LTC1682/LTC1682-3.3/LTC1682-5
Doubler Charge Pumps with
Low Noise Linear Regulator
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FEATURES
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DESCRIPTIO
Low Output Noise: 60µVRMS (100kHz BW)
Adjustable or Fixed Boosted Output
Adjustable Output Voltage Range: 2.5V to 5.5V
Fixed Output Voltages: 3.3V, 5V
Wide Input Voltage Range: 1.8V to 4.4V
Uses Small Ceramic Capacitors
No Inductors Required
Output Current up to 50mA
550kHz Switching Frequency
Low Operating Current: 150µA
Low Shutdown Current: 1µA
Internal Thermal Shutdown and Current Limiting
Available in 8-Pin MSOP and SO Packages
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APPLICATIO S
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VCO Power Supplies in Cellular Phones
2-Way Pagers
Wireless PCMCIA Cards
Portable Medical Instruments
Low Power Data Acquisition
Remote Transmitters
The LTC®1682/LTC1682-3.3/LTC1682-5 are doubler charge
pumps with an internal low noise, low dropout (LDO) linear
regulator. These parts are designed to provide a low noise
boosted supply voltage for powering noise sensitive devices
such as high frequency VCOs in wireless applications.
An internal doubler charge pump converts a 1.8V to 4.4V
input to a boosted output, while the internal LDO regulator
converts the boosted voltage to a low noise regulated output.
The adjustable version allows the user to set VOUT via external
resistors connected to FB. The regulator is capable of supplying up to 50mA of output current. Shutdown reduces the
supply current to < 5µA, removes the load from VIN by
disabling the regulator and discharges VOUT to ground
through a 100Ω switch.
The LTC1682 LDO regulator is stable with only 2µF on the
output. Small ceramic capacitors can be used, reducing PC
board area.
The LTC1682/LTC1682-3.3/LTC1682-5 are short-circuit and
over temperature protected. The parts are available in 8-pin
MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Open-Loop Close-In Phase Noise
4.2V VCO Power Supply, VIN = 2.5V to 4.4V
SHUTDOWN
8
CPO
VOUT
4.7µF
7
VIN
2.5V TO
4.4V
6
C+
1
4.7µF
2
SHDN
36k
LTC1682
VIN
FB
C–
GND
3
0.22µF
4.7µF
5
4.2V
4
1000pF
B
P
VCO
MURATA
MQE001-902
M
C
fOUT
902MHz
AMPLITUDE
10dB/DIV
100k
VC
1µF
15k
1k
1000pF
1000pF
4.7µF
1682 TA01
CENTER = 902MHz
SPAN = 100kHz
SWP = 10 sec
RES BW = 1kHz
VBW = 30Hz
REF = 0dBm
1682 TA02
1
LTC1682/LTC1682-3.3/LTC1682-5
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ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN to Ground ..............................................– 0.3V to 5V
VOUT Voltage ................................................– 0.3V to 6V
CPO to Ground ........................................................ 10V
SHDN, FILT/FB Voltage to
Ground ..................................... – 0.3V to (VIN + 0.3V)
VOUT Short-Circuit Duration ............................ Indefinite
IOUT ...................................................................... 90mA
Operating Temperature Range
Commercial ............................................ 0°C to 70°C
Extended Commercial (Note 2) ........... – 40°C to 85°C
Industrial ........................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Maximum Junction Temperature .......................... 125°C
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PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
LTC1682CMS8
LTC1682CMS8-3.3
LTC1682CMS8-5
LTC1682IMS8
LTC1682IMS8-3.3
LTC1682IMS8-5
TOP VIEW
VOUT
SHDN
FILT/FB*
GND
1
2
3
4
8
7
6
5
CPO
C+
VIN
C–
MS8 PACKAGE
8-LEAD PLASTIC MSOP
*PIN3 = FILT FOR LTC1682-3.3/LTC1682-5
= FB FOR LTC1682
TJMAX = 125°C, θJA = 140°C/ W
MS8 PART MARKING
LTER
LTGT
LTGV
LTHM
LTGU
LTGW
ORDER PART
NUMBER
TOP VIEW
VOUT 1
8
CPO
SHDN 2
7
C+
FILT/FB* 3
6
VIN
GND 4
5
C–
LTC1682CS8
LTC1682CS8-3.3
LTC1682CS8-5
LTC1682IS8
LTC1682IS8-3.3
LTC1682IS8-5
S8 PACKAGE
8-LEAD PLASTIC SO
*PIN3 = FILT FOR LTC1682-3.3/LTC1682-5
= FB FOR LTC1682
TJMAX = 125°C, θJA = 120°C/ W
S8 PART MARKING
1682
168233
16825
1682I
1682I33
1682I5
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are TA = 25°C. SHDN = VIN = 3V; C1 = 0.22µF; C2, C3, C4 = 4.7µF, unless otherwise noted.
