LTC3429BES6#TRMPBF [Linear]
LTC3429 - 600mA, 500kHz Micropower Synchronous Boost Converter with Output Disconnect; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C;
| 型号： | LTC3429BES6#TRMPBF |
| 厂家： | 
Linear |
| 描述： | LTC3429 - 600mA, 500kHz Micropower Synchronous Boost Converter with Output Disconnect; Package: SOT; Pins: 6; Temperature Range: -40°C to 85°C 开关 光电二极管 |
| 文件： | 总12页 (文件大小：197K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3429/LTC3429B
600mA, 500kHz Micropower
Synchronous Boost Converter
with Output Disconnect
U
FEATURES
DESCRIPTIO
■
Up to 96% Efficiency
The LTC®3429/LTC3429B are high efficiency synchro-
nous,fixedfrequency,step-upDC/DCconverterswithtrue
output load disconnect, inrush current limiting and soft-
start in a low profile 6-lead ThinSOTTM package. These
devices are capable of supplying 100mA from a single AA
cell input or 250mA from a 2-cell AA with a 3.3V output.
■
True Output Load Disconnect
■
Inrush Current Limiting and Internal Soft-Start
■
Low Voltage Start-Up: 0.85V
Automatic Burst Mode® Operation with IQ ~ 20µA
■
■
Continuous Switching at Light Loads (LTC3429B)
■
Internal Synchronous Rectifier
A switching frequency of 500kHz minimizes overall solu-
tion footprint by allowing the use of tiny, low profile
inductors and ceramic capacitors. Current mode PWM
control with internal compensation reduces external parts
counttherebysavingcriticalboardrealestate.TheLTC3429
shiftsautomaticallytopowersavingBurstModeoperation
at light loads while the LTC3429B features continuous
switching at light loads. Antiringing control circuitry re-
duces EMI concerns by damping the inductor in discon-
tinuous mode.
■
Current Mode Control with Internal Compensation
■
Short-Circuit Protection
■
500kHz Fixed Frequency Switching
■
Input Range: 0.5V to 4.4V
■
Output Range: 2.5V to 4.3V (Up to 5V with Schottky)
■
Shutdown Current: <1µA
■
Antiringing Control Minimizes EMI
■
Tiny External Components
■
Low Profile (1mm) SOT-23 Package
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The devices also feature low shutdown current of under
1µA. The true output disconnect feature allows the output
to be completely discharged in shutdown. It also limits the
inrush of current during start-up, minimizing surge cur-
rents seen by the input supply.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Burst Mode is a registered
trademark of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology
Corporation.
APPLICATIO S
■
MP3 Players
■
Digital Cameras
■
LCD Bias Supplies
Handheld Instruments
Wireless Handsets
GPS Receivers
■
■
■
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TYPICAL APPLICATIO
2-Cell to 3.3V Efficiency
100
100
V
= 3V
IN
4.7µH
90
80
10
1
EFFICIENCY
+
2-CELL
AA
V
= 2.4V
= 2.4V
IN
4.7µF
SW
V
OUT
3.3V
V
V
IN
LTC3429
SHDN FB
GND
OUT
250mA
70
60
0.1
V
1.02M
604k
IN
10µF
OFF
ON
V
= 3V
IN
0.01
POWER LOSS
50
40
0.001
3429 F01a
0.0001
1000
0.1
1
10
100
Figure 1. 2-Cell to 3.3V Synchronous Boost Converter
OUTPUT CURRENT (mA)
3429 F01b
3429fa
1
LTC3429/LTC3429B
W W U W
U W
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ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
VIN Voltage .............................................. –0.3V to 4.4V
SW Voltage ................................................. –0.3V to 6V
SHDN, FB Voltage ....................................... –0.3V to 6V
VOUT ........................................................... –0.3V to 6V
Operating Temperature Range (Note 2) .. –40°C to 85°C
Storage Temperature Range ................... –65°C to 150°
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
NUMBER
SW 1
GND 2
FB 3
6 V
5 V
IN
LTC3429ES6
LTC3429BES6
OUT
4 SHDN
S6 PART MARKING
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
LTH5
LTBMS
TJMAX = 125°C, θJC = 102°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VOUT = 3.3V, unless otherwise specified.
