LTC3865 Datasheet, PDF (1/36 Pages) Linear Technology – Dual, 2-Phase Synchronous DC/DC Controller with Pin Selectable Outputs

Features
n _{Dual, 180° Phased Controllers}
n _{2-Pin VID Output Voltage Programming from 0.6V}
to 5V
n _{High Efficiency: Up to 95%}
n _{RSENSE or DCR Current Sensing}
n _{Phase-Lockable Fixed Frequency 250kHz to 770kHz}
n _{Adjustable Current Limit}
n _{Dual N-Channel MOSFET Synchronous Drive}
n _{Wide VIN Range: 4.5V to 38V Operation}
n _{Adjustable Soft-Start Current Ramping or Tracking}
n _{Output OV Protection With Reverse Current Limit}
n _{Power Good Output Voltage Monitor}
n _{32-Pin 5mm × 5mm QFN and 38-Lead TSSOP}
Packages
Applications
n _{DC Power Distribution Systems}
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, µModule, Linear Technology and the Linear logo
are registered trademarks and No R_SENSE is a trademark of Linear Technology Corporation. All
other trademarks are the property of their respective owners. U.S. Patents, including 5481178,
5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258.
LTC3865/LTC3865-1
Dual, 2-Phase Synchronous
DC/DC Controller with
Pin Selectable Outputs
Description
The LTC^®3865/LTC3865-1 are high performance dual
synchronous step-down DC/DC switching regulator
controllers that drive all N‑channel synchronous power
MOSFET stages. A constant frequency current mode
architecture allows a phase-lockable frequency of up to
770kHz. Power loss and noise are minimized by operating
the two controller output stages out of phase.
OPTI-LOOP^® compensation allows the transient response
to be optimized over a wide range of output capacitance
and ESR values. Independent track/soft-start pins for
each controller ramp the output voltage during start-up.
Current foldback limits MOSFET heat dissipation during
short-circuit conditions. The MODE/PLLIN pin selects
among Burst Mode^® operation, pulse-skipping mode,
and continuous inductor current mode. The output volt-
ages can be precisely programmed by pin strapping or
external resistors.
The LTC3865/LTC3865-1 are available in low profile (5mm
× 5mm) 32-pin QFN and 38-Lead thermally enhanced
TSSOP packages.
Typical Application
V_OUT1
1.5V
15A
High Efficiency 1.5V/15A, 1.2V/15A Step-Down Converter
2.2Ω
V_IN
+ _22µF 4.5V TO 24V
50V
1µF
0.47µH
2mΩ
+
100µF
C_OUT2,3
4.7µF
0.1µF
100Ω
1000pF
100Ω
1000pF
10k
100pF
V_IN
INTV_CC
TG1
TG2
BOOST1
BOOST2
SW1
SW2
LTC3865
BG1
BG2
SENSE1⁺
PGND
FREQ
SENSE2⁺
SENSE1^–
VID11
VID12
V_OSENSE1
I_TH1
TK/SS1
SGND
SENSE2^–
VID21
VID22
V_OSENSE2
I_TH2
TK/SS2
0.1µF 0.1µF
0.1µF
0.47µH
100Ω
1000pF
2mΩ
100Ω
1000pF
162k 15k
+
100pF
C_OUT5,6
V_OUT2
1.2V
15A
100µF
Efficiency and Power Loss
vs Load Current
100
10
V_IN = 12V
90 V_OUT = 1.5V
80
70
EFFICIENCY
1
60
POWER LOSS
50
40
30
0.1
20
10
0
0.01
0.1
1
10
LOAD CURRENT (A)
0.01
100
3865 TA01b
3865 TA01a
3865f