LINER LTC3250-1.5 High efficiency, low noise, inductorless step-down dc/dc converter Datasheet

LTC3250-1.5/LTC3250-1.2
High Efficiency, Low Noise,
Inductorless Step-Down
DC/DC Converter
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FEATURES
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DESCRIPTIO
2.7V to 5.5V Input Voltage Range
No Inductors
Li-Ion (3.6V) to 1.5V with 81% Efficiency
Low Noise Constant Frequency Operation
Output Voltages: 1.5V ±4%, 1.2V ±4%
Output Current: 250mA
Shutdown Disconnects Load from VIN
Low Operating Current: IQ = 35µA
Low Shutdown Current: ISD < 1µA
Oscillator Frequency = 1.5MHz
Soft-Start Limits Inrush Current at Turn-On
Short-Circuit and Overtemperature Protected
Low Profile (1mm) SOT-23 Package
The LTC®3250-1.5/LTC3250-1.2 are charge pump stepdown DC/DC converters that produce a 1.5V or 1.2V
regulated output from a 2.7V to 5.5V input. The parts use
switched capacitor fractional conversion to achieve typical efficiency two times higher than that of a linear regulator. No inductors are required.
A unique constant frequency architecture provides a low
noise regulated output as well as lower input noise
than conventional charge pump regulators.* High
frequency operation (fOSC = 1.5MHz) simplifies filtering
to further reduce conducted noise. The part also uses
Burst Mode® operation to improve efficiency at light loads.
Low operating current (35µA with no load, <1µA in
shutdown) and low external parts count (three small
ceramic capacitors) make the LTC3250-1.5/LTC3250-1.2
ideally suited for space constrained battery powered applications. The parts are short-circuit and overtemperature
protected, and are available in a low profile (1mm) 6-pin
ThinSOTTM package.
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APPLICATIO S
Handheld Computers
Cellular Phones
■ Digital Cameras
■ Handheld Medical Instruments
■ Low Power DSP Supplies
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, LTC and LT are registered trademarks of Linear Technology Corporation
Burst Mode is a registered trademark of Linear Technology Corporation
ThinSOT is a trademark of Linear Technology Corporation.
*U.S. Patent #6, 411, 531
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TYPICAL APPLICATIO
Efficiency vs Input Voltage
(IOUT = 100mA)
100
Li-Ion to 1.5V Output with Shutdown
90
1µF
80
LTC3250-1.5
C–
VIN
VIN
3.2V TO 4.2V
Li-Ion
C+
VOUT
VOUT = 1.5V ± 4%
100mA
1µF
LTC3250-1.5
OFF ON
SHDN
4.7µF
EFFICIENCY (%)
70
60
50
40
LDO
30
20
GND
10
3250 TA1a
0
3.0
3.5
4.0
4.5
VIN (V)
5.0
5.5
3250 TA01b
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LTC3250-1.5/LTC3250-1.2
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
VIN to GND ................................................... –0.3V to 6V
SHDN to GND ............................... –0.3V to (VIN + 0.3V)
IOUT (Note 2)....................................................... 350mA
Operating Ambient Temperature Range (Note 3)
........................................................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
VIN 1
GND 2
SHDN 3
LTC3250ES6-1.5
LTC3250ES6-1.2
6 C+
5 VOUT
4 C–
S6 PART MARKING
S6 PACKAGE
6-LEAD PLASTIC SOT-23
LTZE
LTAGJ
TJMAX = 150°C, θJA = 230°C/W,
θJC = 102°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, CFLY = 1µF, CIN = 1µF, COUT = 4.7µF unless otherwise noted.
