LTC3545_15 Datasheet, PDF (1/20 Pages) Linear Technology – Triple 800mA Synchronous Step-Down Regulator–2.25MHz

LTC3545/LTC3545-1
Triple 800mA Synchronous
Step-Down Regulator–2.25MHz
FEATURES
DESCRIPTION
■ _{Three 800mA Outputs}
■ _{High Efficiency: Up to 95%}
■ _{2.25V to 5.5V Input Voltage Range}
■ _{Low Ripple (<20mVP-P) Burst Mode}^® _Operation
I_Q: 58μA
■ _{2.25MHz Constant Frequency Operation or}
■ _{Synchronizable to External 1MHz to 3MHz Clock}
■ _{Power Good Indicators Ease Supply Sequencing}
■ _{0.6V Reference Allows Low Output Voltages}
■ _{Current Mode Operation/Excellent Transient Response}
■ _{Low Profile 16-Lead 3mm × 3mm QFN Package}
APPLICATIONS
■ _{Smart Phones}
■ _{Wireless and DSL Modems}
■ _{Digital Still Cameras}
■ _{Portable Instruments}
■ _{Point of Load Regulation}
L, LT, LTC, LTM 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 6580258, 5481178, 6127815, 6498466, 6611131.
The LTC^®3545/LTC3545-1 are triple, high efficiency,
monolithic synchronous buck regulators using a constant
frequency, current mode architecture. The regulators op-
erate independently with separate run pins. The 2.25V to
5.5V input voltage range makes the LTC3545/LTC3545-1
well suited for single Li-Ion battery-powered applications.
Low ripple pulse skip mode or high efficiency Burst Mode
operation is externally selectable. PWM pulse skip mode
operation provides very low output ripple voltage while
Burst Mode operation increases efficiency at low output
loads.
Switching frequency is internally set to 2.25MHz, or the
switching frequency can be synchronized to an external
1MHz to 3MHz clock. Power good indicators easily allow
power on sequencing between the three regulators.
The internal synchronous switches increase efficiency and
eliminate external Schottky diodes. Low output voltages are
supported with the 0.6V feedback reference voltage.
The LTC3545-1 replaces the SYNC/MODE function with a
third PGOOD pin and forces Burst Mode operation.
TYPICAL APPLICATION
High Efficiency Triple Step-Down Converter with Power Sequencing
V_OUT1
1.8V
C1
10μF
V_IN
2.25V TO 5.5V
C5
C4 10μF
10μF
R8
500k
GNDA
R7
500k
RUN1
PGOOD1
V_IN PV_IN
PGND
L2
1.5μH
SW2
C7
20pF
RUN2
V_FB2
PGOOD2
RUN3 LTC3545
R4
226k
R3
226k
L1
1.5μH
C6
20pF
SYNC/MODE
SW1
L3
1.5μH
SW3
C8
20pF
R1
511k
V_FB1
R2
GNDA
255k
V_FB3
PGND
R6
R5
200k _301k
V_OUT2
1.2V
C2
10μF
V_OUT3
1.5V
C3
10μF
3545 TA01
Efficiency and Loss vs Load Current
100
1
90
80
0.1
70
60
50
0.01
40
30
20
10
0
0.0001
0.001
0.001
0.01
V_IN = 2.5V
V_IN = 3.6V
V_IN = 4.2V
0.0001
0.1
1
LOAD CURRENT (A)
T_A = 25°C
V_OUT = 2V
Burst Mode OPERATION
f_OSC = 2.25MHz
SINGLE CHANNEL
3545 TA01b
35451fb
1