LT1308A/LT1308B
High Current, Micropower
Single Cell, 600kHz
DC/DC Converters
DESCRIPTION
FEATURES
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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 Mode™ 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)
Improved Accuracy Low-Battery Detector
Reference: 200mV ± 2%
Available in 8-Lead SO and 14-Lead TSSOP Packages
APPLICATIONS
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GSM/CDMA Phones
Digital Cameras
LCD Bias Supplies
Answer-Back Pagers
GPS Receivers
Battery Backup Supplies
Handheld Computers
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
LT1308 and are recommended for use in new designs.
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
switching at light loads and operates at a quiescent current of 2.5mA. Both devices consume less than 1μA in
shutdown.
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.
The LT1308A/LT1308B are available in the 8-lead SO and
the 14-lead TSSOP packages.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
L1
4.7μH
Li-Ion
CELL
VIN
C1
47μF
SHUTDOWN
95
D1
5V
1A
LBO
LT1308B
SHDN
VC
R1*
309k
FB
GND
47k
VIN = 4.2V
85
SW
LBI
VIN = 3.6V
90
+
C2
220μF
R2
100k
EFFICIENCY (%)
+
Converter Efficiency
80
VIN = 2.5V
VIN = 1.5V
75
70
65
60
100pF
55
C1: AVX TAJC476M010
C2: AVX TPSD227M006
D1: IR 10BQ015
L1: MURATA LQH6C4R7
*R1: 887k FOR VOUT = 12V
50
1308A/B F01a
Figure 1. LT1308B Single Li-Ion Cell to 5V/1A DC/DC Converter
1
10
100
LOAD CURRENT (mA)
1000
1308A/B F01b
1308abfb
1
LT1308A/LT1308B
ABSOLUTE MAXIMUM RATINGS
(Note 1)
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
PIN CONFIGURATION
TOP VIEW
TOP VIEW
VC
1
14 LBO
FB
2
13 LBI
SHDN
3
12 VIN
GND
4
11 VIN
GND
5
10 SW
VC 1
8
LBO
FB 2
7
LBI
SHDN 3
6
VIN
GND
6
9
SW
GND 4
5
SW
GND
7
8
SW
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
OBSOLETE, FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1308ACS8#PBF
LT1308ACS8#TRPBF
1308A
8-Lead Plastic SO
0°C to 70°C
LT1308AIS8#PBF
LT1308AIS8#TRPBF
1308AI
8-Lead Plastic SO
–40°C to 85°C
LT1308BCS8#PBF
LT1308BCS8#TRPBF
1308B
8-Lead Plastic SO
0°C to 70°C
LT1308BIS8#PBF
LT1308BIS8#TRPBF
1308BI
8-Lead Plastic SO
–40°C to 85°C
LT1308ACF#PBF
LT1308ACF#TRPBF
LT1308ACF
14-Lead Plastic TSSOP
0°C to 70°C
LT1308BCF#PBF
LT1308BCF#TRPBF
LT1308BCF
14-Lead Plastic TSSOP
0°C to 70°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT1308ACS8
LT1308ACS8#TR
1308A
8-Lead Plastic SO
0°C to 70°C
LT1308AIS8
LT1308AIS8#TR
1308AI
8-Lead Plastic SO
–40°C to 85°C
LT1308BCS8
LT1308BCS8#TR
1308B
8-Lead Plastic SO
0°C to 70°C
LT1308BIS8
LT1308BIS8#TR
1308BI
8-Lead Plastic SO
–40°C to 85°C
LT1308ACF
LT1308ACF#TR
LT1308ACF
14-Lead Plastic TSSOP
0°C to 70°C
LT1308BCF
LT1308BCF#TR
LT1308BCF
14-Lead Plastic TSSOP
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/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
1308abfb
2
LT1308A/LT1308B