SYMBOL
PARAMETER
VIN
LTC3250-1.5 Operating Voltage Range
CONDITIONS
MIN
●
LTC3250-1.2 Operating Voltage Range
VOUT
MAX
UNITS
5.5
V
●
2.7
5.5
V
IOUT ≤ 50mA 3.1V ≤ VIN ≤ 5.5V
IOUT ≤ 100mA 3.2V ≤ VIN ≤ 5.5V
IOUT ≤ 250mA 3.5V ≤ VIN ≤ 5V
●
●
1.44
1.44
1.44
1.5
1.5
1.5
1.56
1.56
1.56
V
V
IOUT ≤ 150mA 2.7V < VIN < 5.5V
IOUT ≤ 250mA 2.9V ≤ VIN ≤ 5V
●
1.15
1.15
1.2
1.2
1.25
1.25
V
Operating Current
IOUT = 0mA
●
35
60
µA
Shutdown Current
SHDN = 0V
●
0.01
1
LTC3250-1.5 Output Voltage Range
LTC3250-1.2 Output Voltage Range
IIN
TYP
3.1
V
V
µA
VRB
Burst Mode Operation Output Ripple
12
mVP-P
VRC
Continuous Mode Output Ripple
4
mVP-P
fOSC
Switching Frequency
●
1.2
1.5
VIH
SHDN Input Hi Voltage
●
1.2
0.8
VIL
SHDN Input Low Voltage
●
IIH
SHDN Input Current
SHDN = VIN
●
IIL
SHDN Input Current
SHDN = 0V
●
tON
Turn On Time
RLOAD = 6Ω
0.8
ms
LTC3250-1.5 Load Regulation
0 ≤ IOUT ≤ 250mA
0.15
mV/mA
LTC3250-1.2 Load Regulation
0 ≤ IOUT ≤ 250mA
0.12
mV/mA
Line Regulation
IOUT = 250mA
0.2
%/V
Open-Loop Output Impedance
IOUT = 250mA (Note 4)
1.0
Ω
ROL
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Based on long term current density limitations.
Note 3: The LTC3250-1.5E/LTC3250-1.2E are guaranteed to meet
specified performance from 0°C to 70°C. Specifications over the –40°C
and 85°C operating temperature range are assured by design
characterization and correlation with statistical process controls.
0.8
1.8
MHz
V
0.4
V
–1
1
µA
–1
1
µA
Note 4: Output not in regulation; ROL = (VIN/2 - VOUT)/IOUT.
Note 5: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
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LTC3250-1.5/LTC3250-1.2
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TYPICAL PERFOR A CE CHARACTERISTICS
Oscillator Frequency vs
Supply Voltage
No Load Supply Current vs
Supply Voltage
50
1.8
3.1V < VIN < 5.5V (LTC3250-1.5)
2.7V < VIN < 5.5V (LTC3250-1.2)
45
VSHDN Threshold Voltage vs
Supply Voltage
1200
3.1V < VIN < 5.5V (LTC3250-1.5)
2.7V < VIN < 5.5V (LTC3250-1.2)
1100
1.7
TA = 85°C
TA = 25°C
35
TA = –40°C
30
1.6
TA = 85°C
1.5
TA = –40°C
VSHDN (mV)
FREQUENCY (MHz)
1000
40
IIN (µA)
3.1V < VIN < 5.5V (LTC3250-1.5)
2.7V < VIN < 5.5V (LTC3250-1.2)
TA = 25°C
1.4
900
TA = –40°C
TA = 25°C
800
700
TA = 85°C
600
25
1.3
20
2.7
3.1
3.5
3.9 4.3
VIN (V)
4.7
5.1
500
1.2
2.7
5.5
3.2
3.7
4.2
VIN (V)
4.7
400
2.7
5.2
3250 G01
3.2
3.7
4.2
VIN (V)
4.7
5.2
3250 G03
3250 G02
(LTC3250-1.5)
Efficiency vs Output Current
