LT1308ACF-PBF [Linear]
High Current, Micropower Single Cell, 600kHz DC/DC Converters; 大电流，微功率单电池， 600kHz的DC / DC转换器
| 型号： | LT1308ACF-PBF |
| 厂家： | 
Linear |
| 描述： | High Current, Micropower Single Cell, 600kHz DC/DC Converters |
| 文件： | 总20页 (文件大小：765K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1308A/LT1308B
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
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DESCRIPTIO
FEATURES
The LT®1308A/LT1308B are micropower, fixed frequency
step-up DC/DC converters that operate over a 1V to 10V
input voltage range. They are improved versions of the
LT1308andarerecommendedforuseinnewdesigns.The
LT1308A features automatic shifting to power saving
Burst Mode operation at light loads and consumes just
140μA at no load. The LT1308B features continuous
switchingatlightloadsandoperatesataquiescentcurrent
of 2.5mA. Both devices consume less than 1μA in
shutdown.
■
5V at 1A from a Single Li-Ion Cell
■
5V at 800mA in SEPIC Mode from Four NiCd Cells
■
Fixed Frequency Operation: 600kHz
■
Boost Converter Outputs up to 34V
■
Starts into Heavy Loads
Automatic Burst ModeTM Operation at
■
Light Load (LT1308A)
■
Continuous Switching at Light Loads (LT1308B)
■
Low VCESAT Switch: 300mV at 2A
■
Pin-for-Pin Upgrade Compatible with LT1308
■
Lower Quiescent Current in Shutdown: 1μA (Max)
Low-battery detector accuracy is significantly tighter than
the LT1308. The 200mV reference is specified at ± 2% at
room and ±3% over temperature. The shutdown pin
enables the device when it is tied to a 1V or higher source
and does not need to be tied to VIN as on the LT1308. An
internal VC clamp results in improved transient response
and the switch voltage rating has been increased to 36V,
enabling higher output voltage applications.
■
Improved Accuracy Low-Battery Detector
Reference: 200mV ±2%
■
Available in 8-Lead SO and 14-Lead TSSOP Packages
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APPLICATIO S
■
GSM/CDMA Phones
■
Digital Cameras
The LT1308A/LT1308B are available in the 8-lead SO and
the 14-lead TSSOP packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst
Mode is a registered trademark of Linear Technology Corporation. All other trademarks are
the property of their respective owners.
■
LCD Bias Supplies
■
Answer-Back Pagers
■
GPS Receivers
■
Battery Backup Supplies
■
Handheld Computers
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TYPICAL APPLICATIO
Converter Efficiency
L1
D1
4.7μH
95
5V
1A
V
= 3.6V
V
= 4.2V
= 2.5V
IN
IN
90
85
80
75
70
65
60
55
50
V
SW
IN
+
C1
47μF
R1*
LBO
LBI
309k
V
LT1308B
IN
+
Li-Ion
CELL
V
= 1.5V
C2
220μF
IN
SHUTDOWN
SHDN
FB
V
GND
C
R2
100k
47k
100pF
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6C4R7
*R1: 887k FOR V = 12V
OUT
1308A/B F01a
1
10
100
1000
LOAD CURRENT (mA)
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
1308A/B F01b
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LT1308A/LT1308B
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(Note 1)
ABSOLUTE AXI U RATI GS
VIN, SHDN, LBO Voltage ......................................... 10V
SW Voltage ............................................... –0.4V to 36V
FB Voltage ....................................................... VIN + 1V
VC Voltage ................................................................ 2V
LBI Voltage ................................................. –0.1V to 1V
Current into FB Pin .............................................. ±1mA
Operating Temperature Range
Commercial ............................................ 0°C to 70°C
Extended Commerial (Note 2) ........... –40°C to 85°C
Industrial ........................................... –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
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PI CO FIGURATIO
TOP VIEW
LBO
LBI
V
1
2
3
4
5
6
7
14
13
12
11
10
9
C
TOP VIEW
FB
SHDN
GND
V
1
2
3
4
8
LBO
LBI
V
IN
C
FB
SHDN
GND
7
6
5
V
IN
SW
SW
SW
V
GND
IN
GND
SW
GND
8
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 190°C/W
F PACKAGE
14-LEAD PLASTIC TSSOP
(Note 6)
TJMAX = 125°C, θJA = 80°C/W
NOT RECOMMENDED FOR NEW DESIGNS
Contact Linear Technology for Potential Replacement
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ORDER I FOR ATIO
LEAD FREE FINISH
LT1308ACS8#PBF
LT1308AIS8#PBF
LT1308BCS8#PBF
LT1308BIS8#PBF
LT1308ACF#PBF
LT1308BCF#PBF
LEAD BASED FINISH
LT1308ACS8
TAPE AND REEL
LT1308ACS8#TRPBF
LT1308AIS8#TRPBF
LT1308BCS8#TRPBF
LT1308BIS8#TRPBF
LT1308ACF#TRPBF
LT1308BCF#TRPBF
TAPE AND REEL