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. Commercial Grade 0°C to 70°C. VIN = 1.1V, VSHDN = VIN, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
IQ
Quiescent Current
Not Switching, LT1308A
Switching, LT1308B
VSHDN = 0V (LT1308A/LT1308B)
VFB
Feedback Voltage
IB
FB Pin Bias Current
(Note 3)
Reference Line Regulation
1.1V ≤ VIN ≤ 2V
2V ≤ VIN ≤ 10V
MIN
TYP
MAX
UNITS
140
2.5
0.01
240
4
1
μA
mA
μA
1.22
1.24
V
l
27
80
nA
l
0.03
0.01
0.4
0.2
%/V
%/V
0.92
1
l
1.20
Minimum Input Voltage
gm
Error Amp Transconductance
AV
Error Amp Voltage Gain
fOSC
Switching Frequency
∆I = 5μA
VIN = 1.2V
Maximum Duty Cycle
60
μmhos
100
V/V
l
500
600
l
82
90
2
3
4.5
A
350
400
mV
mV
Switch Current Limit
Duty Cycle = 30% (Note 4)
Switch VCESAT
ISW = 2A (25°C, 0°C), VIN = 1.5V
ISW = 2A (70°C), VIN = 1.5V
290
330
Burst Mode Operation Switch Current Limit
(LT1308A)
VIN = 2.5V, Circuit of Figure 1
400
Shutdown Pin Current
VSHDN = 1.1V
VSHDN = 6V
VSHDN = 0V
LBI Threshold Voltage
V
l
l
l
l
196
194
700
kHz
%
mA
2
20
0.01
5
35
0.1
μA
μA
μA
200
200
204
206
mV
mV
LBO Output Low
ISINK = 50μA
l
0.1
0.25
V
LBO Leakage Current
VLBI = 250mV, VLBO = 5V
l
0.01
0.1
μA
LBI Input Bias Current (Note 5)
VLBI = 150mV
33
100
nA
Low-Battery Detector Gain
Switch Leakage Current
3000
VSW = 5V
l
0.01
V/V
10
μA
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
Industrial Grade –40°C to 85°C. VIN = 1.2V, VSHDN = VIN, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
IQ
Quiescent Current
Not Switching, LT1308A
Switching, LT1308B
VSHDN = 0V (LT1308A/LT1308B)
VFB
Feedback Voltage
IB
FB Pin Bias Current
(Note 3)
Reference Line Regulation
1.1V ≤ VIN ≤ 2V
2V ≤ VIN ≤ 10V
Error Amp Transconductance
AV
Error Amp Voltage Gain
TYP
MAX
UNITS
140
2.5
0.01
240
4
1
μA
mA
μA
1.22
1.25
V
l
27
80
nA
l
l
0.05
0.01
0.4
0.2
%/V
%/V
0.92
1
l
l
l
l
Minimum Input Voltage
gm
MIN
∆I = 5μA
1.19
V
60
μmhos
100
V/V
1308abfb
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LT1308A/LT1308B
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. Industrial Grade –40°C to 85°C. VIN = 1.2V, VSHDN = VIN, unless otherwise noted.
SYMBOL
PARAMETER
MIN
TYP
MAX
UNITS
fOSC
Switching Frequency
CONDITIONS
l
500
600
750
kHz
Maximum Duty Cycle
l
82
90
2
3
4.5
A
350
400
mV
mV
Switch Current Limit
Duty Cycle = 30% (Note 4)
Switch VCESAT
ISW = 2A (25°C, – 40°C), VIN = 1.5V
ISW = 2A (85°C), VIN = 1.5V
290
330
Burst Mode Operation Switch Current Limit
(LT1308A)
VIN = 2.5V, Circuit of Figure 1
400
Shutdown Pin Current
VSHDN = 1.1V
VSHDN = 6V
VSHDN = 0V
l
l
LBI Threshold Voltage
196
193
l
%
mA
2
20
0.01
5
35
0.1
μA
μA
μA
200
200
204
207
mV
mV
LBO Output Low
ISINK = 50μA
l
0.1
0.25
V
LBO Leakage Current
VLBI = 250mV, VLBO = 5V
l
0.01
0.1
μA
LBI Input Bias Current (Note 5)
VLBI = 150mV
33
100
nA
Low-Battery Detector Gain
3000
l
VSW = 5V
Switch Leakage Current
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 3: Bias current flows into FB pin.
0.01
V/V
10
μA
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 VIN
pins (Pins 11, 12) together at the device.
