LT3504_15 Datasheet, PDF (1/24 Pages) Linear Technology – Quad 40V/1A Step-Down Switching Regulator with 100 Duty Cycle Operation

Features
n _{Wide Input Range: 3.2V to 40V}
n _{Four 1A Outputs}
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 _{800mV FB Voltage}
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
Applications
n _{Automotive Battery Regulation}
n _{Industrial Control Supplies}
n _{Wall Transformer Regulation}
n _{Distributed Supply Regulation}
LT3504
Quad 40V/1A Step-Down
Switching Regulator with
100% Duty Cycle Operation
Description
The LT^®3504 consists of four 1A output current buck
regulators. The LT3504 has a wide operating input range
of 3.2V to 40V. An on-chip boost regulator allows each
channel to operate up to 100% duty cycle and eliminates
the need for four external charge pump circuits. The LT3504
is designed to minimize external component count and
results in a simple and small application circuit.
The LT3504 operates robustly in fault conditions. Cycle-
by-cycle peak current limit and catch diode current limit
sensing protect the part during overload conditions. Ther-
mal shutdown protects the power switches at elevated
temperatures. Soft-start helps keep the peak inductor
current under control during startup.
The LT3504 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.
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
Quad Buck Regulator in 4 × 5 QFN
V_IN
5.4V to 20V
TRANSIENT TO 40V
1µF
SW4
DA4
SKY
FB4
1µF
LT3504
10µH
SW5
SW3
EN/UVLO
DA3
V_IN
V_IN
V_IN
V_IN
RUN/SS1
FB3
SW2
RUN/SS2
1µF
RUN/SS3
DA2
RUN/SS4
FB2
50nF
RT/SYNC
SW1
18.2k
DA1
FB1
GND
f_SW = 1MHz
10µH
52.3k
5V/1A
10µF
10k
6.8µH
31.6k
3.3V/1A
10µF
10k
4.7µH
22.1k
2.5V/1A
22µF
3.3µH
10k
24.9k
20k
1.8V/1A
22µF
3504 TA01a
For more information www.linear.com/LT3504
LT3504 Start-Up and Shutdown
Waveform. V_IN (Top Trace) Is Ramped
from 0V Up to 8V and Then Back Down
to 0V. The Other Four Traces Are the
Output Voltages of All Four 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
CH2 1V/DIV
CH1 1V/DIV
100ms/DIV
3504 TA01b
3504fa
1