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Linear Technology Electronic Components Datasheet

LTC3858-2 Datasheet

Dual 2-Phase Synchronous Step-Down Controller

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FEATURES
n Low Operating IQ: 170μA (One Channel On)
n Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
n Wide VIN Range: 4V to 38V
n RSENSE or DCR Current Sensing
n Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise
n OPTI-LOOP® Compensation Minimizes COUT
n Phase-Lockable Frequency (75kHz-850kHz)
n Programmable Fixed Frequency (50kHz-900kHz)
n Selectable Continuous, Pulse-Skipping or
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: 8μA
n Internal LDO Powers Gate Drive from VIN or EXTVCC
n No Current Foldback During Start-Up
n 5mm × 5mm QFN Package
APPLICATIONS
n Automotive Systems
n Battery Operated Digital Devices
n Distributed DC Power Systems
LTC3858-2
Low IQ, Dual
2-Phase Synchronous
Step-Down Controller
DESCRIPTION
The LTC®3858-2 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 850kHz. Power loss and noise due to the
input capacitor ESR are minimized by operating the two
controller outputs out of phase.
The 170μA 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
LTC3858-2 differs from the LTC3858 by having the overvolt-
age protection crowbar and short-circuit latchoff disabled.
A wide 4V to 38V input supply range encompasses a wide
range of intermediate bus voltages and battery chemistries.
Independent soft-start pins for each controller ramp the
output voltages during start-up. Current foldback limits
MOSFET heat dissipation during short-circuit conditions.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, μModule, PolyPhase, Linear Technology and the Linear
logo are registered trademarks and No RSENSE and UltraFast are 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.
TYPICAL APPLICATION
VOUT1
3.3V
5A
High Efficiency Dual 8.5V/3.3V Step-Down Converter
3.3μH
0.007Ω
62.5k
150μF
0.1μF
VIN
TG1
INTVCC
TG2
BOOST1
BOOST2
SW1 SW2
BG1 BG2
LTC3858-2
PGND
SENSE1+
SENSE2+
680pF
SENSE1
VFB1
ITH1
SS1
SGND
SENSE2
VFB2
ITH2
SS2
20k 15k
0.1μF
0.1μF
4.7μF
0.1μF
680pF
15k
VIN
22μF 9V TO 38V
50V
7.2μH
0.01Ω
193k
20k
VOUT2
8.5V
3.5A
150μF
38582 TA01a
Efficiency and Power Loss
vs Load Current
100 10000
90
80
EFFICIENCY
70
1000
60 100
POWER LOSS
50
40 10
30
20
10
0
0.0001
0.001 0.01
VIN = 12V
1
VOUT = 3.3V
FIGURE 13 CIRCUIT
0.1
0.1 1 10
OUTPUT CURRENT (A)
38582 TA01b
38582f
1


Linear Technology Electronic Components Datasheet

LTC3858-2 Datasheet

Dual 2-Phase Synchronous Step-Down Controller

No Preview Available !

LTC3858-2
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (VIN)......................... –0.3V to 40V
Topside Driver Voltages
BOOST1, BOOST2 ................................. –0.3V to 46V
Switch Voltage (SW1, SW2) ......................... –5V to 40V
(BOOST1-SW1), (BOOST2-SW2) ................ –0.3V to 6V
RUN1, RUN2 ............................................... –0.3V to 8V
Maximum Current Sourced into Pin
from Source >8V ..............................................100μA
SENSE1+, SENSE2+, SENSE1
SENSE2Voltages ..................................... –0.3V to 28V
PLLIN/MODE Voltage................................... –0.3V to 6V
ILIM, PHASMD, FREQ Voltages ............. –0.3V to INTVCC
EXTVCC ..................................................... –0.3V to 14V
ITH1, ITH2,VFB1, VFB2 Voltages....................... –0.3V to 6V
PGOOD1, PGOOD2 Voltages ....................... –0.3V to 6V
SS1, SS2, INTVCC Voltages ......................... –0.3V to 6V
Operating Junction Temperature Range
(Note 2).................................................. –40°C to 125°C
Maximum Junction Temperature (Note 3) ............ 125°C
Storage Temperature Range .................. –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
32 31 30 29 28 27 26 25
SENSE11
24 BOOST1
FREQ 2
23 BG1
PHASMD 3
CLKOUT 4
PLLIN/MODE 5
SGND 6
RUN1 7
33
SGND
22 VIN
21 PGND
20 EXTVCC
19 INTVCC
18 BG2
RUN2 8
17 BOOST2
9 10 11 12 13 14 15 16
UH PACKAGE
32-LEAD (5mm s 5mm) PLASTIC QFN
TJMAX = 125°C, θJA = 34°C/W
EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3858EUH-2#PBF
LTC3858EUH-2#TRPBF 38582
32-Lead (5mm × 5mm) Plastic QFN
–40°C to 125°C
LTC3858IUH-2#PBF
LTC3858IUH-2#TRPBF 38582
32-Lead (5mm × 5mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 12V, VRUN1,2 = 5V, EXTVCC = 0V unless
otherwise noted.
SYMBOL
VIN
VFB1,2
IFB1,2
VREFLNREG
PARAMETER
Input Supply Operating Voltage
Range
Regulated Feedback Voltage
Feedback Current
Reference Voltage Line Regulation
CONDITIONS
(Note 4) ITH1,2 = 1.2V
–40°C to 125°C
–40°C to 85°C
(Note 4)
(Note 4) VIN = 4.5V to 38V
MIN TYP MAX UNITS
4 38 V
l 0.788
0.792
0.800
0.800
±5
0.002
0.812
0.808
±50
0.02
V
V
nA
%/V
38582f
2


Part Number LTC3858-2
Description Dual 2-Phase Synchronous Step-Down Controller
Maker Linear Technology
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LTC3858-2 Datasheet PDF






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