LTC1682 [Linear]
Doubler Charge Pumps with Low Noise Linear Regulator; 倍电荷泵，低噪声线性稳压器
| 型号： | LTC1682 |
| 厂家： | 
Linear |
| 描述： | Doubler Charge Pumps with Low Noise Linear Regulator |
| 文件： | 总12页 (文件大小：190K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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FEATURES
DESCRIPTIO
TheLTC®1682/LTC1682-3.3/LTC1682-5aredoublercharge
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.
■
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
■
■
■
■
■
■
■
■
■
■
■
An internal doubler charge pump converts a 1.8V to 4.4V
input to a boosted output, while the internal LDO regulator
convertstheboostedvoltagetoalownoiseregulatedoutput.
TheadjustableversionallowstheusertosetVOUT viaexternal
resistorsconnectedtoFB. Theregulatoriscapableofsupply-
ing 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.
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
The LTC1682 LDO regulator is stable with only 2µF on the
output. Small ceramic capacitors can be used, reducing PC
board area.
■
VCO Power Supplies in Cellular Phones
■
2-Way Pagers
■
TheLTC1682/LTC1682-3.3/LTC1682-5areshort-circuitand
over temperature protected. The parts are available in 8-pin
MSOP and SO packages.
Wireless PCMCIA Cards
■
Portable Medical Instruments
■
Low Power Data Acquisition
■
Remote Transmitters
, 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
1
4.2V
4.7µF
8
7
6
5
f
OUT
B
P
V
CPO
OUT
902MHz
1000pF
VCO
4.7µF
MURATA
2
AMPLITUDE
10dB/DIV
+
SHDN
LTC1682
C
MQE001-902
M
100k
36k
C
V
C
V
3
4
IN
1µF
FB
V
C
IN
–
2.5V TO
4.4V
0.22µF
4.7µF
4.7µF
15k
1000pF
1k
1000pF
GND
1682 TA01
CENTER = 902MHz
SPAN = 100kHz
SWP = 10 sec
RES BW = 1kHz
VBW = 30Hz
REF = 0dBm
1682 TA02
1
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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
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
Ground ..................................... –0.3V to (VIN + 0.3V)
VOUT Short-Circuit Duration............................ Indefinite
IOUT...................................................................... 90mA
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PACKAGE/ORDER INFORMATION
ORDER PART
NUMBER
ORDER PART
NUMBER
TOP VIEW
LTC1682CS8
LTC1682CMS8
LTC1682CMS8-3.3
LTC1682CMS8-5
LTC1682IMS8
LTC1682IMS8-3.3
LTC1682IMS8-5
TOP VIEW
CPO
1
2
3
4
8
7
6
5
V
OUT
LTC1682CS8-3.3
LTC1682CS8-5
LTC1682IS8
V
1
2
3
4
8 CPO
7 C
OUT
+
+
C
SHDN
FILT/FB*
GND
SHDN
FILT/FB*
GND
6 V
5 C
IN
V
IN
–
–
C
MS8 PACKAGE
8-LEAD PLASTIC MSOP
LTC1682IS8-3.3
LTC1682IS8-5
S8 PACKAGE
8-LEAD PLASTIC SO
*PIN3 = FILT FOR LTC1682-3.3/LTC1682-5
= FB FOR LTC1682
*PIN3 = FILT FOR LTC1682-3.3/LTC1682-5
= FB FOR LTC1682
MS8 PART MARKING
S8 PART MARKING
T
JMAX = 125°C, θJA = 140°C/ W
TJMAX = 125°C, θJA = 120°C/ W
LTER
LTGT
LTGV
LTHM
LTGU
LTGW
1682
168233 1682I33
16825 1682I5
1682I
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
MIN
TYP
MAX
UNITS
V
Operating Voltage
LTC1682
LTC1682-3.3
LTC1682-5
●
●
●
1.8
2
2.7
4.4
4.4
4.4
V
V
V
IN
I
I
Shutdown Current
Operating Current
SHDN = 0V
●
1
5
µA
VIN
VIN
I
= 0mA, Burst ModeTM Operation
0°C to 70°C
OUT
●
●
150
150
250
300
µA
µA
–40°C to 85°C
FB Input Current
FB Voltage
LTC1682, FB = 1.235V
LTC1682
●
●
–50
50
nA
V
1.210
1.235
1.260
Regulated Output Voltage
LTC1682-3.3, I
= 1mA
= 1mA
●
●
3.23
4.9
3.30
5.0
3.37
5.1
V
V
OUT
LTC1682-5, I
OUT
V
Temperature Coefficient
±50
ppm
kHz
OUT
Charge Pump Oscillator Frequency
I
> 200µA, V = 1.8V to 4.4V
●
480
550
620
OUT
IN
Burst Mode is a trademark of Linear Technology Corporation.
