LTC3864 Datasheet, PDF (1/28 Pages) Linear Technology – 60V Low IQ Step-Down DC/DC Controller with 100% Duty Cycle Capability

LTC3864
60V Low I_Q Step-Down
DC/DC Controller with
100% Duty Cycle Capability
FEATURES
n _{Wide Operating VIN Range: 3.5V to 60V}
n _{Wide VOUT Range: 0.8V to VIN}
n _{Low Operating IQ = 40µA}
n _{Very Low Dropout Operation: 100% Duty Cycle}
n _{Strong High Voltage MOSFET Gate Driver}
n _{Constant Frequency Current Mode Architecture}
n _{Verified FMEA for Adjacent Pin Open/Short}
n _{Selectable High Efficiency Burst Mode}^® _{Operation or}
Pulse-Skipping Mode at Light Loads
n _{Programmable Fixed Frequency: 50kHz to 850kHz}
n _{Phase-Lockable Frequency: 75kHz to 750kHz}
n _{Accurate Current Limit}
n _{Programmable Soft-Start or Voltage Tracking}
n _{Internal Soft-Start Guarantees Smooth Start-Up}
n _{Power Good Output Voltage Monitor}
n _{Low Shutdown IQ = 7µA}
n _{Available in Small 12-Pin Thermally Enhanced MSOP}
and DFN Packages
APPLICATIONS
n _{Industrial and Automotive Power Supplies}
n _{Telecom Power Supplies}
n _{Distributed Power Systems}
DESCRIPTION
The LTC^®3864 is a robust, high voltage step-down DC/DC
controller optimized for automotive and industrial applica-
tions. It drives a P-channel power MOSFET switch allowing
100% duty cycle operation. The wide input and output volt-
age ranges cover a multitude of applications. This device
has been verified with the failure mode and effects analysis
(FMEA) procedure for operation during failure conditions.
The LTC3864 offers excellent light load efficiency, draw-
ing only 40µA quiescent current in a user programmable
Burst Mode operation. Its peak current mode, constant
frequency PWM architecture provides for good control of
switching frequency and output current limit. The switch-
ing frequency can be programmed from 50kHz to 850kHz
with an external resistor and can be synchronized to an
external clock from 75kHz to 750kHz.
The LTC3864 offers programmable soft-start or output
tracking. Safety features include overvoltage protection,
overcurrent and short-circuit protection including fre-
quency foldback and a power good output signal.
The LTC3864 is available in thermally enhanced 12-Pin
MSOP and 3mm × 4mm DFN packages.
L, LT, LTC, LTM, OPTI-LOOP, Linear Technology, Burst Mode and the Linear logo are registered
trademarks and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents including 5731694.
TYPICAL APPLICATION
5.2V to 60V Input, 5V/2A Output, 350kHz Step-Down Converter
0.1µF
V_IN*
5.2V TO 60V
10µF
350kHz
3.3nF
9.09k
RUN
CAP
V_IN
PLLIN/MODE
SS
SENSE
LTC3864
GATE
ITH
FREQ
SGND
PGOOD
25mΩ
10µH
100k 422k
V_OUT*
5V
2A
47µF
×2
*V_OUT FOLLOWS V_IN
WHEN 3.5V ≤ V_IN ≤ 5.2V
PGND
V_FB
80.6k
3864 TA01a
Efficiency
100
Burst Mode
90 ^OPERATION
80
PULSE-SKIPPING
70
60
50
0.01
V_IN = 12V
V_OUT = 5V
0.1
1
LOAD CURRENT (A)
3864 TA01b
3864f
1