100
VIN = 3.6V
TA = 25°C
90
1.56
80
1.54
70
EFFICIENCY (%)
VOUT (V)
1.58
1.52
1.50
1.48
Output Voltage vs Supply Voltage
1.60
TA = 25°C
VIN = 3.3V
1.58
1.54
60
VIN = 5V
50
40
1.48
1.46
1.44
20
1.44
1.42
10
1.42
0
50
100
150
200
IOUT (mA)
250
300
1
10
IOUT (mA)
IOUT = 250mA
1.40
3.0
1000
100
IOUT = 100mA
1.50
30
0
0.1
IOUT = 0mA
1.52
1.46
1.40
TA = 25°C
1.56
VIN = 3.6V
VIN = 4V
VOUT (V)
Output Voltage vs Load Current
1.60
3.5
4.5
4.0
VIN (V)
5.0
3250 G05
3250 G04
5.5
3250 G06
(LTC3250-1.2)
Efficiency vs Output Current
100
VIN = 3.6V
TA = 25°C
90
1.26
80
1.24
70
EFFICIENCY (%)
VOUT (V)
1.28
1.22
1.20
1.18
Output Voltage vs Supply Voltage
1.30
TA = 25°C
1.28
VIN = 2.7V
VIN = 3.5V
60
50
1.24
VIN = 4.5V
40
1.18
1.16
1.14
20
1.14
1.12
10
1.12
0
50
100
150
200
IOUT (mA)
250
300
3250 G12
1
10
IOUT (mA)
100
1000
3250 G13
IOUT = 100mA
1.20
30
0
0.1
IOUT = 0mA
1.22
1.16
1.10
TA = 25°C
1.26
VIN = 3V
VOUT (V)
Output Voltage vs Load Current
1.30
1.10
2.7
IOUT = 250mA
3.2
3.7
4.2
VIN (V)
4.7
5.2
3250 G14
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LTC3250-1.5/LTC3250-1.2
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TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage Soft-Start and
Shutdown (LTC3250-1.5)
Output Current Transient
Response (LTC3250-1.5)
HI
IOUT
SHDN
LOW
250mA
15mA
VOUT
20mV/DIV
AC
VOUT
500mV/DIV
3250 G07
RL = 6Ω
VIN = 3.6V
VIN = 3.6V
Input Voltage Ripple vs Input
Capacitor (LTC3250-1.5)
Line Transient Response
(LTC3250-1.5)
VIN
3250 G08
4.5V
VIN
50mV/DIV
AC
3.5V
VOUT
20mV/DIV
AC
CI = 1µF
VIN
50mV/DIV
AC
3250 G09
IOUT = 200mA
CI = 10µF
IOUT = 250mA
RSOURCE = 0.2Ω
3250 G10
Output Voltage Ripple
(LTC3250-1.5)
VOUT
20mV/DIV
AC
COUT = 4.7µF 1X5R16.3V
IOUT = 250mA
VIN = 3.6V
3250 G11
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LTC3250-1.5/LTC3250-1.2
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PI FU CTIO S
VIN (Pin 1): Input Supply Voltage. Bypass VIN with a ≥1µF
low ESR ceramic capacitor.
C – (Pin 4): Flying Capacitor Negative Terminal
VOUT (Pin 5): Regulated Output Voltage. VOUT is disconnected from VIN during shutdown. Bypass VOUT with a
≥4.7µF low ESR ceramic capacitor (2.5µF min, ESR
<100mΩ).
GND (Pin 2): Ground. Connect to a ground plane for best
performance.
SHDN (Pin 3): Active Low Shutdown Input. A low voltage
on SHDN disables the LTC3250-1.5/LTC3250-1.2. SHDN
must not be allowed to float.
C + (Pin 6): Flying Capacitor Positive Terminal.
