LT8603
42V, Low I
Q
, Quad Output Triple Monolithic
Buck Converter and Boost Controller
FEATURES
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DESCRIPTION
The
LT
®
8603
is a highly flexible, quad output regulator
combining two high input voltage capable monolithic
step-down switching regulators, one low input voltage
capable monolithic step-down regulator, and a boost
controller to satisfy a wide range of applications while
occupying minimal board space.
With the boost controller configured to supply the chip
V
IN
supply, the LT8603 produces three precisely regulated
outputs even when the boost input voltage falls signifi-
cantly below the regulated output voltages, such as dur-
ing an automotive cold crank scenario. Alternatively, with
the boost controller driven from one of the step-down
regulator outputs or configured as a SEPIC, the LT8603
provides four precisely regulated outputs over a wide
input voltage range.
The LT8603 provides robust regulation by including a
cycle-by-cycle current limit for all step-down regulators,
thermal shutdown, and a boost controller that can tolerate
reverse battery connections and negative transient input
voltages down to –42V.
All registered trademarks and trademarks are the property of their respective owners.
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Flexible Power Supply System Capable of Four
Regulated Outputs with V
BATT
<< V
OUT
Two High Voltage Synchronous Buck Regulators
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3V to 42V Input Voltage Range
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Output Currents Up to 2.5A and 1.5A
One Low Voltage Synchronous Buck Regulator
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2.6V to 5.5V Input Voltage Range
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Output Currents Up to 1.8A
One Boost Controller Allows Buck Converters to
Regulate with V
BATT
<< V
OUT
Selectable Burst Mode
®
Operation Allows Low
28µA I
Q
with High Voltage Channels Active
Programmable Power-On Reset
Individual Channel Power Good Indicators
Step-Down Switching Frequency: 250kHz to 2.2MHz
Available in 40-Lead QFN (6mm × 6mm) Package
APPLICATIONS
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Automotive Stop-Start and Cold Crank Ride Through
Last-Gasp CPU Power Hold-Up
Industrial Controls and Power Supplies
TYPICAL APPLICATION
Cold Crank Tolerant Automotive Triple Output Supply
V
BATT
2V TO 42V
(BOOST
START-UP
ABOVE 4.3V)
OUT4
8V FOR
2V < V
BATT
< 8.5V
EN/UVLO V
IN
PV
IN1
PV
IN2
ISP4
INTV
CC4
INTV
CC
FSEL4A
FSEL4B
RT
SYNC
2
CPOR
TRKSS1-2
PV
IN3
RUN3
OUT2
PG1-4
POREN
RESET
4
BIAS
PG1-4
POREN
RST
GND
FB3
8603 TA01a
LT8603 Response to a Cold Crank
Automotive Input Waveform
V
BATT
V
OUT4
ISN4
GATE4
FB4
BST1
SW1
OUT1
5V, 1.5A
LT8603
FB1
BST2
SW2
FB2
SW3
OUT2
3.3V,
2.5A – I
PVIN3
OUT3
1.2V, 1.8A
VOLTAGE
2V/DIV
V
OUT1
V
OUT2
V
OUT3
0V
TIME (10ms/DIV)
8603 TA01b
For more information
www.linear.com/LT8603
1
8603f
LT8603
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
POREN
CPOR
30 RUN3
29 RT
28 INTV
CC
27 FB3
41
GND
26 FB1
25 FB2
24 FB4
23 V
IN
22 EN/UVLO
21 TRKSS1
11 12 13 14 15 16 17 18 19 20
FSEL4A
GND
PG4
FSEL4B
ISN4
ISP4
INTV
CC4
TRKSS2
PV
IN2
GATE4
SYNC
PV
IN1
PV
IN3
SW3
GND
GND
PG3
RST
