LTC3429/LTC3429B
600mA, 500kHz Micropower
Synchronous Boost Converter
with Output Disconnect
FEATURES
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DESCRIPTIO
Up to 96% Efficiency
True Output Load Disconnect
Inrush Current Limiting and Internal Soft-Start
Low Voltage Start-Up: 0.85V
Automatic Burst Mode
®
Operation with I
Q
~ 20µA
Continuous Switching at Light Loads (LTC3429B)
Internal Synchronous Rectifier
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
The LTC
®
3429/LTC3429B are high efficiency synchro-
nous, fixed frequency, step-up DC/DC converters with true
output load disconnect, inrush current limiting and soft-
start in a low profile 6-lead ThinSOT
TM
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.
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
count thereby saving critical board real estate. The LTC3429
shifts automatically to power saving Burst Mode operation
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.
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
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MP3 Players
Digital Cameras
LCD Bias Supplies
Handheld Instruments
Wireless Handsets
GPS Receivers
TYPICAL APPLICATIO
4.7µH
100
V
IN
= 3V
90
V
OUT
3.3V
250mA
10µF
604k
EFFICIENCY (%)
+
EFFICIENCY
V
IN
= 2.4V
2-CELL
AA
4.7µF
V
IN
SW
V
OUT
1.02M
80
70
60
50
LTC3429
OFF ON
SHDN
GND
FB
3429 F01a
Figure 1. 2-Cell to 3.3V Synchronous Boost Converter
40
0.1
U
2-Cell to 3.3V Efficiency
100
10
POWER LOSS (W)
U
U
1
0.1
V
IN
= 3V
0.01
V
IN
= 2.4V
POWER LOSS
0.001
0.0001
1000
3429 F01b
1
10
100
OUTPUT CURRENT (mA)
3429fa
1
LTC3429/LTC3429B
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SW 1
GND 2
FB 3
6 V
IN
5 V
OUT
4 SHDN
V
IN
Voltage .............................................. – 0.3V to 4.4V
SW Voltage ................................................. – 0.3V to 6V
SHDN, FB Voltage ....................................... – 0.3V to 6V
V
OUT
........................................................... – 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
ORDER PART
NUMBER
LTC3429ES6
LTC3429BES6
S6 PART MARKING
LTH5
LTBMS
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JC
= 102°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Start-Up Voltage
Minimum Operating Voltage
Output Voltage Adjust Range
Feedback Voltage
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
Burst Mode Operation Current Threshold
Current Limit Delay to Output
Max Duty Cycle
Switching Frequency
SHDN Input High
SHDN Input Low
SHDN Input Current
Soft-Start Time
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 1.2V, V
OUT
= 3.3V, unless otherwise specified.
CONDITIONS
I
LOAD
= 1mA, V
OUT
= 0V
SHDN = V
IN
(Note 3)
(Note 5)
●
MIN
TYP
0.85
0.5
MAX
1
0.65
5
1.268
50
30
1
550
5
5
UNITS
V
V
V
V
nA
µA
µA
µA
µA
µA
Ω
Ω
mA
mA
ns
%
2.5
1.192
1.230
1
20
0.01
380
0.1
0.1
0.35
0.45
600
850
1.25
40
●
●
V
FB
= 1.25V
V
FB
= 1.4V (Note 4)
V
SHDN
= 0V, Not Including Switch Leakage, V
OUT
= 0V
Measured on V
OUT
, Nonswitching
V
SW
= 5V
V
SW
= 5V, V
OUT
= 0V
L = 4.7µH (LTC3429 Only)
V
FB
= 1.15V
80
380
1
90
500
620
0.35
V
SHDN
= 5.5V
SHDN to 90% of V
OUT
0.01
2.5
1
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
IN
operation after start-up is only limited by the
battery’s ability to provide the necessary power as it enters a deeply
discharged state.
Note 4:
Burst Mode operation I
Q
is measured at V
OUT
. Multiply this value
by V
OUT
/V
IN
to get the equivalent input (battery) current.
Note 5:
For applications where V
OUT
> 4.3V, an external Schottky diode is
required. See the Applications Information.
