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LT1930A 데이터시트 PDF




Linear Technology에서 제조한 전자 부품 LT1930A은 전자 산업 및 응용 분야에서
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부품번호 LT1930A 기능
기능 Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter
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LT1930A 데이터시트, 핀배열, 회로
FEATURES
s 1.2MHz Switching Frequency (LT1930)
s 2.2MHz Switching Frequency (LT1930A)
s Low VCESAT Switch: 400mV at 1A
s High Output Voltage: Up to 34V
s 5V at 480mA from 3.3V Input (LT1930)
s 12V at 250mA from 5V Input (LT1930A)
s Wide Input Range: 2.6V to 16V
s Uses Small Surface Mount Components
s Low Shutdown Current: < 1µA
s Low Profile (1mm) ThinSOTTM Package
s Pin-for-Pin Compatible with the LT1613
U
APPLICATIO S
s TFT-LCD Bias Supply
s Digital Cameras
s Cordless Phones
s Battery Backup
s Medical Diagnostic Equipment
s Local 5V or 12V Supply
s External Modems
s PC Cards
s xDSL Power Supply
, LTC and LT are registered trademarks of Linear Technology Corporation
ThinSOT is a trademark of Linear Technology Corporation.
LT1930/LT1930A
1A, 1.2MHz/2.2MHz,
Step-Up DC/DC Converters
DESCRIPTIO
in ThinSOT
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.
TYPICAL APPLICATIO
L1
VIN
5V
10µH
D1
51
R1
VOUT
12V
300mA
C1
2.2µF
VIN SW
LT1930
4
SHDN SHDN
3
FB
113k
C3*
10pF
C2
4.7µF
GND R2
2 13.3k
C1: TAIYO-YUDEN X5R LMK212BJ225MG
C2: TAIYO-YUDEN X5R EMK316BJ475ML
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CR43-100
*OPTIONAL
1930/A F01
Figure 1. 5V to 12V, 300mA Step-Up DC/DC Converter
Efficiency
90
VIN = 5V
85
VIN = 3.3V
80
75
70
65
60
55
50
0 100 200 300 400
LOAD CURRENT (mA)
1930 TA01
1




LT1930A pdf, 반도체, 판매, 대치품
LT1930/LT1930A
BLOCK DIAGRA
VIN 5
1.255V
REFERENCE
VOUT
R1 (EXTERNAL)
FB
R2 (EXTERNAL)
+
A1
SHUTDOWN
4 SHDN
3 FB
COMPARATOR
RC
A2
+
RQ
S
CC
Σ
RAMP
GENERATOR
1.2MHz
OSCILLATOR*
*2.2MHz FOR LT1930A
1 SW
DRIVER
Q1
+
0.01
2 GND
1930/A BD
Figure 2. Block Diagram
U
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

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LT1930A 전자부품, 판매, 대치품
LT1930/LT1930A
APPLICATIONS INFORMATION
VOUT
0.2V/DIV
AC COUPLED
ILI
0.5A/DIV
AC COUPLED
LOAD 250mA
CURRENT 150mA
200µs/DIV
1930 F04
Figure 5. Transient Response of Step-Up Converter with 33µF
Tantalum Output Capacitor and No Phase Lead Capacitor
DIODE SELECTION
A Schottky diode is recommended for use with the LT1930/
LT1930A. The Motorola MBR0520 is a very good choice.
Where the switch voltage exceeds 20V, use the MBR0530
(a 30V diode). Where the switch voltage exceeds 30V, use
the MBR0540 (a 40V diode). These diodes are rated to
handle an average forward current of 0.5A. In applications
where the average forward current of the diode exceeds
0.5A, a Microsemi UPS5817 rated at 1A is recommended.
SETTING OUTPUT VOLTAGE
To set the output voltage, select the values of R1 and R2
(see Figure 1) according to the following equation.
R1 =
R2
VOUT
1.255V
1
A good value for R2 is 13.3k which sets the current in the
resistor divider chain to 1.255V/13.3k = 94.7µA.
LAYOUT HINTS
The high speed operation of the LT1930/LT1930A
demands careful attention to board layout. You will not get
advertised performance with careless layout. Figure 6
shows the recommended component placement.
VOUT
L1
D1
+
C2
R2
C1
VIN
SHUTDOWN
GND R1 C3
Figure 6. Suggested Layout
1930 F06
Driving SHDN Above 10V
The maximum voltage allowed on the SHDN pin is 10V. If
you wish to use a higher voltage, you must place a resistor
in series with SHDN. A good value is 121k. Figure 7 shows
a circuit where VIN = 16V and SHDN is obtained from VIN.
The voltage on the SHDN pin is kept below 10V.
VIN
16V
C1
L1 D1
51
121k VIN
SW
LT1930
4
SHDN
3
FB
GND
2
R1
R2
VOUT
C2
1930 F07
Figure 7. Keeping SHDN Below 10V
7

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