PARAMETER
CONDITIONS
= 1mA, V
MIN
TYP
0.85
0.5
MAX
1
UNITS
V
Minimum Start-Up Voltage
Minimum Operating Voltage
Output Voltage Adjust Range
Feedback Voltage
I
= 0V
OUT
LOAD
SHDN = V (Note 3)
0.65
5
V
IN
(Note 5)
2.5
V
●
1.192
1.230
1
1.268
50
30
1
V
Feedback Input Current
Quiescent Current (Burst Mode Operation)
Quiescent Current (Shutdown)
Quiescent Current (Active)
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch On Resistance
PMOS Switch On Resistance
NMOS Current Limit
V
V
V
= 1.25V
nA
µA
µA
µA
µA
µA
Ω
FB
= 1.4V (Note 4)
20
FB
= 0V, Not Including Switch Leakage, V
= 0V
0.01
380
0.1
SHDN
OUT
Measured on V , Nonswitching
550
5
OUT
V
SW
V
SW
= 5V
= 5V, V
= 0V
0.1
5
OUT
0.35
0.45
850
1.25
40
Ω
600
mA
mA
ns
%
Burst Mode Operation Current Threshold
Current Limit Delay to Output
Max Duty Cycle
L = 4.7µH (LTC3429 Only)
V
FB
= 1.15V
●
●
80
380
1
90
Switching Frequency
500
620
kHz
V
SHDN Input High
SHDN Input Low
0.35
1
V
SHDN Input Current
V
= 5.5V
0.01
2.5
µA
ms
SHDN
Soft-Start Time
SHDN to 90% of V
OUT
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3429ES6/LTC3429BES6 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: Minimum V operation after start-up is only limited by the
battery’s ability to provide the necessary power as it enters a deeply
discharged state.
IN
Note 4: Burst Mode operation I is measured at V . Multiply this value
Q
OUT
by V /V to get the equivalent input (battery) current.
OUT IN
Note 5: For applications where V
> 4.3V, an external Schottky diode is
OUT
required. See the Applications Information.
3429fa
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LTC3429/LTC3429B
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TYPICAL PERFOR A CE CHARACTERISTICS (T = 25°C unless otherwise specified)
A
Single-Cell to 3.3V Efficiency
(LTC3429 Only)
2-Cell to 3.3V Efficiency
(LTC3429 Only)
Efficiency vs Input Voltage
100
90
100
100
100
100
V
= 3.3V
= 50mA
OUT
OUT
V
= 3V
IN
I
90
80
10
1
90
80
10
1
EFFICIENCY
V
IN
= 1.5V
V
= 2.4V
IN
80
70
EFFICIENCY
V
IN
= 1.2V
70
60
0.1
70
60
0.1
V
= 2.4V
IN
V
IN
= 1.2V
V
= 3V
IN
60
50
40
0.01
0.01
V
IN
= 1.5V
POWER LOSS
V
IN
> V
OUT
POWER LOSS
50
40
0.001
50
40
0.001
PMOS LDO
MODE
0.0001
1000
0.0001
1000
0.5
1.5
2.5
3.5
4.5
0.1
1
10
100
0.1
1
10
100
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
3429 G01
3429 G02
3429 G05
Burst Mode Output Current
Threshold vs Input Voltage
(LTC3429 Only)
Li-Ion to 5V Efficiency
(LTC3429 Only)
2-Cell to 5V Efficiency
(LTC3429 Only)
100
100
100
100
35
30
L = 4.7µH
V
= 4.2V
IN
V
= 3V
90
80
10
1
90
80
10
1
IN
EFFICIENCY
V
= 3.6V
IN
EFFICIENCY
25
20
V
= 2.4V
IN
V
= 2.4V
IN
V = 3.3V
OUT
70
60
0.1
70
60
0.1
V
= 3.6V
IN
15
10
5
V
= 3V
IN
V
= 5V
V
= 4.2V
OUT
3.4
IN
0.01
0.01
POWER LOSS
POWER LOSS
50
40
0.001
50
40
0.001
0.0001
1000
0.0001
1000
0
0.1
1
10
100
2.9
3.9 4.4
0.1
1
10
100
0.9 1.4
1.9 2.4
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
3429 G04
3429 G03
3429 G06
Maximum Load Current
Capability at Output 4% Below
Regulation Point
No Load Input Current
Minimum Start-Up Input Voltage
