Datasheet

LT3504
1
3504fa
For more information www.linear.com/LT3504
Typical applicaTion
FeaTures
applicaTions
DescripTion
Quad 40V/1A Step-Down
Switching Regulator with
100% Duty Cycle Operation
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.
Quad Buck Regulator in 4 × 5 QFN
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
n
Automotive Battery Regulation
n
Industrial Control Supplies
n
Wall Transformer Regulation
n
Distributed Supply Regulation
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
3504 TA01a
SW4
DA4
FB4
SW3
DA3
FB3
SW2
DA2
FB2
SW1
DA1
FB1
SKY
SW5
EN/UVLO
V
IN
V
IN
V
IN
V
IN
RUN/SS1
RUN/SS2
RUN/SS3
RUN/SS4
RT/SYNC
5V/1A
10µH
52.3k
10k
10µF
3.3V/1A
6.8µH10µH
31.6k
10k
10µF
1µF
V
IN
5.4V to 20V
TRANSIENT TO 40V
50nF
F
F
2.5V/1A
4.7µH
22.1k
10k
22µF
1.8V/1A
3.3µH
24.9k
20k
18.2k
f
SW
= 1MHz
22µF
GND
LT3504
100ms/DIV
3504 TA01b
5V CHANNEL BEGINS
100% DC OPERATION
UVLO = ~2.9V
PARTS SHUTS
OFF
3.3V CHANNEL BEGINS
100% DC OPERATION
V
IN
1V/DIV
CH4 1V/DIV
CH3 1V/DIV
CH2 1V/DIV
CH1 1V/DIV

Summary of content (24 pages)