LT1308ACS8#TR
LT1308AIS8#TR
PART MARKING
PACKAGE DESCRIPTION
8-Lead Plastic SO
TEMPERATURE RANGE
0°C to 70°C
1308A
1308AI
8-Lead Plastic SO
–40°C to 85°C
0°C to 70°C
1308B
8-Lead Plastic SO
1308BI
8-Lead Plastic SO
–40°C to 85°C
0°C to 70°C
LT1308ACF
LT1308BCF
PART MARKING
1308A
14-Lead Plastic TSSOP
14-Lead Plastic TSSOP
PACKAGE DESCRIPTION
8-Lead Plastic SO
0°C to 70°C
TEMPERATURE RANGE
0°C to 70°C
LT1308AIS8
1308AI
8-Lead Plastic SO
–40°C to 85°C
0°C to 70°C
LT1308BCS8
LT1308BCS8#TR
LT1308BIS8#TR
1308B
8-Lead Plastic SO
LT1308BIS8
1308BI
8-Lead Plastic SO
–40°C to 85°C
0°C to 70°C
LT1308ACF
LT1308ACF#TR
LT1308ACF
LT1308BCF
14-Lead Plastic TSSOP
14-Lead Plastic TSSOP
LT1308BCF
LT1308BCF#TR
0°C to 70°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
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LT1308A/LT1308B
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature
range, otherwise specifications are TA = 25°C. Commercial Grade 0°C to 70°C. VIN = 1.1V, VSHDN = VIN, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Quiescent Current
Not Switching, LT1308A
Switching, LT1308B
140
2.5
0.01
240
4
1
μA
mA
μA
Q
V
= 0V (LT1308A/LT1308B)
SHDN
V
Feedback Voltage
●
●
●
1.20
1.22
27
1.24
80
V
FB
I
FB Pin Bias Current
Reference Line Regulation
(Note 3)
nA
B
1.1V ≤ V ≤ 2V
0.03
0.01
0.4
0.2
%/V
%/V
IN
2V ≤ V ≤ 10V
IN
Minimum Input Voltage
Error Amp Transconductance
Error Amp Voltage Gain
Switching Frequency
0.92
60
1
V
μmhos
V/V
g
ΔI = 5μA
m
A
100
600
90
V
f
V
= 1.2V
IN
●
●
500
82
2
700
4.5
kHz
OSC
Maximum Duty Cycle
Switch Current Limit
%
Duty Cyle = 30% (Note 4)
3
A
Switch V
I
I
= 2A (25°C, 0°C), V = 1.5V
290
330
350
400
mV
mV
CESAT
SW
SW
IN
= 2A (70°C), V = 1.5V
IN
Burst Mode Operation Switch Current Limit
(LT1308A)
V
= 2.5V, Circuit of Figure 1
400
mA
IN
Shutdown Pin Current
V
V
V
= 1.1V
= 6V
= 0V
●
●
●
2
20
0.01
5
35
0.1
μA
μA
μA
SHDN
SHDN
SHDN
LBI Threshold Voltage
196
194
200
200
204
206
mV
mV
●
●
●
LBO Output Low
I
= 50μA
0.1
0.01
33
0.25
0.1
V
μA
SINK
LBO Leakage Current
V
V
= 250mV, V
= 5V
LBO
LBI
LBI
LBI Input Bias Current (Note 5)
Low-Battery Detector Gain
Switch Leakage Current
= 150mV
100
nA
3000
0.01
V/V
μA
V
= 5V
●
10
SW
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
Industrial Grade –40°C to 85°C. VIN = 1.2V, VSHDN = VIN, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Quiescent Current
Not Switching, LT1308A
Switching, LT1308B
●
●
●
140
2.5
0.01
240
4
1
μA
mA
μA
Q
V
SHDN
= 0V (LT1308A/LT1308B)
V
Feedback Voltage
●
●
1.19
1.22
27
1.25
80
V
FB
I
FB Pin Bias Current
Reference Line Regulation
(Note 3)
nA
B
1.1V ≤ V ≤ 2V
●
●
0.05
0.01
0.4
0.2
%/V
%/V
IN
2V ≤ V ≤ 10V
IN
Minimum Input Voltage
Error Amp Transconductance
Error Amp Voltage Gain
0.92
60
1
V
μmhos
V/V
g
ΔI = 5μA
m
A
100
V
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LT1308A/LT1308B
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature
range, otherwise specifications are TA = 25°C. Industrial Grade –40°C to 85°C. VIN = 1.2V, VSHDN = VIN, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
500
82
TYP
600
90
MAX
UNITS
kHz
%
f
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
●
●
750
OSC
Duty Cyle = 30% (Note 4)
2
3
4.5
A
Switch V
I
I
= 2A (25°C, –40°C), V = 1.5V
290
330
350
400
mV
mV
CESAT
SW
SW
IN
= 2A (85°C), V = 1.5V
IN
Burst Mode Operation Switch Current Limit
(LT1308A)
V
= 2.5V, Circuit of Figure 1
400
mA
IN
Shutdown Pin Current
V
V
V
= 1.1V
= 6V
= 0V
●
●
2
20
0.01
5
35
0.1
μA
μA
μA
SHDN
SHDN
SHDN
LBI Threshold Voltage
196
193
200
200
204
207
mV
mV
●
●
●
LBO Output Low
I
= 50μA
0.1
0.01
33
0.25
0.1
V
μA
SINK
LBO Leakage Current
V
V
= 250mV, V
= 5V
LBO
LBI
LBI
LBI Input Bias Current (Note 5)
Low-Battery Detector Gain
Switch Leakage Current
= 150mV
100
nA
3000
0.01
V/V
μA
V
= 5V
●
10
SW
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT1308ACS8, LT1308ACF, LT1308BCS8 and LT1308BCF are
designed, characterized and expected to meet the industrial temperature
limits, but are not tested at –40°C and 85°C. I grade devices are
guaranteed over the –40°C to 85°C operating temperature range.
Note 4: Switch current limit guaranteed by design and/or correlation to
static tests. Duty cycle affects current limit due to ramp generator (see
Block Diagram).
Note 5: Bias current flows out of LBI pin.
Note 6: Connect the four GND pins (Pins 4–7) together at the device.
Similarly, connect the three SW pins (Pins 8–10) together and the two V
pins (Pins 11, 12) together at the device.
IN
Note 3: Bias current flows into FB pin.