TYPICAL PERFORMANCE CHARACTERISTICS
LT1308B
3.3V Output Efficiency
LT1308A
5V Output Efficiency
95
95
95
90
90
90
VIN = 2.5V
EFFICIENCY (%)
80
VIN = 1.2V
75
VIN = 1.8V
85
70
65
VIN = 2.5V
80
75
VIN = 1.2V
70
65
65
55
55
55
50
50
1308A/B G01
VIN = 2.5V
70
60
1000
VIN = 1.5V
75
60
100
10
LOAD CURRENT (mA)
VIN = 3.6V
80
60
1
VIN = 4.2V
85
EFFICIENCY (%)
VIN = 1.8V
85
EFFICIENCY (%)
LT1308A
3.3V Output Efficiency
50
1
100
10
LOAD CURRENT (mA)
1000
1
10
100
LOAD CURRENT (mA)
1000
1308A/B G02
1308A/B G03
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LT1308A/LT1308B
TYPICAL PERFORMANCE CHARACTERISTICS
LT1308B
12V Output Efficiency
Switch Current Limit vs
Duty Cycle
500
4.0
90
VIN = 5V
400
3.5
CURRENT LIMIT (A)
VIN = 3.3V
80
75
70
65
SWITCH VCESAT (mV)
85
EFFICIENCY (%)
Switch Saturation Voltage
vs Current
3.0
85°C
300
200
2.5
60
25°C
–40°C
100
55
50
10
100
LOAD CURRENT (mA)
1
2.0
1000
0
0
20
60
40
DUTY CYCLE (%)
80
1308A/B G04
10
0
0
2
6
8
4
SHDN PIN VOLTAGE (V)
80
203
70
202
60
201
LBI
50
40
30
199
198
20
197
10
196
–25
0
25
50
TEMPERATURE (°C)
75
195
–50
100
Oscillator Frequency vs
Temperature
1.25
750
170
1.24
500
400
–50
160
1.23
150
1.22
140
1.21
130
1.20
120
1.19
110
450
–2.5
0
25
50
TEMPERATURE (°C)
75
100
1308 • G10
100
VFB (V)
QUIESCENT CURRENT (μA)
180
550
75
Feedback Pin Voltage vs
Temperature
800
600
0
25
50
TEMPERATURE (°C)
1308 • G09
LT1308A Quiescent Current vs
Temperature
650
–25
1308 • G08
1308 G07
FREQUENCY (kHz)
200
FB
0
–50
10
700
2.0
Low Battery Detector Reference
vs Temperature
VREF (mV)
85°C
20
BIAS CURRENT (nA)
SHDN PIN CURRENT (μA)
–40°C
25°C
1.0
0.5
1.5
SWITCH CURRENT (A)
1308 G06
FB, LBI Bias Current vs
Temperature
50
30
0
1308 • G05
SHDN Pin Bias Current vs Voltage
40
100
100
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1308 • G11
1.18
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1308 • G12
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LT1308A/LT1308B
PIN FUNCTIONS
(SO/TSSOP)
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:
VOUT = 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.
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.
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.
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.
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.
LBO (Pin 8/Pin 14): Low-Battery Detector Output. Open
collector, can sink 50μA. A 220kΩ pull-up is recommended. LBO is high impedance when SHDN is grounded.
1308abfb
6
LT1308A/LT1308B
BLOCK DIAGRAMS
VIN
VIN
6
R5
40k
R6
40k
2VBE
Q4
VIN
SHDN
+
VC
gm
VOUT
R1
(EXTERNAL)
FB
Q1
LBI
R2
(EXTERNAL)
+
ERROR
AMPLIFIER
Q2
×10
BIAS
+
7
*
–
LBO
8
ENABLE
A1
R3
30k
R4
140k
3
1
–
FB
2
SHUTDOWN
–
200mV
A4
SW
COMPARATOR
–
RAMP
GENERATOR
+
Σ
+
Q3
Q
R
+
5
DRIVER
FF
S
A2
+
A=3
600kHz
OSCILLATOR
0.03Ω
–
4
*HYSTERESIS IN LT1308A ONLY
GND
1308 BD2a
Figure 2a. LT1308A/LT1308B Block Diagram (SO-8 Package)
VIN
VIN 11
VIN 12
R5
40k
R6
40k
2VBE
Q4
VIN
SHDN
+
VC
gm
VOUT
R1
(EXTERNAL)
FB
R2
(EXTERNAL)
Q1
Q2
×10
LBI
+
ERROR
AMPLIFIER
BIAS
–
+
13
*
R3
30k
R4
140k
3
1
–
FB
2
SHUTDOWN
A1
LBO
14
ENABLE
–
200mV
A4
SW SW SW
8
COMPARATOR
–
RAMP
GENERATOR
+
Σ
+
FF
+
A2
10
Q3
Q
R
9
DRIVER
S
+
A=3
600kHz
OSCILLATOR
0.03Ω
–
*HYSTERESIS IN LT1308A ONLY
4
5
6
7
GND GND GND GND
1308 BD2b
Figure 2b. LT1308A/LT1308B Block Diagram (TSSOP Package)
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LT1308A/LT1308B
APPLICATIONS INFORMATION
OPERATION
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 best understood by referring to the block diagram
in Figure 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 capacitance.
