LTC6903/LTC6904
1kHz - 68MHz Serial
Port Programmable Oscillator
FEATURES
s
s
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
1kHz to 68MHz Square Wave Output
0.5% (Typ) Initial Frequency Accuracy
Frequency Error <1.1% Over All Settings
10ppm/°C Typical Frequency Drift Over
Temperature
0.1% Resolution
1.7mA Typical Supply Current (f < 1MHz, V
S
= 2.7V)
2.7V to 5.5V Single Supply Operation
Jitter <0.4% Typical 1kHz to 8MHz
Easy to Use SPI (LTC6903) or I
2
C (LTC6904) Serial
Interface
Output Enable Pin
–40°C to 125°C Operation
MS8 Package
The LTC
®
6903/LTC6904 are low power self contained
digital frequency sources providing a precision frequency
from 1kHz to 68MHz, set through a serial port. The
LTC6903/LTC6904 require
no external components
other
than a power supply bypass capacitor, and they operate
over a single wide supply range of 2.7V to 5.5V.
The LTC6903/LTC6904 feature a proprietary feedback
loop that linearizes the relationship between digital control
setting and frequency, resulting in a very simple frequency
setting equation:
2078(Hz)
f
=
2
OCT
•
;1kHz
<
f
<
68MHz
DAC
2 –
1024
Where OCT is a 4-bit digital code and DAC is a 10-bit digital
code.
The LTC6903 is controlled by a convenient SPI compatible
serial interface. The LTC6904 uses an industry standard
I
2
C compatible interface.
, LTC and LT are registered trademarks of Linear Technology Corporation.
U.S. Patent Numbers 6342817 and 6614313.
APPLICATIO S
s
s
s
s
s
Precision Digitally Controlled Oscillator
Power Management
Direct Digital Frequency Synthesis (DDS)
Replacement
Replacement for DAC and VCO
Switched Capacitor Filter Clock
TYPICAL APPLICATIO
A Microcontroller Controlling Its Clock
40
5V
MICROCONTROLLER
OSC1/CLKIN
OSC2/CLKOUT
MCLR/V
P–P
RC5/SDO
RC3/SCK/SCL
RC2/CCP1
GND
SDI
LTC6903
SCK
SEN
CLK
1µF
CLK
0.01µF
PIC16F73
POWER-UP CLOCK
FREQUENCY IS 1039Hz
0
–1.0
10
V
+
OE
10Ω
V
S
= 3V
T
A
= 25°C
f = 1039Hz
443
30 UNITS
TESTED
10k
UNITS
20
5V
0.1µF
V
DD
V
SS
V
SS
6903 TA01
U
LTC6903 Frequency Error
Distribution
0
0.5
–0.5
FREQUENCY ERROR (%)
1.0
6903 TA01b
U
U
69034fa
1
LTC6903/LTC6904
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
GND
SDI
SCK
SEN/ADR*
1
2
3
4
8
7
6
5
V
+
OE
CLK
CLK
Total Supply Voltage (V
+
to GND) .............................. 6V
Maximum Voltage on any Pin
........................... (GND – 0.3V)
≤
VPIN
≤
(V
+
+ 0.3V)
Output Short Circuit Duration (Note 2) ............ Indefinite
Operating Temperature Range (Note 3)
LTC6903CMS8/LTC6904CMS8 ........... –40°C to 85°C
LTC6903IMS8/LTC6904IMS8 ............. –40°C to 85°C
LTC6903HMS8/LTC6904HMS8 ......... –40°C to 125°C
Specified Temperature Range (Note 4)
LTC6903CMS8/LTC6904CMS8 ........... –40°C to 85°C
LTC6903IMS8/LTC6904IMS8 ............. –40°C to 85°C
LTC6903HMS8/LTC6904HMS8 ......... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10sec)................... 300°C
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 200°C/W
LTC6903CMS8
LTC6903IMS8
LTC6903HMS8
LTC6904CMS8
LTC6904IMS8
LTC6904HMS8
MS8 PART MARKING*
* SEN (LTC6903)
ADR (LTC6904)
LTABN
LTAES
*The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 2.7V to 5.5V, GND = 0V, unless otherwise noted.
