LTC6906
Micropower, 10kHz to 1MHz
Resistor Set Oscillator
in SOT-23
FEATURES
■
■
■
■
■
■
■
■
■
■
■
DESCRIPTIO
Supply Current: 12µA at 100kHz
<0.65% Frequency Accuracy (from 0°C to 70°C)
Frequency Range: 10kHz to 1MHz
One Resistor Sets the Oscillator Frequency
Single Supply: 2.25V to 5.5V
–40°C to 125°C Operating Temperature Range
No Decoupling Capacitor Needed
Start-Up Time Under 200µs at 1MHz
First Cycle After Power-Up is Accurate
150Ω CMOS Output Driver
Low Profile (1mm) SOT-23 (ThinSOT
TM
) Package
The LTC
®
6906 is a precision programmable oscillator that
is versatile, compact and easy-to-use. Micropower opera-
tion benefits portable and battery-powered equipment. At
100kHz, the LTC6906 consumes 12µA on a 3.3V supply.
A single resistor programs the oscillator frequency over a
10:1 range with better than 0.5% initial accuracy. The
output frequency can be divided by 1, 3 or 10 to span a
100:1 total frequency range, 10kHz to 1MHz.
The LTC6906 is easily programmed according to this
simple formula:
APPLICATIO S
■
■
■
■
■
ƒ
OUT
Low Cost Precision Programmable Oscillator
Rugged, Compact Micropower Replacement for
Crystal and Ceramic Oscillators
High Shock and Vibration Environments
Portable and Battery-Powered Equipment
PDAs and Cellular Phones
⎧
10, DIV Pin
=
V
+
1MHz
⎛
100k
⎞
⎪
=
•
⎜
⎟
, N
=
⎨
3, DIV Pin
=
Open
N
⎝
R
SET
⎠
⎪
1, DIV Pin
=
GND
⎩
No decoupling capacitor is needed in most cases, yielding
an extremely compact solution occupying less than 20mm
2
.
Contact LTC Marketing for a version of the part with a
shutdown feature or lower frequency operation.
The LTC6906 is available in the 6-lead SOT-23 (ThinSOT)
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
Typical Supply Current vs Frequency
Micropower Clock Generator
POWER SUPPLY CURRENT (µA)
NO DECOUPLING
CAPACITOR
NEEDED
LTC6906
2.25V TO 3.6V
÷10
÷3
÷1
V
+
GND
DIV
OUT
GRD
SET
R
SET
100k TO 1M
6906 TA01
90
80
70
60
50
40
30
20
10
0
0
C
L
= 5pF
T
A
= 25°C
V
+
= 3.6V
10kHz TO 1MHz
200
U
V
+
= 2.25V
400
600
800
FREQUENCY (kHz)
1000
1200
6906 G04
U
U
6906fa
1
LTC6906
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
OUT 1
GND 2
DIV 3
6 V
+
5 GRD
4 SET
(Note 1)
V
+
................................................................– 0.3V to 6V
DIV to GND .................................... – 0.3V to (V
+
+ 0.3V)
SET to GND ................................... – 0.3V to (V
+
+ 0.3V)
GRD to GND .................................. – 0.3V to (V
+
+ 0.3V)
Operating Temperature Range (Note 7)
LTC6906C .......................................... – 40°C to 85°C
LTC6906I ............................................ – 40°C to 85°C
LTC6906H ........................................ – 40°C to 125°C
Specified Temperature Range (Note 7)
LTC6906C ............................................... 0°C to 70°C
LTC6906I ............................................ – 40°C to 85°C
LTC6906H ........................................ – 40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
T
JMAX
= 150°C,
θ
JA
= 230°C/W
ORDER PART NUMBER
LTC6906CS6
LTC6906IS6
LTC6906HS6
S6 PART MARKING*
LTBJN
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature range.
*The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL
∆f
PARAMETER
Frequency Accuracy (Notes 2, 3)
The
●
denotes the specifications which apply over the full specified
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 2.25V to 3.6V, C
L
= 5pF, Pin 3 = V
+
unless otherwise noted.
All voltages are with respect to GND.