This Burst Mode operation keeps the output regulated
and reduces average current into the IC, resulting in high
efficiency even at load currents of 1mA or less.
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
oscillations at duty factors greater than 50%) exceeds the
VC signal, comparator A2 changes state, resetting the flipflop 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.
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 disabled
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 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.
This results in the absence of low frequency output voltage
ripple at the expense of efficiency.
The difference between the two devices is clearly illustrated in Figure 3. The top two traces in Figure 3 shows an
LT1308A/LT1308B circuit, using the components indicated
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 decreased by
increasing the inductor value. However, output ripple will
continue to be significantly less than the LT1308A 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.
TRACE A: LT1308A
VOUT, 100mV/DIV
AC COUPLED
TRACE B: LT1308B
VOUT, 100mV/DIV
AC COUPLED
ILOAD
800mA
50mA
200μs/DIV
VIN = 3V
(CIRCUIT OF FIGURE 1)
1308 F03
Figure 3. LT1308A Exhibits Burst Mode Operation Output
Voltage Ripple at 50mA Load, LT1308B Does Not
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8
LT1308A/LT1308B
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 approximately 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 inductance. 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 performance.
You will not get advertised performance with careless
layout. Figure 6 shows recommended component placement for an SO-8 package boost (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
close to the ground pin(s) of the LT1308A/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.
C1
R1
VOUT
100mV/DIV
LBI LBO
GROUND PLANE
1
R2
SHUTDOWN
VSW
10V/DIV
2
3
LT1308A
LT1308B
GND
500ns/DIV
Figure 4. 5V to 12V Boost Converter Waveforms in
Continuous Mode. 10μF Ceramic Capacitor Used at Output
7
L1
6
5
+
MULTIPLE
VIAs
1308 F04
VIN
8
4
ISW
500mA/DIV
+
D1
C2
VOUT
1308 F04
Figure 6. Recommended Component Placement for SO-8
Package Boost Converter. Note Direct High Current Paths
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
VOUT
20mV/DIV
VSW
10V/DIV
ISW
500mA/DIV
500ns/DIV
1308 F05
Figure 5. Converter Waveforms in Discontinuous Mode
Figure 7 shows recommended component placement for
a boost converter using the TSSOP package. Placement
is similar to the SO-8 package layout.
1308abfb
9
LT1308A/LT1308B
APPLICATIONS INFORMATION
C1
R1
R2
1
14
2
13
4
MULTIPLE
VIAs
+
VIN
L1
12
3
SHUTDOWN
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 package
SEPIC is shown in Figure 9.
LBI LBO
GROUND PLANE
LT1308A
LT1308B
VIN
3V TO
10V
11
5
10
6
9
7
8
+
VIN
SW
GND
R1
309k
LT1308B
SHDN
GND
R2
100k
47k
C2
680pF
VOUT
VOUT
5V
500mA
FB
VC
D1
D1
L1B
C1
47μF
SHUTDOWN
+
C2
4.7μF
CERAMIC
L1A
CTX10-2
C1: AVX TAJC476M016
C2: TAIYO YUDEN EMK325BJ475(X5R)
C3: AVX TPSD227M006
D1: IR 10BQ015
L1: COILTRONICS CTX10-2
+
C3
220μF
6.3V
1308A/B F08
1308 F07
Figure 7. Recommended Component
Placement for TSSOP Boost Converter.