PARAMETER
CONDITIONS
VIN Operating Voltage
LTC1682
LTC1682-3.3
LTC1682-5
IVIN Shutdown Current
SHDN = 0V
MIN
●
●
●
TYP
1.8
2
2.7
MAX
UNITS
4.4
4.4
4.4
V
V
V
●
1
5
µA
IOUT = 0mA, Burst Mode Operation
0°C to 70°C
– 40°C to 85°C
●
●
150
150
250
300
µA
µA
FB Input Current
LTC1682, FB = 1.235V
●
– 50
50
nA
FB Voltage
LTC1682
●
1.210
1.235
1.260
V
Regulated Output Voltage
LTC1682-3.3, IOUT = 1mA
LTC1682-5, IOUT = 1mA
●
●
3.23
4.9
3.30
5.0
3.37
5.1
V
V
IOUT > 200µA, VIN = 1.8V to 4.4V
●
480
IVIN Operating Current
TM
±50
VOUT Temperature Coefficient
Charge Pump Oscillator Frequency
Burst Mode is a trademark of Linear Technology Corporation.
2
550
ppm
620
kHz
LTC1682/LTC1682-3.3/LTC1682-5
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are TA = 25°C. SHDN = VIN = 3V; C1 = 0.22µF; C2, C3, C4 = 4.7µF, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
CPO (Charge Pump Output)
Output Resistance
VIN = 1.8V, IOUT = 10mA
VIN = 3V, IOUT = 10mA
VIN = 4.4V, IOUT = 10mA
●
●
●
18
13
11
30
20
17
Ω
Ω
Ω
VOUT Dropout Voltage (Note 3)
LTC1682, IOUT = 10mA, VOUT = 2.57V (Note 5)
LTC1682/LTC1682-3.3, IOUT = 10mA, VOUT = 3.3V
LTC1682/LTC1682-5, IOUT = 10mA, VOUT = 5V
●
●
●
100
75
50
160
120
90
mV
mV
mV
VOUT Enable Time
IOUT = 10mA
VOUT Output Noise Voltage
LTC1682
IOUT = 10mA, 10Hz ≤ f ≤ 100kHz, VOUT = 5V
IOUT = 10mA, 10Hz ≤ f ≤ 2.5MHz, VOUT = 5V
88
800
µVRMS
µVP-P
LTC1682-3.3
IOUT = 10mA, 10Hz ≤ f ≤ 100kHz, CFILT = 1nF
IOUT = 10mA, 10Hz ≤ f ≤ 2.5MHz, CFILT = 1nF
58
500
µVRMS
µVP-P
LTC1682-5
IOUT = 10mA, 10Hz ≤ f ≤ 100kHz, CFILT = 1nF
IOUT = 10mA, 10Hz ≤ f ≤ 2.5MHz, CFILT = 1nF
64
600
µVRMS
µVP-P
2
ms
VOUT Line Regulation
VIN = 3V to 4V, IOUT = 0mA (Note 6)
●
5
20
mV
VOUT Load Regulation
IOUT = 1mA to 10mA
IOUT = 1mA to 50mA (Note 4)
●
3
10
10
mV
mV
VOUT Shutdown Resistance
SHDN = 0V, Resistance Measured to Ground, VIN = 1.8V
SHDN = 0V, Resistance Measured to Ground, VIN = 4.4V
●
●
150
50
350
150
Ω
Ω
SHDN Input Threshold
VIN = 1.8V to 4.4V
●
0.4
1
1.6
V
SHDN Input Current
SHDN = VIN
SHDN = 0V
●
●
–1
–1
1
1
µA
µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1682C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but is not tested at – 40°C and 85°C. The
LTC1682I is guaranteed to meet the extended temperature limits.