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BLOCK DIAGRA
LTC3250-1.5/
LTC3250-1.2
THERMAL
SHUTDOWN
(>160°C)
SWITCH
CONTROL
AND
SOFT-START
SHDN 3
CHARGE
PUMP
1
6 C+
5 VOUT
4 C–
+
BURST
DETECT
CIRCUIT
–
VIN
1.5MHz
OSCILLATOR
VREF
2
3250 BD
GND
3250fa
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LTC3250-1.5/LTC3250-1.2
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OPERATIO (Refer to Simplified Block Diagram)
The LTC3250-1.5/LTC3250-1.2 use a switched capacitor
charge pump to step down VIN to a regulated 1.5V ±4% or
1.2V ±4% (respectively) output voltage. Regulation is
achieved by sensing the output voltage through an internal
resistor divider and modulating the charge pump output
current based on the error signal. A 2-phase nonoverlapping
clock activates the charge pump switches. On the first
phase of the clock current is transferred from VIN, through
the flying capacitor, to VOUT. Not only is current being
delivered to VOUT on the first phase, but the flying capacitor is also being charged up. On the second phase of the
clock the flying capacitor is connected from VOUT to
ground, delivering the charge stored during the first phase
of the clock to VOUT. Using this method of switching, only
half of the output current is delivered from VIN, thus
achieving twice the efficiency over a conventional LDO.
The sequence of charging and dis-charging the flying
capacitor continues at a free running frequency of 1.5MHz
(typ). This constant frequency architecture provides a low
noise regulated output as well as lower input noise than
conventional switch-capacitor charge pump regulators.
The part also has a low current Burst Mode operation to
improve efficiency even at light loads.
In shutdown mode all circuitry is turned off and the
LTC3250-1.5/LTC3250-1.2 draw only leakage current from
the VIN supply. Furthermore, VOUT is disconnected from
VIN. The SHDN pin is a CMOS input with a threshold
voltage of approximately 0.8V. The LTC3250-1.5/LTC32501.2 are in shutdown when a logic low is applied to the
SHDN pin. Since the SHDN pin is a high impedance CMOS
input it should never be allowed to float. To ensure that its
state is defined it must always be driven with a valid logic
level.
Short-Circuit/Thermal Protection
The LTC3250-1.5/LTC3250-1.2 have built-in short-circuit
current limiting as well as overtemperature protection.
During short-circuit conditions, the parts will automatically limit the output current to approximately 500mA. At
higher temperatures, or if the input voltage is high enough
to cause excessive self heating on chip, thermal shutdown
circuitry will shut down the charge pump once the junction
temperature exceeds approximately 160°C. It will reenable
the charge pump once the junction temperature drops
back to approximately 150°C. The LTC3250-1.5/LTC32501.2 will cycle in and out of thermal shutdown without latchup or damage until the short-circuit on VOUT is removed.
Long term overstress (IOUT > 350mA, and/or TJ > 140°C)
should be avoided as it can degrade the performance of the
part.
Soft-Start
To prevent excessive current flow at VIN during start-up,
the LTC3250-1.5/LTC3250-1.2 have a built-in soft-start
circuitry. Soft-start is achieved by increasing the amount
of current available to the output charge storage capacitor
linearly over a period of approximately 500µs. Soft-start is
enabled whenever the device is brought out of shutdown,
and is disabled shortly after regulation is achieved.
Low Current “Burst Mode” Operation
To improve efficiency at low output currents, Burst Mode
operation was included in the design of the LTC3250-1.5/
LTC3250-1.2. An output current sense is used to detect
when the required output current drops below an internally set threshold (30mA typ.). When this occurs, the part
shuts down the internal oscillator and goes into a low
current operating state. The LTC3250-1.5/LTC3250-1.2
will remain in the low current operating state until the
output has dropped enough to require another burst of
current. Unlike traditional charge pumps whose burst
current is dependant on many factors (i.e. supply voltage,
switch resistance, capacitor selection, etc.), the LTC32501.5/LTC3250-1.2’s burst current is set by the burst threshold and hysteresis. This means that the VOUT ripple voltage
in Burst Mode will be fixed and is typically 12mV for a
4.7µF output capacitor.