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1308B
3.3V Output Efficiency
LT1308A
5V Output Efficiency
LT1308A
3.3V Output Efficiency
95
90
85
80
75
70
65
60
55
50
95
90
85
80
75
70
65
60
55
50
95
90
85
80
75
70
65
60
55
50
V
= 4.2V
IN
V
= 2.5V
IN
V
= 1.8V
V
= 3.6V
V
= 2.5V
IN
IN
IN
V
= 1.8V
IN
V
= 1.2V
IN
V
= 1.5V
IN
V
= 1.2V
IN
V
= 2.5V
IN
1
10
100
1000
1
10
100
1000
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1308A/B G01
1308A/B G02
1308A/B G03
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LT1308A/LT1308B
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1308B
12V Output Efficiency
Switch Saturation Voltage
vs Current
Switch Current Limit vs
Duty Cycle
4.0
3.5
3.0
2.5
2.0
90
85
80
75
70
65
60
55
50
500
400
300
200
100
0
V
= 5V
IN
V
= 3.3V
IN
85°C
25°C
–40°C
0
20
40
60
80
100
1
10
100
1000
0
0.5
1.0
1.5
2.0
LOAD CURRENT (mA)
DUTY CYCLE (%)
SWITCH CURRENT (A)
1308A/B G04
1308 • G05
1308 G06
FB, LBI Bias Current vs
Temperature
Low Battery Detector Reference
vs Temperature
SHDN Pin Bias Current vs Voltage
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
203
202
201
200
199
198
197
196
195
–40°C
LBI
25°C
85°C
FB
75
–50
–25
0
25
50
100
0
2
4
6
8
10
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
SHDN PIN VOLTAGE (V)
1308 • G08
1308 G07
1308 • G09
Oscillator Frequency vs
Temperature
LT1308A Quiescent Current vs
Temperature
Feedback Pin Voltage vs
Temperature
180
170
160
150
140
130
120
110
100
1.25
1.24
1.23
1.22
1.21
1.20
1.19
1.18
800
750
700
650
600
550
500
450
400
75
75
–50
–25
0
25
50
100
–50
–2.5
0
25
50
100
75
–50
–25
0
25
50
100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
1308 • G11
1308 • G10
1308 • G12
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LT1308A/LT1308B
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PIN FUNCTIONS
(SO/TSSOP)
SW (Pin 5/Pins 8, 9, 10):Switch Pins. Connect inductor/
diode here. Minimize trace area at these pins to keep EMI
down. For the TSSOP package, connect all SW pins
together at the package.
VC (Pin 1/Pin 1): Compensation Pin for Error Amplifier.
Connect a series RC from this pin to ground. Typical
values are 47kΩ and 100pF. Minimize trace area at VC.
FB (Pin 2/Pin 2): Feedback Pin. Reference voltage is
1.22V. Connect resistive divider tap here. Minimize trace
area at FB. Set VOUT according to:
VIN (Pin 6/Pins 11, 12): Supply Pins. Must have local
bypass capacitor right at the pins, connected directly to
ground. For the TSSOP package, connect both VIN pins
together at the package.
V
OUT = 1.22V(1 + R1/R2).
SHDN (Pin 3/Pin 3): Shutdown. Ground this pin to turn
off switcher. To enable, tie to 1V or more. SHDN does not
need to be at VIN to enable the device.
LBI (Pin 7/Pin 13): Low-Battery Detector Input. 200mV
reference. Voltage on LBI must stay between –100mV
and 1V. Low-battery detector does not function with
SHDN pin grounded. Float LBI pin if not used.
GND (Pin 4/Pins 4, 5, 6, 7): Ground. Connect directly to
local ground plane. Ground plane should enclose all
components associated with the LT1308. PCB copper
connected to these pins also functions as a heat sink. For
the TSSOP package, connect all pins to ground copper to
get the best heat transfer. This keeps chip heating to a
minimum.
LBO (Pin 8/Pin 14): Low-Battery Detector Output. Open
collector, can sink 50μA. A 220kΩ pull-up is recom-
mended.LBOishighimpedancewhenSHDNisgrounded.
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LT1308A/LT1308B
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BLOCK DIAGRA S
V
IN
V
IN
Q4
2V
BE
6
V
IN
R5
40k
R6
40k
SHDN
SHUTDOWN
3
+
V
C
g
1
m
V
OUT
LBI
7
–
+
–
+
–
R1
LBO
8
ERROR
AMPLIFIER
(EXTERNAL)
*
FB
2
ENABLE
200mV
Q1
Q2
FB
×10
BIAS
A4
A1
COMPARATOR
R2
R3
30k
(EXTERNAL)
SW
5
–
+
DRIVER
R4
140k
FF
RAMP
GENERATOR
Q3
R
Q
+
Σ
S
A2
+
+
A = 3
–
0.03Ω
600kHz
OSCILLATOR
4
*HYSTERESIS IN LT1308A ONLY
1308 BD2a
GND
Figure 2a. LT1308A/LT1308B Block Diagram (SO-8 Package)
V
IN
Q4
2V
BE
V
11
12
IN
V
IN
R5
40k
R6
40k
V
SHDN
3
IN
SHUTDOWN
+
V
C
g
1
m
V
OUT
LBI
13
–
+
–
+
–
R1
LBO
14
ERROR
AMPLIFIER
(EXTERNAL)
*
FB
2
ENABLE
200mV
Q1
Q2
FB
×10
BIAS
A4
A1
COMPARATOR
R2
SW SW SW
8 10
R3
30k
(EXTERNAL)
9
–
+
DRIVER
R4
140k
FF
RAMP
GENERATOR
Q3
R
Q
+
Σ
S
A2
+
+
A = 3
–
0.03Ω
600kHz
OSCILLATOR
4
5
6
7
*HYSTERESIS IN LT1308A ONLY
1308 BD2b
GND GND GND GND
Figure 2b. LT1308A/LT1308B Block Diagram (TSSOP Package)
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
OPERATION
Low-battery detector A4’s open-collector output (LBO)
pulls low when the LBI pin voltage drops below 200mV.
There is no hysteresis in A4, allowing it to be used as an
amplifier in some applications. The entire device is dis-
abled when the SHDN pin is brought low. To enable the
converter, SHDN must be at 1V or greater. It need not be
tied to VIN as on the LT1308.
