LTC3615 Datasheet, PDF (1/32 Pages) Linear Technology – Dual 4MHz, 3A Synchronous Step-Down DC/DC Converter

LTC3615
Features
Dual 4MHz, 3A Synchronous
Step-Down DC/DC Converter
Description
n _{High Efficiency: Up to 94%}
n _{Dual Outputs with 2 × 3A Output Current Capability}
n _{Low Output Ripple Burst Mode}^® _{Operation: IQ = 130µA}
n _{2.25V to 5.5V Input Voltage Range}
n _{±1% Output Voltage Accuracy}
n _{Output Voltages Down to 0.6V}
n _{Programmable Slew Rate at Switch Pins}
n _{Low Dropout Operation: 100% Duty Cycle}
n _{Shutdown Current ≤1µA}
n _{Adjustable Switching Frequency Up to 4MHz}
n _{Internal or External Compensation}
n _{Selectable Pulse-Skipping/Forced Continuous/}
Burst Mode Operation with Adjustable Burst Clamp
n _{Optional Active Voltage Positioning (AVP) with}
Internal Compensation
n _{Selectable 0°/90°/180° Phase Shift Between Channels}
n _{Fixed Internal and Programmable External Soft-Start}
n _{Accurate Start-Up Tracking Capability}
n _{DDR Memory Mode IOUT = ±1.5A}
n _{Available in 4mm × 4mm QFN-24 and TSSOP-24 Packages}
Applications
n _{Point-of-Load Supplies}
n _{Distributed Power Supplies}
n _{Portable Computer Systems}
n _{DDR Memory Termination}
n _{Handheld Devices}
The LTC^®3615 is a dual 3A synchronous step-down regula-
tor using a current mode, constant-frequency architecture.
The DC supply current is only 130µA (Burst Mode operation
at no-load) while maintaining the output voltages, drop-
ping to zero current in shutdown. The 2.25V to 5.5V input
supply range makes the LTC3615 ideally suited for single
Li-Ion applications. 100% duty cycle capability provides
low dropout operation, which extends operating time in
battery-operated systems.
The operating frequency is externally programmable up to
4MHz, allowing the use of small surface mount inductors.
0°, 90°, or 180° of phase shift between the two channels
can be selected to minimize input current ripple and
output voltage ripple in a single 6A output configuration.
Programmable slew rate limiting reduces EMI, and external
synchronization can be applied up to 4MHz.
The internal synchronous switches increase efficiency
and eliminate the need for external catch diodes, saving
external components and board space.
The LTC3615 is offered in leadless 24-pin 4mm × 4mm
QFN and thermally enhanced 24-pin TSSOP packages.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 5481178, 5994885, 6304066, 6498466, 6580258,
6611131.
Typical Application
V_IN
100µF
SV_IN PV_IN1
RUN1
TRACK/SS1
PGOOD1
ITH1
LTC3615
SRLIM
R_T/SYNC
MODE
PV_IN2
SW1
FB1
PHASE
RUN2
TRACK/SS2
PGOOD2
ITH2 SGND
SW2
FB2
PGND
3615 TA01a
0.47µH
0.47µH
422k
210k
665k
210k
V_OUT1
1.8V/3A
47µF
V_OUT2
2.5V/3A
47µF
Efficiency and Power Loss vs Load Current
100
10
90
80
1
70
60
0.1
50
40
0.01
30
20
10 ^2.25MHz
0 ^{VOUT = 2.5V}
0.001
0.01
0.1
V_IN = 3.3V
V_IN = 4V
V_IN = 5V
1
0.001
0.0001
OUTPUT CURRENT (A)
3615 TA01b
3615f