LTC3250-1.5/LTC3250-1.2
1
3250fa
DESCRIPTIO
U
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
■
Handheld Computers
■
Cellular Phones
■
Digital Cameras
■
Handheld Medical Instruments
■
Low Power DSP Supplies
■
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 V
IN
■
Low Operating Current: I
Q
= 35µA
■
Low Shutdown Current: I
SD
< 1µA
■
Oscillator Frequency = 1.5MHz
■
Soft-Start Limits Inrush Current at Turn-On
■
Short-Circuit and Overtemperature Protected
■
Low Profile (1mm) SOT-23 Package
High Efficiency, Low Noise,
Inductorless Step-Down
DC/DC Converter
3250 TA1a
LTC3250-1.5
V
IN
V
IN
3.2V TO 4.2V
SHDN
C
+
C
–
V
OUT
GND
ON
OFF
1µF
4.7µF
V
OUT
= 1.5V ± 4%
100mA
Li-Ion 1µF
Efficiency vs Input Voltage
(IOUT = 100mA)
The LTC
®
3250-1.5/LTC3250-1.2 are charge pump step-
down 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 typi-
cal efficiency two times higher than that of a linear regu-
lator. 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 (f
OSC
= 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 appli-
cations. The parts are short-circuit and overtemperature
protected, and are available in a low profile (1mm) 6-pin
ThinSOT
TM
package.
V
IN
(V)
3.0 3.5 4.0 4.5 5.0 5.5
EFFICIENCY (%)
3250 TA01b
100
90
80
70
60
50
40
30
20
10
0
LDO
LTC3250-1.5
Li-Ion to 1.5V Output with Shutdown
, 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
LTC3250-1.5/LTC3250-1.2
2
3250fa
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
LTC3250-1.5 Operating Voltage Range ●3.1 5.5 V
LTC3250-1.2 Operating Voltage Range ●2.7 5.5 V
V
OUT
LTC3250-1.5 Output Voltage Range I
OUT
≤ 50mA 3.1V ≤ V
IN
≤ 5.5V ●1.44 1.5 1.56 V
I
OUT
≤ 100mA 3.2V ≤ V
IN
≤ 5.5V ●1.44 1.5 1.56 V
I
OUT
≤ 250mA 3.5V ≤ V
IN
≤ 5V 1.44 1.5 1.56 V
LTC3250-1.2 Output Voltage Range I
OUT
≤ 150mA 2.7V < V
IN
< 5.5V ●1.15 1.2 1.25 V
I
OUT
≤ 250mA 2.9V ≤ V
IN
≤ 5V 1.15 1.2 1.25 V
I
IN
Operating Current I
OUT
= 0mA ●35 60 µA
Shutdown Current SHDN = 0V ●0.01 1 µA
V
RB
Burst Mode Operation Output Ripple 12 mV
P-P
V
RC
Continuous Mode Output Ripple 4 mV
P-P
f
OSC
Switching Frequency ●1.2 1.5 1.8 MHz
V
IH
SHDN Input Hi Voltage ●1.2 0.8 V
V
IL
SHDN Input Low Voltage ●0.8 0.4 V
I
IH
SHDN Input Current SHDN = V
IN
●–1 1 µA
I
IL
SHDN Input Current SHDN = 0V ●–1 1 µA
t
ON
Turn On Time R
LOAD
= 6Ω0.8 ms
LTC3250-1.5 Load Regulation 0 ≤ I
OUT
≤ 250mA 0.15 mV/mA
LTC3250-1.2 Load Regulation 0 ≤ I
OUT
≤ 250mA 0.12 mV/mA
Line Regulation I
OUT
= 250mA 0.2 %/V
R
OL
Open-Loop Output Impedance I
OUT
= 250mA (Note 4) 1.0 Ω
V
IN
to GND...................................................–0.3V to 6V
SHDN to GND ............................... –0.3V to (V
IN
+ 0.3V)
I
OUT
(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
ORDER PART
NUMBER
S6 PART MARKING
T
JMAX
= 150°C, θ
JA
= 230°C/W,
θ
JC
= 102°C/W
LTZE
LTAGJ
LTC3250ES6-1.5
LTC3250ES6-1.2
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
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.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
6 C
+
5 V
OUT
4 C
–
V
IN
1
TOP VIEW
S6 PACKAGE
6-LEAD PLASTIC SOT-23
GND 2
SHDN 3
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.
Note 4: Output not in regulation; R
OL
= (V
IN
/2 - V
OUT
)/I
OUT
.
