulator, the regulator’s output will experience
a sharp jump and then settle back into regulation. If the
bandwidth of the regulator is sufficiently high, beyond
fOUT/N, then there will not be any regulation issues.
One aspect of the output voltage that will change is the
output ripple voltage. Every switching regulator has some
output ripple at the clock frequency. For most switching
regulator designs with fixed MOSFET’s, fixed inductor,
fixed capacitors, the amount of ripple will vary with the
regulator’s operating frequency (the main exception being hysteretic architecture regulators). An increase in
frequency results in lower ripple and a frequency decrease
gives more ripple. This is true for static frequencies or
dynamic frequency modulated systems. If the modulating
signal was a triangle wave, the regulator’s output would
have a ripple that is amplitude modulated by the triangle
wave. This repetitive signal on the power supply could
cause system problems by mixing with other desired
signals creating distortion. Depending on the switching
regulator’s inductor design and triangle wave frequency,
it may even result in an audible noise. The LTC6909 uses
a pseudorandom noise-like signal. On an oscilloscope, it
looks essentially noise-like of even amplitude. The signal
is broadband and any mixing issues are eliminated. Additionally, the pseudorandom signal repeats at such a low
rate that it is well below the audible range.
The LTC6909 with the spread spectrum frequency modulation enabled results in improved EMC performance. If the
bandwidth of the switching regulator is sufficient, not a
difficult requirement in most cases, the regulator’s regulation, efficiency and load response are maintained while
6909fa
13
LTC6909
Applications Information
peak electromagnetic radiation (or conduction) is reduced.
Output ripple may be somewhat increased, but its behavior
is very much like noise and its system impact is benign.
SUPPLY BYPASSING, SIGNAL CONNECTIons AND
PCB LAYOUT
Using the LTC6909 in spread spectrum mode naturally
eliminates any concerns for output frequency accuracy
and stability as it is continually hopping to new settings.
In fixed frequency applications however, some attention to
V+ supply voltage ripple is required to minimize additional
output frequency error. Ripple frequency components on
the supply line near the programmed output frequency of
the LTC6909 in excess of 30mVP-P could create an additional 0.2% of frequency error. In applications where a fixed
frequency LTC6909 output clock is used to synchronize
the same switching regulator that provides the V+ supply
to the oscillator, noticeable jitter of the clock may occur if
the ripple exceeds 30mVP-P .
The LTC6909’s accuracy is affected as described above
by supply ripple on the V+A pin only. The V+D pin is essentially insensitive to supply ripple. The V+A pin supplies
the power for the analog section of the LTC6909 and its
current is largely constant for a given RSET resistor value.
The V+D pin supplies the digital section including the output drivers and its current requirement consists mainly of
large bursts that digital circuitry requires when switching.
The peak current required by the output drivers is by far
the largest. The current is mainly dependent on output
capacitive loading and the supply voltage.
Figure 6 shows how to connect the V+A and V+D supply
pins to the power supply as well as a suggested PCB layout.
The PCB layout assumes a two layer board with a ground
plane in the layer beneath the part and 0805 sized passive
components. The PCB layout in Figure 6 is a guide and
need not be followed exactly. However, there are several
items to note from the layout as follows:
multiple (three to four minimum) vias to minimize
inductance.
2. Place the bypass capacitors, C1 and C2, as close to the
V+A and V+D pins as possible to minimize the inductance
between the capacitor’s lead and the part’s pins.
3. The connection to the V+A and V+D pins to the main
supply should be through a low impedance path. If
the board has a V+ power plane, use it instead of the
top layer connection shown in Figure 6. Use multiple
vias (three to four minimum) at each point to connect
the V+A and V+D pins to the V+ plane to minimize the
inductance.
4. Connect the bypass capacitors, C1 and C2, directly to the
GND pin using a low inductance path. The connection
from C1 to the GND pin is easily done directly on the top
layer. The C2 path is more difficult but is accomplished
through multiple vias to the ground plane.
5. Connect the RSET resistor directly to the SET pin and
the V+A pin. Connecting the resistor to the V+ supply
through any manner other than directly to the V+A pin
will result greater frequency error.
6. Provide a ground shield around the RSET resistor and
its connections to V+A and SET. The SET pin is a fairly
high impedance point and is susceptible to interference
from noisy signal lines such as the part’s CMOS outputs
OUT1 through OUT8.
7. Route the output signals, OUT1 through OUT8, away from
the SET pin as soon as possible to minimize coupling.
8. When using the LTC6909 with spread spectrum disabled,
an active output is connected to the MOD pin. This is
best done by routing the OUT1 signal under the part
as shown in Figure 6. The ground shield between this
trace and the RSET resistor is very important to minimize
coupling of the OUT1 signal into the SET pin.