Note 3: Dropout voltage is the minimum input/output voltage required to
maintain regulation at the specified output current. In dropout the output
voltage will be equal to: VCPO – VDROPOUT (see Figure 4).
Note 4: Operating conditions are limited by maximum junction
temperature. The regulated output specification will not apply for all
possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range may be
limited. When operating at maximum output current, the input voltage
range may be limited.
Note 5: Limited by the LDO disable switch point of 1.45VIN.
Note 6: The LTC1682 is set to 5V. The feedback current is 25µA.
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LTC1682/LTC1682-3.3/LTC1682-5
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TYPICAL PERFOR A CE CHARACTERISTICS
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TA = 25°C
C1 = 0.22µF
IOUT = 10mA
10
TA = 25°C
8
VCPO = 2(VIN)
7
VCPO (V)
25
20
5
∆VOUT (mV)
30
RCPO (Ω)
VOUT Transient Response
Min and Max VCPO vs VIN
CPO Output Resistance vs VIN
35
0
(A)
6
TA = 25°C
VIN = 3V
VOUT = 4V
COUT = 10µF
–5
–10
(B)
5
15
IOUT (mA)
15
VCPO = 1.45(VIN)
4
10
10
5
3
0
2.5
2.0
3.0
VIN (V)
3.5
4.0
1.5
4.5
1682 G01
2.0
2.5
3.0
VIN (V)
4.0
3.5
0
4.5
LTC1682-5 Output Noise
(BW = 10Hz to 2.5MHz)
100
150
200
TIME (µs)
SHDN (V)
0
4
VOUT (V)
1682 G04
2
2
0
4
TA = 25°C
VIN = 3V
VOUT = 4V
IOUT = 10mA
CCPO = COUT = 10µF
3
2
1
1
0
0
NO LOAD
TA = 25°C
VIN = 3V
VOUT = 4V
COUT = 10µF
1ms/DIV
200µs/DIV
1682 G05
220
565
200
560
OPERATING CURRENT (µA)
OSCILLATION FREQUENCY (kHz)
VIN = 3V
555
550
545
540
535
180
160
TA = 25°C
LTC1682-3.3
LTC1682-5
140
LTC1682
120
100
80
50
25
75
0
TEMPERATURE (°C)
100
125
1682 G07
4
1682 G06
Operating Current vs VIN
(No Load)
Oscillator Frequency vs
Temperature
530
–50 –25
300
Enable to Shutdown Timing
2
3
250
1682 G02
Shutdown to Enable Timing
VOUT
200µV/DIV
100µs/DIV
CCPO = COUT = 4.7µF
VOUT = 5V
TA = 25°C
IOUT = 10mA
CFILT = 1nF
VIN = 3V
50
(A) THE MAXIMUM GENERATED NO LOAD
CPO VOLTAGE
(B) THE MINIMUM ALLOWABLE CPO VOLTAGE,
AT FULL LOAD, TO ENSURE THAT THE LDO
IS NOT DISABLED
1682 G02
SHDN (V)
1.5
VOUT (V)
5
60
1.5
2.0
2.5
3.0
VIN (V)
3.5
4.0
4.5
1682 G08
LTC1682/LTC1682-3.3/LTC1682-5
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TYPICAL PERFOR A CE CHARACTERISTICS
VOUT Voltage vs Output Current
VOUT VOLTAGE (V)
VOUT VOLTAGE (V)
VOUT Voltage vs Temperature
5.030
VIN = 3V
5.020
IOUT = 10mA
5.010
5.000
LTC1682-5
4.990
3.340
3.330
3.320
LTC1682-3.3
3.310
3.300
3.290
1.240
1.238
LTC1682
1.236
1.234
75
0
50
–50 –25
25
TEMPERATURE (°C)
100
125
5.000
4.999
4.998
4.997
4.996
4.995
4.994
4.993
VIN = 3.3V
TA = 25°C
LTC1682-5
3.300
3.299
3.298
3.297
3.296
3.295
3.294
LTC1682-3.3
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
1682 G09
1682 G10
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PIN FUNCTIONS
VOUT (Pin 1): Low Noise Regulated Output Voltage. VOUT
should be bypassed with a ≥ 2µF low ESR capacitor as
close to the pin as possible for best performance. The VOUT
range is 2.5V to 5.5V.
