LTC3890-3 Datasheet, PDF (1/40 Pages) Linear Technology – 60V Low IQ, Dual, 2-Phase Synchronous Step-Down DC/DC Controller

Features
n _{Wide VIN Range: 4V to 60V (65V Abs Max)}
n _{Low Operating IQ: 50µA (One Channel On)}
n _{Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V}
n _{RSENSE or DCR Current Sensing}
n _{Out-of-Phase Controllers Reduce Input Capacitance}
and Power Supply Induced Noise
n _{Phase-Lockable Frequency (75kHz to 850kHz)}
n _{Programmable Fixed Frequency (50kHz to 900kHz)}
n _{Selectable Continuous, Pulse-Skipping or Low Ripple}
Burst Mode^® Operation at Light Loads
n _{Very Low Dropout Operation: 99% Duty Cycle}
n _{Adjustable Output Voltage Soft-Start or Tracking}
n _{Power Good Output Voltage Monitor}
n _{Low Shutdown IQ: <14µA}
n _{Internal LDO Powers Gate Drive from VIN or EXTVCC}
n _{Narrow SSOP Package}
Applications
n _{Automotive Always-On Systems}
n _{Battery Operated Digital Devices}
n _{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.
LTC3890-3
60V Low I_Q, Dual, 2-Phase
Synchronous Step-Down
DC/DC Controller
Description
The LTC^®3890-3 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-
lockable frequency of up to 850kHz. Power loss and supply
noise are minimized by operating the two controller output
stages out-of-phase.
The 50μA no-load quiescent current extends operating life
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.
Independent TRACK/SS pins for each controller ramp the
output voltages during start-up. Current mode control limits
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.
For versions with different and/or additional features, see
the LTC3890 family summary, Table 1, in the Pin Functions
section of this data sheet.
Typical Application
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
V_OUT1
3.3V
5A
4.7µH
0.008Ω
100k
470µF
0.1µF
V_IN
TG1
INTV_CC
TG2
BOOST1
BOOST2
SW1
SW2
BG1
BG2
LTC3890-3
PGND
SENSE1⁺
SENSE2⁺
31.6k
1000pF
SENSE1^–
V_FB1
ITH1
SENSE2^–
V_FB2
ITH2
TRACK/SS1 SGND TRACK/SS2
34.8k _0.1µF
0.1µF
4.7µF
V_IN
9V TO 60V
22µF
0.1µF
8µH
1000pF
34.8k
0.01Ω
100k
10.5k
V_OUT2
8.5V
3A
330µF
38903 TA01a
For more information www.linear.com/3890-3
Efficiency and Power Loss
vs Output Current
100
V_IN = 12V
90 VOUT = 3.3V
80
10000
1000
70
60
100
50
40
10
30
20
1
10
0
0.0001
0.001 0.01 0.1
1
OUTPUT CURRENT (A)
0.1
10
38903 TA01b
38903f
1