CONDITIONS
V
+
= 2.7V to 3.6V 100kHz
≤
f
≤
1MHz
100kHz
≤
f
≤
1MHz, LTC6906C
100kHz
≤
f
≤
1MHz, LTC6906I
f = 1MHz, LTC6906H
f = 100kHz, LTC6906H
V
+
= 2.25V
100kHz
≤
f
≤
1MHz
100kHz
≤
f
≤
1MHz, LTC6906C
100kHz
≤
f
≤
1MHz, LTC6906I
f = 1MHz, LTC6906H
f = 100kHz, LTC6906H
●
●
●
●
MIN
TYP
±0.25
MAX
±0.5
±0.65
±1.3
±1.3
±2.2
±0.7
±0.85
±1.3
±1.3
±2.2
1000
UNITS
%
%
%
%
%
%
%
%
%
%
kΩ
%/°C
%/V
%
%
%
ppm/√kHr
±0.25
●
●
●
●
●
R
SET
∆f/∆T
∆f/∆V
Frequency-Setting Resistor Range
Frequency Drift Over Temp (Note 3)
Frequency Drift Over Supply (Note 3)
Timing Jitter (Note 4)
R
SET
= 316k
V
+
= 2.25V to 3.6V, 100k
≤
R
SET
≤
1000k
Pin 3 = V
+
, 100k
≤
R
SET
≤
1000k
Pin 3 = Open, 100k
≤
R
SET
≤
1000k
Pin 3 = 0V, 100k
≤
R
SET
≤
1000k
Pin 3 = V+
100
±0.005
0.06
0.03
0.07
0.15
300
●
S
f
DC
V
+
I
S
Long-Term Stability of Output Frequency
Duty Cycle
Operating Supply Range (Note 8)
Power Supply Current
●
●
45
2.25
50
12.5
10.0
78
60
55
3.6
18
15
100
80
R
SET
= 1000k, Pin 3 = 0V, R
L
= 10M
(DIV = 1, f
OUT
= 100kHz)
R
SET
= 100k, Pin 3 = 0V, R
L
= 10M
(DIV = 1, f
OUT
= 1MHz)
V
+
= 3.6V
V
+
= 2.25V
V
+
= 3.6V
V
+
= 2.25V
●
●
●
●
2
U
%
V
µA
µA
µA
µA
6906fa
W
U
U
W W
W
LTC6906
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IH
V
IL
I
DIV
V
OH
PARAMETER
High Level DIV Input Voltage
Low Level DIV Input Voltage
DIV Input Current (Note 5)
High Level Output Voltage (Note 5)
The
●
denotes the specifications which apply over the full specified
temperature range, otherwise specifications are at T
A
= 25°C. V
+
= 2.25V to 3.6V, C
L
= 5pF, Pin 3 = V
+
unless otherwise noted.
All voltages are with respect to GND.
CONDITIONS
V
+
= 3.6V
V
+
= 2.25V
V
+
= 3.6V
V
+
= 2.25V
Pin 3 = V
+
Pin 3 = 0V
V
+
= 3.6V
V
+
= 2.25V
V
OL
Low Level Output Voltage (Note 5)
V
+
= 3.6V
V
+
= 2.25V
t
r
t
f
VGS
OUT Rise Time (Note 6)
OUT Fall Time (Note 6)
GRD Pin Voltage Relative to SET Pin
Voltage
V
+
= 3.6V
V
+
= 2.25V
V
+
= 3.6V
V
+
= 2.25V
–10µA
≤
I
GRD
≤
0.3µA
●
●
●
●
●
●
●
MIN
3.1
2.05
TYP
MAX
UNITS
V
V
0.5
0.2
–2
3.40
2.80
2.15
1.75
1
–1
3.59
3.30
2.2
2.0
0.02
0.15
0.03
0.30
10
25
10
25
–10
10
0.2
0.8
0.1
0.5
2
V
V
µA
µA
V
V
V
V
V
V
V
V
ns
ns
ns
ns
mV
I
OH
= – 100µA
I
OH
= – 1mA
I
OH
= – 100µA
I
OH
= – 1mA
I
OL
= 100µA
I
OL
= 1mA
I
OL
= 100µA
I
OL
= 1mA
●
●
●
●
●
●
●
●
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
Some frequencies may be generated using two different values of
R
SET
. For these frequencies, the error is specified assuming that the larger
value of R
SET
is used.
Note 3:
Frequency accuracy is defined as the deviation from the f
OUT
equation.
Note 4:
Jitter is the ratio of the peak-to-peak deviation of the period to the
mean of the period. This specification is based on characterization and is
not 100% tested.
Note 5:
Current into a pin is given as a positive value. Current out of a pin
is given as a negative value.
Note 6:
Output rise and fall times are measured between the 10% and 90%
power supply levels.
Note 7:
The LTC6906C is guaranteed to meet specified performance from
0°C to 70°C. The LTC6906C 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 LTC6906I is guaranteed to meet
specified performance from –40°C to 85°C.
Note 8:
Consult the Applications Information section for operation with
supplies higher than 3.6V.