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.
LTC3250-1.5/LTC3250-1.2
3
3250fa
No Load Supply Current vs
Supply Voltage
Output Voltage vs Supply Voltage
Output Voltage vs Load Current
Oscillator Frequency vs
Supply Voltage
Efficiency vs Output Current
VSHDN Threshold Voltage vs
Supply Voltage
TYPICAL PERFOR A CE CHARACTERISTICS
UW
V
IN
(V)
2.7
I
IN
(µA)
50
45
40
35
30
25
20 5.1
3250 G01
3.5
3.1 3.9 4.3 4.7 5.5
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
3.1V < V
IN
< 5.5V (LTC3250-1.5)
2.7V < V
IN
< 5.5V (LTC3250-1.2)
V
IN
(V)
FREQUENCY (MHz)
1.8
1.7
1.6
1.5
1.4
1.3
1.2
3250 G02
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
3.1V < V
IN
< 5.5V (LTC3250-1.5)
2.7V < V
IN
< 5.5V (LTC3250-1.2)
2.7 4.7
3.2 3.7 4.2 5.2
V
IN
(V)
2.7
V
SHDN
(mV)
1200
1100
1000
900
800
700
600
500
400 4.7
3250 G03
3.2 3.7 4.2 5.2
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
3.1V < V
IN
< 5.5V (LTC3250-1.5)
2.7V < V
IN
< 5.5V (LTC3250-1.2)
I
OUT
(mA)
0
V
OUT
(V)
50 100 150 200
3250 G04
250
1.60
1.58
1.56
1.54
1.52
1.50
1.48
1.46
1.44
1.42
1.40 300
V
IN
= 3.6V
T
A
= 25°C
I
OUT
(mA)
10.1
EFFICIENCY (%)
1000
3250 G05
10 100
100
90
80
70
60
50
40
30
20
10
0
V
IN
= 3.6V
V
IN
= 3.3V
V
IN
= 4V
V
IN
= 5V
T
A
= 25°C
V
IN
(V)
3.0
V
OUT
(V)
1.60
1.58
1.56
1.54
1.52
1.50
1.48
1.46
1.44
1.42
1.40 5.0
3250 G06
3.5 4.0 4.5 5.5
T
A
= 25°C
I
OUT
= 0mA
I
OUT
= 250mA
I
OUT
= 100mA
(LTC3250-1.5)
Output Voltage vs Supply Voltage
Output Voltage vs Load Current Efficiency vs Output Current
(LTC3250-1.2)
I
OUT
(mA)
0
V
OUT
(V)
50 100 150 200
3250 G12
250
1.30
1.28
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10 300
V
IN
= 3.6V
T
A
= 25°C
I
OUT
(mA)
10.1
EFFICIENCY (%)
1000
3250 G13
10 100
100
90
80
70
60
50
40
30
20
10
0
V
IN
= 3V
V
IN
= 2.7V
V
IN
= 3.5V
V
IN
= 4.5V
T
A
= 25°C
V
IN
(V)
2.7
V
OUT
(V)
1.30
1.28
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
1.10 4.7
3250 G14
3.2 3.7 4.2 5.2
I
OUT
= 0mA
I
OUT
= 250mA
I
OUT
= 100mA
T
A
= 25°C
LTC3250-1.5/LTC3250-1.2
4
3250fa
Output Voltage Soft-Start and
Shutdown (LTC3250-1.5) Output Current Transient
Response (LTC3250-1.5)
Line Transient Response
(LTC3250-1.5)
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Output Voltage Ripple
(LTC3250-1.5)
Input Voltage Ripple vs Input
Capacitor (LTC3250-1.5)
250mA
15mA
I
OUT
V
OUT
20mV/DIV
AC
V
IN
= 3.6V
3250 G08
3250 G09
4.5V
3.5V
V
IN
V
OUT
20mV/DIV
AC
I
OUT
= 200mA
V
IN
50mV/DIV
AC
V
IN
50mV/DIV
AC
I
OUT
= 250mA
R
SOURCE
= 0.2Ω
3250 G10
C
I
= 1µF
C
I
= 10µF
VOUT
20mV/DIV
AC
3250 G11
COUT = 4.7µF 1X5R16.3V
IOUT = 250mA
VIN = 3.6V
HI
LOW
SHDN
V
OUT
500mV/DIV
R
L
= 6Ω
V
IN
= 3.6V
3250 G07
LTC3250-1.5/LTC3250-1.2
5
3250fa
V
IN
(Pin 1): Input Supply Voltage. Bypass V
IN
with a ≥1µF
low ESR ceramic capacitor.
