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
LTC3859 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 LTC3859 can operate from
an input supply as low as 2.5V after start-up.
The 55μA no-load quiescent current extends operating run-
time in battery powered systems. OPTI-LOOP compensation
allows the transient response to be optimized over a wide
range of output capacitance and ESR values. The LTC3859
features a precision 0.8V reference for the bucks, 1.2V
reference for the boost and a power good output indicator.
Independent TRACK/SS pins for each controller ramp the out-
put 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 inductor current mode at light loads.
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.
n
n
n
n
n
n
n
n
n
n
n
n
n
Dual Buck Plus Single Boost Synchronous Controllers
Outputs Remain in Regulation Through Cold Crank
Down to 2.5V
Low Operating I
Q
: 55μA (One Channel On)
Wide Bias Input Voltage Range: 4.5V to 38V
Buck Output Voltage Range: 0.8V ≤ V
OUT
≤ 24V
Boost Output Voltage Up to 60V
R
SENSE
or DCR Current Sensing
100% Duty Cycle for Boost Synchronous MOSFET
Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode
®
Operation at Light Loads
Very Low Buck Dropout Operation: 99% Duty Cycle
Adjustable Output Voltage Soft-Start or Tracking
Low Shutdown I
Q
: 14μA
Small 38-Pin 5mm × 7mm QFN and TSSOP Packages
APPLICATIONS
n
n
n
Automotive Always-On and Start-Stop Systems
Battery Operated Digital Devices
Distributed DC Power Systems
TYPICAL APPLICATION
V
OUT3
REGULATED AT 10V WHEN V
IN
< 10V
FOLLOWS V
IN
WHEN V
IN
> 10V
220µF
499k
68.1k
V
IN
2.5V TO 38V
(START-UP ABOVE 5V)
2mΩ
220µF
1.2µH
TG3
SW3
BG3
SENSE3
SENSE3
+
INTV
CC
4.7µF
BOOST1, 2, 3
SW1, 2, 3
0.1µF
I
TH1, 2, 3
–
1µF
V
FB3
V
BIAS
TG1
4.9µH
SW1
LTC3859
BG1
SENSE1
+
SENSE1
–
V
FB1
RUN1, 2, 3
EXTV
CC
TG2
SW2
BG2
SENSE2+
SENSE2–
V
FB2
68.1k
3859 TA01
Efficiency vs Input Voltage
6mΩ
V
OUT1
5V
5A
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
6.5µH
8mΩ
V
OUT2
8.5V
3A
55 FIGURE 12 CIRCUIT
I
LOAD
= 2A
50
0
5
10 15 20 25 30
INPUT VOLTAGE (V)
V
OUT1
= 5V
V
OUT2
= 8.5V
68.1k
357k
220µF
35
40
3859 TA01b
0.1µF
TRACK/SS1, 2
SS3
PGND SGND
649k
68µF
Rev. C
Document Feedback
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1
LTC3859
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 3)
Bias Input Supply Voltage (V
BIAS
) .............. –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
INTV
CC
, (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
–
SENSE2
–
Voltages ..................................... –0.3V to 28V
SENSE3
+
, SENSE3
–
Voltages ..................... –0.3V to 40V
FREQ Voltages ......................................–0.3V to INTV
CC
EXTV
CC
...................................................... –0.3V to 14V
I
TH1
, I
TH2
, I
TH3
, V
FB1
, V
FB2
, V
FB3
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) ............................................. –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
SENSE1
–
SENSE1
+
I
TH1
V
FB1
SENSE1
+
SENSE1
–
TOP VIEW
TRACK/SS1
38 TRACK/SS1
37 PGOOD1
36 TG1
35 SW1
34 BOOST1
33 BG1
32 SW3
31 TG3
30 BOOST3
FREQ 1
PLLIN/MODE 2
SS3 3
SENSE3
+
–
1
2
3
4
5
6
7
8
9
39
PGND
PGOOD1
V
FB1
I
TH1
38 37 36 35 34 33 32
31 SW1
30 BOOST1
29 BG1
28 SW3
27 TG3
39
PGND
26 BOOST3
25 BG3
24 V
BIAS
23 EXTV
CC
22 INTV
CC
21 BG2
20 BOOST2
13 14 15 16 17 18 19
V
FB2
I
TH2
TRACK/SS2
OV3
TG2
SENSE2
+
SW2
FREQ
PLLIN/MODE
SS3
SENSE3
+
SENSE3
–
4
5
SENSE3
V
FB3
10
I
TH3
11
SGND 12
RUN1 13
RUN2 14
RUN3 15
SENSE2
–
SENSE2
+
16
17
29 BG3
28 V
BIAS
27 EXTV
CC
26 INTV
CC
25 BG2
24 BOOST2
23 SW2
22 TG2
21 OV3
20 TRACK/SS2
V
FB3
6
I
TH3
7
SGND 8
RUN1 9
RUN2 10
RUN3 11
SENSE2 12
–
V
FB2
18
I
TH2
19
FE PACKAGE
38-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
q
JA
= 25°C/W
EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB
UHF PACKAGE
38-LEAD (5mm
×
7mm) PLASTIC QFN
T
JMAX
= 125°C,
q
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB
TG1
Rev. C
2
For more information
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LTC3859
ORDER INFORMATION
LEAD FREE FINISH
LTC3859EFE#PBF
LTC3859IFE#PBF
LTC3859EUHF#PBF
LTC3859IUHF#PBF
TAPE AND REEL
LTC3859EFE#TRPBF
LTC3859IFE#TRPBF
LTC3859EUHF#TRPBF
LTC3859IUHF#TRPBF
PART MARKING*
LTC3859FE
LTC3859FE
3859
3859
PACKAGE DESCRIPTION
38-Lead Plastic TSSOP
38-Lead Plastic TSSOP
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications.
Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise noted. (Note 2)
SYMBOL
V
BIAS
V
FB1,2
V
FB3
I
FB1,2,3
V
REFLNREG
V
LOADREG
PARAMETER
Bias Input Supply Operating Voltage
Range
Buck Regulated Feedback Voltage
Boost Regulated Feedback Voltage
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
CONDITIONS
MIN
4.5
(Note 4); I
TH1,2
Voltage = 1.2V
–40°C to 125°C
–40°C to 85°C
(Note 4); I
TH3
Voltage = 1.2V
–40°C to 125°C
–40°C to 85°C
(Note 4)
(Note 4); V
BIAS
= 4.5V to 38V
(Note 4)
Measured in Servo Loop;
DI
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
DI
TH
Voltage = 1.2V to 2V
(Note 4); I
TH1,2,3
= 1.2V;
Sink/Source 5µA
(Note 5)
RUN1 = 5V and RUN2,3 = 0V or
RUN2 = 5V and RUN1,3 = 0V or
RUN3 = 5V and RUN1,2 = 0V
V
FB1, 2
ON = 0.83V (No Load)
V
FB3
= 1.25V
RUN1,2,3 = 5V,
V
FB1,2
= 0.83V (No Load)
V
FB3
= 1.25V
RUN1 = 5V and RUN2,3 = 0V or
RUN2 = 5V and RUN1,3 = 0V
V
FB,ON
= 0.83V (No Load)
RUN3 = 5V and RUN1,2 = 0V
V
FB3
= 1.25V
RUN1 = 5V and RUN2 = 0V or
RUN2 = 5V and RUN1 = 0V
RUN3 = 5V
V
FB1,2
= 0.83V (No Load)
V
FB3
= 1.25V
RUN1,2,3 = 5V,
V
FB1,2
= 0.83V (No Load)
V
FB3
= 1.25V
RUN1,2,3 = 0V
l
l
ELECTRICAL CHARACTERISTICS
TYP
MAX
38
UNITS
V
V
V
V
V
nA
%/V
%
%
mmho
l
0.788
0.792
1.182
1.188
0.800
0.800
1.200
1.200
±5
0.002
0.01
–0.01
2
0.812
0.808
1.218
1.212
±50
0.02
0.1
–0.1
l
g
m1,2,3
I
Q
Transconductance Amplifier g
m
Input DC Supply Current
Pulse-Skipping or
Forced Continuous Mode
(One Channel On)
Pulse-Skipping or
Forced Continuous Mode
(All Channels On)
Sleep Mode
(One Channel On, Buck)
Sleep Mode
(One Channel On, Boost)
Sleep Mode
(Buck and Boost Channel On)
2
mA
3
55
55
65
80
80
100
mA
µA
µA
µA
Sleep Mode
(All Three Channels On)
Shutdown
80
14
120
30
µA
µA
Rev. C
For more information
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3
LTC3859
ELECTRICAL CHARACTERISTICS
SYMBOL
UVLO
V
OVL1,2
I
SENSE1,2
+
I
SENSE3
+
I
SENSE1,2
–
I
SENSE3
–
DF
MAX,TG
DF
MAX,BG
I
TRACK/SS1,2
I
SS3
V
RUN1
ON
V
RUN2,3
ON
V
RUN1,2,3
Hyst
PARAMETER
Undervoltage Lockout
Buck Feedback Overvoltage Protection
SENSE
+
Pin Current
SENSE
+
Pin Current
SENSE
–
Pin Current
SENSE
–
Pin Current
Maximum Duty Factor for TG
Maximum Duty Factor for BG
Soft-Start Charge Current
Soft-Start Charge Current
RUN1 Pin Threshold
RUN2,3 Pin Threshold
RUN Pin Hysteresis
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise noted. (Note 2)
CONDITIONS
INTV
CC
Ramping Up
INTV
CC
Ramping Down
Measured at V
FB1,2
Relative to
Regulated V
FB1,2
Bucks (Channels 1 and 2)
Boost (Channel 3)
Bucks (Channels 1 and 2)
V
OUT1,2
< V
INTVCC
– 0.5V
V
OUT1,2
> V
