FEATURES
n Charge Pump Input Range: 2.7V to 5.5V
n Controller Input Range: 4V to 38V
n Integrated Charge Pump Provides 5V Gate Drive to
Logic Level MOSFETs
n RSENSE or DCR Current Sensing
n ±1.25% Output Voltage Accuracy Over Temperature
n Phase-Lockable Fixed Frequency: 250kHz to 750kHz
n Power Good Output Voltage Monitor
n Adjustable Soft-Start Voltage Ramping
n Current Foldback Disabled During Start-Up
n No Reverse Current During Soft-Start
n Selectable Constant Frequency, Pulse-Skipping, or
Burst Mode Operation
n Output Overvoltage Protection
n Very Low Dropout Operation: 99% Duty Cycle
n Available in a 24-Lead (3mm ¥ 5mm) QFN Package
APPLICATIONS
n General Purpose 3.3V Systems
n Lithium-Ion Powered Devices
n Distributed DC Power Systems
LTC3852
Low Input Voltage,
Synchronous Step-Down
DC/DC Controller
DESCRIPTION
The LTC®3852 is a constant frequency, current mode
step-down DC/DC controller which can be powered by an
onboard charge pump. Input supplies as low as 2.7V, when
doubled by the charge pump, provide 5V to the LTC3852’s
control logic and gate drives, supporting a wide selection
of logic-level N-channel power MOSFETs.
The constant-frequency current mode architecture allows for
a phase-lockable fixed frequency of up to 750kHz. The RUN
pin provides a precision enable threshold while the TRACK/SS
pin combines tracking and adjustable soft-start features.
The MODE/PLLIN pin selects among Burst Mode® oper-
ation, pulse-skipping mode, and continuous current mode.
Current foldback limits MOSFET power dissipation during
short-circuit conditions. Reverse current and current
foldback functions are disabled during soft-start. A power
good output pin indicates when the output is within ±10%
of its designed set point.
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
and No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5408150, 5481178,
5705919, 6498466, 6580258, 6611131.
TYPICAL APPLICATION
High Efficiency Synchronous Step-Down Converter
100k
INTVCC
PGO0D
VIN1
MODE/PLLIN TG
FREQ/PLLFLTR SW
95.3k
1nF
BOOST
TRACK/SS
0.1μF
VIN2
INTVCC
ITH LTC3852 BG
12.1k
100pF
GND2
RUN
SENSE+
OFF ON
CHARGE PUMP
2.2μF
SHDN
SENSE–
C+
VFB
C– GND1 VPUMP
3852 TA01
0.1μF
4.7μF
0.36μH
2.1k
VIN
22μF 2.7V TO 5.5V
VOUT
1.2V
20A
470μF
×2
0.1μF
20k
1%
40.2k
1%
Efficiency and Power Loss
vs Load Current
100
90
80
70
60
50
40
30
20
10
0
1
5
4.5
EFFICIENCY
4
3.5
3
2.5
2
POWER LOSS
1.5
1
0.5
0
10
20
LOAD CURRENT (A)
3852 TA01a
3852f
1