The LT1308A combines a current mode, fixed frequency
PWM architecture with Burst Mode micropower operation
to maintain high efficiency at light loads. Operation can be
bestunderstoodbyreferringtotheblockdiagraminFigure
2. Q1 and Q2 form a bandgap reference core whose loop
is closed around the output of the converter. When VIN is
1V, the feedback voltage of 1.22V, along with an 80mV
drop across R5 and R6, forward biases Q1 and Q2’s base
collector junctions to 300mV. Because this is not enough
to saturate either transistor, FB can be at a higher voltage
than VIN. When there is no load, FB rises slightly above
1.22V, causing VC (the error amplifier’s output) to
decrease. When VC reaches the bias voltage on hysteretic
comparator A1, A1’s output goes low, turning off all
circuitry except the input stage, error amplifier and low-
battery detector. Total current consumption in this state is
140μA. As output loading causes the FB voltage to
decrease, A1’s output goes high, enabling the rest of the
IC. Switch current is limited to approximately 400mA
initially after A1’s output goes high. If the load is light, the
output voltage (and FB voltage) will increase until A1’s
output goes low, turning off the rest of the LT1308A. Low
frequency ripple voltage appears at the output. The ripple
frequency is dependent on load current and output capaci-
tance. This Burst Mode operation keeps the output regu-
lated and reduces average current into the IC, resulting in
high efficiency even at load currents of 1mA or less.
The LT1308B differs from the LT1308A in that there is no
hysteresis in comparator A1. Also, the bias point on A1 is
set lower than on the LT1308B so that switching can occur
at inductor current less than 100mA. Because A1 has no
hysteresis, there is no Burst Mode operation at light loads
and the device continues switching at constant frequency.
Thisresultsintheabsenceoflowfrequencyoutputvoltage
ripple at the expense of efficiency.
The difference between the two devices is clearly illus-
trated in Figure 3. The top two traces in Figure 3 shows an
LT1308A/LT1308B circuit, using the components indi-
cated in Figure 1, set to a 5V output. Input voltage is 3V.
Load current is stepped from 50mA to 800mA for both
circuits. Low frequency Burst Mode operation voltage
ripple is observed on Trace A, while none is observed on
Trace B.
At light loads, the LT1308B will begin to skip alternate
cycles. The load point at which this occurs can be de-
creased by increasing the inductor value. However, output
ripplewillcontinuetobesignificantlylessthantheLT1308A
output ripple. Further, the LT1308B can be forced into
micropower mode, where IQ falls from 3mA to 200μA by
sinking 40μA or more out of the VC pin. This stops
switching by causing A1’s output to go low.
If the output load increases sufficiently, A1’s output
remains high, resulting in continuous operation. When the
LT1308A is running continuously, peak switch current is
controlled by VC to regulate the output voltage. The switch
is turned on at the beginning of each switch cycle. When
the summation of a signal representing switch current and
a ramp generator (introduced to avoid subharmonic oscil-
lations at duty factors greater than 50%) exceeds the VC
signal,comparatorA2changesstate,resettingtheflip-flop
and turning off the switch. Output voltage increases as
switch current is increased. The output, attenuated by a
resistor divider, appears at the FB pin, closing the overall
loop. Frequency compensation is provided by an external
series RC network connected between the VC pin and
ground.
TRACE A: LT1308A
VOUT, 100mV/DIV
AC COUPLED
TRACE B: LT1308B
VOUT, 100mV/DIV
AC COUPLED
800mA
ILOAD
50mA
V
IN = 3V
200μs/DIV
1308 F03
(CIRCUIT OF FIGURE 1)
Figure 3. LT1308A Exhibits Burst Mode Operation Output
Voltage Ripple at 50mA Load, LT1308B Does Not
1308abfa
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
Waveforms for a LT1308B 5V to 12V boost converter
using a 10μF ceramic output capacitor are pictured in
Figures 4 and 5. In Figure 4, the converter is operating in
continuous mode, delivering a load current of approxi-
mately 500mA. The top trace is the output. The voltage
increases as inductor current is dumped into the output
capacitor during the switch off time, and the voltage
decreases when the switch is on. Ripple voltage is in this
case due to capacitance, as the ceramic capacitor has little
ESR. The middle trace is the switch voltage. This voltage
alternates between a VCESAT and VOUT plus the diode drop.
The lower trace is the switch current. At the beginning of
the switch cycle, the current is 1.2A. At the end of the
switch on time, the current has increased to 2A, at which
point the switch turns off and the inductor current flows
into the output capacitor through the diode. Figure 5
depicts converter waveforms at a light load. Here the
converter operates in discontinuous mode. The inductor
current reaches zero during the switch off time, resulting
in some ringing at the switch node. The ring frequency is
set by switch capacitance, diode capacitance and induc-
tance. This ringing has little energy, and its sinusoidal
shape suggests it is free from harmonics. Minimizing the
copper area at the switch node will prevent this from
causing interference problems.
LAYOUT HINTS
The LT1308A/LT1308B switch current at high speed,
mandating careful attention to layout for proper perfor-
mance. You will not get advertised performance with
carelesslayout.Figure6showsrecommendedcomponent
placementforanSO-8packageboost(step-up)converter.
Follow this closely in your PC layout. Note the direct path
of the switching loops. Input capacitor C1 must be placed
close (<5mm) to the IC package. As little as 10mm of wire
or PC trace from CIN to VIN will cause problems such as
inability to regulate or oscillation.
The negative terminal of output capacitor C2 should tie
closetothegroundpin(s)oftheLT1308A/LT1308B.Doing
this reduces dI/dt in the ground copper which keeps high
frequency spikes to a minimum. The DC/DC converter
ground should tie to the PC board ground plane at one
place only, to avoid introducing dI/dt in the ground plane.