vs Load Current
vs Input Voltage (LTC3429 Only)
1.9
1.7
1.5
1.3
1.1
0.9
0.7
1000
100
10
600
500
400
300
200
100
0
L = 4.7µH
L = 4.7µH
CURRENT
SINK LOAD
V
= 3.3V
V
= 5V
OUT
OUT
RESISTOR
LOAD
V
= 5V
OUT
V
= 3.3V
OUT
3
3.5
0
50
100
150
0.5
1
1.5
2
2.5
4
4.5
0.9 1.4 1.9
INPUT VOLTAGE (V)
4.4
2.4 2.9 3.4
3.9
INPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
3429 G09
3429 G08
3429 G07
3429fa
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LTC3429/LTC3429B
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TYPICAL PERFOR A CE CHARACTERISTICS (T = 25°C unless otherwise specified)
A
Normalized Oscillator Frequency
vs Temperature
Burst Mode Quiescent Current
vs Temperature (LTC3429 Only)
Output Voltage vs Temperature
3.44
3.40
3.36
3.32
3.28
3.24
3.20
3.16
1.02
1.00
40
35
30
25
20
15
10
5
V
OUT
= 1.5V
IN
I
= 30mA
V
= 5V
OUT
0.98
V
OUT
= 3.3V
0.96
0.94
0.92
0
–29
0
20 40
100
–60 –40 –20
0
40
80 100
20 40
TEMPERATURE (°C)
–60 –40
60 80
20
60
–60 –40 –20
0
60 80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
3429 G10
3429 G11
3429 G12
SW Pin Discontinuous Mode
Antiringing Operation
Fixed Frequency and Burst Mode
Operation (LTC3429 Only)
SW Pin Fixed Frequency
Continuous Mode Operation
V
OUT
V
V
SW
1V/DIV
SW
1V/DIV
100mV/DIV
AC-COUPLED
50mA
I
OUT
120µA
3429 G14
3429 G15
3429 G13
V
V
I
= 1.5V
200ns/DIV
V
V
I
= 1.5V
5ms/DIV
V
V
I
= 1.5V
200ns/DIV
IN
OUT
IN
OUT
= 120µA TO 50mA STEP
IN
OUT
= 3.3V
= 3.3V
= 3.3V
= 20mA
= 50mA
OUT
OUT
L = 10µH
= 10µF
OUT
= 150pF
PL
OUT
L = 10µH
L = 10µH
C
C
= 10µF
C
C
C
C
= 10µF
OUT
= 150pF
OUT
= 150pF
PL
PL
Inrush Current Control
and Soft-Start
Inrush Current Control
and Soft-Start
Output Voltage Transient
Response
V
OUT
V
OUT
2V/DIV
1V/DIV
V
OUT
100mV/DIV
AC-COUPLED
INDUCTOR
CURRENT
100mA/DIV
INDUCTOR
CURRENT
200mA/DIV
90mA
I
OUT
40mA
3429 G16
3429 G17
3429 G18
V
V
I
= 1.5V
100µs/DIV
V
V
I
= 1.5V
500µs/DIV
V
V
I
= 2.5V
= 5V
OUT
L = 4.7µH
= 10µF
OUT
= 100pF
PL
2ms/DIV
IN
OUT
IN
OUT
IN
OUT
= 3.3V
= 40mA TO 90mA STEP
= 3.3V
= 10mA
= 50mA
OUT
OUT
L = 10µH
L = 4.7µH
C
C
= 10µF
C
C
= 10µF
C
C
OUT
OUT
PL
= 150pF
= 100pF
PL
3429fa
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LTC3429/LTC3429B
U
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PI FU CTIO S
SW (Pin 1): Switch Pin. Connect inductor between SW
and VIN. Keep these PCB trace lengths as short and wide
as possible to reduce EMI and voltage overshoot. If the
inductor current falls to zero, or SHDN is low, an internal
150Ω antiringing switch is connected from SW to VIN to
minimize EMI.
SHDN = Low: Shutdown, quiescent current <1µA.
Outputcapacitorcanbecompletelydischargedthrough
the load or feedback resistors. A 150Ω resistor is
internally connected between SW and VIN.
V
OUT (Pin 5): Output Voltage Sense Input and Drain of the
Internal Synchronous Rectifier MOSFET. Bias is derived
from VOUT. PCB trace length from VOUT to the output filter
capacitor(s)shouldbeasshortandwideaspossible.VOUT
is completely disconnected from VIN when SHDN is low
due to the output disconnect feature.