INTVCC
+ 0.5V
Boost (Channel 3)
V
SENSE3
+, V
SENSE3
– = 12V
Bucks (Channels 1,2) in Dropout, FREQ = 0V
Boost (Channel 3) in Overvoltage
Bucks (Channels 1,2) in Overvoltage
Boost (Channel 3)
V
TRACK/SS1,2
= 0V
V
SS3
= 0V
V
RUN1
Rising
V
RUN2,3
Rising
V
FB1,2
= 0.7V, V
SENSE1,2
– = 3.3V
V
FB1,2,3
= 1.1V, V
SENSE3
+ = 12V
l
l
l
l
MIN
3.5
7
TYP
4.15
3.8
10
MAX
4.5
4.0
13
±1
UNITS
V
V
%
µA
µA
170
±2
±1
98
99
100
100
96
1.0
1.0
1.25
1.28
80
50
700
µA
µA
µA
%
%
%
%
µA
µA
V
V
mV
mV
V
0.7
0.7
1.19
1.23
43
2.5
1.4
1.4
1.31
1.33
57
38
V
SENSE1,2,3(MAX)
Maximum Current Sense Threshold
V
SENSE3(CM)
Gate Driver
TG1,2
BG1,2
TG3
BG3
TG1,2,3 t
r
TG1,2,3 t
f
BG1,2,3 t
r
BG1,2,3 t
f
TG/BG t
1D
BG/TG t
1D
t
ON(MIN)1,2
t
ON(MIN)3
Pull-Up On-Resistance
Pull-Down On-Resistance
Pull-Up On-Resistance
Pull-Down On-Resistance
Pull-Up On-Resistance
Pull-Down On-Resistance
Pull-Up On-Resistance
Pull-Down On-Resistance
TG Transition Time:
Rise Time
Fall Time
BG Transition Time:
Rise Time
Fall Time
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
Buck Minimum On-Time
Boost Minimum On-Time
SENSE3 Pins Common Mode Range
(BOOST Converter Input Supply Voltage)
l
2.5
1.5
2.4
1.1
1.2
1.0
1.2
1.0
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF Each Driver Bucks (Channels 1, 2)
Boost (Channel 3)
C
LOAD
= 3300pF Each Driver Bucks (Channels 1, 2)
Boost (Channel 3)
(Note 7)
(Note 7)
25
16
28
13
30
70
30
70
95
120
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
Rev. C
4
For more information
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LTC3859
ELECTRICAL CHARACTERISTICS
SYMBOL
V
INTVCCVBIAS
V
LDOVBIAS
V
INTVCCEXT
V
LDOEXT
V
EXTVCC
V
LDOHYS
f
25k
f
65k
f
105k
f
LOW
f
HIGH
f
SYNC
PGOOD1 Output
V
PGL1
I
PGOOD1
V
PG1
PGOOD1 Voltage Low
PGOOD1 Leakage Current
PGOOD1 Trip Level
I
PGOOD1
= 2mA
V
PGOOD1
= 5V
V
FB1
with Respect to Set Regulated Voltage
V
FB1
Ramping Negative
Hysteresis
V
FB1
Ramping Positive
Hysteresis
–13
7
–10
2.5
10
2.5
20
0.2
6
10
1.5
65
0.2
0.4
±1
–7
13
V
µA
%
%
%
%
µs
V
µA
%
%
µA
PARAMETER
Internal V
CC
Voltage
INTV
CC
Load Regulation
Internal V
CC
Voltage
INTV
CC
Load Regulation
EXTV
CC
Switchover Voltage
EXTV
CC
Hysteresis
Programmable Frequency
Programmable Frequency
Programmable Frequency
Low Fixed Frequency
High Fixed Frequency
Synchronizable Frequency
R
FREQ
= 25k; PLLIN/MODE = DC Voltage
R
FREQ
= 65k; PLLIN/MODE = DC Voltage
R
FREQ
= 105k; PLLIN/MODE = DC Voltage
V
FREQ
= 0V PLLIN/MODE = DC Voltage
V
FREQ
= INTV
CC
; PLLIN/MODE = DC Voltage
PLLIN/MODE = External Clock
l
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