SYMBOL
∆fi
∆f
PARAMETER
Initial Frequency Accuracy
Total Frequency Accuracy (Note 7)
CONDITIONS
f = 1.039kHz, V
+
= 3V, C
LOAD
= 5pF
Single Output Active:
Over All Settings, V
+
= 2.7V, C
LOAD
= 5pF
Over All Settings, V
+
= 5.5V, C
LOAD
= 5pF
LTC6903CMS8, LTC6904CMS8:
Over All Settings, V
+
= 2.7V, C
LOAD
= 5pF
Over All Settings, V
+
= 5.5V, C
LOAD
= 5pF
LTC6903HMS8, LTC6903IMS8,
LTC6904HMS8, LTC6904IMS8:
Over All Settings, V
+
= 2.7V, C
LOAD
= 5pF
Over All Settings, V
+
= 5.5V, C
LOAD
= 5pF
MIN
TYP
MAX
±0.75
0.5
0.5
q
q
ELECTRICAL CHARACTERISTICS
UNITS
%
%
%
%
%
1.1
1.6
1.65
2
0.5
0.5
q
q
0.5
0.5
68
1.039
10
0.05
300
0.4
1
1.9
2.2
f
MAX
f
MIN
∆f/∆T
∆f/∆V
Maximum Operating Frequency
Minimum Operating Frequency
Frequency Drift Over Temperature
Frequency Drift Over Supply
Long Term Frequency Stability
Timing Jitter
(See Graph)
Duty Cycle
1.039kHz to 8.5MHz
1.039kHz to 68MHz
1.039kHz to 1MHz
1.039kHz to 68MHz
CLK, CLK Pins, V
+
= 2.7V
V
+
V
+
= 5.5V, 4mA Load
= 2.7V, 4mA Load
q
q
q
q
q
q
q
q
q
ppm/°C
%/V
ppm/√kHr
%
%
51
%
%
Ω
V
V
V
V
0.3
0.45
0.15
0.2
V
V
V
V
69034fa
49
50
50
45
5.3
2.3
5.45
2.55
0.15
0.25
0.05
0.05
R
OUT
V
OH
Output Resistance
High Level Output Voltage
4.8
2
5.2
2.3
V
+
= 5.5V, 1mA Load
V
+
= 2.7V, 1mA Load
V
OL
Low Level Output Voltage
V
+
= 5.5V, 4mA Load
V
+
= 2.7V, 4mA Load
V
+
= 5.5V, 1mA Load
V
+
= 2.7V, 1mA Load
2
U
%
%
MHz
kHz
W
U
U
W W
W
LTC6903/LTC6904
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 2.7V to 5.5V, GND = 0V, unless otherwise noted.
SYMBOL
t
r
t
f
PARAMETER
Output Rise Time (10% - 90%)
Output Fall Time (10% - 90%)
CONDITIONS
V
+
= 5.5V, R
LOAD
=
∞,
C
LOAD
= 5pF
V
+
= 2.7V, R
LOAD
=
∞,
C
LOAD
= 5pF
V
+
= 5.5V, R
LOAD
=
∞,
C
LOAD
= 5pF
V
+
= 2.7V, R
LOAD
=
∞,
C
LOAD
= 5pF
MIN
TYP
1
1
1
1
MAX
UNITS
ns
ns
ns
ns
ELECTRICAL CHARACTERISTICS
POWER REQUIRE E TS
SYMBOL
V
S
I
S
, SHDN
I
S
, DC
PARAMETER
Supply Voltage
V
+
Supply Current, Shutdown
The
q
denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
+
= 2.7V to 5.5V, GND = 0V, unless otherwise noted.
CONDITIONS
Applied Between V
+
V
S
= 2.7V
V
S
= 5.5V
f = 68MHz, 5pF Load, V
+
= 2.7V
f < 1MHz, V
+
= 2.7V
f = 68MHz, 5pF Load, V
+
= 5.5V
f < 1MHz, V
+
= 5.5V
and GND
q
q
q
q
q
q
q
V
+
Supply Current, Single Output
Enabled
SERIAL PORT ELECTRICAL CHARACTERISTICS
+
SYMBOL
V
IH
V
IL
I
IN
PARAMETER
Min High Level Input Voltage
SEN, SCK, SDI Pins
Max Low Level Input Voltage
SEN, SCK, SDI Pins
Digital Input Leakage
SEN, SCK, SDI Pins
CONDITIONS
The
q
denotes the specifications which apply over
the full operating temperature range, otherwise specifications are at T
A
= 25°C. V = 2.7V to 5.5V, GND = 0V, unless otherwise noted.
MIN
q
q
q
TI I G CHARACTERISTICS
+
The
q
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V = 2.7V to 5.5V, GND = 0V, unless otherwise noted.
SYMBOL
PARAMETER
LTC6903 (Notes 5, 6)
f
SCK
t
CKHI
t
CKLO
t
su
t
hLD
t
LCH
t
FCK
Serial Port Clock Frequency
Min Clock High Time
Min Clock Low Time
Min Setup Time - SDI to SCK
Min Hold Time - SCK to SDI
Min Latch Time - SEN to SEN
Min First Clock - SEN to SCK
q
q
q
q
q
q
q
q
q
q
q
q
LTC6904 (Notes 5, 6)
f
SMB
SMBus Operating Frequency
t
BUF
Bus Free Time Between Stop and Start Condition
t
HD, STA
Hold Time After (Repeated) Start Condition
t
SU, STA
Repeated Start Condition Setup Time
t
SU, STO
Stop Condition Setup Time
U W
MIN
2.7
TYP
0.25
0.6
3.6
1.7
7
1.9
MAX
5.5
0.6
2.2
7
3.1
15
4.5
UNITS
V
mA
mA
mA
mA
mA
mA
TYP
MAX
0.67 V
+
UNITS
V
V
0.33 V
+
10
µA
UW
MIN
TYP
MAX
20
25
25
10
10
400
20
UNITS
MHz
ns
ns
ns
ns
ns
ns
kHz
µs
µs
µs
µs
10
4.7
4.0
4.7
4.0
100
69034fa
3
LTC6903/LTC6904
TI I G CHARACTERISTICS
+
The
q
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V = 2.7V to 5.5V, GND = 0V, unless otherwise noted.
