LTC3827 Datasheet, PDF (1/36 Pages) Linear Technology – Low IQ, Dual, 2-Phase Synchronous Step-Down Controller

LTC3827
Low I_Q, Dual, 2-Phase
Synchronous Step-Down Controller
FEATURES
DESCRIPTION
n _{Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 10V}
n _{Low Operating IQ: 80μA (One Channel On)}
n _{Out-of-Phase Controllers Reduce Required Input}
Capacitance and Power Supply Induced Noise
n _OPTI-LOOP^® _{Compensation Minimizes COUT}
n _{±1% Output Voltage Accuracy}
n _{Wide VIN Range: 4V to 36V Operation}
n _{Phase-Lockable Fixed Frequency 140kHz to 650kHz}
n _{Selectable Continuous, Pulse Skipping or Low Ripple}
Burst Mode^® Operation at Light Loads
n _{Dual N-Channel MOSFET Synchronous Drive}
n _{Very Low Dropout Operation: 99% Duty Cycle}
n _{Adjustable Output Voltage Soft-Start or Tracking}
n _{Output Current Foldback Limiting}
n _{Power Good Output Voltage Monitor}
n _{Output Overvoltage Protection}
n _{Low Shutdown IQ: 8μA}
n _{Internal LDO Powers Gate Drive from VIN or VOUT}
n _{Small 5mm × 5mm QFN Package}
APPLICATIONS
n _{Automotive Systems}
n _{Battery-Operated Digital Devices}
n _{Distributed DC Power Systems}
The LTC^®3827 is a high performance dual step-down
switching regulator controller that drives all N-channel
synchronous power MOSFET stages. A constant frequency
current mode architecture allows a phase-lockable fre-
quency of up to 650kHz. Power loss and noise due to the
ESR of the input capacitor ESR are minimized by operating
the two controller output stages out of phase.
The 80μA no-load quiescent current extends operating
life 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
LTC3827 features a precision 0.8V reference and a power
good output indicator. A wide 4V to 36V input supply range
encompasses all battery chemistries.
Independent TRACK/SS pins for each controller ramp the
output voltage during start-up. Current foldback limits
MOSFET heat dissipation during short-circuit conditions.
The PLLIN/MODE pin selects among Burst Mode opera-
tion, pulse skipping mode, or continuous inductor cur-
rent mode at light loads. For a leaded package version
(28-lead SSOP), see the LTC3827-1 datasheet.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
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, 5929620, 6177787, 6144194, 5408150, 6580258, 6304066, 570919.
TYPICAL APPLICATION
V_OUT1
3.3V
5A
3.3μH
0.015Ω
62.5k
150μF
High Efficiency Dual 8.5V/3.3V Step-Down Converter
+
4.7μF
0.1μF
V_IN
TG1
BOOST1
SW1
INTV_CC
TG2
BOOST2
SW2
1μF
0.1μF
22μF
50V
V_IN
4V TO 36V
7.2μH
BG1
BG2
LTC3827
PGND
SENSE1⁺
SENSE2⁺
0.015Ω
SENSE1^–
SENSE2^–
V_FB1
V_FB2
I_TH1
I_TH2
20k
220pF _{TRACK/SS1 SGND TRACK/SS2}
15k
0.1μF
0.1μF
220pF
15k
192.5k
20k
V_OUT2
8.5V
3.5A
150μF
3827 TA01
Efficiency and Power Loss
vs Load Current
100
100000
90
EFFICIENCY
V_IN = 12V; V_OUT = 3.3V
10000
80
70
1000
60
50
100
40
30
POWER LOSS 10
20
10
0
0.001 0.01
1
FIGURE 13 CIRCUIT
0.1
0.1 1 10 100 1000 10000
LOAD CURRENT (mA)
3827 TA01b
3827ff
1