Placement is Similar to Figure 4
LBI LBO
GROUND PLANE
C1
R1
Figure 8. SEPIC (Single-Ended Primary
Inductance Converter) Converts 3V to 10V
Input to a 5V/500mA Regulated Output
+
1
2
R2
3
SHUTDOWN
8
LT1308A
LT1308B
7
6
L1A
L1B
5
4
MULTIPLE
VIAs
VIN
C3
C2
+
GND
D1
VOUT
1308 F09
Figure 9. Recommended Component Placement for SEPIC
1308abfb
10
LT1308A/LT1308B
APPLICATIONS INFORMATION
SHDN PIN
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, floating this pin has the same effect as
grounding, which is to shut the device down, reducing
current drain to 1μA or less.
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.
VLBO
1V/DIV
LOW-BATTERY DETECTOR
The low-battery detector on the LT1308A/LT1308B features improved accuracy and drive capability compared
to the LT1308. The 200mV reference has an accuracy of
± 2% and the open-collector output can sink 50μA. The
LT1308A/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 reference
can also be accessed as shown in Figure 11.
5V
R1
VIN
LBI
LT1308A
LT1308B
+
100k
LBO
R2
100k
TO PROCESSOR
–
200mV
INTERNAL
REFERENCE
GND
VBAT
R1 =
195
200
VLBI (mV)
205
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 operating voltage
from the output (a technique known as “bootstrapping”).
Figure 13 details start-up waveforms of Figure 1’s circuit
with a 20Ω load and VIN of 1.5V. 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.
VLB – 200mV
2μA
VOUT
2V/DIV
1308 F10
Figure 10. Setting Low-Battery Detector Trip Point
IL1
1A/DIV
VSHDN
5V/DIV
200k
2N3906
VIN
LBO
VBAT
VREF
200mV
LBI
+
10k
10μF
LT1308A
LT1308B
GND
1ms/DIV
1308 F13
Figure 13. 5V Boost Converter of Figure 1.
Start-Up from 1.5V Input into 20Ω Load
1308 F11
Figure 11. Accessing 200mV Reference
1308abfb
11
LT1308A/LT1308B
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 programmable
soft-start can be implemented with 4 discrete components. A 5V to 12V boost converter using the LT1308B
is detailed in Figure 16. C4 differentiates VOUT, 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 current out the
VC pin, creating a feedback loop where the slope of VOUT
is limited as follows:
VOUT
1V/DIV
IL1
2A/DIV
VSHDN
5V/DIV
1308 F14
500μs/DIV
Figure 14. 5V Boost Converter of Figure 1.
Start-Up from 3V Input into 5Ω Load
ΔVOUT
0.7V
=
Δt
33k • C4
VOUT
2V/DIV
ISW
2A/DIV
With C4 = 33nF, VOUT/t is limited to 640mV/ms. Start-up
waveforms for Figure 16’s circuit are pictured in Figure 17.
Without the soft-start circuit implemented, the inrush 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 detailed in
Figure 18, while the time required to reach final output
voltage increases to about 15ms. C4 can be adjusted to
achieve any output slew rate desired.
VSHDN
5V/DIV
1308 F15
500μs/DIV
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
VIN
5V
VIN
+
SHUTDOWN
C1
47μF
D1
VOUT
12V
500mA
SW
SHDN
LT1308B
100k
330pF
10k
C2
10μF
FB
GND
VC
C4
33nF
Q1
R3
33k
R4
33k
11.3k
RC
47k
CC
100pF
SOFT-START
COMPONENTS
C1: AVX TAJ476M010
C2: TAIYO YUDEN TMK432BJ106MM
D1: IR 10BQ015
L1: MURATA LQH6C4R7
Q1: 2N3904
1308 F16
Figure 16. 5V to 12V Boost Converter with Soft-Start Components Q1, C4, R3 and R4
1308abfb
12
LT1308A/LT1308B
APPLICATIONS INFORMATION
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
50μs/DIV
1308 F17
Figure 17. Start-Up Waveforms of Figure 16’s Circuit
without Soft-Start Components
Table 1 lists some inductors we have found to perform
well in LT1308A/LT1308B application circuits. This is not
an exclusive list.
