LT3506/LT3506A
Dual Monolithic 1.6A
Step-Down Switching Regulator
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Wide Input Voltage Range, 3.6V to 25V
Two 1.6A Output Switching Regulators with Internal
Power Switches
Constant Switching Frequency
LT3506: 575kHz
LT3506A: 1.1MHz
Anti-Phase Switching Reduces Ripple
Accurate 0.8V Reference, ±1%
Independent Shutdown/Soft-Start Pins
Independent Power Good Indicators Ease Supply
Sequencing
Uses Small Inductors and Ceramic Capacitors
Small 16-Lead Thermally Enhanced 5mm
×
4mm
DFN and TSSOP Surface Mount Packages
The LT
®
3506 is a dual current mode PWM step-down DC/DC
converter with internal 2A power switches. Both convert-
ers are synchronized to a single oscillator and run with
opposite phases, reducing input ripple current. The output
voltages are set with external resistor dividers, and each
regulator has independent shutdown and soft-start circuits.
Each regulator generates a power-good signal when its
output is in regulation, easing power supply sequencing
and interfacing with microcontrollers and DSPs.
The LT3506 switching frequency is 575kHz and the LT3506A
is 1.1MHz. These high switching frequencies allow the
use of tiny inductors and capacitors, resulting in a very
small dual 1.6A output solution. Constant frequency and
ceramic capacitors combine to produce low, predictable
output ripple voltage. With its wide input range of 3.6V to
25V, the LT3506 regulates a wide variety of power sources,
from 4-cell batteries and 5V logic rails to unregulated wall
transformers, lead acid batteries and distributed-power
supplies. Current mode PWM architecture provides fast
transient response with simple compensation components
and cycle-by-cycle current limiting. Frequency foldback
and thermal shutdown provide additional protection.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
APPLICATIO S
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Disk Drives
DSP Power Supplies
Wall Transformer Regulation
Distributed Power Regulation
DSL Modems
Cable Modems
V
IN
4.5V TO 25V
22µF
V
IN1
V
IN2
BOOST1
V
OUT1
1.8V
1.6A
4.7µH
18.7k
1000pF
0.22µF
SW1
FB1
V
C1
47µF
15k
D1
15k
LT3506
RUN/SS1 RUN/SS2
100k
100k
PGOOD1
PGOOD2
1.5nF
PGOOD1
PGOOD2
GND
1.5nF
SW2
FB2
V
C2
10k
BOOST2
0.22µF
EFFICIENCY (%)
U
TYPICAL APPLICATIO
1/2 BAT-54A
1/2 BAT-54A
6.4µH
33.2k
V
OUT2
3.3V
1.6A
2200pF
D2
10.7k
22µF
3506 F01
D1, D2: ON SEMI MBR5230LT3
U
Efficiency
100
V
IN
= 5V
V
OUT
= 3.3V
V
OUT
= 1.8V
90
80
70
60
50
0
0.5
1.0
I
OUT
(A)
1.5
2.0
3506 TA01b
FEATURES
DESCRIPTIO
U
3506afb
LINER [ LINEAR TECHNOLOGY ]