GND (Pin 2): Signal and Power Ground. Provide a short
directPCBpathbetweenGNDandthe(–)sideoftheoutput
capacitor(s).
FB (Pin 3): Feedback Input to the gm Error Amplifier.
Connect resistor divider tap to this pin. The output voltage
can be adjusted from 2.5V to 5V by:
VIN (Pin 6): Battery Input Voltage. The device gets its
start-up bias from VIN. Once VOUT exceeds VIN, bias
comes from VOUT. Thus, once started, operation is com-
pletelyindependentfromVIN.Operationisonlylimitedby
the output power level and the battery’s internal series
resistance.
VOUT = 1.23V • [1 + (R1/R2)]
SHDN (Pin 4): Logic Controlled Shutdown Input.
SHDN = High: Normal free running operation, 500kHz
typical operating frequency.
W
BLOCK DIAGRA
L1
+
V
IN
SW
1
6
C
1V TO 4.4V
IN
+
–
V
OUT
V
IN
GOOD
2.3V
WELL
START-UP
OSC
A/B
MUX
A
B
SWITCH
V
OUT
5
2.5V TO 5V
0.45Ω
0.35Ω
SYNC
DRIVE
CONTROL
PWM
CONTROL
C
PL
RAMP
GEN
500kHz
R1
CURRENT
SENSE
(OPTIONAL)
Σ
SLOPE
COMP
PWM
COMPARATOR
+
–
–
FB
3
–
+
C
OUT
g
m
ERROR
AMP
1.23V
REF
R
C
80k
C
P2
2.5pF
Burst Mode
OPERATION
CONTROL
C
C
SLEEP
R2
150pF
SHDN
4
2
GND
SHUTDOWN
CONTROL
SHUTDOWN
3429 BD
3429fa
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LTC3429/LTC3429B
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OPERATIO
The LTC3429/LTC3429B are 500kHz, synchronous boost
converters housed in a 6-lead SOT-23 package. Able to
operate from an input voltage below 1V, the device fea-
tures fixed frequency, current mode PWM control for
exceptional line and load regulation. Low RDS(ON) internal
MOSFET switches enable the device to maintain high
efficiency over a wide range of load current. Detailed
descriptions of the different operating modes follow.
OperationcanbebestunderstoodbyreferringtotheBlock
Diagram.
LOW NOISE FIXED FREQUENCY OPERATION
Oscillator
The frequency of operation is internally set to 500kHz.
Error Amp
Theerroramplifierisaninternallycompensatedtranscon-
ductance type (current output) with a transconductance
(gm) = 33 microsiemens. The internal 1.23V reference
voltageiscomparedtothevoltageattheFBpintogenerate
an error signal at the output of the error amplifier. A volt-
age divider from VOUT to ground programs the output
voltage via FB from 2.5V to 5V using the equation:
LOW VOLTAGE START-UP
The LTC3429/LTC3429B include an independent start-up
oscillator designed to start up at input voltages of 0.85V
typically. The frequency and duty cycle of the start-up
oscillator are internally set to 150kHz and 67% respec-
tively. In this mode, the IC operates completely open-loop
and the current limit is also set internally to 850mA. Once
the output voltage exceeds 2.3V, the start-up circuitry is
disabled and normal close-loop PWM operation is initi-
ated. In normal mode, the LTC3429/LTC3429B power
themselves from VOUT instead of VIN. This allows the
battery voltage to drop to as low as 0.5V without affecting
the circuit operation. The only limiting factor in the appli-
cation becomes the ability of the battery to supply suffi-
cient energy to the output. Soft-start and inrush current
limiting are provided during start-up as well as normal
mode operation.
VOUT = 1.23V • [1 + (R1/R2)]
Current Sensing
Lossless current sensing converts the NMOS switch
current signal to a voltage to be summed with the internal
slope compensation. The summed signal is compared to
the error amplifier output to provide a peak current
control command for the PWM. Peak switch current is
limited to approximately 850mA independent of input or
output voltage. The switch current signal is blanked for
60ns to enhance noise rejection.
Zero Current Comparator
The zero current comparator monitors the inductor cur-
rent to the output and shuts off the synchronous rectifier
once this current reduces to approximately 27mA. This
prevents the inductor current from reversing in polarity
thereby improving efficiency at light loads.