Table 1
VENDOR
12V
VOUT
5V
PART NO.
VALUE
PHONE NO.
Murata
LQH6C4R7
4.7μH
770-436-1300
Sumida
CDRH734R7
4.7μH
847-956-0666
CTX5-1
5μH
561-241-7876
LPO2506IB-472
4.7μH
847-639-6400
Coiltronics
Coilcraft
IL1
1A/DIV
Capacitors
VSHDN
10V/DIV
5ms/DIV
1308 F18
Figure 18. Start-Up Waveforms of Figure 16’s Circuit
with Soft-Start Components Added
COMPONENT SELECTION
Diodes
We have found ON Semiconductor MBRS130 and International Rectifier 10BQ015 to perform well. For applications where VOUT exceeds 30V, use 40V diodes such as
MBRS140 or 10BQ040.
Height limited applications may benefit from the use of the
MBRM120. This component is only 1mm tall and offers
performance similar to the MBRS130.
Inductors
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 inductance
decreasing by more than 50% to 60%. Second, the DCR
of the inductor should have low DCR, under 0.05Ω so
Equivalent Series Resistance (ESR) is the main issue
regarding selection of capacitors, especially the output
capacitors.
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
switch current. The performance of the AVX TPSD227M006
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, so the
ESR of the output capacitor is 60mV/2A or 0.03Ω. Ripple
can be further reduced by paralleling ceramic units.
Table 2 lists some capacitors we have found to perform
well in the LT1308A/LT1308B application circuits. This is
not an exclusive list.
Table 2
VENDOR
SERIES
PART NO.
VALUE
PHONE NO.
AVX
TPS
TPSD227M006
220μF, 6V
803-448-9411
AVX
TPS
TPSD107M010
100μF, 10V
803-448-9411
Taiyo Yuden
X5R
LMK432BJ226
22μF, 10V
408-573-4150
Taiyo Yuden
X5R
TMK432BJ106
10μF, 25V
408-573-4150
1308abfb
13
LT1308A/LT1308B
APPLICATIONS INFORMATION
Ceramic Capacitors
Multilayer ceramic capacitors have become popular, due
to their small size, low cost, and near-zero ESR. Ceramic
capacitors can be used successfully in LT1308A/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 values can
be adjusted to achieve stability. A phase lead capacitor can
also be used to tune up load step response to optimum
levels, as detailed in the following paragraphs.
Figure 19 details a 5V to 12V boost converter using either
a tantalum or ceramic capacitor for C2. The input capacitor has little effect on loop stability, as long as minimum
capacitance requirements are met. The phase lead capacitor 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.
L1
4.7μH
VIN
5V
VIN
VOUT
500mV/DIV
IL1
1A/DIV
LOAD 500mA
CURRENT 50mA
200μs/DIV
Figure 20. Load Step Response of LT1308B 5V to 12V
Boost Converter with 47μF Tantalum Output Capacitor
VOUT
500mV/DIV
VOUT
12V
500mA
LOAD 500mA
CURRENT 50mA
200μs/DIV
SW
LT1308B
R3
10k
1308 F20
IL1
1A/DIV
D1
SHDN
R1
100k
Figure 21. Load Step Response with 47μF Tantalum
Output Capacitor and Phase Lead Capacitor CPL
CPL
330pF
FB
1308 F21
C2
GND
VC
+
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 margin
is low. Figure 23 depicts load step response using the 10μF
ceramic output capacitor and CPL. Response is clean and
no ringing is evident. Ceramic capacitors have the added
benefit of lowering ripple at the switching frequency 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.