2
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
V
V
V
= 1.8V, I
= 10mA
OUT
= 10mA
●
●
●
18
13
11
30
20
17
Ω
Ω
Ω
IN
IN
IN
= 3V, I
OUT
= 4.4V, I
= 10mA
OUT
V
Dropout Voltage (Note 3)
LTC1682, I
LTC1682/LTC1682-3.3, I
LTC1682/LTC1682-5, I
= 10mA, V = 2.57V (Note 5)
OUT
●
●
●
100
75
50
160
120
90
mV
mV
mV
OUT
OUT
= 10mA, V
= 3.3V
= 5V
OUT
OUT
= 10mA, V
OUT
OUT
V
V
Enable Time
I
= 10mA
OUT
2
ms
OUT
OUT
Output Noise Voltage
LTC1682
I
I
= 10mA, 10Hz ≤ f ≤ 100kHz, V
= 10mA, 10Hz ≤ f ≤ 2.5MHz, V
= 5V
= 5V
88
800
µV
µV
µV
OUT
OUT
OUT
RMS
µV
P-P
OUT
LTC1682-3.3
LTC1682-5
I
I
= 10mA, 10Hz ≤ f ≤ 100kHz, C
= 1nF
= 1nF
58
500
OUT
OUT
FILT
RMS
= 10mA, 10Hz ≤ f ≤ 2.5MHz, C
µV
P-P
FILT
I
I
= 10mA, 10Hz ≤ f ≤ 100kHz, C
= 1nF
= 1nF
64
600
OUT
OUT
FILT
RMS
= 10mA, 10Hz ≤ f ≤ 2.5MHz, C
µV
P-P
FILT
V
V
Line Regulation
Load Regulation
V
= 3V to 4V, I
= 0mA (Note 6)
●
●
5
20
10
mV
OUT
OUT
IN
OUT
I
I
= 1mA to 10mA
= 1mA to 50mA (Note 4)
3
10
mV
mV
OUT
OUT
V
Shutdown Resistance
SHDN = 0V, Resistance Measured to Ground, V = 1.8V
●
●
150
50
350
150
Ω
Ω
OUT
IN
SHDN = 0V, Resistance Measured to Ground, V = 4.4V
IN
SHDN Input Threshold
SHDN Input Current
V
= 1.8V to 4.4V
●
0.4
1
1.6
V
IN
SHDN = V
SHDN = 0V
●
●
–1
–1
1
1
µA
µA
IN
Note 1: Absolute Maximum Ratings are those values beyond which the life
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.
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 5: Limited by the LDO disable switch point of 1.45V .
Note 3: Dropout voltage is the minimum input/output voltage required to
IN
maintain regulation at the specified output current. In dropout the output
Note 6: The LTC1682 is set to 5V. The feedback current is 25µA.
voltage will be equal to: V
– V
(see Figure 4).