FILT (Pin 3) (LTC1682-3.3/LTC1682-5): This pin is used
to filter the internal voltage reference. Typically a 1nF
capacitor is connected from FILT to ground.
SHDN (Pin 2): Shutdown Input. A logic low on the SHDN
pin puts the part in shutdown mode. A logic high enables
the part. To continuously enable the part connect SHDN to
VIN. When the part is in shutdown, VOUT will be connected
to ground via a 100Ω switch and CPO will be high
impedance disconnected from VIN.
C – (Pin 5): Flying Capacitor Negative Input.
FB (Pin 3) (LTC1682): The voltage on this pin is compared
to the internal reference voltage (1.235V) by the error
amplifier to keep the output in regulation. An external
resistor divider is required between VOUT and FB to adjust
the output voltage.
GND (Pin 4): System Ground.
VIN (Pin 6): Input Voltage, 1.8V to 4.4V. VIN should be
bypassed with a ≥ 2µF low ESR capacitor as close to the
pin as possible for best performance. A minimum capacitance value of 0.1µF is required.
C + (Pin 7): Flying Capacitor Positive Input.
CPO (Pin 8): Unregulated Charge Pump Output Voltage.
Approximately 1.95(VIN) at low loads. Bypass with a ≥ 2µF
low ESR capacitor. If a minimum VOUT enable time is
required, the CPO capacitor should be 2× the VOUT
capacitor.
5
LTC1682/LTC1682-3.3/LTC1682-5
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BLOCK DIAGRA SM
C1
0.22µF
C+
5
C–
CHARGE PUMP
AND
SLEW CONTROL
C4
4.7µF
8
ENB
CLK1
CPO
C3
4.7µF
275k
–
6
VIN
7
+
38k
SHDN
2
+
POWERON
RESET
550kHz
OSCILLATOR
REG B
–
SD
328k
REGEN
ENB
1:100
–
+
VIN
1
VOUT
LDO
C2
4.7µF
REGEN
SD
VREF = 1.235V
100Ω
1µA/2µA
3
FB
4
GND
R1
R2
1682 F01
Figure 1. LTC1682 Block Diagram
6
LTC1682/LTC1682-3.3/LTC1682-5
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BLOCK DIAGRA SM
C1
0.22µF
C+
5
C–
CHARGE PUMP
AND
SLEW CONTROL
C4
4.7µF
8
CPO
C3
4.7µF
275k
–
6
VIN
7
ENB
CLK1
+
38k
SHDN
2
+
POWERON
RESET
550kHz
OSCILLATOR
REG B
–
SD
FILT
1nF
328k
REGEN
ENB
–
3
200k
1:100
+
VIN
1
VOUT
LDO
C2
4.7µF
REGEN
SD
VREF = 1.235V
RA
120k/65.5k
RB
200k
100Ω
1µA/2µA
4
1682 F02
GND
Figure 2. LTC1682-3.3/LTC1682-5 Block Diagram
7
LTC1682/LTC1682-3.3/LTC1682-5
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APPLICATIONS INFORMATION
Operation
The LDO is used to filter the ripple on CPO and to set an
output voltage independent of CPO. VOUT is set by an
external or internal resistor divider. The LDO requires a
capacitor on VOUT for stability and improved load transient
response. A low ESR capacitor of ≥ 2µF should be used.
