LTC1928-5
Doubler Charge Pump with
Low Noise Linear Regulator
in ThinSOT
FEATURES
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DESCRIPTION
The
LTC
®
1928-5
is a doubler charge pump with an internal
low noise, low dropout (LDO) linear regulator. The part is
designed to provide a low noise boosted supply voltage for
powering noise sensitive devices such as high frequency
VCOs in wireless applications.
An internal charge pump converts a 2.7V to 4.4V input to a
boosted output, while the internal LDO regulator converts
the boosted voltage to a low noise regulated output. The
regulator is capable of supplying up to 30mA of output
current. Shutdown reduces the supply current to <8µA,
removes the load from V
IN
by disabling the regulator and
discharges V
OUT
to ground through a 200Ω switch.
The LTC1928-5 LDO regulator is stable with only 2µF on
the output. Small ceramic capacitors can be used, reduc-
ing PC board area.
The LTC1928-5 is short-circuit and overtemperature pro-
tected. The part is available in a 6-pin low profile (1mm)
ThinSOT package.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT and Burst Mode are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
Low Output Noise: 90µV
RMS
(100kHz BW)
Fixed Output Voltage: 5V
Input Voltage Range: 2.7V to 4.4V
No Inductors Required
Uses Small Ceramic Capacitors
Output Current Up to 30mA
550kHz Switching Frequency
Low Operating Current: 190µA
Low Shutdown Current: 4µA
Internal Thermal Shutdown and Current Limiting
Low Profile (1mm) ThinSOT™ Package
APPLICATIONS
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VCO Power Supplies for Cellular Phones
2-Way Pagers
Wireless PCMCIA Cards
Portable Medical Instruments
Low Power Data Acquisition
Remote Transmitters
White LED Drivers
GaAs Switches
TYPICAL APPLICATION
Output Noise (BW = 10Hz to 2.5MHz)
LTC1928-5
V
IN
2.7V TO 4.4V
1
4.7µF
0.47µF
5
6
V
IN
CP
V
OUT
CPO
3
4
2
4.7µF
5V
V
OUT
4.7µF
V
OUT
200µV/DIV
CN/SHDN GND
19285 F01
Figure 1. Low Noise 5V Power Supply
C
CPO
= C
OUT
= 4.7µF 100µs/DIV
I
OUT
= 10mA
V
IN
= 3V
V
OUT
= 5A
T
A
= 25°C
19285 TA01
19285fa
For more information
www.linear.com/LTC 1928-5
1
LTC1928-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
V
IN
1
GND 2
V
OUT
3
6 CN/SHDN
5 CP
4 CPO
V
IN
to Ground ............................................... –0.3V to 5V
V
OUT
Voltage ........................................... –0.3V to 5.25V
CPO to Ground ..........................................................10V
CN/SHDN to Ground ..................... –0.3V to (V
IN
+ 0.3V)
V
OUT
Short-Circuit Duration ............................. Indefinite
I
OUT
........................................................................40mA
Operating Temperature Range (Note 2)....–40°C to 85°C
Maximum Junction Temperature ........................ 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
S6 PACKAGE
6-LEAD PLASTIC SOT-23
T
JMAX
= 125°C,
θ
JA
= 230°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC1928ES6-5#PBF
TAPE AND REEL
LTC1928ES6-5#TRPBF
PART MARKING
LTKT
PACKAGE DESCRIPTION
6-Lead Plastic SOT-23
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3V, C
FLY
= 0.47µF, C
OUT
, C
CPO
, C
IN
= 4.7µF unless otherwise
specified.
PARAMETER
V
IN
Operating Voltage
I
VIN
Shutdown Current
I
VIN
Operating Current
Regulated Output Voltage
V
OUT
Temperature Coefficient
Charge Pump Oscillator Frequency
CPO Output Resistance
V
OUT
Dropout Voltage (Note 3)
V
OUT
Enable Time
V
OUT
Output Noise Voltage
V
OUT
Line Regulation
V
OUT
Load Regulation
V
OUT
Shutdown Resistance
I
OUT
> 500µA, V
IN
= 2.7V to 4.4V
V
IN
= 2.7V, I
OUT
= 10mA
V
IN
= 4.4V, I
OUT
= 10mA
I
OUT
= 10mA, V
OUT
= 5V
R
LOAD
= 2k
I
OUT
= 10mA, 10Hz ≤ f ≤ 100kHz
I
OUT
= 10mA, 10Hz ≤ f ≤ 2.5MHz
V
IN
= 2.7V to 4.4V, I
OUT
= 0
I
OUT
= 1mA to 10mA
I
OUT
= 1mA to 30mA (Note 4)
CN/SHDN = 0V (Note 5)
V
IN
= 2.7V, Resistance Measured to Ground
V
IN
= 4.4V, Resistance Measured to Ground
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
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TYP
4
190
MAX
4.4
8
330
5.1
620
30
24
100
UNITS
V
µA
µA
V
ppm
kHz
Ω
Ω
mV
ms
µV
RMS
µV
P-P
2.7
SHDN
= 0V (Note 5)
I
OUT
= 0mA, Burst Mode™ Operation
I
OUT
= 1mA
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4.9
480
5
±50
550
17
14
0.6
90
800
4
2
4
160
100
20
10
mV
mV
mV
Ω
Ω
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400
300
19285fa
2
For more information
www.linear.com/LTC 1928-5
LTC1928-5
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3V, C
FLY
= 0.47µF, C
OUT
, C
CPO
, C
IN
= 4.7µF unless otherwise
specified.