Soft-Start
TheLTC3429/LTC3429Bprovidesoft-startbychargingan
internal capacitor with a very weak current source. The
voltage on this capacitor, in turn, slowly ramps the peak
inductor current from zero to a maximum value of 850mA.
The soft-start time is typically 2.5ms, the time it takes to
charge the capacitor from zero to 1.35V. However, this
time varies greatly with load current, output voltage and
input voltage (see Typical Performance Characteristics,
Inrush Current Control and Soft-Start). The soft-start
capacitor is discharged completely in the event of a
commanded shutdown or a thermal shutdown. It is dis-
charged only partially in case of a short circuit at the
output.
Antiringing Control
The antiringing control circuitry prevents high frequency
ringing of the SW pin as the inductor current goes to zero
in discontinuous mode. The damping of the resonant
circuit formed by L and CSW (capacitance on SW pin) is
achieved by placing a 150Ω resistor across the inductor.
Synchronous Rectifier
To prevent the inductor current from running away, the
PMOS synchronous rectifier is only enabled when VOUT
(VIN + 0.1V) and the FB pin is >0.8V.
>
3429fa
6
LTC3429/LTC3429B
U
OPERATIO
Thermal Shutdown
Diagram). However, this may adversely affect the effi-
ciency and the quiescent current requirement at light
loads. Typical values of CPL range from 15pF to 220pF.
An internal temperature monitor will start to reduce the
peak current limit if the die temperature exceeds 125°C. If
the die temperature continues to rise and reaches 160°C,
the part will go into thermal shutdown, all switches will be
turned off and the soft-start capacitor will be reset. The
part will be enabled again when the die temperature drops
by about 15°C.
OUTPUT DISCONNECT AND INRUSH LIMITING
TheLTC3429/LTC3429Baredesignedtoallowtrueoutput
disconnect by eliminating body diode conduction of the
internal PMOS rectifier. This allows VOUT to go to zero
volts during shutdown, drawing zero current from the
input source. It also allows for inrush current limiting at
start-up, minimizing surge currents seen by the input
supply.Notethattoobtaintheadvantageofoutputdiscon-
nect, there must not be an external Schottky diode con-
Burst Mode OPERATION (LTC3429 Only)
Portable devices frequently spend extended time in low
power or standby mode, only switching to high power
consumption when specific functions are enabled. To
improve battery life in these types of products, it is
important to maintain a high power conversion efficiency
over a wide output power range. The LTC3429 provides
automatic Burst Mode operation to increase efficiency of
the power converter at light loads. Burst Mode operation
is initiated if the output load current falls below an inter-
nally programmed threshold. This threshold has an in-
verse dependence on the duty cycle of the converter and
also the value of the external inductor (See Typical Perfor-
manceCharacteristics,OutputCurrentBurstModeThresh-
old vs VIN). Once Burst Mode operation is initiated, only
the circuitry required to monitor the output is kept alive
and the rest of the device is turned off. This is referred to
as the sleep state in which the IC consumes only 20µA
fromtheoutputcapacitor.Whentheoutputvoltagedroops
byabout1%fromitsnominalvalue, thepartwakesupand
commencesnormalPWMoperation.Theoutputcapacitor
recharges and causes the part to re-enter the sleep state
if the output load remains less than the Burst Mode
threshold. The frequency of this intermittent PWM or
burst operation depends on the load current; that is, as the
load current drops further below the burst threshold, the
LTC3429 turns on less frequently. When the load current
increases above the burst threshold, the LTC3429
seamlessly resumes continuous PWM operation. Thus,
Burst Mode operation maximizes the efficiency at very
light loads by minimizing switching and quiescent losses.
However, theoutputrippletypicallyincreasestoabout2%
peak-to-peak. Burst Mode ripple can be reduced, in some
circumstances, by placing a small phase-lead capacitor
(CPL) between VOUT and FB pins (refer to the Block
nected between the SWITCH pin and VOUT
.
Board layout is extremely critical to minimize voltage
overshoot on the SWITCH pin due to stray inductance.
Keep the output filter capacitor as close as possible to the
VOUT pin and use very low ESR/ESL ceramic capacitors
tied to a good ground plane. For applications with VOUT
over 4.3V, a Schottky diode is required to limit the peak
SWITCH voltage to less than 6V unless some form of
external snubbing is employed. This diode must also be
placed very close to the pins to minimize stray inductance.