The LTC1682 uses a switched-capacitor charge pump to
generate a CPO voltage of approximately 2(VIN). CPO
powers an internal low dropout linear regulator that supplies a regulated output at VOUT. Internal comparators are
used to sense CPO and VIN voltages for power-up conditioning. The output current is sensed to determine the
charge pump operating mode. A trimmed internal bandgap
is used as the voltage reference and a trimmed internal
oscillator is used to control the charge pump switches.
Output Voltage Selection
The LTC1682-3.3/LTC1682-5 versions have internal
resistor networks to set the regulated output voltage. The
LTC1682 output voltage is set using an external resistor
divider (see Figure 3). The output voltage is determined
using the following formula:
The charge pump is a doubler configuration that uses one
external flying capacitor. When enabled, a 2-phase
nonoverlapping clock controls the charge pump switches.
At start-up, the LDO is disabled and the load is removed
from CPO. When CPO reaches 1.75(VIN) the LDO is
enabled. If CPO falls below 1.45(VIN) the LDO will be
disabled. Generally, the charge pump runs open loop with
continuous clocking for low noise. If CPO is greater than
1.95(VIN) and IOUT is less than 100µA, the charge pump
will operate in Burst Mode operation for increased efficiency but slightly higher output noise. In Burst Mode
operation, the clock is disabled when CPO reaches 1.95(VIN)
and enabled when CPO droops by about 100mV. The
switching frequency is precisely controlled to ensure that
the frequency is above 455kHz and at the optimum rate to
ensure maximum efficiency. The switch edge rates are
also controlled to minimize noise. The effective output
resistance at CPO is dependent on the voltage at VIN, CPO
and the junction temperature. A low ESR capacitor of ≥ 2µF
should be used at CPO for minimum noise.
EXTERNAL LDO
8
C3
4.7µF
7
IN
3.3V
C5
OUT
GND
VIN
3.6V
C4
4.7µF
6
C1
0.22µF
5
VOUT = 1.235V(1 + R1/R2)
The output voltage range is 2.5V to 5.5V.
Maximum VOUT and IOUT Calculations
The maximum available output voltage and current can be
calculated based on the open circuit CPO voltage, the
dropout voltage of the LDO and the effective output
resistance of the charge pump. The open circuit CPO
voltage is approximately 2(VIN) (see Figure 4).
RCPO
+
+
–
–
VOUT
VDROPOUT
2VIN
CCPO
ILOAD
1682 F04
Figure 4. Equivalent Circuit
CPO
C+
VOUT
SHDN
LTC1682
VIN
C–
FB
GND
1
C2
4.7µF
2
3
4
5.1V
VRIPPLE = 800µVP-P
R1
56k
VOUT = 1.235V(1 + R1/R2)
R2
18k
1682 F03
Figure 3. Powering an Auxiliary Regulator from CPO
8
RDROPOUT
VCPO
LTC1682/LTC1682-3.3/LTC1682-5
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APPLICATIONS INFORMATION
The following formula can be used to find the maximum
output voltage that may be programmed for a given
minimum input voltage and output current load:
VOUT(MAX) = (2)(VIN(MIN)) – (IOUT)(RCPO) – VDROPOUT
with the condition that (IOUT)(RCPO) < 0.55VIN.
Example:
VIN(MIN) = 3V
IOUT = 10mA
RCPO(MAX) = 20Ω
Max unloaded CPO voltage = 6V
Loaded CPO voltage = 6V – (10mA)(20Ω) = 5.8V
VDROPOUT(MAX) = 0.08V
VOUT(MAX) = (6V) – (0.2V) – (0.08V) = 5.72V
VOUT < 5.5V and (IOUT)(RCPO) < 0.55VIN, 0.2V < 1.65V.