Power Efficiency
The power efficiency (η) of the LTC3250-1.5/LTC32501.2 are approximately double that of a conventional linear
regulator. This occurs because the input current for a 2 to
1 step-down charge pump is approximately half the output
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LTC3250-1.5/LTC3250-1.2
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OPERATIO
(Refer to Simplified Block Diagram)
current. For an ideal 2 to 1 step-down charge pump the
power efficiency is given by:
η≡
POUT VOUT • IOUT 2VOUT
=
=
PIN
VIN
1
VIN • IOUT
2
The switching losses and quiescent current of the
LTC3250-1.5/LTC3250-1.2 are designed to minimize efficiency loss over the entire output current range, causing
only a couple % error from the theoritical efficiency. For
example with VIN = 3.6V, IOUT = 100mA and VOUT regulating to 1.5V the measured efficiency is 80.6% which is in
close agreement with the theoretical 83.3% calculation.
0.15Ω for the LTC3250-1.5 and 0.12Ω for the
LTC3250-1.2. For a 250mA load current change the output
voltage will change by about 37mV for the LTC3250-1.5
and by 30mV for the LTC 3250-1.2. If the ESR of the output
capacitor is greater than the closed-loop-output impedance the part will cease to roll-off in a simple one-pole
fashion and poor load transient response or instability
could result. Ceramic capacitors typically have exceptional ESR performance and combined with a tight board
layout should yield excellent stability and load transient
performance.
Further output noise reduction can be achieved by filtering
the LTC3250-1.5/LTC3250-1.2 output through a very small
series inductor as shown in Figure 1. A 10nH inductor will
VOUT Capacitor Selection
The ESR and value of capacitors used with the LTC32501.5/LTC3250-1.2 determine several important parameters
such as regulator control loop stability, output ripple, and
charge pump strength.
10nH
(TRACE INDUCTANCE)
VOUT
LTC3250-1.5/
LTC3250-1.2
VOUT
4.7µF
0.22µF
GND
3250 F01
The value of COUT directly controls the amount of output
ripple for a given load current. Increasing the size of COUT
will reduce the output ripple.
Figure 1. 10nH Inductor Used for
Additional Output Noise Reduction
To reduce output noise and ripple, it is suggested that a
low ESR (<0.1Ω) ceramic capacitor (4.7µF or greater) be
used for COUT. Tantalum and aluminum capacitors are not
recommended because of their high ESR.
reject the fast output transients, thereby presenting a
nearly constant output voltage. For economy the 10nH
inductor can be fabricated on the PC board with about 1cm
(0.4") of PC board trace.
Both ESR and value of the COUT can significantly affect the
stability of the LTC3250-1.5/LTC3250-1.2. As shown in
the block diagram, the LTC3250-1.5/LTC3250-1.2 use a
control loop to adjust the strength of the charge pump to
match the current required at the output. The error signal
of this loop is stored directly on the output charge storage
capacitor. Thus the charge storage capacitor also serves
to form the dominant pole for the control loop. To prevent
ringing or instability it is important for the output capacitor
to maintain at least 2.5µF of capacitance over all conditions (see “Ceramic Capacitor Selection Guidelines” section).
VIN Capacitor Selection
Likewise excessive ESR on the output capacitor will tend
to degrade the loop stability of the LTC3250-1.5/LTC32501.2. The closed-loop output resistance is designed to be
The constant frequency architecture used by the
LTC3250-1.5/LTC3250-1.2 makes input noise filtering
much less demanding than conventional charge pump
regulators. On a cycle by cycle basis, the LTC3250-1.5/
LTC3250-1.2 input current will go from IOUT/2 to 0mA.
Lower ESR will reduce the voltage steps caused by changing input current, while the absolute capacitor value will
determine the level of ripple. For optimal input noise and
ripple reduction, it is recommended that a low ESR 1µF or
greater ceramic capacitor be used for CIN (see “Ceramic
Capacitor Selection Guidelines” section). Aluminum and
tantalum capacitors are not recommended because of
their high ESR.