CPO
DROPOUT
3
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TYPICAL PERFOR A CE CHARACTERISTICS
VOUT Transient Response
Min and Max VCPO vs VIN
CPO Output Resistance vs VIN
35
30
25
20
15
10
5
9
8
7
6
5
4
3
10
5
T
= 25°C
T
= 25°C
A
A
C1 = 0.22µF
= 10mA
I
OUT
0
V
= 2(V
(A)
)
IN
CPO
T
= 25°C
A
V
V
C
= 3V
–5
–10
15
10
5
IN
= 4V
OUT
OUT
= 10µF
(B)
V
= 1.45(V )
IN
CPO
0
250
1.5
2.5
3.0
(V)
3.5
4.0
4.5
1.5
2.5
3.0
3.5
4.0
4.5
0
50
100
150
200
300
2.0
2.0
TIME (µs)
V
V
(V)
IN
IN
1682 G01
1682 G02
(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
LTC1682-5 Output Noise
(BW = 10Hz to 2.5MHz)
Enable to Shutdown Timing
Shutdown to Enable Timing
2
2
0
4
3
2
1
0
0
4
3
2
1
0
VOUT
200µV/DIV
T
= 25°C
A
V
V
= 3V
IN
= 4V
OUT
OUT
I
= 10mA
NO LOAD
C
= C
= 10µF
CPO
OUT
T
= 25°C
A
V
V
C
= 3V
IN
100µs/DIV
1682 G04
= 4V
OUT
OUT
= 10µF
CCPO = COUT = 4.7µF
IOUT = 10mA
VIN = 3V
VOUT = 5V
TA = 25°C
CFILT = 1nF
200µs/DIV
1ms/DIV
1682 G05
1682 G06
Operating Current vs VIN
(No Load)
Oscillator Frequency vs
Temperature
220
200
180
160
140
120
100
80
565
560
555
550
545
540
535
530
T
= 25°C
A
V
IN
= 3V
LTC1682-3.3
LTC1682-5
LTC1682
60
1.5
2.5
3.0
(V)
3.5
4.0
4.5
2.0
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
V
IN
1682 G08
1682 G07
4
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TYPICAL PERFOR A CE CHARACTERISTICS
VOUT Voltage vs Temperature
VOUT Voltage vs Output Current
5.030
5.020
5.010
5.000
4.990
3.340
3.330
3.320
3.310
3.300
3.290
1.240
1.238
1.236
1.234
5.000
4.999
4.998
4.997
4.996
4.995
4.994
4.993
V
I
= 3V
OUT
V
T
= 3.3V
IN
IN
A
= 10mA
= 25°C
LTC1682-5
LTC1682-5
LTC1682-3.3
3.300
3.299
3.298
3.297
3.296
3.295
3.294
LTC1682-3.3
LTC1682
–50 –25
0
25
50
75 100 125
0
5
10 15 20 25 30 35 40 45 50
OUTPUT CURRENT (mA)
1682 G10
TEMPERATURE (°C)
1682 G09
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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
closetothepinaspossibleforbestperformance.TheVOUT
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.
GND (Pin 4): System 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.
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 capaci-
tance value of 0.1µF is required.
C+ (Pin 7): Flying Capacitor Positive 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.
CPO (Pin 8): Unregulated Charge Pump Output Voltage.
Approximately1.95(VIN)atlowloads.Bypasswitha≥2µF
low ESR capacitor. If a minimum VOUT enable time is
required, the CPO capacitor should be 2× the VOUT
capacitor.