2
U
kHz
V
V
µA
ms
3429fa
W
U
U
W W
W
LTC3429/LTC3429B
TYPICAL PERFOR A CE CHARACTERISTICS
(T
A
= 25°C unless otherwise specified)
Single-Cell to 3.3V Efficiency
(LTC3429 Only)
100
90
100
10
100
V
IN
= 3V
V
IN
= 1.5V
EFFICIENCY
V
IN
= 1.2V
70
60
V
IN
= 1.5V
POWER LOSS
50
40
0.1
POWER LOSS
0.001
0.0001
1000
3429 G01
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
80
V
IN
= 1.2V
1
10
100
OUTPUT CURRENT (mA)
2-Cell to 5V Efficiency
(LTC3429 Only)
100
90
V
IN
= 3V
EFFICIENCY
V
IN
= 2.4V
V
IN
= 2.4V
V
IN
= 3V
60
POWER LOSS
50
40
0.1
0.001
0.0001
1000
3429 G03
V
IN
= 3.6V
OUTPUT CURRENT (mA)
EFFICIENCY (%)
EFFICIENCY (%)
80
70
1
10
100
OUTPUT CURRENT (mA)
No Load Input Current
vs Input Voltage (LTC3429 Only)
1000
L = 4.7µH
OUTPUT CURRENT (mA)
INPUT CURRENT (µA)
400
V
OUT
= 3.3V
300
V
OUT
= 5V
200
100
INPUT VOLTAGE (V)
V
OUT
= 5V
100
V
OUT
= 3.3V
10
0.9
1.4
1.9 2.4 2.9 3.4
INPUT VOLTAGE (V)
U W
1
2-Cell to 3.3V Efficiency
(LTC3429 Only)
100
EFFICIENCY
V
IN
= 2.4V
10
100
90
Efficiency vs Input Voltage
V
OUT
= 3.3V
I
OUT
= 50mA
90
POWER LOSS (W)
POWER LOSS (W)
80
70
60
50
40
0.1
1
0.1
V
IN
= 3V
0.01
80
70
60
50
40
0.5
1.5
2.5
3.5
INPUT VOLTAGE (V)
4.5
3429 G05
0.1
0.01
V
IN
= 2.4V
0.001
0.0001
1000
3429 G02
V
IN
> V
OUT
PMOS LDO
MODE
1
10
100
OUTPUT CURRENT (mA)
Li-Ion to 5V Efficiency
(LTC3429 Only)
100
10
100
V
IN
= 4.2V
90
EFFICIENCY
10
100
Burst Mode Output Current
Threshold vs Input Voltage
(LTC3429 Only)
35
30
25
20
V
OUT
= 3.3V
15
V
OUT
= 5V
10
5
0
0.9
L = 4.7µH
POWER LOSS (W)
POWER LOSS (W)
1
0.1
0.01
80
70
60
50
40
0.1
1
0.1
V
IN
= 4.2V
POWER LOSS
0.01
V
IN
= 3.6V
0.001
0.0001
1000
3429 G04
1
10
100
OUTPUT CURRENT (mA)
1.4
3.4
1.9 2.4 2.9
INPUT VOLTAGE (V)
3.9
4.4
3429 G06
Maximum Load Current
Capability at Output 4% Below
Regulation Point
600
500
L = 4.7µH
1.9
1.7
1.5
1.3
1.1
0.9
0.7
Minimum Start-Up Input Voltage
vs Load Current
CURRENT
SINK LOAD
RESISTOR
LOAD
3.9
4.4
0
0.5
1
3 3.5
1.5 2 2.5
INPUT VOLTAGE (V)
4
4.5
0
50
100
OUTPUT CURRENT (mA)
150
3429 G09
3429 G07
3429 G08
3429fa
3
LTC3429/LTC3429B
TYPICAL PERFOR A CE CHARACTERISTICS
(T
A
= 25°C unless otherwise specified)
Output Voltage vs Temperature
3.44
3.40
3.36
V
IN
= 1.5V
I
OUT
= 30mA
NORMALIZED FREQUECY
QUIESCENT CURRENT (µA)
V
OUT
(V)
3.32
3.28
3.24
3.20
3.16
20 40 60
–60 –40 –29 0
TEMPERATURE (°C)
SW Pin Fixed Frequency
Continuous Mode Operation
V
SW
1V/DIV
V
IN
= 1.5V
V
OUT
= 3.3V
I
OUT
= 50mA
L = 10µH
C
OUT
= 10µF
C
PL
= 150pF
200ns/DIV
Output Voltage Transient
Response
V
OUT
100mV/DIV
AC-COUPLED
90mA
I
OUT
40mA
V
IN
= 1.5V
100µs/DIV
V
OUT
= 3.3V
I
OUT
= 40mA TO 90mA STEP
L = 10µH
C
OUT
= 10µF
C
PL
= 150pF
3429 G16
4
U W
80
3429 G10
Normalized Oscillator Frequency
vs Temperature
1.02
40
35
Burst Mode Quiescent Current
vs Temperature (LTC3429 Only)
1.00
V
OUT
= 5V
30
25
20
15
10