See the Applications Information.
SHORT CIRCUIT PROTECTION
Unlike most boost converters, the LTC3429/LTC3429B
allowtheiroutputtobeshortcircuitedduetotheoutputdis-
connect feature. The devices incorporate internal features
suchascurrentlimitfoldback,thermalregulationandther-
mal shutdown for protection from an excessive overload
or short circuit. In the event of a short circuit, the internal
soft-startcapacitorgetspartiallydischarged. This, inturn,
causes the maximum current limit to foldback to a smaller
value. Inadditiontothis, athermalregulationcircuitstarts
to dial back the current limit farther if the die temperature
rises above 125°C. If the die temperature still reaches
160°C, the device shuts off entirely.
VIN > VOUT OPERATION
The LTC3429/LTC3429B will maintain voltage regulation
even if the input voltage is above the output voltage. This
3429fa
7
LTC3429/LTC3429B
U
OPERATIO
is achieved by terminating the switching of the synchro- mode, there will be more power dissipation within the IC.
nous PMOS and applying VIN statically on its gate. This This will cause a sharp drop in the efficiency (see Typical
ensures that the slope of the inductor current will reverse PerformanceCharacteristics,EfficiencyvsVIN).Themaxi-
during the time current is flowing to the output. Since the mum output current should be limited in order to maintain
PMOS no longer acts as a low impedance switch in this an acceptable junction temperature.
W U U
APPLICATIO S I FOR ATIO
U
PCB LAYOUT GUIDELINES
inductor ripple current. Increasing the inductance above
10µH will increase size while providing little improvement
in output current capability.
The high speed operation of the LTC3429/LTC3429B
demandscarefulattentiontoboardlayout. Youwillnotget
advertised performance with careless layout. Figure 2
shows the recommended component placement. A large
groundpincopperareawillhelptolowerthechiptempera-
ture. A multilayer board with a separate ground plane is
ideal, but not absolutely necessary.
The approximate output current capability of the LTC3429
versusinductancevalueisgivenintheequationbelowand
illustrated graphically in Figure 3.
V •D
f •L • 2
⎛
⎝
⎞
⎟
⎠
IN
IOUT(MAX) = η • I –
• 1–D
(
)
⎜
P
where:
η = estimated efficiency
IP = peak current limit value (0.6A)
VIN = input (battery) voltage
1
2
3
SW
V
6
5
4
IN
V
IN
GND V
OUT
D = steady-state duty ratio = (VOUT – VIN)/VOUT
f = switching frequency (500kHz typical)
L = inductance value
FB SHDN
SHDN
V
OUT
3429 F02
200
V
= 1.2V
IN
RECOMMENDED COMPONENT PLACEMENT. TRACES
CARRYING HIGH CURRENT ARE DIRECT. TRACE AREA AT
FB PIN IS SMALL. LEAD LENGTH TO BATTERY IS SHORT
180
160
140
120
100
80
V
V
= 3.3V
= 5V
OUT
OUT
Figure 2. Recommended Component Placement
for Single Layer Board
COMPONENT SELECTION
60
40
Inductor Selection
20
0
The LTC3429/LTC3429B can utilize small surface mount
and chip inductors due to its fast 500kHz switching
frequency. Typically, a 4.7µH inductor is recommended
for most applications. Larger values of inductance will
allow greater output current capability by reducing the
3
5
7
9
11 13 15 17 19 21 23
INDUCTANCE (µH)
3429 F03
Figure 3. Maximum Output Current vs
Inductance Based on 90% Efficiency
3429fa
8
LTC3429/LTC3429B
W U U
APPLICATIO S I FOR ATIO
U
Theinductorcurrentrippleistypicallysetfor20%to40%
of the maximum inductor current (IP). High frequency
ferrite core inductor materials reduce frequency
dependent power losses compared to cheaper powdered
irontypes, improvingefficiency. Theinductorshouldhave
low ESR (series resistance of the windings) to reduce the
I2R power losses, and must be able to handle the peak
inductor current without saturating. Molded chokes and
some chip inductors usually do not have enough core to
support the peak inductor currents of 850mA seen on the
LTC3429/LTC3429B. To minimize radiated noise, use a
toroid, pot core or shielded bobbin inductor. See Table 1
for some suggested components and suppliers.
