LTC3546_15 Datasheet, PDF (1/30 Pages) Linear Technology – Dual Synchronous, 3A/1A or 2A/2A Configurable Step-Down DC/DC Regulator

LTC3546
Dual Synchronous, 3A/1A
or 2A/2A Configurable
Step-Down DC/DC Regulator
Features
n _{VIN Range: 2.25V to 5.5V}
n _{VOUT Range: 0.6V to 5V}
n _{Programmable Frequency Operation; 2.25MHz, or}
Adjustable Between 0.75MHz to 4MHz
n _{Low RDS(ON) Internal Switches}
n _{High Efficiency: Up to 96%}
n _{No Schottky Diodes Required}
n _{Short-Circuit Protected}
n _{Current Mode Operation for Excellent Line and Load}
Transient Response
n _{Low Ripple Burst Mode Operation (30mVP-P),}
I_Q = 160µA
n _{Ultralow Shutdown Current: IQ < 1µA}
n _{Low Dropout Operation: 100% Duty Cycle}
n _{Power Good Output For Each Channel}
n _{Externally or Internally Programmable Burst Level}
n _{External or Internal Soft-Start or Supply Tracking}
n _{Available in Thermally Enhanced 28-Lead}
(4mm × 5mm) QFN and TSSOP Packages
Applications
n _{Netbooks/Ultra-Mobile PCs}
n _{PC Cards}
n _{Wireless and DSL Modems}
n _{Point of Load DC/DC Conversion}
Description
The LTC^®3546 is a dual, constant-frequency, synchronous
step down DC/DC converter for medium power applications.
The design consists of 2A and 1A primary output switches.
In addition to the 2A/1A capability, a 1A dependant output
switch can be externally connected to either of the primary
outputs to produce 3A/1A dual regulator or 2A/2A dual
regulator configurations.
Supply operation is from 2.25V to 5.5V. The switch-
ing frequency can be set to 2.25MHz, adjustable from
0.75MHz to 4MHz, or synchronized to an external clock.
Each output is adjustable from 0.6V to 5V and has output
tracking on power-up. Internal synchronous low R_DS(ON)
power switches provide high efficiency without external
Schottky diodes.
User-selectable modes (Burst Mode^® operation, pulse
skipping and forced continuous) allow a trade-off between
ripple noise and power efficiency. Burst Mode operation
provides high efficiency at light loads. Pulse-skipping
mode provides low ripple noise at light loads.
The device is capable of low dropout configurations and
both channels can operate at 100% duty cycle. In shut-
down, the device draws <1µA.
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. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258.
Typical Application
V_IN
3.6V TO
5.5V
V_OUT2
2.5V, 3A
68µF
C_IN
22µF
0.56µH
100pF
95.3k
V_IN
30.1k VIN
13k
10pF
1000pF
V_IN1 V_CCA V_CCD V_IN2
SYNC/MODE
PGOOD2
PGOOD1
SW2A
SW1
SW2B
SW1D
RUN2 LTC3546 RUN1
V_FB2
BMC2
V_FB1
BMC1
TRACK/SS2 TRACK/SS1
PHASE
FREQ
I_TH2
I_TH1
PGND2 GNDA PGND1
EXPOSED PAD
1.22µH
V_IN
V_IN
100pF
30.1k
30.1k
V_OUT1
1.2V, 1A
22µF
13k
1000pF
10pF
3546 TA01a
For more information www.linear.com/3546
V_OUT2 Efficiency (Burst Mode Operation)
100
100
SW1D CONNECTED TO SW2
V_IN = 3.6V
95 VOUT = 2.5V
10
90
EFFICIENCY
1
85
0.1
80
0.01
POWER LOSS
75
0.001
70
0.001
0.01
0.1
1
LOAD CURRENT (A)
0.0001
10
3546 TA01b
3546fc
1