LBI
LBO
GROUND PLANE
C1
+
V
IN
R1
1
2
3
4
8
7
6
5
LT1308A
LT1308B
L1
R2
VOUT
100mV/DIV
SHUTDOWN
VSW
10V/DIV
MULTIPLE
VIAs
+
D1
ISW
1A/DIV
C2
GND
V
OUT
500ns/DIV
Figure 4. 5V to 12V Boost Converter Waveforms in
Continuous Mode. 10μF Ceramic Capacitor Used at Output
1308 F04
Figure 6. Recommended Component Placement for SO-8
Package Boost Converter. Note Direct High Current Paths
VOUT
20mV/DIV
Using Wide PC Traces. Minimize Trace Area at Pin 1 (VC) and
Pin 2 (FB). Use Multiple Vias to Tie Pin 4 Copper to Ground
Plane. Use Vias at One Location Only to Avoid Introducing
Switching Currents into the Ground Plane
VSW
10V/DIV
ISW
500mA/DIV
Figure 7 shows recommended component placement for
a boost converter using the TSSOP package. Placement is
500ns/DIV
similar to the SO-8 package layout.
Figure 5. Converter Waveforms in Discontinuous Mode
1308abfa
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
A SEPIC (Single-Ended Primary Inductance Converter)
schematic is shown in Figure 8. This converter topology
produces a regulated output over an input voltage range
that spans (i.e., can be higher or lower than) the output.
Recommended component placement for an SO-8 pack-
age SEPIC is shown in Figure 9.
LBI
LBO
GROUND PLANE
C1
+
V
IN
R1
1
2
3
4
5
6
7
14
C2
13
12
11
10
9
L1
4.7μF
CERAMIC
R2
L1A
CTX10-2
D1
SHUTDOWN
V
IN
3V TO
10V
LT1308A
LT1308B
V
SW
IN
+
MULTIPLE
VIAs
L1B
C1
47μF
R1
309k
LT1308B
V
OUT
8
5V
SHUTDOWN
SHDN
FB
GND
500mA
V
C
+
R2
100k
D1
+
C3
220μF
6.3V
47k
C2
GND
680pF
V
OUT
C1: AVX TAJC476M016
C2: TAIYO YUDEN EMK325BJ475(X5R)
C3: AVX TPSD227M006
D1: IR 10BQ015
L1: COILTRONICS CTX10-2
1308A/B F08
1308 F07
Figure 7. Recommended Component
Placement for TSSOP Boost Converter.
Placement is Similar to Figure 4.
Figure 8. SEPIC (Single-Ended Primary
Inductance Converter) Converts 3V to 10V
Input to a 5V/500mA Regulated Output
LBI
LBO
GROUND PLANE
C1
+
V
IN
R1
1
2
8
7
6
5
LT1308A
LT1308B
R2
SHUTDOWN
3
4
L1A
C2
L1B
MULTIPLE
VIAs
C3
+
GND
D1
V
OUT
1308 F09
Figure 9. Recommended Component Placement for SEPIC
1308abfa
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
SHDN PIN
A cross plot of the low-battery detector is shown in
Figure 12. The LBI pin is swept with an input which varies
from 195mV to 205mV, and LBO (with a 100k pull-up
resistor) is displayed.
The LT1308A/LT1308B SHDN pin is improved over the
LT1308. The pin does not require tying to VIN to enable the
device, but needs only a logic level signal. The voltage on
the SHDN pin can vary from 1V to 10V independent of VIN.
Further, floatingthispinhasthesameeffectasgrounding,
which is to shut the device down, reducing current drain
to 1μA or less.
VLBO
1V/DIV
LOW-BATTERY DETECTOR
The low-battery detector on the LT1308A/LT1308B fea-
tures improved accuracy and drive capability compared to
theLT1308.The200mVreferencehasanaccuracyof±2%
andtheopen-collectoroutputcansink50μA.TheLT1308A/
LT1308B low-battery detector is a simple PNP input gain
stage with an open-collector NPN output. The negative
input of the gain stage is tied internally to a 200mV
reference. The positive input is the LBI pin. Arrangement
as a low-battery detector is straightforward. Figure 10
details hookup. R1 and R2 need only be low enough in
value so that the bias current of the LBI pin doesn’t cause
large errors. For R2, 100k is adequate. The 200mV refer-
ence can also be accessed as shown in Figure 11.
195
200
205
VLBI (mV)
1308 F12
Figure 12. Low-Battery Detector
Input/Output Characteristic
START-UP
The LT1308A/LT1308B can start up into heavy loads,
unlike many CMOS DC/DC converters that derive operat-
ing voltage from the output (a technique known as
“bootstrapping”). Figure13 detailsstart-upwaveformsof
Figure1’scircuitwitha20ΩloadandVIN of1.5V. Inductor
current rises to 3.5A as the output capacitor is charged.
After the output reaches 5V, inductor current is about 1A.
In Figure 14, the load is 5Ω and input voltage is 3V. Output
voltage reaches 5V in 500μs after the device is enabled.
Figure 15 shows start-up behavior of Figure 5’s SEPIC
circuit, driven from a 9V input with a 10Ω load. The output
reaches 5V in about 1ms after the device is enabled.
5V
R1
V
LT1308A
LT1308B
IN
100k
LBI
+
–
LBO
TO PROCESSOR
R2
100k
200mV
V
– 200mV
2μA
LB
VOUT
2V/DIV
R1 =
INTERNAL
V
BAT
REFERENCE
GND
1308 F10
IL1
1A/DIV
Figure 10. Setting Low-Battery Detector Trip Point
VSHDN
5V/DIV
1ms/DIV
1308 F13
200k
V
IN
2N3906
REF
LBO
LBI
Figure 13. 5V Boost Converter of Figure 1.
Start-Up from 1.5V Input into 20Ω Load
V
LT1308A
LT1308B
BAT
V
200mV
+
GND
10k
10μF
1308 F11
Figure 11. Accessing 200mV Reference
1308abfa
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
when operating from a battery composed of alkaline
cells. The inrush current may cause sufficiency internal
voltage drop to trigger a low-battery indicator. A pro-
grammablesoft-startcanbeimplementedwith4discrete
components. A 5V to 12V boost converter using the
VOUT
1V/DIV
IL1
2A/DIV
LT1308B is detailed in Figure 16. C4 differentiates VOUT
,
VSHDN
5V/DIV
500μs/DIV
1308 F14
causing a current to flow into R3 as VOUT increases.
