LTC3869-2_15 Datasheet, PDF (1/42 Pages) Linear Technology – Dual, 2-Phase Synchronous Step-Down DC/DC Controllers

Features
n _{Dual, 180° Phased Controllers Reduce Required}
Input Capacitance and Power Supply Induced Noise
n _{Accurate Multiphase Current Matching}
n _{RSENSE or DCR Current Sensing}
n _{±0.75% 0.6V Output Voltage Accuracy}
n _{Phase-Lockable Fixed Frequency 250kHz to 780kHz}
n _{High Efficiency: Up to 95%}
n _{Dual N-channel MOSFET Synchronous Drive}
n _{Wide VIN Range: 4V to 38V (40V Max) Operation}
n _{Wide VOUT Range: 0.6V to 12.5V Operation}
n _{Adjustable Soft-Start Current Ramping or Tracking}
n _{Foldback Output Current Limiting}
n _{Output Overvoltage Protection}
n _{Power Good Output Voltage Monitor}
n _{5V Low Dropout Regulator}
n _{Small 28-Lead QFN and Narrow SSOP Packages}
Applications
n _{Server Systems}
n _{Telecom Systems}
n _{Industrial and Medical Instruments}
n _{High Power Battery-Operated Devices}
n _{DC Power Distribution Systems}
LTC3869/LTC3869-2
Dual, 2-Phase
Synchronous Step-Down
DC/DC Controllers
Description
The LTC^®3869 is a high performance dual synchronous
step-down switching regulator controller that drives all
N-channel synchronous power MOSFET stages. A constant
frequency current mode architecture allows a phase-
lockable frequency of up to 780kHz. Power loss and noise
due to the ESR of the input capacitors 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. A wide 4V to 38V input supply range
encompasses most battery chemistries. Independent TK/
SS 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, or continuous inductor current mode and allows
the IC to be synchronized to an external clock.
The LTC3869 is available in a 4mm × 5mm QFN package
and the LTC3869-2 is available in an SSOP-28 package.
The LTC3869 is pin-compatible with the LTC3850.
L, LT, LTC, LTM, Linear Technology, the Linear logo, OPTI-LOOP, Burst Mode and PolyPhase
are registered trademarks and No R_SENSE is a trademark of Linear Technology Corporation. All
other trademarks are the property of their respective owners. Protected by U.S. Patents including
5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6580258, 6498466, 6611131.
Typical Application
3.2µH
V_OUT1
5V
5A
+
147k
47µF
High Efficiency Dual 5V/3.3V Step-Down Converter
+
4.7µF
0.1µF
f_IN
500kHz
470pF
20k
15k
V_IN PGOOD INTV_CC
TG1
TG2
BOOST1
SW1
BG1
LTC3869
BOOST2
SW2
BG2
MODE/PLLIN
I_LIM
SENSE1⁺
RUN1
SENSE1^–
V_FB1
I_TH1
TK/SS1
SGND
PGND
FREQ
SENSE2⁺
RUN2
SENSE2^–
V_FB2
I_TH2
TK/SS2
0.1µF
0.1µF
1µF
0.1µF
22µF
V_IN
7V TO
24V
2.2µH
90.9k
V_OUT2
3.3V
5A
470pF
122k
20k
15k
+
56µF
3869 TA01
For more information www.linear.com/LTC3869
Efficiency and Power Loss
100
90
80
70
60
50
40
30
20
10
0
0.01
V_IN = 12V, V_OUT = 3.3V
V_IN = 12V, V_OUT = 5V
1300
1200
1100
EFFICIENCY
1000
900
800
700
600
POWER LOSS ₅₀₀
0.1
1
LOAD CURRENT (A)
400
10
3869 TA01b
38692fa
1