LTC3865/LTC3865-1
1
3865fb
TYPICAL APPLICATION
DESCRIPTION
Dual, 2-Phase Synchronous
DC/DC Controller with
Pin Selectable Outputs
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 profi le (5mm
× 5mm) 32-pin QFN and 38-Lead thermally enhanced
TSSOP packages.
FEATURES
APPLICATIONS
n
Dual, 180° Phased Controllers
n
2-Pin VID Output Voltage Programming from 0.6V
to 5V
n
High Effi ciency: Up to 95%
n
R
SENSE
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 V
IN
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
n
DC Power Distribution Systems
High Effi ciency 1.5V/15A, 1.2V/15A Step-Down Converter
0.1µF
0.47µH
1000pF
1000pF
1000pF
22µF
50V
10k
V
OUT1
1.5V
15A
0.1µF
0.47µH
1000pF
100µF
15k
162k
V
OUT2
1.2V
15A
TG1 TG2
BOOST1 BOOST2
SW1 SW2
BG1
BG2
SGND
PGND
FREQ
SENSE1
+
SENSE2
+
SENSE1
–
SENSE2
–
V
OSENSE1
V
OSENSE2
I
TH1
I
TH2
V
IN
INTV
CC
TK/SS1 TK/SS2
V
IN
4.5V TO 24V
3865 TA01a
0.1µF
100pF
0.1µF
LTC3865
VID11
VID12
VID21
VID22
4.7µF
100µF
C
OUT2,3
100pF
100Ω
100Ω
100Ω
100Ω
2.2Ω
1µF
2mΩ
2mΩ
+
C
OUT5,6
+
+
LOAD CURRENT (A)
30
EFFICIENCY (%)
POWER LOSS (W)
90
100
20
10
80
50
70
60
40
0.01 1 10 100
3865 TA01b
0
0.1
10
1
0.01
0.1
V
IN
= 12V
V
OUT
= 1.5V
EFFICIENCY
POWER LOSS
Effi ciency and Power Loss
vs Load Current
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.