When this current exceeds 0.7V/33k, or 21μA, current
flows into the base of Q1. Q1’s collector then pulls
currentouttheVC pin, creatingafeedbackloopwherethe
slope of VOUT is limited as follows:
Figure 14. 5V Boost Converter of Figure 1.
Start-Up from 3V Input into 5Ω Load
VOUT
2V/DIV
ΔVOUT
Δt
0.7V
33k •C4
=
ISW
With C4 = 33nF, VOUT/t is limited to 640mV/ms. Start-up
waveforms for Figure 16’s circuit are pictured in Figure
17.Withoutthesoft-startcircuitimplemented,theinrush
current reaches 3A. The circuit reaches final output
voltage in approximately 250μs. Adding the soft-start
components reduces inductor current to less than 1A, as
detailedinFigure18,whilethetimerequiredtoreachfinal
output voltage increases to about 15ms. C4 can be
adjusted to achieve any output slew rate desired.
2A/DIV
VSHDN
5V/DIV
500μs/DIV
1308 F15
Figure 15. 5V SEPIC Start-Up from 9V Input into 10Ω Load
Soft-Start
In some cases it may be undesirable for the LT1308A/
LT1308B to operate at current limit during start-up, e.g.,
L1
4.7μH
D1
V
OUT
V
IN
5V
12V
500mA
V
SW
IN
+
SHDN
SHUTDOWN
C1
47μF
LT1308B
330pF
11.3k
100k
10k
C2
10μF
FB
GND
V
C
C4
33nF
R4
33k
R
C
Q1
47k
C
C
R3
33k
100pF
SOFT-START
COMPONENTS
C1: AVX TAJ476M010
1308 F16
C2: TAIYO YUDEN TMK432BJ106MM
D1: IR 10BQ015
L1: MURATA LQH6C4R7
Q1: 2N3904
Figure 16. 5V to 12V Boost Converter with Soft-Start Components Q1, C4, R3 and R4.
1308abfa
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
so that copper loss is minimized. Acceptable inductance
values range between 2μH and 20μH, with 4.7μH best for
most applications. Lower value inductors are physically
smaller than higher value inductors for the same current
capability.
12V
VOUT
5V/DIV
5V
IL1
1A/DIV
VSHDN
10V/DIV
Table1listssomeinductorswehavefoundtoperformwell
in LT1308A/LT1308B application circuits. This is not an
exclusive list.
50μs/DIV
1308 F17
Figure 17. Start-Up Waveforms of Figure 16’s Circuit
without Soft-Start Components
Table 1
VENDOR
Murata
PART NO.
LQH6C4R7
CDRH734R7
CTX5-1
VALUE
4.7μH
4.7μH
5μH
PHONE NO.
770-436-1300
847-956-0666
561-241-7876
847-639-6400
12V
Sumida
VOUT
5V
Coiltronics
Coilcraft
LPO2506IB-472
4.7μH
IL1
1A/DIV
VSHDN
10V/DIV
Capacitors
5ms/DIV
1308 F18
Equivalent Series Resistance (ESR) is the main issue
regarding selection of capacitors, especially the output
capacitors.
Figure 18. Start-Up Waveforms of Figure 16’s Circuit
with Soft-Start Components Added
The output capacitors specified for use with the LT1308A/
LT1308B circuits have low ESR and are specifically
designed for power supply applications. Output voltage
ripple of a boost converter is equal to ESR multiplied by
switchcurrent.TheperformanceoftheAVXTPSD227M006
220μF tantalum can be evaluated by referring to Figure 3.
When the load is 800mA, the peak switch current is
approximately 2A. Output voltage ripple is about 60mVP-
P,sotheESRoftheoutputcapacitoris60mV/2Aor0.03Ω.
Ripplecanbefurtherreducedbyparallelingceramicunits.
COMPONENT SELECTION
Diodes
WehavefoundONSemiconductorMBRS130andInterna-
tional Rectifier 10BQ015 to perform well. For applications
where VOUT exceeds 30V, use 40V diodes such as
MBRS140 or 10BQ040.
Heightlimitedapplicationsmaybenefitfromtheuseofthe
MBRM120. This component is only 1mm tall and offers
performance similar to the MBRS130.
Table 2 lists some capacitors we have found to perform
well in the LT1308A/LT1308B application circuits. This is
not an exclusive list.
Inductors
Table 2
Suitable inductors for use with the LT1308A/LT1308B
must fulfill two requirements. First, the inductor must be
able to handle current of 2A steady-state, as well as
support transient and start-up current over 3A without
inductancedecreasingbymorethan50%to60%.Second,
theDCRoftheinductorshouldhavelowDCR,under0.05Ω
VENDOR
AVX
SERIES
TPS
PART NO.
VALUE
PHONE NO.
TPSD227M006 220μF, 6V 803-448-9411
TPSD107M010 100μF, 10V 803-448-9411
LMK432BJ226 22μF, 10V 408-573-4150
TMK432BJ106 10μF, 25V 408-573-4150
AVX
TPS
Taiyo Yuden
Taiyo Yuden
X5R
X5R
1308abfa
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LT1308A/LT1308B
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APPLICATIONS INFORMATION
Ceramic Capacitors
Without CPL, load step response is pictured in Figure 22.
Although the output settles faster than the tantalum case,
there is appreciable ringing, again suggesting phase mar-
gin is low. Figure 23 depicts load step response using the
10μFceramicoutputcapacitorandCPL. Responseisclean
and no ringing is evident. Ceramic capacitors have the
addedbenefitofloweringrippleattheswitchingfrequency
due to their very low ESR. By applying CPL in tandem with
the series RC at the VC pin, loop response can be tailored
to optimize response using ceramic output capacitors.