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LTC3250-1.5/LTC3250-1.2
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OPERATIO (Refer to Simplified Block Diagram)
Flying Capacitor Selection
Warning: A polarized capacitor such as tantalum or
aluminum should never be used for the flying capacitor
since its voltage can reverse upon start-up of the
LTC3250-1.5/LTC3250-1.2. Ceramic capacitors should
always be used for the flying capacitor.
The flying capacitor controls the strength of the charge
pump. In order to achieve the rated output current it is
necessary for the flying capacitor to have at least 0.4µF of
capacitance over operating temperature with a 2V bias
(see “Ceramic Capacitor Selection Guidelines” section). If
only 100mA or less of output current is required for the
application the flying capacitor minimum can be reduced
to 0.15µF.
Ceramic Capacitor Selection Guidelines
Capacitors of different materials lose their capacitance
with higher temperature and voltage at different rates. For
example, a ceramic capacitor made of X7R material will
retain most of its capacitance from –40°C to 85°C whereas
a Z5U or Y5V style capacitor will lose considerable capacitance over that range (60% to 80% loss typ.). Z5U and Y5V
capacitors may also have a very strong voltage coefficient
causing them to lose an additional 60% or more of their
capacitance when the rated voltage is applied. Therefore,
when comparing different capacitors it is often more
appropriate to compare the amount of achievable capacitance for a given case size rather than discussing the
specified capacitance value. For example, over rated voltage and temperature conditions, a 4.7µF, 10V, Y5V
ceramic capacitor in a 0805 case may not provide any
more capacitance than a 1µF, 10V, X7R available in the
same 0805 case. In fact over bias and temperature range,
the 1µF, 10V, X7R will provide more capacitance than the
4.7µF, 10V, Y5V. The capacitor manufacturer’s data sheet
should be consulted to determine what value of capacitor
is needed to ensure minimum capacitance values are met
over operating temperature and bias voltage.
Below is a list of ceramic capacitor manufacturers and
how to contact them:
AVX
1-(803)-448-1943
www.avxcorp.com
Kemet
1-(864)-963-6300
www.kemet.com
Murata
1-(800)-831-9172
www.murata.com
Taiyo Yuden
1-(800)-348-2496
www.t-yuden.com
Vishay
1-(800)-487-9437
www.vishay.com
Layout Considerations
Due to the high switching frequency and transient currents
produced by the LTC3250-1.5/LTC3250-1.2 careful board
layout is necessary for optimal performance. A true ground
plane and short connections to all capacitors will improve
performance and ensure proper regulation under all conditions. Figure 2 shows the recommended layout configuration.
1µF
VOUT
VIN
1µF
4.7µF
GND
SHDN
3250 F02
LTC3250-1.5/LTC3250-1.2
VIA TO GROUND PLANE
Figure 2. Recommended Layout
The flying capacitor pins, C + and C – will have very high
edge rate wave forms. The large dv/dt on these pins can
couple energy capacitively to adjacent printed circuit board
runs. Magnetic fields can also be generated if the flying
capacitors are not close to the LTC3250-1.5/LTC3250-1.2
(i.e. the loop area is large). To decouple capacitive energy
transfer, a Faraday shield may be used. This is a grounded
PC trace between the sensitive node and the LTC3250-1.5/
LTC3250-1.2 pins. For a high quality AC ground it should
be returned to a solid ground plane that extends all the way
to the LTC3250-1.5/LTC3250-1.2.
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LTC3250-1.5/LTC3250-1.2
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OPERATIO
(Refer to Simplified Block Diagram)
Thermal Management
For higher input voltages and maximum output current
there can be substantial power dissipation in the
LTC3250-1.5/LTC3250-1.2. If the junction temperature
increases above approximately 160°C the thermal shutdown circuitry will automatically deactivate the output. To
reduce the maximum junction temperature, a good thermal connection to the PC board is recommended. Connecting the GND pin (Pin 2) to a ground plane, and
maintaining a solid ground plane under the device can
reduce the thermal resistance of the package and PC board
considerably.
