LTC3250-1.5/LTC3250-1.2
High Efficiency, Low Noise,
Inductorless Step-Down
DC/DC Converter
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
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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 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
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.
, 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
APPLICATIO S
Handheld Computers
s
Cellular Phones
s
Digital Cameras
s
Handheld Medical Instruments
s
Low Power DSP Supplies
s
TYPICAL APPLICATIO
1µF
Efficiency vs Input Voltage
(I
OUT
= 100mA)
100
90
80
70
EFFICIENCY (%)
Li-Ion to 1.5V Output with Shutdown
60
50
40
30
20
10
LDO
V
IN
3.2V TO 4.2V
Li-Ion
1µF
C
–
V
IN
C
+
V
OUT
4.7µF
V
OUT
= 1.5V
±
4%
100mA
LTC3250-1.5
OFF ON
SHDN
GND
3250 TA1a
0
3.0
U
LTC3250-1.5
3.5
4.0
4.5
V
IN
(V)
5.0
5.5
3250 TA01b
U
U
3250fa
1
LTC3250-1.5/LTC3250-1.2
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
V
IN
1
GND 2
SHDN 3
6 C
+
5 V
OUT
4 C
–
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
LTC3250ES6-1.5
LTC3250ES6-1.2
S6 PART MARKING
LTZE
LTAGJ
S6 PACKAGE
6-LEAD PLASTIC SOT-23
T
JMAX
= 150°C,
θ
JA
= 230°C/W,
θ
JC
= 102°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, C
FLY
= 1µF, C
IN
= 1µF, C
OUT
= 4.7µF unless otherwise noted.
SYMBOL
V
IN
V
OUT
PARAMETER
LTC3250-1.5 Operating Voltage Range
LTC3250-1.2 Operating Voltage Range
LTC3250-1.5 Output Voltage Range
I
OUT
≤
50mA 3.1V
≤
V
IN
≤
5.5V
I
OUT
≤
100mA 3.2V
≤
V
IN
≤
5.5V
I
OUT
≤
250mA 3.5V
≤
V
IN
≤
5V
I
OUT
≤
150mA 2.7V < V
IN
< 5.5V
I
OUT
≤
250mA 2.9V
≤
V
IN
≤
5V
I
OUT
= 0mA
SHDN = 0V
CONDITIONS
q
q
q
q
q
q
q
ELECTRICAL CHARACTERISTICS
MIN
3.1
2.7
1.44
1.44
1.44
1.15
1.15
TYP
MAX
5.5
5.5
UNITS
V
V
V
1.5
1.5
1.5
1.2
1.2
35
0.01
12
4
1.56
1.56
1.56
1.25
1.25
60
1
LTC3250-1.2 Output Voltage Range
I
IN
V
RB
V
RC
f
OSC
V
IH
V
IL
I
IH
I
IL
t
ON
Operating Current
Shutdown Current
Burst Mode Operation Output Ripple
Continuous Mode Output Ripple
Switching Frequency
SHDN Input Hi Voltage
SHDN Input Low Voltage
SHDN Input Current
SHDN Input Current
Turn On Time
LTC3250-1.5 Load Regulation
LTC3250-1.2 Load Regulation
Line Regulation
R
OL
Open-Loop Output Impedance
mV
P-P
mV
P-P
1.8
0.4
1
1
MHz
V
V
µA
µA
ms
mV/mA
mV/mA
%/V
Ω
q
q
q
1.2
1.2
–1
–1
1.5
0.8
0.8
SHDN = V
IN
SHDN = 0V
R
LOAD
= 6Ω
0
≤
I
OUT
≤
250mA
0
≤
I
OUT
≤
250mA
I
OUT
= 250mA
I
OUT
= 250mA (Note 4)
q
q
0.8
0.15
0.12
0.2
1.0
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.
