FEATURES
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LT1930/LT1930A
1A, 1.2MHz/2.2MHz,
Step-Up DC/DC Converters
in ThinSOT
DESCRIPTIO
The LT
®
1930 and LT1930A are the industry’s highest
power SOT-23 switching regulators. Both include an
internal 1A, 36V switch allowing high current outputs to be
generated in a small footprint. The LT1930 switches at
1.2MHz, allowing the use of tiny, low cost and low height
capacitors and inductors. The faster LT1930A switches at
2.2MHz, enabling further reductions in inductor size.
Complete regulator solutions approaching one tenth of a
square inch in area are achievable with these devices.
Multiple output power supplies can now use a separate
regulator for each output voltage, replacing cumbersome
quasi-regulated approaches using a single regulator and
custom transformers.
A constant frequency internally compensated current mode
PWM architecture results in low, predictable output noise
that is easy to filter. Low ESR ceramic capacitors can be
used at the output, further reducing noise to the millivolt
level. The high voltage switch on the LT1930/LT1930A is
rated at 36V, making the device ideal for boost converters
up to 34V as well as for single-ended primary inductance
converter (SEPIC) and flyback designs. The LT1930 can
generate 5V at up to 480mA from a 3.3V supply or 5V at
300mA from four alkaline cells in a SEPIC design.
The LT1930/LT1930A are available in the 5-lead ThinSOT
package.
1.2MHz Switching Frequency (LT1930)
2.2MHz Switching Frequency (LT1930A)
Low V
CESAT
Switch: 400mV at 1A
High Output Voltage: Up to 34V
5V at 480mA from 3.3V Input (LT1930)
12V at 250mA from 5V Input (LT1930A)
Wide Input Range: 2.6V to 16V
Uses Small Surface Mount Components
Low Shutdown Current: < 1µA
Low Profile (1mm) ThinSOT
TM
Package
Pin-for-Pin Compatible with the LT1613
APPLICATIO S
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TFT-LCD Bias Supply
Digital Cameras
Cordless Phones
Battery Backup
Medical Diagnostic Equipment
Local 5V or 12V Supply
External Modems
PC Cards
xDSL Power Supply
, LTC and LT are registered trademarks of Linear Technology Corporation
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
V
IN
5V
C1
2.2µF
SHDN
4
L1
10µH
5
V
IN
LT1930
SHDN
GND
2
FB
3
1
SW
D1
90
V
OUT
12V
300mA
85
V
IN
= 3.3V
80
R1
113k
EFFICIENCY (%)
C3*
10pF
C2
4.7µF
75
70
65
60
R2
13.3k
C1: TAIYO-YUDEN X5R LMK212BJ225MG
C2: TAIYO-YUDEN X5R EMK316BJ475ML
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CR43-100
*OPTIONAL
1930/A F01
55
50
0
200
100
300
LOAD CURRENT (mA)
400
1930 TA01
Figure 1. 5V to 12V, 300mA Step-Up DC/DC Converter
U
U
U
Efficiency
V
IN
= 5V
1
LT1930/LT1930A
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SW 1
GND 2
FB 3
4 SHDN
5 V
IN
V
IN
Voltage .............................................................. 16V
SW Voltage ................................................– 0.4V to 36V
FB Voltage .............................................................. 2.5V
Current Into FB Pin ..............................................
±1mA
SHDN Voltage ......................................................... 10V
Maximum Junction Temperature ......................... 125°C
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LT1930ES5
LT1930AES5
S5 PART MARKING
LTKS
LTSQ
S5 PACKAGE
5-LEAD PLASTIC SOT-23
T
JMAX
= 125°C,
θ
JA
= 256°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 3V, V
SHDN
= V
IN
unless otherwise noted. (Note 2)
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
q
CONDITIONS
MIN
LT1930
TYP
2.45
MAX
2.6
16
1.270
1.280
360
6
1
0.05
1.4
1.6
2
600
1
MIN
LT1930A
TYP
2.45
MAX
2.6
16
1.270
1.280
720
8
1
0.05
2.6
2.9
2.5
600
1
0.5
UNITS
V
V
V
V
nA
mA
µA
%/V
MHz
MHz
%
A
mV
µA
V
V
µA
µA
1.240
1.230
1.255
120
4.2
0.01
0.01
1.240
1.230
1.255
240
5.5
0.01
0.01
FB Pin Bias Current
Quiescent Current
Quiescent Current in Shutdown
Reference Line Regulation
Switching Frequency
V
FB
= 1.255V
V
SHDN
= 2.4V, Not Switching
V
SHDN
= 0V, V
IN
= 3V
2.6V
≤
V
IN
≤
16V
q
q
1
0.85
84
1
1.2
90
1.2
400
0.01
1.8
1.6
75
1
2.2
90
1.2
400
0.01
Maximum Duty Cycle
Switch Current Limit
Switch V
CESAT
Switch Leakage Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
V
SHDN
= 3V
V
SHDN
= 0V
(Note 3)
I
SW
= 1A
V
SW
= 5V
q
2.4
0.5
16
0
32
0.1
2.4
35
0
70
0.1
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LT1930E/LT1930AE are 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:
Current limit guaranteed by design and/or correlation to static test.
