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:
f
OUT
= 20MHz • 10k/(R
SET
• 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.
■
■
■
■
■
■
■
■
■
■
1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-Phase Outputs
One External Resistor Sets the Output Frequency
from 12.5kHz to 6.67MHz
Optional Spread Spectrum Frequency for Improved
EMI Performance
±10% Frequency Spreading
Outputs Can Be Held Low or Floated (Hi-Z)
Three Spread Spectrum Modulation Rates
f
OUT
/16, f
OUT
/32 and f
OUT
/64
400μA Supply Current
Operates from a Single 2.7V to 5.5V Supply
Fast Start-Up Time
First Cycle Accurate
Outputs Are High Impedance Until Frequency Settles
MS16 Package
APPLICATIONS
■
Synchronizing Multiple Switching Power Supplies
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
6342817, 6614313, 7417509.
TYPICAL APPLICATION
Providing a 4-Phase Synchronizing Clock to LTM Modules
0
10V TO 14V
INTV
CC
LTC6909
OUT1
V
+
D
GND
71.5k
0.1μF
V
+
A
SET
PH0
PH1
PH2
MOD
OUT2
OUT3
OUT4
OUT6
OUT7
OUT8
LTM4601-1
ENABLE SSFM
0.01μF
DISABLE SSFM
6909 TA01
150kHz to 30MHz Output
Frequency Spectrum
(9kHz Res BW)
SSFM DISABLED
OUTPUT (dBc)
–10
–20
–30
–40
–50
0
SSFM ENABLED
SSFM = f
OUT
/32
0.1μF
LTM4601
S0FT-START
1.5V
48A
TRACKING
LTM4601-1
TRACKING
LTM4601-1
TRACKING
OUTPUT (dBc)
OUT5
–10
–20
–30
–40
–50
150kHz
30MHz
FREQUENCY
(FUNDAMENTAL AND HARMONICS SHOWN)
6909 TA01b
6909f
1
LTC6909
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
V
+
A 1
GND
PH0
PH1
OUT1
OUT2
OUT3
OUT4
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SET
PH2
MOD
V
+
D
OUT8
OUT7
OUT6
OUT5
Supply Voltage (V
+
A) to GND ......................................6V
Supply Voltage (V
+
D) to GND......................................6V
Maximum Voltage
on Any Pin ................ (GND – 0.3V) ≤ V
PIN
≤ (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
MS PACKAGE
16-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 125°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC6909CMS#PBF
LTC6909IMS#PBF
LTC6909HMS#PBF
TAPE AND REEL
LTC6909CMS#TRPBF
LTC6909IMS#TRPBF
LTC6909HMS#TRPBF
PART MARKING*
6909
6909
6909
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–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
SYMBOL
Δf
MASTER
PARAMETER
Frequency Accuracy (Notes 4, 5)
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C or as noted. Test conditions are V
+
= V
+
A = V
+
D = 2.7V to 5.5V, R
L
= 5k,
C
L
= 5pF unless otherwise noted. The modulation is turned off (MOD is connected to OUT1) and PH = 8 unless otherwise specified.
R
SET
is defined as the resistor connected from the SET pin to the V
+
A pin.
CONDITIONS
V
+
= 5V
PH = 3
500kHz ≤ f
MASTER
≤ 10MHz
500kHz ≤ f
MASTER
≤ 10MHz
100kHz ≤ f
MASTER
< 500kHz
10MHz ≤ f
MASTER
≤ 20MHz
500kHz ≤ f
MASTER
≤ 10MHz
500kHz ≤ f
MASTER
≤ 10MHz
100kHz ≤ f
MASTER
< 500kHz
●
●
●
●
●
●
●
●
MIN
TYP
±1
±2.5
±3
±3.5
±0.5
±2
±2.5
±0.004
0.4
0.04
MAX
±2.5
±3
±4.5
±3.5
±2.5
±3
±4.5
0.9
0.35
UNITS
%
%
%
%
%
%
%
%/°C
%/V
%/V
V
+
= 2.7V
PH = 3
Δf
OUT
/ΔT
Frequency Drift Over Temperature
R
SET
= 100k
Δf
OUT
/ΔV
+
Frequency Drift Over Supply
V
+
= 4.5V to 5.5V, R
SET
= 100k
V
+
= 2.7V to 3.6V, R
SET
= 100k
6909f
2
LTC6909
ELECTRICAL CHARACTERISTICS
SYMBOL
R
SET
PARAMETER
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C or as noted. Test conditions are V
+
= V
+
A = V
+
D = 2.7V to 5.5V, R
L
= 5k,
C
L
= 5pF unless otherwise noted. The modulation is turned off (MOD is connected to OUT1) and PH = 8 unless otherwise specified.