3250fa
2
U
V
V
V
W
U
U
W W
W
V
µA
µA
LTC3250-1.5/LTC3250-1.2
TYPICAL PERFOR A CE CHARACTERISTICS
No Load Supply Current vs
Supply Voltage
50
45
T
A
= 85°C
40
I
IN
(µA)
FREQUENCY (MHz)
3.1V < V
IN
< 5.5V (LTC3250-1.5)
2.7V < V
IN
< 5.5V (LTC3250-1.2)
T
A
= 25°C
35
T
A
= –40°C
30
25
20
2.7
V
SHDN
(mV)
3.1
3.5
3.9 4.3
V
IN
(V)
4.7
(LTC3250-1.5)
Output Voltage vs Load Current
1.60
1.58
1.56
EFFICIENCY (%)
V
IN
= 3.6V
T
A
= 25°C
1.54
V
OUT
(V)
1.50
1.48
1.46
1.44
1.42
1.40
0
50
100
150
200
I
OUT
(mA)
250
300
50
40
30
20
10
0
0.1
1
10
I
OUT
(mA)
V
IN
= 5V
V
OUT
(V)
1.52
(LTC3250-1.2)
Output Voltage vs Load Current
1.30
1.28
1.26
V
IN
= 3.6V
T
A
= 25°C
100
90
80
70
V
IN
= 3V
EFFICIENCY (%)
1.24
V
OUT
(V)
V
OUT
(V)
1.22
1.20
1.18
1.16
1.14
1.12
1.10
0
50
100
150
200
I
OUT
(mA)
250
300
U W
5.1
Oscillator Frequency vs
Supply Voltage
1.8
1.7
1.6
T
A
= 85°C
1.5
T
A
= –40°C
1.4
1.3
1.2
2.7
T
A
= 25°C
3.1V < V
IN
< 5.5V (LTC3250-1.5)
2.7V < V
IN
< 5.5V (LTC3250-1.2)
1200
1100
1000
900
800
700
600
500
V
SHDN
Threshold Voltage vs
Supply Voltage
3.1V < V
IN
< 5.5V (LTC3250-1.5)
2.7V < V
IN
< 5.5V (LTC3250-1.2)
T
A
= –40°C
T
A
= 25°C
T
A
= 85°C
5.5
3.2
3.7
4.2
V
IN
(V)
4.7
5.2
3250 G02
400
2.7
3.2
3.7
4.2
V
IN
(V)
4.7
5.2
3250 G03
3250 G01
Efficiency vs Output Current
100
90
80
70
60
T
A
= 25°C
1.60
Output Voltage vs Supply Voltage
1.58
1.56
1.54
1.52
1.50
1.48
1.46
1.44
1.42
I
OUT
= 0mA
I
OUT
= 100mA
I
OUT
= 250mA
T
A
= 25°C
V
IN
= 3.3V
V
IN
= 3.6V
V
IN
= 4V
100
1000
3250 G05
1.40
3.0
3.5
4.5
4.0
V
IN
(V)
5.0
5.5
3250 G06
3250 G04
Efficiency vs Output Current
T
A
= 25°C
1.30
Output Voltage vs Supply Voltage
1.28
1.26
1.24
1.22
1.20
1.18
1.16
1.14
1.12
I
OUT
= 250mA
T
A
= 25°C
V
IN
= 2.7V
60
50
40
30
20
10
0
0.1
1
10
I
OUT
(mA)
V
IN
= 3.5V
V
IN
= 4.5V
I
OUT
= 0mA
I
OUT
= 100mA
100
1000
3250 G13
1.10
2.7
3.2
3.7
4.2
V
IN
(V)
4.7
5.2
3250 G14
3250 G12
3250fa
3
LTC3250-1.5/LTC3250-1.2
TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage Soft-Start and
Shutdown (LTC3250-1.5)
HI
SHDN
LOW
I
OUT
250mA
15mA
V
OUT
500mV/DIV
R
L
= 6Ω
V
IN
= 3.6V
Line Transient Response
(LTC3250-1.5)
4.5V
3.5V
V
IN
50mV/DIV
AC
V
IN
V
OUT
20mV/DIV
AC
I
OUT
= 200mA
4
U W
Output Current Transient
Response (LTC3250-1.5)
V
OUT
20mV/DIV
AC
3250 G07
V
IN
= 3.6V
3250 G08
Input Voltage Ripple vs Input
Capacitor (LTC3250-1.5)
C
I
= 1µF
V
IN
50mV/DIV
AC
C
I
= 10µF
3250 G09
I
OUT
= 250mA
R
SOURCE
= 0.2Ω
3250 G10
Output Voltage Ripple
(LTC3250-1.5)
V
OUT
20mV/DIV
AC
C
OUT
= 4.7µF 1X5R16.3V
I
OUT
= 250mA
V
IN
= 3.6V
3250 G11
3250fa
LTC3250-1.5/LTC3250-1.2
PI FU CTIO S
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.
BLOCK DIAGRA
V
REF
+
BURST
DETECT
CIRCUIT
–
W
U
U
U
LTC3250-1.5/
LTC3250-1.2
THERMAL
SHUTDOWN
(>160°C)
SHDN 3
SWITCH
CONTROL
AND
SOFT-START
1.5MHz
OSCILLATOR
V
IN
1
CHARGE
PUMP
6 C
+
5 V
OUT
4 C
–
2
GND
3250 BD
3250fa
5
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