1. There should be a ground plane underneath and around
the part. Connect the GND pin to this plane through
6909fa
14
LTC6909
Applications Information
To assist in an orderly start-up sequence, the LTC6909’s
outputs are in a high impedance state for the first 128
master clock cycles after power-up. This ensures that
the first clock cycle is very close to the desired operating
frequency.
Powering up and down complex multiphase switching
regulator circuits is always chaotic and can have serious
system consequences if it is not done carefully. In addition
to the LTC6909’s muting of the outputs to ensure first cycle
accuracy, the PH0-PH1-PH2 codes 000 (all outputs are
10000
START-UP DELAY (µs)
9. The connections for PH0, PH1 and PH2 are not shown
in Figure 6. These pins are connected to either GND or
V+D depending on the output phasing required for the
application. Connection to ground is done underneath
the part. Connecting PH2 to V+D is also straightforward.
Connecting PH0 or PH1 to V+D may require one or
both traces to go down a layer. If you are dynamically
changing one or all of the PH pins, place a 10k resistor in series with the signal line. Locate the resistor
fairly close to the PH pin. This signal typically comes
from a microcontroller or the power good signal from
a switching regulator and is usually quite noisy. The
series resistor provides some isolation between the
noisy signal and the LTC6909.
Start-Up ISSUES AND CONSIDERATIONS
The start-up time and settling time to within 1% of the
final value is estimated by the following equation:
25µs
t START ≈RSET •
+10µs
1k
TA = 25°C
V+ = 3V
1000
100
10
10k
1k
100k
RSET (Ω)
1M
10M
6909 F07
For instance, with RSET = 100k, the LTC6909 will settle to
within 1% of its 1MHz final value in approximately 260µs.
Figure 7 shows the start-up time for various RSET resistors.
RSET
C1
0.1µF
V +A
GROUND
PLANE
Figure 7. Start-Up Time
LTC6909
SET
GND
PH2
PH0
MOD
PH1
V+D
OUT1
OUT8
RSET
C1
C2
0.1µF
GROUND
PLANE
DIRECT, LOW IMPEDANCE
CONNECTION TO THE V+
SUPPLY
V+A
SET
GND
PH2
PH0
MOD
PH1
V+D
OUT1
OUT8
OUT2
OUT7
OUT3
OUT6
OUT4
OUT5
C2
6909 F06
Figure 6. Supply Bypassing and PCB Layout
6909fa
15
LTC6909
Applications Information
high impedance) and 001 (all outputs are low) are useful
for controlling the clocking of switching regulators during
start-up. At start-up, most switching regulators ignore the
clock input until a power good state is achieved. Nearly
all of Linear Technology’s switching regulators operate in
this manner. However, some switching regulators from
other vendors do not ignore the clock input on start-up
and yet are not synchronizable until the power good state
is reached. Attempting to synchronize these switching
regulators before they reach the power good state can
lead to problems. For these switching regulators it is best
to have the LTC6909 held in the PH0-PH1-PH2 codes
000 or 001 until the switching regulator issues a power
good signal. In most cases, simply connecting a switching regulator’s power good signal to the PH0, PH1 and/
or PH2 pins accomplishes this. At most, an additional
single logic inverter is required to switch from either the
000 or 001 states to any of the other six states through
a power good signal.
Another way to use the PH0, PH1 and PH2 inputs to assist with power-up/down issues is to use an external part
to provide a supply monitor or an undervoltage lockout
(UVLO). There are several parts available that combine a
comparator with a reference to fulfill this function. The
LTC6909 does not have its own internal UVLO. If the
supply is below 2.7V, frequency accuracy may suffer. At
a supply voltage around 2V or lower, the LTC6909 will
operate erratically or will stop. It may stop randomly in a
logic high or low state.
Figure 8 shows a circuit using an LTC1998 to monitor the
supply voltage and control the logic state of the PH0 and
PH1 pins. The LTC1998’s threshold is set at 2.5V with
50mV of hysteresis. On power-up, as the supply ramps
up, the LTC1998 holds PH0 and PH1 low, keeping the
LTC6909’s outputs in a high impedance state. Once the
supply is above 2.55V, the LTC1998 pulls the PH0 and PH1
pins high, setting the LTC6909 into the 4-phase operating
mode. On power-down, the supply ramps down and the
LTC1998’s output goes low once the supply is below 2.45V.
This puts the LTC6909’s outputs in the high impedance
state. All switch overs are synchronized to the LTC6909’s
internal oscillator to avoid glitches and runt pulses.
To adjust the on/off supply voltage threshold, change the
configuration of the LTC1998. As with the power good
signal, at most an additional single logic inverter is required
to switch from either the 000 or 001 states to any of the
other six states.