2
U
W
U
U
W W
W
LT1930/LT1930A
TYPICAL PERFOR A CE CHARACTERISTICS
Quiescent Current
7.0
NOT SWITCHING
6.5
QUIESCENT CURRENT (mA)
1.27
SHDN PIN CURRENT (µA)
1.28
6.0
5.5
5.0
4.5
4.0
3.5
3.0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1.23
1.22
–50
LT1930A
FB VOLTAGE (V)
LT1930
Current Limit
1.6
1.4
0.45
0.40
0.35
0.30
CURRENT LI MIT (A)
1.2
V
CESAT
(V)
1.0
0.8
0.6
0.4
0.2
0
10
20
30
40 50 60 70
DUTY CYCLE (%)
80
90
FREQUENCY (MHz)
PI FU CTIO S
SW (Pin 1):
Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to reduce EMI.
GND (Pin 2):
Ground. Tie directly to local ground plane.
FB (Pin 3):
Feedback Pin. Reference voltage is 1.255V.
Connect resistive divider tap here. Minimize trace area at
FB. Set V
OUT
according to V
OUT
= 1.255V(1 + R1/R2).
SHDN (Pin 4):
Shutdown Pin. Tie to 2.4V or more to enable
device. Ground to shut down.
V
IN
(Pin 5):
Input Supply Pin. Must be locally bypassed.
U W
1930/A G01
1930/A G04
FB Pin Voltage
90
80
70
60
50
40
30
20
10
0
–25
0
25
50
TEMPERATURE (°C)
75
100
SHDN Pin Current
LT1930A
1.26
1.25
1.24
LT1930
–10
0
1
4
3
SHDN PIN VOLTAGE (V)
2
5
6
1930/A G03
1930/A G02
Switch Saturation Voltage
2.5
2.3
2.1
1.9
1.7
1.5
1.3
1.1
0.9
0.7
0
0.2
0.4
0.6
0.8
SWITCH CURRENT (A)
1.0
1.2
Oscillator Frequency
LT1930A
0.25
0.20
0.15
0.10
0.05
0
LT1930
0.5
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
1930/A G05
1930/A G06
U
U
U
3
LT1930/LT1930A
BLOCK DIAGRA
V
IN
5
A1
–
V
OUT
R1 (EXTERNAL)
FB
R2 (EXTERNAL)
R
C
C
C
Σ
–
RAMP
GENERATOR
SHUTDOWN
4 SHDN
3
FB
1.2MHz
OSCILLATOR*
*2.2MHz FOR LT1930A
Figure 2. Block Diagram
OPERATIO
The LT1930 uses a constant frequency, current-mode
control scheme to provide excellent line and load regula-
tion. Operation can be best understood by referring to the
block diagram in Figure 2. At the start of each oscillator
cycle, the SR latch is set, which turns on the power switch
Q1. A voltage proportional to the switch current is added
to a stabilizing ramp and the resulting sum is fed into the
positive terminal of the PWM comparator A2. When this
voltage exceeds the level at the negative input of A2, the SR
latch is reset turning off the power switch. The level at the
negative input of A2 is set by the error amplifier A1, and is
simply an amplified version of the difference between the
feedback voltage and the reference voltage of 1.255V. In
this manner, the error amplifier sets the correct peak
current level to keep the output in regulation. If the error
amplifier’s output increases, more current is delivered to
the output; if it decreases, less current is delivered. The
LT1930 has a current limit circuit not shown in Figure 2.
The switch current is constantly monitored and not al-
lowed to exceed the maximum switch current (typically
1.2A). If the switch current reaches this value, the SR latch
is reset regardless of the state of comparator A2. This
current limit helps protect the power switch as well as the
external components connected to the LT1930.
The block diagram for the LT1930A (not shown) is iden-
tical except that the oscillator frequency is 2.2MHz.
