LT3434_15 Datasheet, PDF (1/24 Pages) Linear Technology – High Voltage 3A, 200kHz Step-Down Switching Regulator with 100µA Quiescent Current

LT3434
High Voltage 3A, 200kHz
Step-Down Switching Regulator
with 100µA Quiescent Current
FEATURES
■ _{Wide Input Range: 3.3V to 60V}
■ _{3A Peak Switch Current}
■ _{Burst Mode}^® _{Operation: 100µA Quiescent Current**}
■ _{Low Shutdown Current: IQ < 1µA}
■ _{Power Good Flag with Programmable Threshold}
■ _{Load Dump Protection to 60V}
■ _{200kHz Switching Frequency}
■ _{Saturating Switch Design: 0.1Ω}
■ _{Peak Switch Current Maintained Over}
Full Duty Cycle Range*
■ _{1.25V Feedback Reference Voltage}
■ _{Easily Synchronizable}
■ _{Soft-Start Capability}
■ _{Small 16-Pin Thermally Enhanced TSSOP Package}
U
APPLICATIO S
■ _{High Voltage Power Conversion}
■ _{14V and 42V Automotive Systems}
■ _{Industrial Power Systems}
■ _{Distributed Power Systems}
■ _{Battery-Powered Systems}
, 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. *Protected by U.S. Patents including
6498466. **See Burst Mode Operation section for conditions.
DESCRIPTIO
The LT^®3434 is a 200kHz monolithic buck switching
regulator that accepts input voltages up to 60V. A high
efficiency 3A, 0.1Ω switch is included on the die along with
all the necessary oscillator, control and logic circuitry.
Current mode topology is used for fast transient response
and good loop stability.
Innovative design techniques integrated in a new high
voltage process achieve high efficiency over a wide input
range. Efficiency is maintained over a wide output current
range by employing Burst Mode operation at low currents,
utilizing the output to bias the internal circuitry, and by
using a supply boost capacitor to fully saturate the power
switch. Patented circuitry maintains peak switch current
over the full duty cycle range.* Shutdown reduces input
supply current to less than 1µA. External synchronization
can be implemented by driving the SYNC pin with logic-level
inputs. A single capacitor from the C_SS pin to the output
provides a controlled output voltage ramp (soft-start). The
device also has a power good flag with a programmable
threshold and time-out, and thermal shutdown protection.
The LT3434 is available in a 16-pin TSSOP package with
Exposed Pad leadframe for low thermal resistance.
TYPICAL APPLICATIO
14V to 3.3V Step-Down Converter with
100µA No Load Quiescent Current
V_IN
4700pF
10k
4.7µF
100V
CER
470pF
1µF
V_IN BOOST
SHDN
SW
0.68µF 33µH ₄₁₄₈
LT3434 0.1µF
V_C
C_SS
30MQ100
C_T
SYNC
GND
V_BIAS
FB
PGFB
PG
27pF
165k
1%
100k
1%
V_OUT
3.3V
2A
100µF
6.3V
TANT
3434 TA01
Supply Current vs
Input Voltage
150
V_OUT = 3.3V
125
100
75
50
25
0
0 10 20 30 40 50 60
INPUT VOLTAGE (V)
3434 TA02a
Efficiency and Power Loss
vs Load Current
100
10
V_IN = 12V
V_OUT = 5V
EFFICIENCY
75
1
V_OUT = 3.3V
50
0.1
TYPICAL POWER
LOSS
25
0.01
0
0.0001 0.001 0.01 0.1
LOAD CURRENT (A)
0.001
1
10
3434 TA02b
3434fb
1