5
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BLOCK DIAGRA SM
C1
0.22µF
+
–
C
C
7
5
CHARGE PUMP
AND
CPO
6
V
8
IN
SLEW CONTROL
C3
4.7µF
C4
275k
4.7µF
–
+
ENB
CLK1
38k
+
–
POWER-
ON
RESET
550kHz
OSCILLATOR
REG B
SHDN
2
SD
328k
REGEN
ENB
1:100
–
V
+
IN
1
V
OUT
LDO
C2
4.7µF
REGEN
SD
V
= 1.235V
REF
100Ω
1µA/2µA
FB
GND
3
4
R1
R2
1682 F01
Figure 1. LTC1682 Block Diagram
6
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BLOCK DIAGRA SM
C1
0.22µF
+
–
C
C
7
5
CHARGE PUMP
AND
CPO
6
V
8
IN
SLEW CONTROL
C3
4.7µF
C4
4.7µF
275k
–
+
ENB
CLK1
38k
+
–
POWER-
ON
550kHz
OSCILLATOR
REG B
SHDN
2
3
RESET
SD
328k
REGEN
ENB
1:100
–
FILT
200k
1nF
+
V
IN
1
V
OUT
LDO
C2
4.7µF
REGEN
SD
V
= 1.235V
REF
RA
120k/65.5k
RB
200k
100Ω
1µA/2µA
1682 F02
4
GND
Figure 2. LTC1682-3.3/LTC1682-5 Block Diagram
7
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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
capacitoronVOUTforstabilityandimprovedload 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 sup-
plies a regulated output at VOUT. Internal comparators are
used to sense CPO and VIN voltages for power-up condi-
tioning. The output current is sensed to determine the
chargepumpoperatingmode.Atrimmedinternalbandgap
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
nonoverlappingclockcontrolsthechargepumpswitches.
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 effi-
ciency but slightly higher output noise. In Burst Mode
operation,theclockisdisabledwhenCPOreaches1.95(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
andthejunctiontemperature.AlowESRcapacitorof≥2µF
should be used at CPO for minimum noise.
V
OUT = 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).
R
R
DROPOUT
CPO
V
CPO
V
OUT
I
+
–
V
DROPOUT
+
2V
C
LOAD
IN
CPO
–
1682 F04
Figure 4. Equivalent Circuit
EXTERNAL LDO
8
1
2
5.1V
RIPPLE
CPO
V
OUT
V
= 800µV
P-P
C3
C2
4.7µF
4.7µF
7
+
C
SHDN
FB
R1
IN
LTC1682
56k
3.3V
V
6
5
3
4
IN
V
OUT
= 1.235V(1 + R1/R2)
OUT
GND
V
IN
–
3.6V
C1
0.22µF
R2
18k
C4
C5
4.7µF
C
GND
1682 F03
Figure 3. Powering an Auxiliary Regulator from CPO
8
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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:
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.
V
OUT(MAX) = (2)(VIN(MIN)) – (IOUT)(RCPO) – VDROPOUT
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
with the condition that (IOUT)(RCPO) < 0.55VIN.
Example:
VIN(MIN) = 3V
on CPO which would reflect as lower ripple on VOUT
.
IOUT = 10mA
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.
RCPO(MAX) = 20Ω
Max unloaded CPO voltage = 6V
Loaded CPO voltage = 6V – (10mA)(20Ω) = 5.8V
V
DROPOUT(MAX) = 0.08V
VOUT(MAX) = (6V) – (0.2V) – (0.08V) = 5.72V
VOUT < 5.5V and (IOUT)(RCPO) < 0.55VIN, 0.2V < 1.65V.
Forminimumnoiseapplications,theLDOmustbekeptout
of dropout to prevent CPO noise from coupling into VOUT
A 1nF filter capacitor for the LTC1682-3.3/LTC1682-5
should be connected between the FILT pin and ground for
optimum noise performance.
.
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
requires5mA,thenthemaximumavailablecurrentatVOUT
will be reduced by 5mA.
Output Ripple
The output noise and ripple on CPO includes a spike
component from the charge pump switches and a droop
componentwhichisdependentontheloadcurrentandthe
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.
RipplecomponentsonCPOaregreatlyreducedatVOUT by
the LDO; however, C2 should also be a low ESR capacitor
to improve filtering of the CPO noise.
Short-Circuit and Thermal Protection
VOUT can be shorted to ground indefinitely. Internal cir-
cuitry will limit the output current. If the junction tempera-
ture 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.
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 addi-
tion, CPO will be high impedance and disconnected from
VIN.
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
If shutdown is not required, connect SHDN to VIN which
will continuously enable the part.