Derating Power at Higher Temperatures
To prevent an overtemperature condition in high power
applications Figure 3 should be used to determine the
maximum combination of ambient temperature and power
1.2
dissipation. The power dissipated in the LTC3250-1.5/
LTC3250-1.2 should always fall under the line shown (i.e.
within the safe region) for a given ambient temperature.
The power dissipated in the LTC3250-1.5/LTC3250-1.2 is
given by the expression:
V

PD =  IN – VOUT  IOUT
 2

This derating curve assumes a maximum thermal resistance, θJA , of 175°C/W for the 6-pin ThinSOT-23. This
thermal resistances can be achieved from a printed circuit
board layout with a solid ground plane (2000mm2)on at
least one layer with a good thermal connection to the
ground pin of the LTC3250-1.5/LTC3250-1.2. Operation
outside of this curve will cause the junction temperature to
exceed 140°C which may trigger the thermal shutdown
circuitry and ultimately reduce the life of the device.
θJA = 175°C/W
TJ = 140°C
POWER DISSIPATION (W)
1.0
0.8
0.6
0.4
0.2
0
–50
0
25
50
75
–25
AMBIENT TEMPERATURE (°C)
100
3250 • F03
Figure 3. Maximum Power Dissipation vs Ambient Temperature
3250fa
9
LTC3250-1.5/LTC3250-1.2
U
TYPICAL APPLICATIO S
Efficiency vs Output Current
100
Fixed 3.3V Input to 1.5V Output with Shutdown
90
1µF
TA = 25°C
VIN = 3.3V
80
1
VIN = 3.3V
6
C–
VIN
C+ 5
VOUT
VOUT = 1.5V ±4%
1µF
LTC3250-1.5
OFF ON
3
SHDN
4.7µF
GND
EFFICIENCY (%)
70
4
60
50
40
30
2
20
10
3250 TA02a
0
0.1
10
IOUT (mA)
1
1000
100
3250 TA02b
Efficiency vs Output Current
Li-Ion or 3-Cell NiMH to 1.5V Output with Shutdown
100
1µF
90
TA = 25°C
VIN = 3.6V
80
1-CELL Li-Ion OR
3-CELL NiMH
1µF
OFF ON
6
C+ 5
VOUT
C–
VIN
LTC3250-1.5
3
SHDN
GND
70
VOUT = 1.5V ±4%
4.7µF
EFFICIENCY (%)
4
1
VIN = 4V
60
VIN = 5V
50
40
30
2
20
3250 TA03a
10
0
0.1
10
IOUT (mA)
1
1000
100
3250 TA03b
Efficiency vs Input Voltage
(IOUT = 100mA)
3-Cell NiMH to 1.2V Output with Shutdown
100
1µF
90
TA = 25°C
80
VIN = 2.7V TO 5V
3-CELL NiMH
1µF
OFF ON
C–
VIN
6
C+ 5
VOUT
LTC3250-1.2
3
SHDN
GND
70
VOUT = 1.2V ±4%
4.7µF
EFFICIENCY (%)
4
1
60
LTC3250
50
40
LDO
30
2
20
3250 TA05a
10
0
2.7
3.2
3.7
4.2
VIN (V)
4.7
5.2
3250 TA05b
3250fa
10
LTC3250-1.5/LTC3250-1.2
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62
MAX
2.90 BSC
(NOTE 4)
0.95
REF
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
0.09 – 0.20
(NOTE 3)
1.90 BSC
S6 TSOT-23 0302
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
3250fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LTC3250-1.5/LTC3250-1.2
U