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 4): Flying Capacitor Negative Terminal
V
OUT
(Pin 5): Regulated Output Voltage. V
OUT
is discon-
nected from V
IN
during shutdown. Bypass V
OUT
with a
≥4.7µF low ESR ceramic capacitor (2.5µF min, ESR
<100mΩ).
C
+
(Pin 6): Flying Capacitor Positive Terminal.
UU
U
PI FU CTIO S
BLOCK DIAGRA
W
3250 BD
–
+
3
1
2
6
5
4
THERMAL
SHUTDOWN
(>160°C) SWITCH
CONTROL
AND
SOFT-START
1.5MHz
OSCILLATOR
CHARGE
PUMP
BURST
DETECT
CIRCUIT
GND
SHDN
V
IN
C
+
C
–
V
OUT
LTC3250-1.5/
LTC3250-1.2
V
REF
LTC3250-1.5/LTC3250-1.2
6
3250fa
The LTC3250-1.5/LTC3250-1.2 use a switched capacitor
charge pump to step down V
IN
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 V
IN
, through
the flying capacitor, to V
OUT
. Not only is current being
delivered to V
OUT
on the first phase, but the flying capaci-
tor is also being charged up. On the second phase of the
clock the flying capacitor is connected from V
OUT
to
ground, delivering the charge stored during the first phase
of the clock to V
OUT
. Using this method of switching, only
half of the output current is delivered from V
IN
, 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 V
IN
supply. Furthermore, V
OUT
is disconnected from
V
IN
. The SHDN pin is a CMOS input with a threshold
voltage of approximately 0.8V. The LTC3250-1.5/LTC3250-
1.2 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 automati-
cally 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/LTC3250-
1.2 will cycle in and out of thermal shutdown without latch-
up or damage until the short-circuit on V
OUT
is removed.
Long term overstress (I
OUT
> 350mA, and/or T
J
> 140°C)
should be avoided as it can degrade the performance of the
part.
Soft-Start
To prevent excessive current flow at V
IN
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 inter-
nally 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 LTC3250-
1.5/LTC3250-1.2’s burst current is set by the burst thresh-
old and hysteresis. This means that the V
OUT
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/LTC3250-
1.2 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
OPERATIO
U
(Refer to Simplified Block Diagram)
LTC3250-1.5/LTC3250-1.2
7
3250fa
current. For an ideal 2 to 1 step-down charge pump the
power efficiency is given by:
η≡ = =
P
P
VI
VI
V
V
OUT
IN
OUT OUT
IN OUT
OUT
IN
•
•1
2
2
The switching losses and quiescent current of the
LTC3250-1.5/LTC3250-1.2 are designed to minimize effi-
ciency loss over the entire output current range, causing
only a couple % error from the theoritical efficiency. For
example with V
IN
= 3.6V, I
OUT
= 100mA and V
OUT
regulat-
ing to 1.5V the measured efficiency is 80.6% which is in
close agreement with the theoretical 83.3% calculation.
V
OUT
Capacitor Selection
The ESR and value of capacitors used with the LTC3250-
1.5/LTC3250-1.2 determine several important parameters
such as regulator control loop stability, output ripple, and
charge pump strength.
The value of C
OUT
directly controls the amount of output
ripple for a given load current. Increasing the size of C
OUT
will reduce the output ripple.
To reduce output noise and ripple, it is suggested that a
low ESR (<0.1Ω) ceramic capacitor (4.7µF or greater) be
used for C
OUT
. Tantalum and aluminum capacitors are not
recommended because of their high ESR.
Both ESR and value of the C
OUT
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 condi-
tions (see “Ceramic Capacitor Selection Guidelines” sec-
tion).
Likewise excessive ESR on the output capacitor will tend
to degrade the loop stability of the LTC3250-1.5/LTC3250-
1.2. The closed-loop output resistance is designed to be
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 imped-
ance 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 excep-
tional 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
OPERATIO
U
(Refer to Simplified Block Diagram)
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.
V
IN
Capacitor Selection
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 I
OUT
/2 to 0mA.
Lower ESR will reduce the voltage steps caused by chang-
ing 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 C
IN
(see “Ceramic
Capacitor Selection Guidelines” section). Aluminum and
tantalum capacitors are not recommended because of
their high ESR.