9
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W U U
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 perfor-
mance and ensure proper regulation (Figure 5).
The FILT pin on the LTC1682-3.3/LTC1682-5 is a high
impedance node. Leakage currents at this pin must be
minimized.
Thermal Considerations
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 – VOUT) +
VIN(4mA). The device dissipates the majority of its heat
through its pins, especially GND (Pin 4). Thermal resis-
tance 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 maxi-
mum 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.
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.
V
OUT
C3
C2
1
2
3
4
8
V
IN
SHDN
7
6
5
LTC1682-3.3/5
C4
C
FILT
GND
C1
1682 F05
Figure 5
BNC CABLES
OR COUPLERS
COUPLING
CAPACITOR
PREAMPLIFIER
1822
LTC1682
BATTERY OR
LOW NOISE DC
POWER SUPPLY
V
OUT
+
DEMO
INPUT
BANDWIDTH
FILTER
BOARD
20dB
OSCILLOSCOPE
R*
–
R
LOAD
1682 F06
R*
CONNECT BNC AND
GROUND TO THE
R
PLACE BANDWIDTH FILTER
COMPONENTS IN SHIELDED BOX
WITH COAXIAL CONNECTORS
LOAD
R*
OUTPUT CAPACITOR
PLACE COUPLING
GROUND TERMINAL E5
CAPACITOR IN SHIELDED
BOX WITH COAXIAL
CONNECTOR
*50Ω TERMINATIONS NOTE: KEEP BNC CONNECTIONS
HP-11048C OR
EQUIVALENT
AS SHORT AS POSSIBLE
Figure 6. LTC1682 Noise Measurement Test Setup
10
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TYPICAL APPLICATION
3.3V to Low Noise 3.3V Converter
SHUTDOWN
8
7
6
5
1
2
3
4
3.3V
V
CPO
V
OUT
= 500µV
C2
4.7µF
RIPPLE
P-P
C3
4.7µF
+
C
SHDN
FILT
LTC1682-3.3
V
IN
3.3V
V
C
IN
C
C4
4.7µF
C1
0.22µF
FILT
1nF
–
GND
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)
8
7
6
5
0.040 ± 0.006
(1.02 ± 0.15)
0.034 ± 0.004
(0.86 ± 0.102)
0.007
(0.18)
0° – 6° TYP
0.118 ± 0.004**
(3.00 ± 0.102)
SEATING
PLANE
0.192 ± 0.004
(4.88 ± 0.10)
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.0256
(0.65)
TYP
MSOP (MS8) 1197
1
2
3
4
* 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
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
(0.254 – 0.508)
7
5
8
6
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
TYP
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
SO8 0996
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
1
3
4
2
11
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TYPICAL APPLICATION
Wide Input Range VCO Supply (VIN > 4.4V)
V
IN
3V TO 6V
Q1
FMMT3904
R1
5V
470Ω
LOW NOISE
8
7
6
5
1
2
3
4
V
CPO
OUT
C3
C2
4.7µF
4.7µF
VCO
+
SHDN
LTC1682-5
C
SHUTDOWN
C
D1
1N4148
FILT
V
3V
(REQUIRED FOR
START-UP)
IN
1682 ta04
C1
0.22µF
C4
4.7µF
FILT
1nF
–
GND
C
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1340
Low Noise, Voltage-Boosted Varactor Driver
Generates 5V Varactor Drive from 3V Supply
I = 6µA; Short Circuit/Thermal Protected
CC
LTC1517-X
LT1521
Micropower, Regulated Charge Pump Doubler in SOT-23
300mA Low Dropout Regulator
Micropower; Good Transient Response
Ultralow Power: Typical Operating I = 6µA
LTC1522
Micropower, Regulated 5V Charge Pump
100mA Low Noise LDO Regulator in SOT-23
CC
LT1761 Series
I
= 20µA; 20µV
Output Noise
CC
RMS
128235fs, sn128235 LT/TP 0799 4K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1999
12 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
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