Multilayer ceramic capacitors have become popular, due
to their small size, low cost, and near-zero ESR. Ceramic
capacitorscanbeusedsuccessfullyinLT1308A/LT1308B
designs provided loop stability is considered. A tantalum
capacitor has some ESR and this causes an "ESR zero" in
the regulator loop. This zero is beneficial to loop stability.
Ceramics do not have appreciable ESR, so the zero is lost
when they are used. However, the LT1308A/LT1308B
have external compensation pin (VC) so component val-
ues can be adjusted to achieve stability. A phase lead
capacitor can also be used to tune up load step response
tooptimumlevels, asdetailedinthefollowingparagraphs.
VOUT
500mV/DIV
Figure 19 details a 5V to 12V boost converter using either
a tantalum or ceramic capacitor for C2. The input capaci-
tor has little effect on loop stability, as long as minimum
capacitance requirements are met. The phase lead capaci-
tor CPL parallels feedback resistor R1. Figure 20 shows
load step response of a 50mA to 500mA load step using a
47μF tantalum capacitor at the output. Without the phase
lead capacitor, there is some ringing, suggesting the
phase margin is low. CPL is then added, and response to
the same load step is pictured in Figure 21. Some phase
margin is restored, improving the response. Next, C2 is
replaced by a 10μF, X5R dielectric, ceramic capacitor.
IL1
1A/DIV
500mA
LOAD
CURRENT
50mA
200μs/DIV
1308 F20
Figure 20. Load Step Response of LT1308B 5V to 12V
Boost Converter with 47μF Tantalum Output Capacitor
VOUT
500mV/DIV
L1
4.7μH
IL1
D1
V
1A/DIV
OUT
V
IN
12V
5V
500mA
500mA
LOAD
CURRENT
50mA
V
SW
200μs/DIV
IN
1308 F21
SHDN
Figure 21. Load Step Response with 47μF Tantalum
Output Capacitor and Phase Lead Capacitor CPL
C
R1
100k
PL
LT1308B
R3
10k
330pF
FB
GND
C2
V
C
VOUT
1V/DIV
+
C1
47μF
R2
11.3k
47k
IL1
1A/DIV
100pF
500mA
LOAD
C1: AVX TAJC476M010
CURRENT
C2: AVX TPSD476M016 (47μF) OR
50mA
1308 F19
TAIYO YUDEN TMK432BJ106MM (10μF)
D1: IR 10BQ015
L1: MURATA LQH6C4R7
200μs/DIV
1308 F22
Figure 22. Load Step Response with 10μF X5R
Figure 19. 5V to 12V Boost Converter
Ceramic Output Capacitor
1308abfa
14
LT1308A/LT1308B
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APPLICATIONS INFORMATION
VOUT
VOUT
VIN = 4.2V
500mV/DIV
VOUT
VIN = 3.6V
IL1
1A/DIV
VOUT
VIN = 3V
ILOAD
500mA
LOAD
1A
CURRENT
10mA
50mA
200μs/DIV
V
OUT TRACES =
200μs/DIV
1308 F23
200mV/DIV
1308 F25
Figure 23. Load Step Response with 10μF X5R
Ceramic Output Capacitor and CPL
Figure 25. LT1308A Li-Ion to 5V Boost Converter
Transient Response to 1A Load Step
GSM AND CDMA PHONES
TheLT1308A/LT1308Baresuitableforconvertingasingle
Li-Ion cell to 5V for powering RF power stages in GSM or
CDMA phones. Improvements in the LT1308A/LT1308B
error amplifiers allow external compensation values to be
reduced, resulting in faster transient response compared
to the LT1308. The circuit of Figure 24 (same as Figure 1,
printed again for convenience) provides a 5V, 1A output
from a Li-Ion cell. Figure 25 details transient response at
the LT1308A operating at a VIN of 4.2V, 3.6V and 3V.
Ripple voltage in Burst Mode operation can be seen at
10mA load. Figure 26 shows transient response of the
LT1308B under the same conditions. Note the lack of
Burst Mode ripple at 10mA load.
VOUT
VIN = 4.2V
VOUT
VIN = 3.6V
VOUT
VIN = 3V
ILOAD
1A
10mA
VOUT TRACES =
200mV/DIV
100μs/DIV
1308 F26
Figure 26. LT1308B Li-Ion to 5V Boost
Converter Transient Response to 1A Load Step
L1
4.7μH
D1
5V
1A
V
IN
SW
+
C1
47μF
R1
LT1308B
309k
+
Li-Ion
CELL
C2
220μF
SHUTDOWN
SHDN
FB
GND
V
C
R2
100k
47k
100pF
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6N4R7
1308A/B F24
Figure 24. Li-Ion to 5V Boost Converter Delivers 1A
1308abfa
15
LT1308A/LT1308B
TYPICAL APPLICATIO S
U
Triple Output TFTLCD Bias Supply
D2
V
OFF
–9V
C4
10mA
1μF
D3
V
ON
27V
C5
1μF
0.22μF
0.22μF
15mA
D4
C6
1μF
0.22μF
L1
4.7μH
D1
V
IN
5V
AV
DD
6
5
10V
V
SW
IN
500mA
3
1
SHDN
76.8k
10.7k
C2, C3
10μF
×2
C1
LT1308B
4.7μF
2
FB
V
C
GND
4
220k
100pF
C1:TAIYO-YUDEN JMK212BJ475MG
C2, C3:TAIYO-YUDEN LMK325BJ106MN
1308 TA02
C4, C5, C6:TAIYO-YUDEN EMK212BJ105MG
D1: MBRM120
D2,D3,D4: BAT54S
L1: TOKO 817FY-4R7M
TFTLCD Bias Supply Transient Response
AV
DD
500mV/DIV
V
ON
500mV/DIV
V
OFF
500mV/DIV
800mA
I
LOAD
200mA