For minimum noise applications, the LDO must be kept out
of dropout to prevent CPO noise from coupling into VOUT.
External CPO Loading
The CPO output can drive an external load (an LDO, for
example). The current required by this additional load will
reduce the available current from VOUT. If the external load
requires 5mA, then the maximum available current at VOUT
will be reduced by 5mA.
Short-Circuit and Thermal Protection
VOUT can be shorted to ground indefinitely. Internal circuitry will limit the output current. If the junction temperature exceeds 150°C, the part will shut down. Excessive
power dissipation due to heavy loads will also cause the
part to shut down when the junction temperature exceeds
150°C. The part will become enabled when the junction
temperature drops below 140°C. If the fault condition
remains in place, the part will cycle between the shutdown
and enabled states.
Capacitor Selection
For best performance it is recommended that low ESR
capacitors be used for C2, C3 and C4 in Figure 1 to
reduce noise and ripple. C2 must be ≥ 2µF and C3 must
be equal to or greater than C2. C4 is dependent on the
source impedance. The charge pump demands large
instantaneous currents which may induce ripple onto
a common voltage rail. C4 should be ≥ 2µF and a spike
reducing resistor of 2.2Ω may be required between
VIN and the supply.
A low ESR ceramic capacitor is recommended for the
flying capacitor C1 with a value of 0.22µF. At low load or
high VIN a smaller capacitor could be used to reduce ripple
on CPO which would reflect as lower ripple on VOUT.
If a minimum enable time is required, the CPO output filter
capacitor should be at least 2× the VOUT filter capacitor.
When the LDO is first enabled, the CPO capacitor will
dump a large amount of charge into the VOUT capacitor. If
the drop in the CPO voltage falls below 1.45(VIN), the LDO
will be disabled and the CPO voltage will have to charge up
to 1.75(VIN) to enable the LDO. The resulting cycling
extends the enable time.
A 1nF filter capacitor for the LTC1682-3.3/LTC1682-5
should be connected between the FILT pin and ground for
optimum noise performance.
Output Ripple
The output noise and ripple on CPO includes a spike
component from the charge pump switches and a droop
component which is dependent on the load current and the
value of C3. The charge pump has been carefully designed
to minimize the spike component; however, low ESR
capacitors are essential to reduce the remaining spike
energy effect on the CPO voltage. C3 should be increased
for high load currents to minimize the droop component.
Ripple components on CPO are greatly reduced at VOUT by
the LDO; however, C2 should also be a low ESR capacitor
to improve filtering of the CPO noise.
Shutdown
When SHDN pin is pulled low (< 0.4V), the part will be in
shutdown, the supply current will be < 5µA and VOUT will
be connected to ground through a 100Ω switch. In addition, CPO will be high impedance and disconnected from
VIN.
If shutdown is not required, connect SHDN to VIN which
will continuously enable the part.
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LTC1682/LTC1682-3.3/LTC1682-5
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APPLICATIONS INFORMATION
Power-On Reset
General Layout Considerations
Upon initial power-up, a power-on reset circuit ensures
that the internal functions are correctly initialized when
power is applied. Once VIN reaches approximately 1V, the
power-on reset circuit will enable the part as long as the
SHDN pin is held high.
Due to the high switching frequency and high transient
currents produced by the device, careful board layout is a
must. A clean board layout using a ground plane and short
connections to all capacitors will improve noise performance and ensure proper regulation (Figure 5).
Thermal Considerations
The FILT pin on the LTC1682-3.3/LTC1682-5 is a high
impedance node. Leakage currents at this pin must be
minimized.
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
device power dissipation PD = IOUT (2VIN – V OUT) +
VIN(4mA). The device dissipates the majority of its heat
through its pins, especially GND (Pin 4). Thermal resistance to ambient can be optimized by connecting GND to
a large copper region on the PCB, which serves as a heat
sink. Applications which operate the LTC1682 near maximum power levels should maximize the copper area at all
pins except C +, C – and FILT/FB and ensure that there is
some airflow over the part to carry away excess heat.