VOUT
500mV/DIV
C1
47μF
47k
R2
11.3k
IL1
1A/DIV
100pF
C1: AVX TAJC476M010
C2: AVX TPSD476M016 (47μF) OR
TAIYO YUDEN TMK432BJ106MM (10μF)
D1: IR 10BQ015
L1: MURATA LQH6C4R7
Figure 19. 5V to 12V Boost Converter
LOAD 500mA
CURRENT 50mA
1308 F19
200μs/DIV
1308 F22
Figure 22. Load Step Response with 10μF X5R
Ceramic Output Capacitor
1308abfb
14
LT1308A/LT1308B
APPLICATIONS INFORMATION
VOUT
VIN = 4.2V
VOUT
500mV/DIV
VOUT
VIN = 3.6V
IL1
1A/DIV
VOUT
VIN = 3V
ILOAD
1A
1mA
LOAD 500mA
CURRENT 50mA
1308 F23
200μs/DIV
VOUT TRACES =
200mV/DIV
200μs/DIV
1308 F25
Figure 25. LT1308A Li-Ion to 5V Boost Converter
Transient Response to 1A Load Step
Figure 23. Load Step Response with 10μF X5R
Ceramic Output Capacitor and CPL
GSM AND CDMA PHONES
The LT1308A/LT1308B are suitable for converting a single
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.
L1
4.7μH
+
Li-Ion
CELL
VIN
C1
47μF
SHUTDOWN
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
D1
5V
1A
SW
R1
309k
LT1308B
SHDN
VC
FB
GND
47k
+
C2
220μF
R2
100k
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
1308abfb
15
LT1308A/LT1308B
TYPICAL APPLICATIONS
Triple Output TFTLCD Bias Supply
D2
VOFF
–9V
10mA
C4
1μF
D3
C5
1μF
0.22μF
0.22μF
VON
27V
15mA
D4
C6
1μF
0.22μF
L1
4.7μH
VIN
5V
3
C1
4.7μF
D1
6
5
VIN
SW
AVDD
10V
500mA
SHDN
76.8k
C2, C3
10μF
×2
LT1308B
1
220k
VC
FB
2
GND
4
10.7k
100pF
C1:TAIYO-YUDEN JMK212BJ475MG
C2, C3:TAIYO-YUDEN LMK325BJ106MN
C4, C5, C6:TAIYO-YUDEN EMK212BJ105MG
D1: MBRM120
D2,D3,D4: BAT54S
L1: TOKO 817FY-4R7M
1308 TA02
TFTLCD Bias Supply Transient Response
AVDD
500mV/DIV
VON
500mV/DIV
VOFF
500mV/DIV
ILOAD
800mA
200mA
100μs/DIV
1308abfb
16
LT1308A/LT1308B
TYPICAL APPLICATIONS
40nF EL Panel Driver
T1
1:12
VBAT
3V TO 6V
+
D3
4
3
C1
47μF
D2
1
6
D1
3.3V
REGULATED
1μF
100k
Q1
VIN
47k
324k
3.3k
49.9k
17k
C2
1μF
200V
SHUTDOWN
SHDN
GND
LBI
VC
22nF
4.3M
FB
LT1308A
2M
150k
SW
LBO
Q2
400V
100pF
EL PANEL
≤40nF
10k
47pF
1308 TA03
C1: AVX TAJC476M010
C2: VITRAMON VJ225Y105KXCAT
D1: BAT54
D2, D3: BAV21
High Voltage Supply 350V at 1.2mA
10nF
250V
VIN
2.7V TO 6V
T1
1:12
+
3
C1
47μF
D1
SEPIC Converts 3V to 10V Input to a 5V/500mA Regulated Output
D3
10nF
250V
D2
4
1
10nF
250V
6
Q1: MMBT3906
Q2: ZETEX FCX458
T1: MIDCOM 31105
D4
VOUT
350V
1.2mA
VIN
3V TO
10V
+
VIN
SHUTDOWN
SHUTDOWN
SW
SW
R1
309k
LT1308B
SHDN
VOUT
5V
500mA
FB
GND
47k
SHDN
D1
L1B
C1
47μF
VC
VIN
C2
4.7μF
CERAMIC
L1A
CTX10-2
R2
100k
680pF
+
C3
220μF
6.3V
LT1308A
10M
100pF
47k
C1: AVX TAJC476M016
C2: TAIYO YUDEN EMK325BJ475(X5R)
C3: AVX TPSD227M006
FB
VC
GND
D1: IR 10BQ015
L1: COILTRONICS CTX10-2
1308A/B TA05
34.8k
10nF
D1, D2, D3: BAV21 200mA, 250V
D4: MBR0540
T1: MIDCOM 31105R LP = 1.5μH
1308 TA04
1308abfb
17
LT1308A/LT1308B
PACKAGE DESCRIPTION
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
7
8
.245
MIN
6
5
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
× 45°
(0.254 – 0.508)
2
3
4
.053 – .069