R
SET
is defined as the resistor connected from the SET pin to the V
+
A pin.
CONDITIONS
MIN
10
20
●
TYP
MAX
2000
2000
UNITS
kΩ
kΩ
%
ppm/
√
kHr
Range of the R
SET
Resistor
4.5V ≤ V
+
≤ 5.5V
+
A Pin and 2.7V ≤ V
+
≤ 4.5V
Connected Between the V
the SET Pin
Frequency Spread with SSFM
Enabled
Long-Term Stability of the Output
Frequency (Note 9)
Duty Cycle (Note 6)
SSFM Disabled
R
SET
= 2M, R
L
= ∞, PH = 8, MOD = V
+
,
(f
OUT
= 12.5kHz), SSFM = f
OUT
/64
V
+
= 5V
V
+
= 2.7V
R
SET
= 20k, R
L
= ∞, PH = 3, MOD = GND,
(f
OUT
= 3.33MHz), SSFM = f
OUT
/16
V
+
= 5V
V
+
= 2.7V
R
SET
= 2M, R
L
= ∞, PH = 8, MOD = OUT1,
(f
OUT
= 12.5kHz), SSFM Off
V
+
= 5V
V
+
= 2.7V
●
●
R
SET
= 100k
MOD Pin = V
+
, GND or Open
±7
±10
300
±13
45
2.7
50
55
5.5
%
V
V
+
A, V
+
D
I
S
Operating Supply Voltage Range
V
+
Combined Supply Current
●
●
0.6
0.55
0.85
0.8
mA
mA
●
●
2.4
1.55
2.7
1.8
mA
mA
●
●
●
●
0.4
0.37
V
+
– 0.4
0.65
0.6
0.4
mA
mA
V
V
μA
μA
V
V
μA
V
V
V
V
V
IH_MOD
V
IL_MOD
I
MOD
V
IH_PH
V
IL_PH
I
IN_PHX
V
OH
High Level MOD Input Voltage
Low Level MOD Input Voltage
MOD Input Current (Note 7)
High Level PHx Input Voltage
Low Level PHx Input Voltage
High Level Output Voltage
(OUT1 Through OUT8)(Note 7)
MOD Pin = V
+
, V
+
= 5V
MOD Pin = GND, V
+
= 5V
PHx Refers to PH0, PH1 and PH2
PHx Refers to PH0, PH1 and PH2
V
+
= 5V
V
+
= 2.7V
No Load
5mA Load to GND
No Load
3mA Load to GND
No Load
5mA Load to V
+
No Load
3mA Load to V
+
●
●
●
●
●
●
●
●
●
–4
V
+
– 0.4
2
–2
4
0.4
±1
4.35
2.1
4.92
4.65
2.63
2.4
0.07
0.25
0.07
0.25
1.6
2.5
1.6
2
0.55
0.55
Digital Input Current, PH0, PH1, PH2 0V < V
IN
< V
+
V
OL
Low Level Output Voltage
(OUT1 Through OUT8)(Note 7)
V
+
= 5V
V
+
= 2.7V
V
V
V
V
ns
ns
ns
ns
t
r
t
f
Output Rise Time (Note 8)
Output Fall Time (Note 8)
V
+
= 5V
V
+
= 2.7V
V
+
= 5V
V
+
= 2.7V
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.
6909f
3
LTC6909
ELECTRICAL CHARACTERISTICS
Note 4:
f
MASTER
is the internal master oscillator frequency. The output
frequency is f
MASTER
/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 f
OUT
equation. f
MASTER
= 20MHz • 10k/R
SET
, f
OUT
= 20MHz • 10k/(R
SET
• 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.
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