100μs/DIV
1308abfa
16
LT1308A/LT1308B
U
TYPICAL APPLICATIO S
40nF EL Panel Driver
T1
1:12
D2
D3
V
BAT
3V TO 6V
4
+
3
C1
47μF
1
6
D1
3.3V
REGULATED
1μF
100k
V
SW
IN
4.3M
Q1
LBO
FB
47k
LT1308A
2M
17k
C2
1μF
200V
324k
150k
3.3k
LBI
V
SHUTDOWN
SHDN
GND
C
Q2
400V
EL PANEL
≤40nF
100pF
47pF
22nF
49.9k
10k
1308 TA03
Q1: MMBT3906
C1: AVX TAJC476M010
Q2: ZETEX FCX458
C2: VITRAMON VJ225Y105KXCAT
D1: BAT54
T1: MIDCOM 31105
D2, D3: BAV21
SEPIC Converts 3V to 10V Input to a 5V/500mA Regulated Output
High Voltage Supply 350V at 1.2mA
10nF
250V
D3
V
OUT
350V
1.2mA
10nF
250V
T1
D2
D1
C2
1:12
V
IN
2.7V TO 6V
4.7μF
L1A
+
3
4
CERAMIC
C1
47μF
D1
CTX10-2
LT1308B
V
IN
10nF
250V
3V TO
10V
1
6
V
SW
IN
+
D4
L1B
C1
47μF
R1
309k
V
OUT
5V
SHUTDOWN
SHDN
FB
GND
V
SW
IN
500mA
V
C
SHUTDOWN
SHDN
R2
100k
LT1308A
+
C3
47k
220μF
10M
6.3V
FB
V
680pF
C
GND
47k
10nF
100pF
34.8k
C1: AVX TAJC476M016
C2: TAIYO YUDEN EMK325BJ475(X5R)
C3: AVX TPSD227M006
D1: IR 10BQ015
L1: COILTRONICS CTX10-2
1308A/B TA05
D1, D2, D3: BAV21 200mA, 250V
D4: MBR0540
1308 TA04
T1: MIDCOM 31105R L = 1.5μH
P
1308abfa
17
LT1308A/LT1308B
U
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
.045 ±.005
NOTE 3
.050 BSC
7
5
8
6
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
3
4
2
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
INCHES
1. DIMENSIONS IN
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
SO8 0303
1308abfa
18
LT1308A/LT1308B
U
PACKAGE DESCRIPTION
F Package
14-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1650)
4.90 – 5.10*
(.193 – .201)
14 13 12 11 10
9
8
1.05 ± 0.10
4.50 ±0.10
6.40
(.252)
BSC
6.60 ±0.10
0.45 ± 0.05
0.65 BSC
5
6
7
1
2
3
4
RECOMMENDED SOLDER PAD LAYOUT
1.10
(.0433)
MAX
4.30 – 4.50**
(.169 – .177)
0.25
REF
0° – 8°
0.65
(.0256)
BSC
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
0.05 – 0.15
(.002 – .006)
F14 TSSOP 0204
0.19 – 0.30
(.0075 – .0118)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED .152mm (.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
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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-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
19
LT1308A/LT1308B
U
TYPICAL APPLICATIO
Li-Ion to 12V/300mA Step-Up DC/DC Converter
L1
4.7μH
D1
2.7V TO 4.2V
12V
300mA
V
SW
IN
+
C1
47μF
R1
887k
LT1308B
+
Li-Ion
CELL
C2
100μF
SHUTDOWN
SHDN
FB
GND
V
C
R2
100k
47k
330pF
C1: AVX TAJC476M010
C2: AVX TPSD107M016
D1: IR 10BQ015
L1: MURATA LQH6C4R7
1308A/B TA01
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
5V/600mA from 2V, 2A Internal Switch, 200μA I
LT1302
High Output Current Micropower DC/DC Converter
2-Cell Micropower DC/DC Converter
Q
LT1304
5V/200mA, Low-Battery Detector Active in Shutdown
3.3V at 75mA from One Cell, MSOP Package
LT1307/LT1307B Single Cell, Micropower, 600kHz PWM DC/DC Converters
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LT1317/LT1317B Micropower, 600kHz PWM DC/DC Converters
1.5V Minimum, Precise Control of Peak Current Limit
100μA I , Operate with V as Low as 1.5V
Q
IN
LTC®1474
LTC1516
LTC1522
LT1610
Micropower Step-Down DC/DC Converter
2-Cell to 5V Regulated Charge Pump
94% Efficiency, 10μA I , 9V to 5V at 250mA
Q
12μA I , No Inudctors, 5V at 50mA from 3V Input
Q
Micropower, 5V Charge Pump DC/DC Converter
Single-Cell Micropower DC/DC Converter
Inverting 1.4MHz Switching Regulator in 5-Lead SOT-23
1.4MHz Switching Regulator in 5-Lead SOT-23
Micropower Step-Up DC/DC in 5-Lead SOT-23
Micropower Inverting DC/DC Converter in SOT-23
Doubler Charge Pump with Low Noise LDO
600kHz, 1A Switch PWM DC/DC Converter
1.1MHz, 1A Switch DC/DC Converter
Regulated 5V ± 4% Output, 20mA from 3V Input
3V at 30mA from 1V, 1.7MHz Fixed Frequency
–5V at 150mA from 5V Input, Tiny SOT-23 package
5V at 200mA from 4.4V Input, Tiny SOT-23 package
LT1611
LT1613
LT1615
20μA I , 36V, 350mA Switch
Q
LT1617
V
= 1V to 15V; V
to –34V
IN
OUT
LTC1682
LT1949
Adjustable or Fixed 3.3V, 5V Outputs, 60μV
Output Noise
RMS
1.1A, 0.5Ω, 30V Internal Switch, V as Low as 1.5V
IN
LT1949-1
1.1MHz Version of LT1949
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LT 0807 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
© LINEAR TECHNOLOGY CORPORATION 1999
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