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Linear Technology Electronic Components Datasheet

LTC3859A Datasheet

Buck/Buck/Boost Synchronous Controller

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LTC3859A
Low IQ, Triple Output,
Buck/Buck/Boost Synchronous Controller
with Improved Burst Mode Operation
Features
Description
nn Dual Buck Plus Single Boost Synchronous Controllers
nn Outputs Remain in Regulation Through Cold Crank
Down to 2.5V
nn Low Operating IQ: 55μA (One Channel On)
nn Wide Bias Input Voltage Range: 4.5V to 38V
nn Buck Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
nn Boost Output Voltage Up to 60V
nn RSENSE or DCR Current Sensing
nn 100% Duty Cycle for Boost Synchronous MOSFET
Even in Burst Mode® Operation
nn Phase-Lockable Frequency (75kHz to 850kHz)
nn Programmable Fixed Frequency (50kHz to 900kHz)
nn Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode Operation at Light Loads
nn Very Low Buck Dropout Operation: 99% Duty Cycle
nn Adjustable Output Voltage Soft-Start or Tracking
nn Low Shutdown IQ: 14μA
nn Small 38-Pin 5mm × 7mm QFN and TSSOP Packages
Applications
nn Automotive Always-On and Start-Stop Systems
nn Battery Operated Digital Devices
nn Distributed DC Power Systems
nn Multioutput Buck-Boost Applications
The LTC®3859A is a high performance triple output (buck/
buck/boost) synchronous DC/DC switching regulator
controller that drives all N-channel power MOSFET stages.
Constant frequency current mode architecture allows
a phase-lockable switching frequency of up to 850kHz.
The LTC3859A operates from a wide 4.5V to 38V input
supply range. When biased from the output of the boost
converter or another auxiliary supply, the LTC3859A can
operate from an input supply as low as 2.5V after start-up.
The 55μA no-load quiescent current extends operating
runtime in battery powered systems. OPTI-LOOP com-
pensation allows the transient response to be optimized
over a wide range of output capacitance and ESR values.
The LTC3859A features a precision 0.8V reference for the
bucks, 1.2V reference for the boost and a power good
output indicator. The PLLIN/MODE pin selects among
Burst Mode operation, pulse-skipping mode, or continu-
ous inductor current mode at light loads.
Compared to the LTC3859, the LTC3859A's boost controller
has improved performance in Burst Mode operation when
the input voltage is higher than the regulated output voltage.
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP and µModule are registered trademarks and
No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5481178, 5705919,
5929620, 6144194, 6177787, 6580258.
Typical Application
VOUT3
REGULATED AT 10V WHEN VIN < 10V
FOLLOWS VIN WHEN VIN > 10V
220µF
499k
1µF
VFB3
68.1k
VBIAS
TG1
VIN
2.5V TO 38V
(START-UP ABOVE 5V)
2mΩ 1.2µH
220µF
4.7µF
SW1, 2, 3
TG3 SW1
SW3 LTC3859A
BG1
BG3
SENSE3
SENSE3+
INTVCC
BOOST1, 2, 3
0.1µF
ITH1, 2, 3
SENSE1+
SENSE1
VFB1
RUN1, 2, 3
EXTVCC
TG2
SW2
BG2
VOUT1
4.9µH 6mΩ
68.1k 357k
6.5µH 8mΩ
0.1µF
SENSE2+
TRACK/SS1, 2
SENSE2–
SS3 VFB2
PGND SGND
3859 TA01a
68.1k 649k
VOUT1
5V
5A
220µF
VOUT2
8.5V
3A
68µF
Efficiency vs Input Voltage
100
95 VOUT2 = 8.5V
90 VOUT1 = 5V
85
80
75
70
65
60
55 FIGURE 12 CIRCUIT
50 ILOAD = 2A
0 5 10 15 20 25 30
INPUT VOLTAGE (V)
35 40
3859A TA01b
3859afa
1


Linear Technology Electronic Components Datasheet

LTC3859A Datasheet

Buck/Buck/Boost Synchronous Controller

No Preview Available !

LTC3859A
Absolute Maximum Ratings (Notes 1, 3)
Bias Input Supply Voltage (VBIAS)............... –0.3V to 40V
Buck Top Side Driver Voltages
(BOOST1, BOOST2) .............................. –0.3V to 46V
Boost Top Side Driver Voltages
(BOOST3) ............................................. –0.3V to 76V
Buck Switch Voltage (SW1, SW2) ................. –5V to 40V
Boost Switch Voltage (SW3) ......................... –5V to 70V
INTVCC, (BOOST1–SW1),
(BOOST2–SW2), (BOOST3–SW3),........... –0.3V to 6V
RUN1, RUN2, RUN3 ..................................... –0.3V to 8V
Maximum Current Sourced Into Pin
from Source >8V...............................................100µA
SENSE1+, SENSE2+, SENSE1
SENSE2Voltages...................................... –0.3V to 28V
SENSE3+, SENSE3Voltages...................... –0.3V to 40V
FREQ Voltages.......................................–0.3V to INTVCC
EXTVCC....................................................... –0.3V to 14V
ITH1, ITH2, ITH3, VFB1, VFB2, VFB3 Voltages..... –0.3V to 6V
PLLIN/MODE, PGOOD1, OV3 Voltages ......... –0.3V to 6V
TRACK/SS1, TRACK/SS2, SS3 Voltages ...... –0.3V to 6V
Operating Junction Temperature Range (Note 2)
LTC3859AE, LTC3859AI..................... –40°C to 125°C
LTC3859AH........................................ –40°C to 150°C
LTC3859AMP...................................... –55°C to 150°C
Storage Temperature Range............... –65°C to 150°C
Pin Configuration
TOP VIEW
ITH1
VFB1
SENSE1+
SENSE1
1
2
3
4
FREQ 5
PLLIN/MODE 6
SS3
SENSE3+
SENSE3
7
8
9
VFB3
ITH3
SGND
10
11
12
RUN1 13
RUN2 14
RUN3
SENSE2
SENSE2+
15
16
17
VFB2 18
ITH2 19
39
PGND
38 TRACK/SS1
37 PGOOD1
36 TG1
35 SW1
34 BOOST1
33 BG1
32 SW3
31 TG3
30 BOOST3
29 BG3
28 VBIAS
27 EXTVCC
26 INTVCC
25 BG2
24 BOOST2
23 SW2
22 TG2
21 OV3
20 TRACK/SS2
FE PACKAGE
38-LEAD PLASTIC TSSOP
TJMAX = 150°C, qJA = 25°C/W
EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB
TOP VIEW
FREQ 1
PLLIN/MODE 2
SS3 3
SENSE3+ 4
SENSE35
VFB3
ITH3
SGND
6
7
8
RUN1 9
RUN2 10
RUN3 11
SENSE212
38 37 36 35 34 33 32
39
PGND
13 14 15 16 17 18 19
31 SW1
30 BOOST1
29 BG1
28 SW3
27 TG3
26 BOOST3
25 BG3
24 VBIAS
23 EXTVCC
22 INTVCC
21 BG2
20 BOOST2
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
TJMAX = 150°C, qJA = 34.7°C/W
EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB
3859afa
2


Part Number LTC3859A
Description Buck/Buck/Boost Synchronous Controller
Maker Linear Technology
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