LT3514_15 Datasheet, PDF (1/26 Pages) Linear Technology – Triple Step-Down Switching Regulator with 100 Duty Cycle Operation

FEATURES
n _{Wide Input Voltage Range: 3.2V to 36V}
(40V Transient)
n _{Three Outputs: 2A, 1A, 1A}
n _{100% Duty Cycle Operation}
n _{Resistor-Programmed Constant Frequency}
n _{Short-Circuit Robust}
n _{Wide SYNC Range: 350kHz to 2.2MHz}
n _{Anti-Phase Switching Reduces Ripple}
n _{Feedback Voltage: 800mV}
n _{Independent Run/Soft-Start Pins}
n _{Shutdown with UVLO}
n _{Internal Compensation}
n _{Thermal Shutdown}
n _{Tiny 28-Lead (4mm × 5mm) Thermally Enhanced}
QFN Package
n _{24-Lead Exposed Pad TSSOP}
APPLICATIONS
n _{Automotive Battery Regulation}
n _{Industrial Control Supplies}
n _{Wall Transformer Regulation}
n _{Distributed Supply Regulation}
LT3514
Triple Step-Down Switching
Regulator with 100%
Duty Cycle Operation
DESCRIPTION
The LT^®3514 consists of three buck regulators (2A, 1A,
1A output current). The device has a wide operating input
range of 3.2V to 36V. An on-chip boost regulator allows
each channel to operate up to 100% duty cycle. The LT3514
is designed to minimize external component count and
results in a simple and small application circuit.
The LT3514 operates robustly in fault conditions. Cycle-
by-cycle peak current limit and catch diode current limit
sensing protect the IC during overload conditions. Ther-
mal shutdown protects the power switches at elevated
temperatures. Soft-start helps control the peak inductor
current during startup.
The LT3514 also features output voltage tracking and
sequencing, programmable frequency, programmable
undervoltage lockout, and a power good pin to indicate
when all outputs are in regulation.
The LT3514 has one fewer channel (CH2) than the LT3504,
and has one channel (CH3) that outputs 2A instead of 1A.
The LT3514 in QFN is pin compatible with the LT3504. The
LT3504 provides four 1A outputs.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
Triple Buck Regulator
V_IN
5.4V TO 20V
TRANSIENT TO 40V
1µF
1µF
×2
SKY
SW1
SW5
10µH
LT3514
DA1
FB1
V_IN
V_IN
SW3
EN/UVLO
DA3
PG PG
FB3
47nF
18.2k
1MHz
RUN/SS1
RUN/SS3 ^SW4
RUN/SS4
DA4
RT/SYNC FB4
GND
3.3µH
4.7µH
8.2µH
100pF
12.7k
10.2k
47pF
31.6k
10.2k
22pF
53.6k
10.2k
1.8V/1A
22µF
3.3V/2A
47µF
5V/1A
22µF
3514 TA01a
LT3514 Start-Up and Shutdown
Waveform. V_IN (Top Trace) Is Ramped
from OV Up to 8V and Then Back Down
to 0V. The Other Three Traces Are the
Output Voltages of All Three Channels
5V CHANNEL BEGINS
100% DC OPERATION
3.3V CHANNEL BEGINS
100% DC OPERATION
V_IN 1V/DIV
CH4 1V/DIV
UVLO = ~2.9V
PARTS SHUTS
OFF
CH3 1V/DIV
CH1 1V/DIV
100ms/DIV
3514 TA01b
3514fa
For more information www.linear.com/LT3514
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