6906fa
3
LTC6906
TYPICAL PERFOR A CE CHARACTERISTICS
Typical Frequency Error
vs Power Supply
0.50
0.40
0.30
FREQUENCY ERROR (%)
FREQUENCY ERROR (%)
0.20
0.10
0
–0.10
–0.20
–0.30
–0.40
R
SET
= 1M
R
SET
= 100k
ERROR (%)
–0.50
2.25
3
4
SUPPLY VOLTAGE (V)
Typical Supply Current
vs Frequency
90
80
POWER SUPPLY CURRENT (µA)
C
L
= 5pF
T
A
= 25°C
POWER SUPPLY CURRENT (µA)
70
60
50
40
30
20
10
0
0
200
140
120
100
80
60
40
20
0
100kHz, 2.25V
0
20
10
30
LOAD CAPACITANCE (pF)
40
6906 G05
SET PIN VOLTAGE (V)
V
+
= 3.6V
V
+
= 2.25V
400
600
800
FREQUENCY (kHz)
Typical Supply Current
vs Temperature, 1MHz
90
C
L
= 5pF
85
SUPPLY CURRENT (µA)
18
80
75
70
65
60
55
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
6906 G07
SUPPLY CURRENT (µA)
4
U W
5
6906 G01
Typical Frequency Error
vs Temperature
2
1
R
SET
= 100k
0
3.6V
–1
3.6V
–2
–3
–4
–5
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
6906 G02
Typical Frequency Error vs R
SET
0.50
0.40
2.25V
0.30
0.20
2.25V
0.10
0
V
+
= 2.25V
V
+
= 5V
–0.10
R
SET
= 1M
–0.20
–0.30
–0.40
–0.50
0
200
400
600
800
R
SET
(kΩ)
1000
1200
6906 G03
Typical Supply Current
vs Load Capacitance
200
180
160
T
A
= 25°C
1MHz, 3.6V
0.80
0.75
0.70
0.65
0.60
0.55
0.50
0.45
0.40
0.35
V
SET
vs Temperature (V
SET
is the
Voltage Measured at the R
SET
Pin)
R
SET
= 100k
1MHz, 2.25V
V
SET
AT
V
+
= 3.6V
V
SET
AT
V
+
= 2.25V
100kHz, 3.6V
1000
1200
0.30
–60 –40 –20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
6906 G06
6906 G04
Typical Supply Current
vs Temperature, 100kHz
17
16
15
14
13
12
11
10
9
8
–50 –30 –10 10 30 50 70 90 110 130 150
TEMPERATURE (°C)
6906 G08
C
L
= 5pF
I
SUPPLY
AT V
+
= 3.6V
I
SUPPLY
AT V
+
= 3.6V
I
SUPPLY
AT V
+
= 2.25V
I
SUPPLY
AT V
+
= 2.25V
6906fa
LTC6906
PI FU CTIO S
OUT (Pin 1):
Oscillator Output. The OUT pin swings from
GND to V
+
with an output resistance of approximately
150Ω. For micropower operation, the load resistance
must be kept as high as possible and the load capacitance
as low as possible.
GND (Pin 2):
Ground.
DIV (Pin 3):
Divider Setting Input. This three-level input
selects one of three internal digital divider settings, deter-
mining the value of N in the frequency equation. Tie to GND
for
÷1,
leave floating for
÷3
and tie to V
+
for
÷10.
When left
floating, the LTC6906 pulls Pin 3 to mid-supply with a
2.5M resistor. When Pin 3 is floating, care should be taken
to reduce coupling from the OUT pin and its trace to Pin 3.
Coupling can be reduced by increasing the physical space
between traces or by shielding the DIV pin with grounded
metal.
SET (Pin 4):
Frequency Setting Resistor Input. Connect a
resistor, R
SET
, from this pin to GND to set the oscillator
frequency. For best performance use a precision metal- or
thin-film resistor of 0.5% or better tolerance and 50ppm/°C
or better temperature coefficient. For lower accuracy
applications, an inexpensive 1% thick-film resistor may be
used. Limit the capacitance in parallel with R
SET
to less
than 10pF to reduce jitter and to ensure stability. Capaci-
tance greater than 10pF could cause the LTC6906 internal
feedback circuits to oscillate. The voltage on the SET pin
is approximately 650mV and decreases with temperature
by about –2.2mV/°C.
GRD (Pin 5):
Guard Signal. This pin can be used to reduce
PC board leakage across the frequency setting resistor,
R
SET
. The GRD pin is held within a few millivolts of the SET
pin and shunts leakage current away from the SET pin. To
control leakage, connect a bare copper trace (a trace with
no solder mask) to GRD and loop it around the SET pin and
all PC board metal connected to SET.
V
+
(Pin 6):
Voltage Supply (2.25V to 3.6V). This supply is
internally decoupled with a 20Ω resistor in series with an
800pF capacitor. No external decoupling capacitor is
required for OUT pin loads less than 50pF. V
+
should be
kept reasonably free of noise and ripple.
BLOCK DIAGRA
DECOUPLING
NETWORK
6
2
V
+
20Ω
GND
800pF
I
FB
V
SET
≅
V
GRD
≅
650mV
V
SET
R
SET
5
GRD
4
SET
I
SET
= I
FB
BUFFER
V
SET
+
–
W
U
U
U
FREQUENCY-TO-CURRENT
CONVERTERS
f
OSC
I
FB
THREE-LEVEL
INPUT
DETECTOR
V
+
5M
DIV
5M
DIVIDER
SELECT
3
V
SET
OP AMP
VOLTAGE
CONTROLLED
OSCILLATOR
(MASTER OSCILLATOR)
f
OSC
= 1MHz • 100kΩ/R
SET
f
OSC
PROGRAMMABLE
DIVIDER (n)
(÷1,
÷3, ÷10)
150Ω DRIVER
OUT
1
6906 BD
6906fa
5
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