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

LTC3890-2
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 _{Selectable Current Limit}
n _{Very Low Dropout Operation: 99% Duty Cycle}
n _{Adjustable Output Voltage Soft-Start or Tracking}
n _{Power Good Output Voltage Monitors}
n _{Low Shutdown IQ : < 14μA}
n _{Internal LDO Powers Gate Drive from VIN or EXTVCC}
n _{Small Low Profile (0.75mm) 5mm × 5mm QFN Package}
APPLICATIONS
n _{Automotive Always-On Systems}
n _{Battery Operated Digital Devices}
n _{Distributed DC Power Systems}
60V Low I_Q, Dual, 2-Phase
Synchronous Step-Down
DC/DC Controller
DESCRIPTION
The LTC^®3890-2 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 noise
due to the ESR of the input capacitor are minimized by
operating the two controller output stages out-of-phase.
The 50μA no-load quiescent current extends operating run
time in battery-powered systems. OPTI-LOOP^® compensa-
tion 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.
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
V_OUT1
3.3V
5A
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
4.7μH
0.1μF
V_IN
TG1
BOOST1
SW1
INTV_CC
TG2
BOOST2
SW2
4.7μF
V_IN
9V TO 60V
22μF
0.1μF
8μH
BG1
BG2
LTC3890-2
PGND
SENSE1⁺
SENSE2⁺
0.008Ω
100k
470μF
31.6k
1000pF
SENSE1^–
V_FB1
ITH1
SENSE2^–
V_FB2
ITH2
TRACK/SS1 SGND TRACK/SS2
34.8k _0.1μF
0.1μF
1000pF
34.8k
0.01Ω
100k
10.5k
V_OUT2
8.5V
3A
330μF
38902 TA01a
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
38902 TA01b
38902f
1