LTC3890 Datasheet, PDF (1/36 Pages) Linear Technology – 60V Low IQ, Dual, 2-Phase Synchronous Step-Down DC/DC Controller

LTC3890
FEATURES
60V Low I_Q,
Dual, 2-Phase Synchronous
Step-Down DC/DC Controller
DESCRIPTION
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 Required 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 _{Output Overvoltage Protection}
n _{Low Shutdown IQ : < 14μA}
n _{Internal LDO Powers Gate Drive from VIN or EXTVCC}
n _{No Current Foldback During Start-up}
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}
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
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. 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.
Independent TRACK/SS pins for each controller ramp the
output voltages during start-up. Current foldback limits
MOSFET heat dissipation during short-circuit conditions.
The PLLIN/MODE pin selects among Burst Mode operation,
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.
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.
TYPICAL APPLICATION
V_OUT1
3.3V
5A
High Efficiency Dual 8.5V/3.3V Output Step-Down Converter
4.7μF
V_IN
9V TO 60V
22μF
V_IN
TG1
INTV_CC
TG2
4.7μH
0.1μF
BOOST1
BOOST2
0.1μF
8μH
SW1
SW2
BG1
BG2
LTC3890
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
3890 TA01
Efficiency and Power Loss vs
Output Current (Buck)
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
3890 TA01b
3890f
1