LTC3890
60V Low I ,
Q
Dual, 2-Phase Synchronous
Step-Down DC/DC Controller
DESCRIPTION
FEATURES
The LTC®3890 is a high performance dual step-down
switching regulator DC/DC controller that drives all N-
channel synchronous power MOSFET stages. A constant
frequency current mode architecture allows a phase-lock-
able frequency of up to 850kHz. Power loss and noise due
totheESRoftheinputcapacitorareminimizedbyoperating
the two controller output 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
Wide Output Voltage Range: 0.8V ≤ V
≤ 24V
OUT
R
or DCR Current Sensing
SENSE
Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise
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
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The50ꢀAno-loadquiescentcurrentextendsoperatingrun
timeinbattery-poweredsystems.OPTI-LOOP® compensa-
tion allows the transient response to be optimized over
a wide range of output capacitance and ESR values. The
LTC3890 features a precision 0.8V reference and power
good output indicators. A wide 4V to 60V input supply
range encompasses a wide range of intermediate bus
voltages and battery chemistries.
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Selectable Current Limit
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Power Good Output Voltage Monitors
Output Overvoltage Protection
Low Shutdown I : < 14μA
Internal LDO Powers Gate Drive from V or EXTV
No Current Foldback During Start-up
Q
Independent TRACK/SS pins for each controller ramp the
IN
CC
output voltages during start-up. Current foldback limits
MOSFET heat dissipation during short-circuit conditions.
ThePLLIN/MODEpinselectsamongBurstModeoperation,
pulse skipping mode, or continuous conduction mode at
light loads. For a leaded package version (28-lead Narrow
SSOP), see the LTC3890-1 data sheet.
Small Low Profile (0.75mm) 5mm × 5mm QFN Package
APPLICATIONS
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Automotive Always-On Systems
L, LT, LTC, LTM, Burst Mode and OPTI-LOOP 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.
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Battery Operated Digital Devices
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Distributed DC Power Systems
TYPICAL APPLICATION
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
Efficiency and Power Loss vs
V
IN
Output Current (Buck)
9V TO 60V
22μF
4.7μF
10000
1000
100
100
90
80
70
60
50
40
30
20
V
V
= 12V
OUT
IN
V
IN
INTV
CC
= 3.3V
TG1
TG2
0.1μF
0.1μF
BOOST1
SW1
BOOST2
SW2
4.7μH
8μH
BG1
BG2
LTC3890
PGND
10
+
+
SENSE1
SENSE1
SENSE2
0.01Ω
0.008Ω
1
–
–
V
SENSE2
OUT2
V
OUT1
3.3V
5A
10
0
8.5V
3A
V
V
ITH2
FB1
FB2
0.1
10
100k
100k
10.5k
ITH1
0.0001 0.001
0.01
0.1
1
470μF
1000pF
34.8k
1000pF
34.8k
330μF
TRACK/SS1 SGND TRACK/SS2
0.1μF
OUTPUT CURRENT (A)
31.6k
3890 TA01b
0.1μF
3890 TA01
3890f
1