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PDF LTC3429 Data sheet ( Hoja de datos )
| Número de pieza | LTC3429 | |
| Descripción | 500kHz Micropower Synchronous Boost Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3429ww/wL.DTatCaSh3eet44U2.co9mB
600mA, 500kHz Micropower
Synchronous Boost Converter
with Output Disconnect
FEATURES
■ 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 IQ ~ 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
U
APPLICATIO S
■ MP3 Players
■ Digital Cameras
■ LCD Bias Supplies
■ Handheld Instruments
■ Wireless Handsets
■ GPS Receivers
DESCRIPTIO
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 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.
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.
TYPICAL APPLICATIO
+
2-CELL
AA
4.7µH
4.7µF
OFF ON
SW
VIN VOUT
LTC3429
SHDN FB
GND
1.02M
604k
VOUT
3.3V
250mA
10µF
3429 F01a
Figure 1. 2-Cell to 3.3V Synchronous Boost Converter
2-Cell to 3.3V Efficiency
100
VIN = 3V
90 EFFICIENCY
VIN = 2.4V
80
100
10
1
70
60
50
40
0.1
VIN = 2.4V
0.1
VIN = 3V 0.01
POWER LOSS
0.001
1 10 100
OUTPUT CURRENT (mA)
0.0001
1000
3429 F01b
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1 page  
LTC3429ww/wL.DTatCaSh3eet44U2.co9mB
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.
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 gm Error Amplifier.
Connect resistor divider tap to this pin. The output voltage
can be adjusted from 2.5V to 5V by:
VOUT = 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 VIN.
VOUT (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) should be as short and wide as possible. VOUT
is completely disconnected from VIN when SHDN is low
due to the output disconnect feature.
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-
pletely independent from VIN. Operation is only limited by
the output power level and the battery’s internal series
resistance.
BLOCK DIAGRA
+
1V TO 4.4V
6 VIN
CIN
RAMP
GEN
500kHz
START-UP
OSC
A A/B
MUX
B
PWM
CONTROL
PWM
COMPARATOR
SLOPE
COMP
SLEEP
Burst Mode
OPERATION
CONTROL
L1
1 SW
VOUT
GOOD
2.3V
0.45Ω
VIN
WELL
SWITCH
VOUT
5
2.5V TO 5V
SYNC
DRIVE
CONTROL
Σ
0.35Ω
CURRENT
SENSE
CPL
(OPTIONAL)
R1
RC
80k
CC
150pF
CP2
2.5pF
gm
ERROR
AMP
FB
3
1.23V
REF
R2
COUT
SHDN
4
SHUTDOWN
CONTROL
SHUTDOWN
2 GND
3429 BD
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5 Page 
PACKAGE DESCRIPTIO
LTC3429ww/wL.DTatCaSh3eet44U2.co9mB
S6 Package
6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
0.62 0.95
MAX REF
1.22 REF
2.90 BSC
(NOTE 4)
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC 1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.20 BSC
DATUM ‘A’
0.95 BSC
0.80 – 0.90
1.00 MAX
0.30 – 0.50 REF
0.09 – 0.20
NOTE:
(NOTE 3)
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
1.90 BSC
0.30 – 0.45
6 PLCS (NOTE 3)
0.01 – 0.10
S6 TSOT-23 0302
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-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC3429.PDF ] | |
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