LTC3890-1
60V Low I , Dual, 2-Phase
Q
Synchronous Step-Down
DC/DC Controller
DESCRIPTION
FEATURES
The LTC®3890-1 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.
n
Wide V Range: 4V to 60V (65V Abs Max)
IN
n
Low Operating I : 50µA (One Channel On)
Q
n
n
n
Wide Output Voltage Range: 0.8V ≤ V
≤ 24V
OUT
R
SENSE
or DCR Current Sensing
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
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Power Good Output Voltage Monitor
Output Overvoltage Protection
Low Shutdown I : <14µA
Internal LDO Powers Gate Drive from V or EXTV
No Current Foldback During Start-Up
Narrow SSOP Package
n
n
n
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.
n
n
n
n
n
n
n
n
Independent TRACK/SS pins for each controller ramp the
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.
Q
IN
CC
APPLICATIONS
Foraleadless32-pinQFNpackagewithadditionalfeatures
of adjustable current limit, clock out, phase modulation
and two PGOOD outputs, see the LTC3890 data sheet.
L, LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP 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.
n
Automotive Always-On Systems
n
Battery Operated Digital Devices
n
Distributed DC Power Systems
TYPICAL APPLICATION
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
Efficiency and Power Loss
V
vs Output Current
IN
9V TO 60V
22µF
10000
1000
100
100
90
80
70
60
50
40
30
20
4.7µF
V
V
= 12V
IN
OUT
V
IN
INTV
CC
= 3.3V
TG1
TG2
0.1µF
0.1µF
BOOST1
SW1
BOOST2
SW2
4.7µH
8µH
BG1
BG2
LTC3890-1
PGND
10
+
+
SENSE1
SENSE1
SENSE2
0.01Ω
0.008Ω
1
–
–
V
8.5V
3A
SENSE2
10
0
OUT2
V
OUT1
3.3V
5A
V
V
FB1
FB2
0.1
10
100k
470µF
100k
10.5k
ITH1
ITH2
0.0001 0.001
0.01
0.1
1
1000pF
34.8k
1000pF
OUTPUT CURRENT (A)
330µF
TRACK/SS1 SGND TRACK/SS2
0.1µF
38901 TA01b
31.6k
34.8k
0.1µF
38901 TA01a
38901fb
1