5
V
OUT
= 3.3V
0.98
0.96
0.94
100
0.92
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
80
100
0
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
80
100
3429 G11
3429 G12
SW Pin Discontinuous Mode
Antiringing Operation
Fixed Frequency and Burst Mode
Operation (LTC3429 Only)
V
SW
1V/DIV
V
OUT
100mV/DIV
AC-COUPLED
50mA
I
OUT
120µA
3429 G13
V
IN
= 1.5V
V
OUT
= 3.3V
I
OUT
= 20mA
L = 10µH
C
OUT
= 10µF
C
PL
= 150pF
200ns/DIV
3429 G14
V
IN
= 1.5V
5ms/DIV
V
OUT
= 3.3V
I
OUT
= 120µA TO 50mA STEP
L = 10µH
C
OUT
= 10µF
C
PL
= 150pF
3429 G15
Inrush Current Control
and Soft-Start
Inrush Current Control
and Soft-Start
V
OUT
1V/DIV
V
OUT
2V/DIV
INDUCTOR
CURRENT
100mA/DIV
INDUCTOR
CURRENT
200mA/DIV
V
IN
= 1.5V
V
OUT
= 3.3V
I
OUT
= 10mA
L = 4.7µH
C
OUT
= 10µF
C
PL
= 100pF
500µs/DIV
3429 G17
V
IN
= 2.5V
V
OUT
= 5V
I
OUT
= 50mA
L = 4.7µH
C
OUT
= 10µF
C
PL
= 100pF
2ms/DIV
3429 G18
3429fa
LTC3429/LTC3429B
PI FU CTIO S
SW (Pin 1):
Switch Pin. Connect inductor between SW
and V
IN
. 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 V
IN
to
minimize EMI.
GND (Pin 2):
Signal and Power Ground. Provide a short
direct PCB path between GND and the (–) side of the output
capacitor(s).
FB (Pin 3):
Feedback Input to the
g
m
Error Amplifier.
Connect resistor divider tap to this pin. The output voltage
can be adjusted from 2.5V to 5V by:
V
OUT
= 1.23V • [1 + (R1/R2)]
SHDN (Pin 4):
Logic Controlled Shutdown Input.
SHDN = High: Normal free running operation, 500kHz
typical operating frequency.
SHDN = Low: Shutdown, quiescent current < 1µA.
Output capacitor can be completely discharged through
the load or feedback resistors. A 150Ω resistor is
internally connected between SW and V
IN
.
V
OUT
(Pin 5):
Output Voltage Sense Input and Drain of the
Internal Synchronous Rectifier MOSFET. Bias is derived
from V
OUT
. PCB trace length from V
OUT
to the output filter
capacitor(s) should be as short and wide as possible. V
OUT
is completely disconnected from V
IN
when SHDN is low
due to the output disconnect feature.
V
IN
(Pin 6):
Battery Input Voltage. The device gets its
start-up bias from V
IN
. Once V
OUT
exceeds V
IN
, bias
comes from V
OUT
. Thus, once started, operation is com-
pletely independent from V
IN
. Operation is only limited by
the output power level and the battery’s internal series
resistance.
BLOCK DIAGRA
+
1V TO 4.4V
6
V
IN
V
OUT
GOOD
START-UP
OSC
A
B
A/B
MUX
PWM
CONTROL
RAMP
GEN
500kHz
PWM
COMPARATOR
SYNC
DRIVE
CONTROL
SLOPE
COMP
Σ
SLEEP
Burst Mode
OPERATION
CONTROL
C
C
150pF
C
P2
2.5pF
SHDN
4
SHUTDOWN
CONTROL
SHUTDOWN
2
GND
3429 BD
+
R
C
80k
g
m
ERROR
AMP
–
–
+
–
–
+
W
U
U
U
L1
C
IN
1
SW
V
IN
2.3V
0.45Ω
WELL
SWITCH
V
OUT
5
2.5V TO 5V
0.35Ω
C
PL
(OPTIONAL)
R1
CURRENT
SENSE
FB
3
1.23V
REF
R2
C
OUT
3429fa
5
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