Figure 1. 10nH Inductor Used for
Additional Output Noise Reduction
3250 F01
LTC3250-1.5/
LTC3250-1.2
V
OUT
GND
4.7µF 0.22µF
V
OUT
10nH
(TRACE INDUCTANCE)
LTC3250-1.5/LTC3250-1.2
8
3250fa
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 capaci-
tance 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 capaci-
tance for a given case size rather than discussing the
specified capacitance value. For example, over rated volt-
age 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 con-
ditions. Figure 2 shows the recommended layout configu-
ration.
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.
OPERATIO
U
(Refer to Simplified Block Diagram)
GND
V
OUT
V
IN
SHDN
LTC3250-1.5/LTC3250-1.2
1µF
4.7µF
1µF
3250 F02
VIA TO GROUND PLANE
LTC3250-1.5/LTC3250-1.2
9
3250fa
OPERATIO
U
(Refer to Simplified Block Diagram)
Figure 3. Maximum Power Dissipation vs Ambient Temperature
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 shut-
down circuitry will automatically deactivate the output. To
reduce the maximum junction temperature, a good ther-
mal connection to the PC board is recommended. Con-
necting 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
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:
PVVI
DIN OUT OUT
=
2–
This derating curve assumes a maximum thermal resis-
tance, θ
JA
, 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 (2000mm
2
)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.
AMBIENT TEMPERATURE (°C)
–50
POWER DISSIPATION (W)
–25 02550
3250 • F03
75 100
θ
JA
= 175°C/W
T
J
= 140°C
1.2
1.0
0.8
0.6
0.4
0.2
0
LTC3250-1.5/LTC3250-1.2
10
3250fa
3250 TA05a
LTC3250-1.2
V
IN
3-CELL NiMH
V
IN
= 2.7V TO 5V
SHDN
C
+
C
–
V
OUT
4
32
15
6
GND
ON
OFF
1µF
4.7µF
1µF
V
OUT
= 1.2V ±4%
3250 TA02a
LTC3250-1.5
V
IN
V
IN
= 3.3V
SHDN
C
+
C
–
V
OUT
4
32
15
6
GND
ON
OFF
1µF
4.7µF
V
OUT
= 1.5V ±4%
1µF
I
OUT
(mA)
10.1
EFFICIENCY (%)
1000
3250 TA02b
10 100
100
90
80
70
60
50
40
30
20
10
0
V
IN
= 3.3V
T
A
= 25°C
3250 TA03a
LTC3250-1.5
V
IN
1-CELL Li-Ion OR
3-CELL NiMH
SHDN
C
+
C
–
V
OUT
4
32
15
6
GND
ON
OFF
1µF
1µF
4.7µF
V
OUT
= 1.5V ±4%
I
OUT
(mA)
10.1
EFFICIENCY (%)
1000
3250 TA03b
10 100
100
90
80
70
60
50
40
30
20
10
0
V
IN
= 3.6V
V
IN
= 4V
V
IN
= 5V
T
A
= 25°C
TYPICAL APPLICATIO S
U
Efficiency vs Output Current
Efficiency vs Output Current
Fixed 3.3V Input to 1.5V Output with Shutdown
Li-Ion or 3-Cell NiMH to 1.5V Output with Shutdown
Efficiency vs Input Voltage
(IOUT = 100mA)
3-Cell NiMH to 1.2V Output with Shutdown
V
IN
(V)
3.22.7
EFFICIENCY (%)
5.24.7
3250 TA05b
3.7 4.2
100
90
80
70
60
50
40
30
20
10
0
LTC3250
LDO
T
A
= 25°C
LTC3250-1.5/LTC3250-1.2
11
3250fa
PACKAGE DESCRIPTIO
U
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
1.50 – 1.75
(NOTE 4)
2.80 BSC
0.30 – 0.45
6 PLCS (NOTE 3)
DATUM ‘A’
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302
2.90 BSC
(NOTE 4)
0.95 BSC
1.90 BSC
0.80 – 0.90
1.00 MAX 0.01 – 0.10
0.20 BSC
0.30 – 0.50 REF
PIN ONE ID