V+
RSET
1
0.1µF
1
0.1µF 2
3
LTC1998
BATT
BATTLO
GND
VLOGIC
VTHA
VHA
2
6
3
5
4
4
953k
5
6
49.9k
7
8
LTC6909
V+A
SET
GND
PH2
PH0
MOD
PH1
V+D
OUT1
OUT8
OUT2
OUT7
OUT3
OUT6
OUT4
OUT5
16
15
14
13
12
0.1µF
11
10
9
6909 F08
Figure 8. Adding a UVLO Feature to the LTC6909. In This Example, the LTC6909 Is in 4-Phase Mode
for a V+ > ≈2.5V (PHx = 011) and the Outputs Are All High Impedance for V+ < ≈2.5V (PHx = 000)
6909fa
16
LTC6909
Typical Applications
Simply Parallel Multiple DC/DC µModule® Regulator Systems to Achieve Higher Output Current. Board Layout Is as
Easy as Copying and Pasting Each µModule Regulator’s Layout With Very Few External Components Required
CLOCK SYNC
0° PHASE
VIN
10V TO 14V
51.1k
+
0.1µF
LTC6909
V+A
SET
GND
PH2
PH0
PH1
OUT1
OUT2
OUT3
OUT4
MOD
V+D
OUT8
OUT7
OUT6
OUT5
392k
PLLIN TRACK/SS
VOUT
VIN
PGOOD
MPGM
RUN
COMP
INTVCC
DRVCC
CIN*
100µF
25V
10µF
25V
×2
71.5k
51.1k
LTM4601
SGND
PGND
5%
MARGIN
SSFM
ENABLED
TRACK/SS CONTROL
22µF
6.3V
470µF
6.3V
VOUT_LCL
DIFFVOUT
VOSNS+
VOSNS–
fSET
VOUT
1.5V
48A MAX
220pF
RSET
10k
+
120pF
MARGIN CONTROL
SSFM DISABLED
0.1µF
VFB
MARG0
MARG1
60.4k + R
SET
N
RSET
N = NUMBER OF PHASES
VOUT = 0.6V
CLOCK SYNC
90° PHASE
4.5V TO 20V
TRACK/SS CONTROL
VIN
PGOOD
0.01µF
MPGM
RUN
COMP
INTVCC
DRVCC
10µF
25V
×2
PLLIN TRACK/SS
VOUT
LTM4601-1
392k
SGND
PGND
VFB
MARG0
MARG1
22µF
6.3V
+
VOUT_LCL
NC3
NC2
NC1
470µF
6.3V
fSET
CLOCK SYNC
180° PHASE
4.5V TO 20V
TRACK/SS CONTROL
VIN
PGOOD
MPGM
RUN
COMP
INTVCC
DRVCC
10µF
25V
×2
PLLIN TRACK/SS
VOUT
LTM4601-1
392k
SGND
PGND
VFB
MARG0
MARG1
22µF
6.3V
+
VOUT_LCL
NC3
NC2
NC1
470µF
6.3V
fSET
CLOCK SYNC
270° PHASE
4.5V TO 20V
TRACK/SS CONTROL
VIN
PGOOD
PGOOD
MPGM
RUN
COMP
INTVCC
DRVCC
10µF
25V
×2
0.1µF
PLLIN TRACK/SS
VOUT
LTM4601-1
392k
SGND
PGND
VFB
MARG0
MARG1
VOUT_LCL
NC3
NC2
NC1
22µF
6.3V
+
470µF
6.3V
fSET
6909 TA02
*CIN OPTIONAL TO REDUCE ANY LC RINGING.