PARAMETER
q
q
q
q
q
q
SYMBOL
LTC6904 (Notes 5, 6)
t
HD, DAT
Data Hold Time
t
SU, DAT
Data Setup Time
t
LOW
Clock Low Period
t
HIGH
Clock High Period
t
f
Clock, Data Fall Time
t
r
Clock, Data Rise Time
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
A heatsink may be required to keep the junction temperature
below the absolute maximum when the output is shorted indefinitely.
Note 3:
The LTC6903CMS8, LTC6904CMS8, LTC6903IMS8, and
LTC6904IMS8 are guaranteed functional over the operating temperature
range of –40°C to 85°C. The LTC6903HMS8 and LTC6904HMS8 are
guaranteed functional over the extended operating temperature range of
–40°C to 125°C.
Note 4:
The LTC6903CMS8 and LTC6904CMS8 are guaranteed to meet
the specified performance limits over the 0°C to 70°C temperature range
TYPICAL PERFOR A CE CHARACTERISTICS
Integral Nonlinearity
1.0
1.0
DIFFERENTIAL NONLINEARITY (LSB)
0.8
INTEGRAL NONLINEARITY (LSB)
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
0
200
400
600
DAC SETTING
800
1000
6903 G01
FREQUENCY (%)
4
U W
UW
MIN
300
250
4.7
4.0
TYP
MAX
UNITS
ns
ns
µs
µs
ns
ns
50
300
1000
and are designed, characterized and expected to meet the specified
performance from –40°C to 85°C but are not tested or QA sampled at
these temperatures. The LTC6903IMS8 and LTC6904IMS8 are guaranteed
to meet the specified performance limits over the –40°C to 85°C
temperature range. The LTC6903HMS8 and LTC6904HMS8 are
guaranteed to meet the specified performance limits over the –40°C to
125°C temperature range.
Note 5:
All values are referenced to V
IH
and V
IL
levels.
Note 6:
Guaranteed by design and not subject to test.
Note 7:
Parts with tighter frequency accuracy are available. Consult LTC
Marketing for details.
Differential Nonlinearity
0.10
0.08
0.06
0.04
0.02
0
–0.02
–0.04
–0.06
–0.08
0
200
400
600
DAC SETTING
800
1000
6903 G01
Frequency vs Temperature
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–0.10
–40 –20
0
20 40 60 80
TEMPERATURE (°C)
100 120
6903 G03
69034fa
LTC6903/LTC6904
TYPICAL PERFOR A CE CHARACTERISTICS
Peak-to-Peak Jitter vs Frequency
10
V
+
= 3V
10
9
PEAK-TO-PEAK JITTER (%)
7
6
5
4
3
2
1
V
+
= 3V
V
+
= 5V
OUTPUT RESISTANCE (Ω)
SUPPLY CURRENT (mA)
1
0.1
0.01
0.1
1
10
FREQUENCY (MHz)
Output Spectrum at 20MHz
20
0
0.5V/DIV
0.5V/DIV
10dB/DIV
–80
15MHz
20MHz
PI FU CTIO S
GND (Pin 1):
Negative Power Supply (Ground). Should be
tied directly to a ground plane for best performance.
SDI ( Pin 2 ):
Serial Data Input. Data for serial transfer is
presented on this pin.
SCK (Pin 3):
Serial Port Clock. Input, positive edge trig-
gered. Clocks serial data in on rising edge.
SEN (Pin 4):
Serial Port Enable (6903 Only). Input, active
LOW. Initiates serial transaction when brought LOW,
finalizes transaction when brought HIGH after 16 clocks.
ADR (Pin 4):
Serial Port Address (6904 Only). Sets the I
2
C
serial port address.
CLK (Pin 5):
Auxiliary Clock Output. Frequency set by
serial port.
CLK (Pin 6):
Main Clock Output. Frequency set by serial
port.
OE (Pin 7):
Asynchronous Output Enable. CLK and CLK are
set LOW when this pin is LOW.
V
+
(Pin 8):
Positive Power Supply. This supply must be
kept free from noise and ripple. It should be bypassed
directly to a ground plane with a quality 0.1µF capacitor.
Additional bypass may be necessary for operation at high
frequency or under larger loads.
69034fa
U W
6903 G04
6903 G07
Supply Current vs Output
Frequency
60
50
40
30
20
10
Output Resistance vs Supply
Voltage
8
100
0
0.001
0.01
0.1
1
FREQUENCY (MHz)
10
100
6903 G05
0
2.5
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
5.5
6903 G06
Output Waveform at 68MHz
Output Waveform at 20MHz
C
L
= 10pF
V
+
= 3V
25MHz
5ns/DIV
3468 G08
C
L
= 10pF
V
+
= 3V
10ns/DIV
3468 G09
U
U
U
5
