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LT3506/LT3506A
Dual Monolithic 1.6A
Step-Down Switching Regulator
FEATURES
■ 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
APPLICATIOUS
■ Disk Drives
■ DSP Power Supplies
■ Wall Transformer Regulation
■ Distributed Power Regulation
■ DSL Modems
■ Cable Modems
DESCRIPTIO
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.
TYPICAL APPLICATIO
VOUT1
1.8V
1.6A
VIN
4.5V TO 25V
4.7µH
18.7k
47µF 15k
22µF
0.22µF
1000pF
VIN1 VIN2
BOOST1 BOOST2
SW1 SW2
FB1 FB2
VC1 VC2
1/2 BAT-54A
1/2 BAT-54A
0.22µF
2200pF
6.4µH
33.2k
D1 15k
LT3506
10k D2 10.7k
PGOOD1
PGOOD2
100k
100k
1.5nF
RUN/SS1 RUN/SS2
PGOOD1
1.5nF
PGOOD2
GND
D1, D2: ON SEMI MBR5230LT3
VOUT2
3.3V
1.6A
22µF
3506 F01
100 VIN = 5V
Efficiency
90 VOUT = 3.3V
80 VOUT = 1.8V
70
60
50
0
0.5 1.0 1.5 2.0
IOUT (A)
3506 TA01b
3506afb