C2
Measuring Output Noise
Measuring the LTC1682 low noise levels requires care.
Figure 6 shows a test setup for taking the measurement.
Good connection and signal handling technique should
yield about 500µVP-P over a 2.5MHz bandwidth. The noise
measurement involves AC coupling the LTC1682 output
into the test setup’s input and terminating this connection
with 50Ω. Coaxial connections must be maintained to
preserve measurement integrity.
VOUT
C3
1
SHDN
8
7 VIN
2
LTC1682-3.3/5
CFILT
3
6
4
5
C4
GND
C1
1682 F05
Figure 5
BNC CABLES
OR COUPLERS
BATTERY OR
LOW NOISE DC
POWER SUPPLY
COUPLING
CAPACITOR
PREAMPLIFIER
1822
LTC1682 VOUT
DEMO
BOARD
+
RLOAD
CONNECT BNC AND
RLOAD GROUND TO THE
OUTPUT CAPACITOR
GROUND TERMINAL E5
–
R*
BANDWIDTH
FILTER
20dB
OSCILLOSCOPE
R*
1682 F06
PLACE BANDWIDTH FILTER
COMPONENTS IN SHIELDED BOX
WITH COAXIAL CONNECTORS
R*
PLACE COUPLING
CAPACITOR IN SHIELDED
BOX WITH COAXIAL
CONNECTOR
*50Ω TERMINATIONS
HP-11048C OR
EQUIVALENT
NOTE: KEEP BNC CONNECTIONS
AS SHORT AS POSSIBLE
Figure 6. LTC1682 Noise Measurement Test Setup
10
INPUT
LTC1682/LTC1682-3.3/LTC1682-5
U
TYPICAL APPLICATION
3.3V to Low Noise 3.3V Converter
SHUTDOWN
8
C3
4.7µF
VIN
3.3V
7
6
C4
4.7µF
C1
0.22µF
5
CPO
VOUT
C+
SHDN
LTC1682-3.3
VIN
C–
FILT
GND
1
C2
4.7µF
2
3.3V
VRIPPLE = 500µVP-P
3
CFILT
1nF
4
1682 TA03
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.034 ± 0.004
(0.86 ± 0.102)
8
7 6
5
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
TYP
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.118 ± 0.004**
(3.00 ± 0.102)
0.192 ± 0.004
(4.88 ± 0.10)
MSOP (MS8) 1197
1
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
2 3
4
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
8
7
6
5
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.050
(1.270)
TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
SO8 0996
1
2
3
4
11
LTC1682/LTC1682-3.3/LTC1682-5
U
TYPICAL APPLICATION
Wide Input Range VCO Supply (VIN > 4.4V)
VIN
3V TO 6V
Q1
FMMT3904
R1
470Ω
8
C3
4.7µF
D1
1N4148
3V
(REQUIRED FOR
START-UP)
C4
4.7µF
7
6
C1
0.22µF
5
CPO
C+
VOUT
SHDN
LTC1682-5
VIN
C–
FILT
GND
5V
LOW NOISE
1
2
SHUTDOWN
C2
4.7µF
VCO
3
1682 ta04
4
CFILT
1nF
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1340
Low Noise, Voltage-Boosted Varactor Driver
Generates 5V Varactor Drive from 3V Supply
LTC1517-X
Micropower, Regulated Charge Pump Doubler in SOT-23
ICC = 6µA; Short Circuit/Thermal Protected
LT1521
300mA Low Dropout Regulator
Micropower; Good Transient Response
LTC1522
Micropower, Regulated 5V Charge Pump
Ultralow Power: Typical Operating ICC = 6µA
LT1761 Series
100mA Low Noise LDO Regulator in SOT-23
ICC = 20µA; 20µVRMS Output Noise
12
Linear Technology Corporation
128235fs, sn128235 LT/TP 0799 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 1999
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