(1.346 – 1.752)
.008 – .010
(0.203 – 0.254)
.004 – .010
(0.101 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
1. DIMENSIONS IN
INCHES
(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
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
6.60 ±0.10
6.40
(.252)
BSC
4.50 ±0.10
0.45 ± 0.05
0.65 BSC
1 2 3 4 5 6 7
RECOMMENDED SOLDER PAD LAYOUT
4.30 – 4.50**
(.169 – .177)
0.09 – 0.20
(.0035 – .0079)
0.25
REF
0.50 – 0.75
(.020 – .030)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
1.10
(.0433)
MAX
0° – 8°
0.65
(.0256)
BSC
0.19 – 0.30
(.0075 – .0118)
TYP
0.05 – 0.15
(.002 – .006)
F14 TSSOP 0204
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
1308abfb
18
LT1308A/LT1308B
REVISION HISTORY
REV
DATE
DESCRIPTION
B
12/10
Obsoleted F Package
(Revision history begins at Rev B)
PAGE NUMBER
2
1308abfb
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT1308A/LT1308B
TYPICAL APPLICATION
Li-Ion to 12V/300mA Step-Up DC/DC Converter
L1
4.7μH
2.7V TO 4.2V
+
Li-Ion
CELL
VIN
C1
47μF
D1
12V
300mA
SW
R1
887k
LT1308B
SHUTDOWN
SHDN
VC
FB
GND
47k
+
C2
100μF
R2
100k
330pF
C1: AVX TAJC476M010
C2: AVX TPSD107M016
D1: IR 10BQ015
L1: MURATA LQH6C4R7
1308A/B TA01
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1302
High Output Current Micropower DC/DC Converter
5V/600mA from 2V, 2A Internal Switch, 200μA IQ
LT1304
2-Cell Micropower DC/DC Converter
5V/200mA, Low-Battery Detector Active in Shutdown
LT1307/LT1307B
Single Cell, Micropower, 600kHz PWM DC/DC Converters
3.3V at 75mA from One Cell, MSOP Package
LT1316
Burst Mode Operation DC/DC with Programmable Current Limit
1.5V Minimum, Precise Control of Peak Current Limit
LT1317/LT1317B
Micropower, 600kHz PWM DC/DC Converters
100μA IQ, Operate with VIN as Low as 1.5V
LTC®1474
Micropower Step-Down DC/DC Converter
94% Efficiency, 10μA IQ, 9V to 5V at 250mA
LTC1516
2-Cell to 5V Regulated Charge Pump
12μA IQ, No Inudctors, 5V at 50mA from 3V Input
LTC1522
Micropower, 5V Charge Pump DC/DC Converter
Regulated 5V ± 4% Output, 20mA from 3V Input
LT1610
Single-Cell Micropower DC/DC Converter
3V at 30mA from 1V, 1.7MHz Fixed Frequency
LT1611
Inverting 1.4MHz Switching Regulator in 5-Lead SOT-23
–5V at 150mA from 5V Input, Tiny SOT-23 package
LT1613
1.4MHz Switching Regulator in 5-Lead SOT-23
5V at 200mA from 4.4V Input, Tiny SOT-23 package
LT1615
Micropower Step-Up DC/DC in 5-Lead SOT-23
20μA IQ, 36V, 350mA Switch
LT1617
Micropower Inverting DC/DC Converter in SOT-23
VIN = 1V to 15V; VOUT to –34V
LTC1682
Doubler Charge Pump with Low Noise LDO
Adjustable or Fixed 3.3V, 5V Outputs, 60μVRMS Output Noise
LT1949
600kHz, 1A Switch PWM DC/DC Converter
1.1A, 0.5Ω, 30V Internal Switch, VIN as Low as 1.5V
LT1949-1
1.1MHz, 1A Switch DC/DC Converter
1.1MHz Version of LT1949
1308abfb
20 Linear Technology Corporation
LT 1210 REV B • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 1999