CN/SHDN Input Threshold
CN/SHDN Input Current
V
IN
= 2.7V to 4.4V (Note 5)
CN/SHDN = 0V (Note 5)
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ELECTRICAL CHARACTERISTICS
0.15
–1
0.5
–3
1.6
–6
V
µA
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:
The LTC1928ES6-5 is guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
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: V
CPO
– V
DROPOUT
(see Figure 2).
TYPICAL PERFORMANCE CHARACTERISTICS
CPO Output Resistance vs V
IN
35
T
A
= 25°C
C
FLY
= 0.47µF
30 I
OUT
= 10mA
25
R
CPO
( )
V
CPO
(V)
20
15
10
3
5
2.5
3.0
3.5
V
IN
(V)
4.0
4.5
19285 G01
9
8
7
6
5
4
Min and Max V
CPO
vs V
IN
T
A
= 25°C
V
CPO
= 2(V
IN
)
(A)
(B)
V
CPO
= 1.45(V
IN
)
I
OUT
(mA)
∆V
OUT
(mV)
10
5
0
–5
–10
15
10
5
0
V
OUT
Transient Response
T
A
= 25°C
V
IN
= 3V
V
OUT
= 5V
C
OUT
= 4.7µF
2.5
3.0
3.5
V
IN
(V)
4.0
4.5
0
50
100
150
200
TIME (µs)
250
300
(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
19285 G02
19285 G03
Shutdown to Enable Timing
(Figure 5)
SHDN (V)
SHDN (V)
2
0
5
4
V
OUT
(V)
V
OUT
(V)
3
2
1
0
T
A
= 25°C
V
IN
= 3V
V
OUT
= 5V
I
OUT
= 10mA
C
OUT
= C
CPO
= 4.7µF
200s/DIV
19285 G04
Enable to Shutdown Timing
(Figure 5)
5.040
2
0
V
OUT
VOLTAGE (V)
5
4
3
2
1
0
NO LOAD
T
A
= 25°C
V
IN
= 3V
V
OUT
= 5V
C
OUT
= 4.7µF
1ms/DIV
19285 G05
V
OUT
Voltage vs Temperature
V
IN
= 3V
I
OUT
= 10mA
5.030
5.020
5.010
5.000
4.990
4.980
–50 –25
50
75
25
0
TEMPERATURE (°C)
100
125
19285 G06
19285fa
For more information
www.linear.com/LTC 1928-5
3
LTC1928-5
TYPICAL PERFORMANCE CHARACTERISTICS
Operating Current vs V
IN
(No Load)
260
240
OPERATING CURRENT (µA)
220
200
180
160
140
120
100
2.5
3.0
3.5
V
IN
(V)
4.0
4.5
19285 G07
Efficiency vs Supply Voltage
100
90
80
70
60
50
40
T
A
= 25°C
I
OUT
= 15mA
C
FLY
= 0.47µF
OUTPUT VOLTAGE (V)
4.901
4.900
4.989
4.988
4.987
4.986
4.985
4.984
4.983
2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4
SUPPLY VOLTAGE (V)
19285 G08
Output Voltage vs Output Current
T
A
= 25°C
V
IN
= 3V
C
FLY
= 0.47µF
T
A
= 25°C
EFFICIENCY (%)
4.982
0
5
10 15 20 25 30
OUTPUT CURRENT (mA)
35
40
19285 G09
PIN FUNCTIONS
V
IN
(Pin 1):
Input Voltage, 2.7V to 4.4V. V
IN
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.
GND (Pin 2):
System Ground.
V
OUT
(Pin 3):
Low Noise Regulated Output Voltage. V
OUT
should be bypassed with a ≥2µF low ESR capacitor as
close to the pin as possible for best performance. The
V
OUT
voltage is internally set to 5V.
CPO (Pin 4):
Boosted Unregulated Voltage. Approximately
1.95V
IN
at low loads. Bypass with a ≥2µF low ESR capacitor.
CP (Pin 5):
Flying Capacitor Positive Input.
CN/SHDN (Pin 6):
Flying Capacitor Negative Input and
SHDN.
When this pin is pulled to ground through a 100Ω
resistor, the part will go into shutdown within approxi-
mately 30µs.
19285fa
4
For more information
www.linear.com/LTC 1928-5
LTC1928-5
BLOCK DIAGRAM
C
FLY
0.47µF
CP
5
6
CN/SHDN
V
IN
C
IN
4.7µF
1
CHARGE PUMP
AND
SLEW CONTROL
ENB
CLK B
4
CPO
C
CPO
4.7µF
POR/
SHDN
CONTROL
SD
550kHz
OSCILLATOR
BURST
+
–
+
–
V
REF
= 1.235V
SD
160
APPLICATIONS INFORMATION
Operation
The LTC1928-5 uses a switched-capacitor charge pump to
generate a CPO voltage of approximately 2V
IN
. CPO pow-
ers an internal low dropout linear regulator that supplies
a regulated output at V
OUT
. Internal comparators are used
to sense CPO and V
IN
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.
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 1.75V
IN
the LDO is enabled.
If CPO falls below 1.45V
IN
the LDO will be disabled. Gen-
erally, the charge pump runs open loop with continuous
clocking for low noise. If CPO is greater than 1.95V
IN
and
I
OUT
is less than 200µA, 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 1.95V
IN
and enabled when
CPO droops by about 150mV. 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 V
IN
, CPO, the flying capacitor
value C
FLY
and the junction temperature. A low ESR capaci-
tor of ≥2µF should be used at CPO for minimum noise.
The LDO is used to filter the ripple on CPO and to set an
output voltage independent of CPO. V
OUT
is set by an in-
19285fa
For more information
www.linear.com/LTC 1928-5
–
+
3
2
19285 BD
V
OUT
C
OUT
4.7µF
GND
5
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