4
+
–
W
1.255V
REFERENCE
+
1 SW
COMPARATOR
DRIVER
A2
R
S
Q
Q1
+
0.01Ω
2 GND
1930/A BD
U
LT1930/LT1930A
APPLICATIONS INFORMATION
LT1930 AND LT1930A DIFFERENCES
Switching Frequency
The key difference between the LT1930 and LT1930A is
the faster switching frequency of the LT1930A. At 2.2MHz,
the LT1930A switches at nearly twice the rate of the
LT1930. Care must be taken in deciding which part to use.
The high switching frequency of the LT1930A allows
smaller cheaper inductors and capacitors to be used in a
given application, but with a slight decrease in efficiency
and maximum output current when compared to the
LT1930. Generally, if efficiency and maximum output
current are critical, the LT1930 should be used. If applica-
tion size and cost are more important, the LT1930A will be
the better choice. In many applications, tiny inexpensive
chip inductors can be used with the LT1930A, reducing
solution cost.
Duty Cycle
The maximum duty cycle (DC) of the LT1930A is 75%
compared to 84% for the LT1930. The duty cycle for a
given application using the boost topology is given by:
ELT5KT4R7M
ELT5KT6R8M
4.7
6.8
240
360
5.2
×
5.2
×
1.1
DC
=
| V
OUT
| – | V
IN
|
| V
OUT
|
For a 5V to 12V application, the DC is 58.3% indicating that
the LT1930A could be used. A 5V to 24V application has
a DC of 79.2% making the LT1930 the right choice. The
LT1930A can still be used in applications where the DC, as
calculated above, is above 75%. However, the part must
be operated in the discontinuous conduction mode so that
the actual duty cycle is reduced.
INDUCTOR SELECTION
Several inductors that work well with the LT1930 are listed
in Table 1 and those for the LT1930A are listed in Table 2.
These tables are not complete, and there are many other
manufacturers and devices that can be used. Consult each
manufacturer for more detailed information and for their
entire selection of related parts, as many different sizes and
shapes are available. Ferrite core inductors should be used
to obtain the best efficiency, as core losses at 1.2MHz are
much lower for ferrite cores than for cheaper powdered-
U
W
U
U
iron types. Choose an inductor that can handle at least 1A
without saturating, and ensure that the inductor has a low
DCR (copper-wire resistance) to minimize I
2
R power losses.
A 4.7µH or 10µH inductor will be the best choice for most
LT1930 designs. For LT1930A designs, a 2.2µH to 4.7µH
inductor will usually suffice. Note that in some applica-
tions, the current handling requirements of the inductor
can be lower, such as in the SEPIC topology where each
inductor only carries one-half of the total switch current.
Table 1. Recommended Inductors – LT1930
L
(µH)
4.1
10
4.7
10
4.7
10
MAX
DCR
mΩ
57
124
109
182
60
75
SIZE
L
×
W
×
H
(mm)
4.5
×
4.7
×
2.0
3.2
×
2.5
×
2.0
4.5
×
6.6
×
2.9
PART
CDRH5D18-4R1
CDRH5D18-100
CR43-4R7
CR43-100
DS1608-472
DS1608-103
VENDOR
Sumida
(847) 956-0666
www.sumida.com
Coilcraft
(847) 639-6400
www.coilcraft.com
Panasonic
(408) 945-5660
www.panasonic.com
Table 2. Recommended Inductors – LT1930A
L
(µH)
2.2
4.7
2.2
3.3
2.7
3.3
3.3
MAX
DCR
mΩ
126
195
71
86
100
110
204
SIZE
L
×
W
×
H
(mm)
3.2
×
2.5
×
2.0
PART
LQH3C2R2M24
LQH3C4R7M24
CR43-2R2
CR43-3R3
1008PS-272
1008PS-332
ELT5KT3R3M
VENDOR
Murata
(404) 573-4150
www.murata.com
Sumida
(847) 956-0666
www.sumida.com
Coilcraft
(800) 322-2645
www.coilcraft.com
Panasonic
(408) 945-5660
www.panasonic.com
4.5
×
4.0
×
3.0
3.7
×
3.7
×
2.6
5.2
×
5.2
×
1.1
The inductors shown in Table 2 for use with the LT1930A
were chosen for small size. For better efficiency, use
similar valued inductors with a larger volume. For
example, the Sumida CR43 series in values ranging from
2.2µH to 4.7µH will give an LT1930A application a few
percentage points increase in efficiency, compared to the
smaller Murata LQH3C Series.
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