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
3.85 MAX
0.62
MAX 0.95
REF
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
1.4 MIN
2.62 REF
1.22 REF
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTC3250-1.5/LTC3250-1.2
12
3250fa
PART NUMBER DESCRIPTION COMMENTS
LTC1514 50mA, 650kHz, Step Up/Down Charge Pump V
IN
: 2.7V to 10V, V
OUT
: 3V/5V,
with Low Battery Comparator Regulated Output, I
Q
: 60µA, I
SD
: 10µA, S8 Package
LTC1515 50mA, 650kHz, Step Up/Down Charge Pump V
IN
: 2.7V to 10V, V
OUT
: 3.3V or 5V,
with Power On Reset Regulated Output, I
Q
: 60µA, I
SD
: <1µA, S8 Package
LT1776 500mA (I
OUT
), 200kHz, High Efficiency Step-Down 90% Efficiency, V
IN
: 7.4V to 40V, V
OUT(MIN)
: 1.24V,
DC/DC Converter I
Q
: 3.2mA, I
SD
: 30µA, N8,S8 Packages
LTC1911-1.5/LTC1911-1.8 250mA,1.5MHz, High Efficiency Step-Down 75% Efficiency, V
IN
: 2.7V to 5.5V, V
OUT
: 1.5V/1.8V,
Charge Pump Regulated Output, I
Q
: 180µA, I
SD
: 10µA, MS8 Package
LTC3251 500mA, Spread Spectrum, High Efficiency Up to 90% Efficiency, V
IN
: 2.7V to 5.5V, V
OUT
: 0.9V to 1.6V,
Step-Down Charge Pump Regulated Output, I
Q
: 9µA, I
SD
: <1µA, MS Package
LTC3252 Dual 250mA (I
OUT
), Spread Spectrum, Inductorless (CS), Up to 90% Efficiency, V
IN
: 2.7V to 5.5V, V
OUT
: 0.9V to 1.6V,
Step-Down DC/DC Converter I
Q
: 60µA, I
SD
: <1µA, DFN Package
LTC3405/LTC3405A 300mA (I
OUT
), 1.5MHz, Synchronous Step-Down 95% Efficiency, V
IN
: 2.7V to 6V, V
OUT(MIN)
: 0.8V,
DC/DC Converter I
Q
: 20µA, I
SD
: <1µA, ThinSOT Package
LTC3406/LTC3406B 600mA (I
OUT
), 1.5MHz, Synchronous Step-Down 95% Efficiency, V
IN
: 2.5 to 5.5V, V
OUT(MIN)
: 0.6V,
DC/DC Converter I
Q
: 20µA, I
SD
: <1µA, ThinSOT Package
LTC3411 1.25A (I
OUT
), 4MHz, Synchronous Step-Down 95% Efficiency, V
IN
: 2.5V to 5.5V, V
OUT(MIN)
: 0.8V,
DC/DC Converter I
Q
: 60µA, I
SD
: <1µA, MS Package
LTC3412 2.5A (I
OUT
), 4MHz, Synchronous Step-Down 95% Efficiency, V
IN
: 2.5V to 5.5V, V
OUT(MIN)
: 0.8V,
DC/DC Converter I
Q
: 60µA, I
SD
: <1µA, TSSOP16E Package
LTC3440 600mA (I
OUT
), 2MHz, Synchronous Buck-Boost 95% Efficiency, V
IN
: 2.5V to 5.5V, V
OUT
: 2.5V to 5.5V,
DC/DC Converter I
Q
: 25µA, I
SD
: <1µA, MS Package
LTC3441 1.2A (I
OUT
), 1MHz, Synchronous Buck-Boost 95% Efficiency, V
IN
: 2.4V to 5.5V, V
OUT
: 2.4V to 5.25V,
DC/DC Converter I
Q
: 25µA, I
SD
: <1µA, DFN Package
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
LINE AR TE CHNO LOGY CO R P O R ATION 2001
LT/TP 1203 1K REV A • PRINTED IN USA
RELATED PARTS
U
TYPICAL APPLICATIO
3250-1.5 TA04
V
IN
MODE
SHDN
RT
GND
OUT
SW1
SW2
FB
V
C
LTC3440
7
2
8
1
5
6
3
4
9
10
10µH
V
IN
SHDN
GND
V
OUT
C
+
C
–
LTC3200-5
340k
200k
V
IN
SHDN
C2
+
C2
–
OUT
C1
+
C1
–
GND
LTC1911-1.8
V
IN
OUT
C
+
C
–
SHDN
GND
LTC3250-1.5
10µF
1µF
1µF
1µF
1µF
1µF
22µF
10µF
4.7µF
1µF
10µF
1µF
ON
OFF
Li-Ion
5V
100mA
3.3V
500mA
1.8V
250mA
1.5V
250mA
300pF 120k
60k
5
3
2
1
6
4
1
8
2
3
6
7
5
4
5
6
4
1
3
2
Multiple High Efficiency Outputs from Single Li-Ion Battery