NOT NEEDED FOR LOW INDUCTANCE PLANE CONNECTION
6909fa
17
LTC6909
Typical applications
Using Additional Standard Logic Inverters to Achieve 10- and 14-Phase Outputs
(Inverters Are 74HC04 or Equivalent)
10 OUTPUT PHASES (OUTPUTS SHIFTED BY 36 DEGREES)
0.1µF
0.1µF
14 OUTPUT PHASES (OUTPUTS SHIFTED BY 25.71 DEGREES)
V+
LTC6909
OUT1
V+D
RSET
0.1µF
V+
0° (360°)
LTC6909
OUT1
V+D
0° (360°)
GND
OUT2
180°
GND
OUT2
180°
V+A
OUT3
72°
V+A
OUT3
51.43°
SET
OUT4
252°
SET
OUT4
231.43°
PH0
OUT5
144°
PH0
OUT5
102.86°
PH1
OUT6
324°
PH1
OUT6
282.86°
PH2
OUT7
216°
PH2
OUT7
154.29°
MOD
OUT8
36°
MOD
OUT8
334.29°
0.1µF
RSET
288°
205.71°
108°
25.71°
257.14°
77.14°
308.57°
128.57°
6909 TA03
6909fa
18
LTC6909
Typical applications
Combining Eight Outputs With a Lowpass Filter to Create a Sine Wave
2.7V TO 5.5V
249k
1
0.1µF
2
3
4
V+A
SET
GND
PH2
LTC6909
PH0
16
500mV/DIV
15
MOD 14
V+D 13
PH1
0.1µF
787k
5
402k
6
140k
7
80.6k
8
1
OPEN
2
3
4
21k
5
6
7
0.1µF
8
OUT1
OUT8
OUT2
OUT7
OUT3
OUT6
OUT4
OUT5
V+
LP
SA
LTC1563-2
NC
INVA
LPB
NC
INVB
NC
NC
LPA
SB
AGND
NC
V–
EN
787k
12
V+ = 5V
THD = 0.2%
11 402k
2µs/DIV
6909 TA06
10 140k
9
80.6k
16
0.1µF
15
14
13
12
16.2k
100kHz
SINE WAVE
OUTPUT
20k
11
10
9
16.2k
6909 TA04
6909fa
19
LTC6909
Package Description
MS Package
16-Lead Plastic MSOP
Package
(Reference LTCMS
DWG
# 05-08-1669 Rev Ø)
16-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1669 Rev Ø)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
4.039 ± 0.102
(.159 ± .004)
(NOTE 3)
0.50
(.0197)
BSC
0.305 ± 0.038
(.0120 ± .0015)
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
DETAIL “A”
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
0° – 6° TYP
0.280 ± 0.076
(.011 ± .003)
REF
16151413121110 9
GAUGE PLANE
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
0.18
(.007)
SEATING
PLANE
1.10
(.043)
MAX
0.17 – 0.27
(.007 – .011)
TYP
1234567 8
0.50
(.0197)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.86
(.034)
REF
0.1016 ± 0.0508
(.004 ± .002)
MSOP (MS16) 1107 REV Ø
6909fa
20
LTC6909
Revision History
REV
DATE
DESCRIPTION
PAGE NUMBER
A
1/11
Revised typical value for ∆fMASTER, 10MHz ≤ fMASTER ≤ 20MHz to ±2.7.
2
Revised Typical Applications drawings for 10 and 14 output phases.
18
6909fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
21
LTC6909
Typical Application
Providing an 8-Phase Synchronizing Clock to LTM Modules
INPUT
SUPPLY
INTVCC
0.1µF
LTM4601
LTC6909
OUT1
V+D
35.7k
0.1µF
GND
OUT2
V+A
OUT3
SET
OUT4
PH0
OUT5
PH1
OUT6
PH2
OUT7
MOD
OUT8
S0FT-START
OUTPUT1
TRACKING
LTM4601-1
OUTPUT2
TRACKING
LTM4601-1
OUTPUT3
TRACKING
LTM4601-1
OUTPUT4
TRACKING
LTM4601-1
OUTPUT3
TRACKING
LTM4601-1
OUTPUT4
TRACKING
LTM4601-1
OUTPUT3
TRACKING
LTM4601-1
OUTPUT4
6909 TA05
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LTC1799
1kHz to 33MHz ThinSOT™ Oscillator, Resistor Set
Wide Frequency Range
LTC6900
1kHz to 20MHz ThinSOT Oscillator, Resistor Set
Low Power, Wide Frequency Range
LTC6902
Multiphase Oscillator with Spread Spectrum Modulation
2-, 3- or 4-Phase Outputs
LTC6903/LTC6904
1kHz to 68MHz Serial Port Programmable Oscillator
0.1% Frequency Resolution, I2C or SPI Interface
LTC6905
17MHz to 170MHz ThinSOT Oscillator, Resistor Set
High Frequency, 100µs Start-Up, 7ps RMS Jitter
LTC6905-XXX
Fixed Frequency ThinSOT Oscillators, Up to 133MHz
No Trim Components Required
LTC6906
Micropower ThinSOT Oscillator, Resistor Set
10kHz to 1MHz, 12mA at 100kHz
LTC6907
Micropower ThinSOT Oscillator, Resistor Set
40kHz to 4MHz, 36µA at 400kHz
LTC6908-1
50kHz to 10MHz Dual Output ThinSOT Oscillator, Resistor Set
Complementary Outputs (0°/180°)
LTC6908-2
50kHz to 10MHz Dual Output ThinSOT Oscillator, Resistor Set
Quadrature Outputs (0°/90°)
LTC6930-XXX
Fixed Frequency Oscillator, 32.768kHz to 8.192MHz
0.09% Accuracy, 110μs Startup Time, 105μA at 32kHz
6909fa
22
Linear Technology Corporation
LT 0111 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2009
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