Output and Input Capacitor Selection
LowESR(equivalentseriesresistance)capacitorsshould
be used to minimize the output voltage ripple. Multilayer
ceramic capacitors are an excellent choice as they have
extremely low ESR and are available in small footprints. A
4.7µF to 15µF output capacitor is sufficient for most
applications. Larger values up to 22µF may be used to
obtain extremely low output voltage ripple and improve
transient response. An additional phase lead capacitor
may be required with output capacitors larger than 10µF
to maintain acceptable phase margin. X5R and X7R
dielectric materials are preferred for their ability to main-
taincapacitanceoverwidevoltageandtemperatureranges.
Table 1. Recommended Inductors
MAX
Low ESR input capacitors reduce input switching noise
and reduce the peak current drawn from the battery. It
follows that ceramic capacitors are also a good choice for
input decoupling and should be located as close as pos-
sible to the device. A 10µF input capacitor is sufficient for
virtually any application. Larger values may be used with-
out limitations. Table 2 shows a list of several ceramic
capacitor manufacturers. Consult the manufacturers di-
rectly for detailed information on their entire selection of
ceramic capacitors.
L
(µH)
DCR
mΩ
HEIGHT
(mm)
PART
VENDOR
CDRH5D18-4R1
CDRH5D18-100
CDRH3D16-4R7
CDRH3D16-6R8
CR43-4R7
CR43-100
CMD4D06-4R7MC
CMD4D06-3R3MC
4.1
10
4.7
57
2.0
2.0
1.8
1.8
3.5
3.5
0.8
0.8
Sumida
www.sumida.com
124
105
170
109
182
216
174
4.7
10
4.7
3.3
DS1608-472
DS1608-103
DO1608C-472
4.7
10
4.7
60
75
90
2.9
2.9
2.9
Coilcraft
www.coilcraft.com
Table 2. Capacitor Vendor Information
SUPPLIER
AVX
WEBSITE
www.avxcorp.com
www.murata.com
www.t-yuden.com
D52LC-4R7M
D52LC-100M
4.7
10
84
137
2.0
2.0
Toko
www.tokoam.com
Murata
LQH32CN4R7M24
4.7
195
2.2
Murata
www.murata.com
Taiyo Yuden
3429fa
9
LTC3429/LTC3429B
U
TYPICAL APPLICATIO S
Applications Where VOUT > 4.3V
improvement but will negate the output disconnect fea-
ture. If output disconnect is required, an active snubber
networkissuggestedasshownbelow.ExamplesofSchot-
tky diodes are: MBR0520L, PMEG2010EA, 1N5817 or
equivalent.
When the output voltage is programmed above 4.3V, it is
necessarytoaddaSchottkydiodeeitherfromSWtoVOUT
or to add a snubber network in order to maintain an
acceptablepeakvoltageontheSWpin.TheSchottkydiode
between SW and VOUT will provide a peak efficiency
,
Application Circuit for VOUT > 4.3V Where Inrush Current Limiting and Output Disconnect are Required
L1
Li-Ion to 5V Efficiency
D1*
4.7µH
V
100
100
IN
2.7V TO 4.2V
C3*
0.22µF
1
V
= 4.2V
IN
+
C1
4.7µF
MP1
Li-Ion
SW
V
90
80
10
1
OUT
6
5
3
5V
V
V
OUT
IN
EFFICIENCY
V
= 3.6V
IN
250mA
R1
1.82M
LTC3429
SHDN FB
GND
4
C2
10µF
OFF
ON
R2
604k
70
60
0.1
V
= 3.6V
IN
2
V
= 4.2V
IN
3429 TA04
0.01
*LOCATE COMPONENTS CLOSE TO THE PIN
C1: TAIYO YUDEN X5R JMK212BJ475MM
C2: TAIYO YUDEN X5R JMK212BJ106MM
D1: MOTOROLA MBR0520L
POWER LOSS
50
40
0.001
0.0001
1000
L1: COILCRAFT D0160C-472
0.1
1
10
100
MP1: ZETEX ZXM61P02F
OUTPUT CURRENT (mA)
3429 TA04b
Application Circuit for VOUT > 4.3V Where Inrush Current Limiting and Output Disconnect are Not Required
L1
4.7µH
