LTC3546 Datasheet, PDF (1/28 Pages) Linear Technology – Dual Synchronous, 3A/1A or 2A/2A Confi gurable 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 28-Lead (4mm × 5mm) QFN Package}
APPLICATIONS
n _{PDAs/Ultra-Mobile PCs}
n _{Digital Cameras}
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 applica-
tions. The design consists of a 2A and a 1A primary output
switch. 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. Switching frequency
can be set to 2.25MHz, adjustable 0.75MHz to 4MHz, or
synchronized to an external clock. Each output is adjustable
from 0.6V to 5V and has turn-on supply tracking. Internal
synchronous low R_DS(ON), power switches provide high
efficiency without external Schottky diodes.
User selectable modes (Burst Mode^® operation, pulse skip,
and forced continuous) allow trade-off between ripple noise
and low power efficiency. Burst Mode operation provides
high efficiency at light loads. Pulse skip 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 and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V_IN
2.25V 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
V_FB2
BMC2
LTC3546
RUN1
V_FB1
BMC1
TRACK/SS2 TRACK/SS1
PHASE
I_TH2
FREQ
I_TH1
PGND2 GNDA PGND1
EXPOSED PAD
1.22μH
100pF
V_IN
V_IN
30.1k
30.1k
V_OUT1
1.2V, 1A
22μF
13k
1000pF
10pF
3546 TA01a
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
3546f
1