TYPICAL APPLICATIO
Multiple High Efficiency Outputs from Single Li-Ion Battery
5
Li-Ion
5V
100mA
1
VIN
VOUT
LTC3200-5
3
6
SHDN
C+
1µF
2
7
2
10µF
8
60k 1
5
GND
VIN
4
C–
OUT
1µF
1µF
6
3.3V
500mA
22µF
3
MODE
SW1
LTC3440
4
SHDN
SW2
RT
FB
GND
VC
10µH
340k
9
200k
10
300pF
6
VIN
OUT
LTC1911-1.8
7
8
SHDN
C1+
120k
1
10µF
1µF
2
C2+
C1–
3
C2–
GND
VIN
OUT
1
3
OFF ON
SHDN
C+
5
2
GND
C–
1µF
4
5
1.5V
250mA
6
LTC3250-1.5
1µF
1.8V
250mA
10µF
4.7µF
1µF
4
3250-1.5 TA04
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1514
50mA, 650kHz, Step Up/Down Charge Pump
with Low Battery Comparator
VIN: 2.7V to 10V, VOUT: 3V/5V,
Regulated Output, IQ: 60µA, ISD: 10µA, S8 Package
LTC1515
50mA, 650kHz, Step Up/Down Charge Pump
with Power On Reset
VIN: 2.7V to 10V, VOUT: 3.3V or 5V,
Regulated Output, IQ: 60µA, ISD: <1µA, S8 Package
LT1776
500mA (IOUT), 200kHz, High Efficiency Step-Down
DC/DC Converter
90% Efficiency, VIN: 7.4V to 40V, VOUT(MIN): 1.24V,
IQ: 3.2mA, ISD: 30µA, N8,S8 Packages
LTC1911-1.5/LTC1911-1.8 250mA,1.5MHz, High Efficiency Step-Down
Charge Pump
75% Efficiency, VIN: 2.7V to 5.5V, VOUT: 1.5V/1.8V,
Regulated Output, IQ: 180µA, ISD: 10µA, MS8 Package
LTC3251
500mA, Spread Spectrum, High Efficiency
Step-Down Charge Pump
Up to 90% Efficiency, VIN: 2.7V to 5.5V, VOUT: 0.9V to 1.6V,
Regulated Output, IQ: 9µA, ISD: <1µA, MS Package
LTC3252
Dual 250mA (IOUT), Spread Spectrum, Inductorless (CS),
Step-Down DC/DC Converter
Up to 90% Efficiency, VIN: 2.7V to 5.5V, VOUT: 0.9V to 1.6V,
IQ: 60µA, ISD: <1µA, DFN Package
LTC3405/LTC3405A
300mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.7V to 6V, VOUT(MIN): 0.8V,
IQ: 20µA, ISD: <1µA, ThinSOT Package
LTC3406/LTC3406B
600mA (IOUT), 1.5MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.5 to 5.5V, VOUT(MIN): 0.6V,
IQ: 20µA, ISD: <1µA, ThinSOT Package
LTC3411
1.25A (IOUT), 4MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN): 0.8V,
IQ: 60µA, ISD: <1µA, MS Package
LTC3412
2.5A (IOUT), 4MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN): 0.8V,
IQ: 60µA, ISD: <1µA, TSSOP16E Package
LTC3440
600mA (IOUT), 2MHz, Synchronous Buck-Boost
DC/DC Converter
95% Efficiency, VIN: 2.5V to 5.5V, VOUT: 2.5V to 5.5V,
IQ: 25µA, ISD: <1µA, MS Package
LTC3441
1.2A (IOUT), 1MHz, Synchronous Buck-Boost
DC/DC Converter
95% Efficiency, VIN: 2.4V to 5.5V, VOUT: 2.4V to 5.25V,
IQ: 25µA, ISD: <1µA, DFN Package
3250fa
12
Linear Technology Corporation
LT/TP 1203 1K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507 ● www.linear.com
 LINEAR TECHNOLOGY CORPORATION 2001