2-Cell to 5V Efficiency
D1*
100
100
V
IN
+
1
C1
2 AA
CELL
SW
4.7µF
V
= 3V
IN
V
90
80
10
1
OUT
6
5
3
V
V
5V
IN
LTC3429
SHDN FB
GND
OUT
150mA
EFFICIENCY
R1
V
= 2.4V
IN
1.82M
4
C2
OFF
ON
10µF
V
= 2.4V
IN
70
60
0.1
R2
604k
2
V
= 3V
IN
0.01
3429 TA05
POWER LOSS
*LOCATE COMPONENTS CLOSE TO THE PIN
C1: TAIYO YUDEN X5R JMK212BJ475MM
C2: TAIYO YUDEN X5R JMK212BJ106MM
D1: MOTOROLA MBR0520L
50
40
0.001
0.0001
1000
L1: COILCRAFT D0160C-472
0.1
1
10
100
OUTPUT CURRENT (mA)
3429 TA05b
3429fa
10
LTC3429/LTC3429B
U
PACKAGE DESCRIPTIO
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
2.90 BSC
(NOTE 4)
0.62
MAX
0.95
REF
1.22 REF
1.4 MIN
1.50 – 1.75
2.80 BSC
3.85 MAX 2.62 REF
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45
6 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
DATUM ‘A’
0.01 – 0.10
1.00 MAX
0.30 – 0.50 REF
1.90 BSC
0.09 – 0.20
(NOTE 3)
S6 TSOT-23 0302
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
3429fa
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.
11
LTC3429/LTC3429B
U
TYPICAL APPLICATIO
Single AA Cell to 2.5V Synchronous Boost Converter
Single AA Cell to 3.3V
L1
4.7µH
L1
4.7µH
1
1
+
+
SINGLE
AA CELL
SINGLE
C1
C1
4.7µF
AA CELL
SW
SW
4.7µF
V
V
OUT
OUT
6
4
5
3
6
4
5
3
3.3V
2.5V
V
V
V
IN
V
OUT
IN
LTC3429
SHDN FB
GND
OUT
100mA
130mA
R1
R1
LTC3429
SHDN FB
GND
1.02M
1.02M
C2
C2
10µF
OFF
ON
OFF
ON
10µF
R2
604k
R2
1.02M
2
2
3429 TA03
3429 TA06
C1: TAIYO YUDEN X5R JMK212BJ475MM
C2: TAIYO YUDEN X5R JMK212BJ106MM
L1: COILCRAFT D0160C-472
C1: TAIYO YUDEN X5R JMK212BJ475MM
C2: TAIYO YUDEN X5R JMK212BJ106MM
L1: COILCRAFT D0160C-472
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DESCRIPTION
COMMENTS
LT1613
550mA (I ), 1.4MHz High Efficiency Step-Up DC/DC
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90% Efficiency, V : 0.9V to 10V, V
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1.5A (I ), 1.25MHz High Efficiency Step-Up DC/DC
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MS8E
LTC3400/LTC3400B 600mA (I ), 1.2MHz, Synchronous Step-Up
92% Efficiency, V : 0.85V to 5V, V
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OUT(MAX) Q
SW
IN
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I
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LTC3401/LTC3402
LTC3421
1A/2A (I ), 3MHz, Synchronous Step-Up
DC/DC Converters
97% Efficiency, V : 0.5V to 5V, V
MS10
= 5.5V, I = 38µA, I < 1µA,
OUT(MAX) Q SD
SW
IN
3A (I ), 3MHz, Synchronous Step-Up DC/DC
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 12µA,
Q
SW
IN
OUT(MAX)
OUT(MAX)
Converter with Output Disconnect
I
< 1µA, QFN24
SD
LTC3425
5A (I ), 8MHz, 4-Phase Synchronous Step-Up DC/DC 95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 12µA,
Q
SW
IN
Converter with Output Disconnect
I
< 1µA, QFN32
SD
LT3464
85mA (I ), High Efficiency Step-Up DC/DC Converter V : 2.3V to 10V, V
with Integrated Schottky and PNP Disconnect
= 34V, I = 25µA, I < 1µA, ThinSOT
OUT(MAX) Q SD
SW
IN
No R
is a trademark of Linear Technology Corporation.
SENSE
3429fa
LT/TP 1104 1K REV A • PRINTED IN USA
12 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
©LINEAR TECHNOLOGY CORPORATION 2004
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