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
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 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
output voltages 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 current
mode at light loads.
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
Automotive Always-On and Start-Stop Systems
Battery Operated Digital Devices
Distributed DC Power Systems
APPLICATIONS
n
n
n
L,
LT, LTC, LTM, Burst Mode, OPTI-LOOP and μModule are registered trademarks and
No R
SENSE
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
V
OUT3
REGULATED AT 10V WHEN V
IN
< 10V
FOLLOWS V
IN
WHEN V
IN
> 10V
220μF
499k
V
FB3
68.1k
4.9μH
V
IN
2.5V TO 38V
(START-UP ABOVE 5V)
2mΩ
220μF
BG3
SENSE3
–
SENSE3
+
INTV
CC
4.7μF
BOOST1, 2, 3
SW1, 2, 3
0.1μF
I
TH1, 2, 3
TG2
SW2
BG2
6.5μH
8mΩ
V
OUT2
8.5V
3A
SENSE1
+
SENSE1
–
V
FB1
68.1k
RUN1, 2, 3
EXTV
CC
357k
220μF
1.2μH
TG3
SW3
SW1
BG1
6mΩ
V
OUT1
5V
5A
EFFICIENCY (%)
1μF
V
BIAS
TG1
100
95
90
85
80
75
70
65
60
55 FIGURE 12 CIRCUIT
I
LOAD
= 2A
50
10 15 20 25 30
5
0
INPUT VOLTAGE (V)
V
OUT1
= 5V
V
OUT2
= 8.5V
Efficiency vs Input Voltage
LTC3859
35
40
3859 TA01b
0.1μF
SENSE2+
SENSE2–
TRACK/SS1, 2
V
FB2
SS3
PGND SGND
3859 TA01
68.1k
649k
68μF
3859f
1
LTC3859
ABSOLUTE MAXIMUM RATINGS
(Note 1)
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
PLLIN/MODE, 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
PGOOD1, OV3 Voltages .............................. –0.3V to 6V
TRACK/SS1, TRACK/SS2, SS3 Voltages ..... –0.3V to 6V
Operating Junction Temperature Range
(Notes 2, 3)........................................ –40°C to 125°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range................... –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
TRACK/SS1
SENSE1
–
SENSE1
+
I
TH1
V
FB1
SENSE1
+
SENSE1
–
FREQ
PLLIN/MODE
SS3
SENSE3
+
SENSE3
–
1
2
3
4
5
6
7
8
9
39
PGND
38 TRACK/SS1
37 PGOOD1
36 TG1
35 SW1
34 BOOST1
33 BG1
32 SW3
31 TG3
30 BOOST3
29 BG3
28 V
BIAS
27 EXTV
CC
26 INTV
CC
25 BG2
24 BOOST2
23 SW2
22 TG2
21 OV3
20 TRACK/SS2
FREQ 1
PLLIN/MODE 2
SS3 3
SENSE3
SENSE3
+
–
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
OV3
TG2
TRACK/SS2
SENSE2
+
SW2
V
FB2
I
TH2
4
5
V
FB3
10
I
TH3
11
SGND 12
RUN1 13
RUN2 14
RUN3 15
SENSE2
–
SENSE2
+
16
17
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,
θ
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,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB
TG1
3859f
2
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
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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
SYMBOL
V
BIAS
V
FB1,2
PARAMETER
Bias Input Supply Operating Voltage
Range
Buck Regulated Feedback Voltage
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
J
≈ T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise noted.
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
IN
= 4V to 38V
(Note 4)
Measured in Servo Loop;
ΔI
TH
Voltage = 1.2V to 0.7V
Measured in Servo Loop;
ΔI
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
l
TYP
MAX
38
UNITS
V
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
V
V
V
V
nA
%/V
%
%
mmho
V
FB3
Boost Regulated Feedback Voltage
l
I
FB1,2,3
V
REFLNREG
V
LOADREG
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
g
m1,2,3
I
Q
Transconductance Amplifier g
m
Input DC Supply Current
Pulse-Skipping or
Forced Continuous Mode
(One Channel On)
2
mA
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)
3
mA
55
80
μA
55
65
80
100
μA
μA
Sleep Mode
(All Three Channels On)
Shutdown
80
120
μA
14
30
μA
3859f
3
LTC3859
ELECTRICAL CHARACTERISTICS
SYMBOL
UVLO
V
OVL1,2
I
SENSE1,2
+
I
SENSE3
+
I
SENSE1,2
–
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
J
≈ T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise noted.
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
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
700
±1
98
99
100
100
96
1.0
1.0
1.25
1.28
80
50
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
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
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
Internal V
CC
Voltage
INTV
CC
Load Regulation
SENSE3 Pins Common Mode Range
(BOOST Converter Input Supply Voltage)
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)
6V < V
BIAS
< 38V, V
EXTVCC
= 0V, I
INTVCC
= 0mA
I
CC
= 0mA to 50mA, V
EXTVCC
= 0V
5.0
25
16
28
13
30
70
30
70
95
120
5.4
0.7
5.6
2
Ω
Ω
Ω
Ω
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
V
%
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
V
INTVCCVBIAS
V
LDOVBIAS
INTV
CC
Linear Regulator
3859f
4
LTC3859
ELECTRICAL CHARACTERISTICS
SYMBOL
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
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
J
≈ T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise noted.
CONDITIONS
6V < V
EXTVCC
< 13V, I
INTVCC
= 0mA
I
CC
= 0mA to 50mA, V
EXTVCC
= 8.5V
EXTV
CC
Ramping Positive
4.5
MIN
5.0
TYP
5.4
0.7
4.7
200
115
375
320
485
75
440
835
350
535
380
585
850
505
MAX
5.6
2
UNITS
V
%
V
mV
kHz
kHz
kHz
kHz
kHz
kHz
Oscillator and Phase-Locked Loop
T
PG1
V
OV3L
I
OV3
V
OV
Delay For Reporting a Fault
OV3 Voltage Low
OV3 Leakage Current
OV3 Trip Level
I
OV3
= 2mA
V
OV3
= 5V
V
FB
With Respect to Set Regulated Voltage
Hysteresis
V
BOOST3
= 16V; V
SW3
= 12V;
Forced Continuous Mode
OV3 Boost Overvoltage Indicator Output
0.4
±1
13
BOOST3 Charge Pump
I
BST3
BOOST3 Charge Pump Available Output
Current
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3859 is tested under pulsed conditions such that T
J
≈ T
A
.
The LTC3859E is guaranteed to meet performance specifications from
0°C to 125°C. Specifications over the –40°C to 125°C operating junction
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3859I is guaranteed over the full
–40°C to 125°C operating junction temperature range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
= 34°C/W for the QFN package and
θ
JA
= 25°C/W for the TSSOP
package.
Note 4:
The LTC3859 is tested in a feedback loop that servos V
ITH1,2,3
to a
specified voltage and measures the resultant V
FB1,2,3
. The specification at
85°C is not tested in production. This specification is assured by design,
characterization and correlation to production testing at 125°C.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications information.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
See Minimum On-Time Considerations in the Applications
