LTC3890-3
60V Low I , Dual, 2-Phase
Q
Synchronous Step-Down
DC/DC Controller
DescripTion
FeaTures
The LTC®3890-3 is a high performance dual step-down
switching regulator DC/DC controller that drives all
N-channelsynchronouspowerMOSFETstages.Aconstant
frequency current mode architecture allows a phase-
lockablefrequencyofupto850kHz.Powerlossandsupply
noiseareminimizedbyoperatingthetwocontrolleroutput
stages out-of-phase.
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Wide V Range: 4V to 60V (65V Abs Max)
IN
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Low Operating I : 50µA (One Channel On)
Q
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Wide Output Voltage Range: 0.8V ≤ V
≤ 24V
OUT
R
or DCR Current Sensing
SENSE
Out-of-Phase Controllers Reduce Input Capacitance
and Power Supply Induced Noise
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Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode® Operation at Light Loads
The50μAno-loadquiescentcurrentextendsoperatinglife
in battery-powered systems. OPTI-LOOP® compensation
allows the transient response to be optimized over a wide
range of output capacitance and ESR values. A wide 4V
to 60V input supply range encompasses a wide range of
intermediate bus voltages and battery chemistries.
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Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Power Good Output Voltage Monitor
Low Shutdown I : <14µA
Q
Independent TRACK/SS pins for each controller ramp the
outputvoltagesduringstart-up.Currentmodecontrollimits
the inductor current during short-circuit conditions. The
PLLIN/MODE pin selects among Burst Mode operation,
pulse-skipping mode, or continuous conduction mode at
light loads.
Internal LDO Powers Gate Drive from V or EXTV
Narrow SSOP Package
IN
CC
applicaTions
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Automotive Always-On Systems
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Battery Operated Digital Devices
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For versions with different and/or additional features, see
theLTC3890familysummary, Table1, inthePinFunctions
section of this data sheet.
Distributed DC Power Systems
L, LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP, PolyPhase and the Linear logo
are registered trademarks 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, 6304066, 6580258, 7230497.
Typical applicaTion
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
Efficiency and Power Loss
vs Output Current
V
IN
9V TO 60V
10000
1000
100
100
90
80
70
60
50
40
30
20
22µF
V
V
= 12V
IN
OUT
4.7µF
= 3.3V
V
INTV
CC
IN
TG1
TG2
0.1µF
0.1µF
BOOST1
SW1
BOOST2
SW2
4.7µH
8µH
BG1
BG2
LTC3890-3
10
PGND
+
+
SENSE1
SENSE2
1
0.01Ω
100k
0.008Ω
10
0
–
–
V
8.5V
3A
SENSE2
OUT2
SENSE1
V
OUT1
3.3V
5A
0.1
10
V
V
FB1
FB2
0.0001 0.001
0.01
0.1
1
100k
470µF
ITH1
ITH2
OUTPUT CURRENT (A)
1000pF
34.8k
1000pF
330µF
TRACK/SS1 SGND TRACK/SS2
0.1µF
38903 TA01b
10.5k
31.6k
34.8k
0.1µF
38903 TA01a
38903f
1
For more information www.linear.com/3890-3