Supply Voltages
V
IN
, PV
IN1,2
............................................ –0.3V to 42V
PV
IN3
....................................................... –0.3V to 6V
EN/UVLO.................................................................. 42V
ISP4, ISN4 .................................................. –42V to 42V
TRKSS1-2, RUN3, FB4, PG1-4, SYNC .........................6V
FSEL4A, FSEL4B,
RST
.................................................6V
FB1-3, CPOR, POREN...............................................3.6V
BIAS ........................................................... –0.3V to 15V
Operating Junction Temperature (Notes 2, 5)
LT8603E ............................................ –40°C to 125°C
LT8603I ............................................. –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
40 39 38 37 36 35 34 33 32 31
PG1 1
GND 2
SW1 3
BST1 4
BST2 5
SW2 6
SW2 7
GND 8
BIAS 9
PG2 10
UJ PACKAGE
40-LEAD (6mm
×
6mm) PLASTIC QFN
θ
JA
= 33°C/W,
θ
JC
= 2°C/W
EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT8603EUJ#PBF
LT8603IUJ#PBF
TAPE AND REEL
LT8603EUJ#TRPBF
LT8603IUJ#TRPBF
http://www.linear.com/product/LT8603#orderinfo
PART MARKING*
LT8603UJ
LT8603UJ
PACKAGE DESCRIPTION
40-Lead (6mm × 6mm) Plastic QFN
40-Lead (6mm × 6mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult ADI 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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
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8603f
For more information
www.linear.com/LT8603
LT8603
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, EN/UVLO = 3V unless otherwise noted. (Note 2)
PARAMETER
Bias and Internal Regulators
Minimum Operating V
IN
for Channels 1, 2 and 3
Minimum V
IN
to Start for Channels 1, 2 and 3
Minimum Operating V
IN
for Channel 4
Minimum V
IN
to Start for Channel 4
V
IN
Quiescent Current, Shutdown
Total Operating Current V
BATT
EN/UVLO Threshold
EN/UVLO Input Current
INTV
CC4
Regulated Voltage
INTV
CC4
Regulator Load Regulation
Oscillator
Switching Frequency
SYNC Input Frequency Range
SYNC Input Voltage Low
SYNC Input Voltage High
SYNC Input Current
FSEL4A, FSEL4B Input Voltage Low
FSEL4A, FSEL4B Input Voltage High
FSEL4A, FSEL4B Input Current
Channel 1
Feedback Voltage FB1
Input Current FB1
FB1 Line Regulation
SW1 Peak Current Limit (Note 3)
SW1 Leakage Current
SW1 Top On-Resistance
SW1 Bottom On-Resistance
Lower FB1 Power Good Threshold
Upper FB1 Power Good Threshold
Power Good Threshold Hysteresis
PG1 Output Voltage Low
PG1 Leakage Current
TRKSS1 Pull-Up Current
I
PG1
= 350μA
PG1 = 5V, FB1 = 1V
TRKSS1 = 0.2V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
2.7
3.1
3.0
4.0
0.1
28
50
MAX
3.0
3.3
3.2
4.15
1
UNITS
V
V
V
V
μA
μA
μA
V
BIAS
= 0V, EN/UVLO = 0.4V
V
BATT
= 12V, Channels 1 and 2 Active, No-Load (Note 4)
V
BATT
= 12V, All Channels Active, No-Load (Note 4)
EN/UVLO Rising
EN/UVLO Falling
EN/UVLO = 1.2V
V
BIAS
= 0V
V
BIAS
= 6V
INTV
CC4
at 1mA – INTV
CC4
at 40mA
R
T
= 28.7kΩ
R
T
= 243kΩ
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1.15
1.1
–50
4.4
4.7
1.2
1.15
4.6
5
70
1.25
1.2
50
4.8
5.2
V
V
nA
V
V
mV
1.8
0.224
0.25
1.2
–100
2
–100
0.985
–100
2
0.25
2.2
0.284
2.2
0.3
100
0.4
100
MHz
MHz
MHz
V
V
nA
V
V
nA
V
nA
%/V
A
μA
mΩ
mΩ
1
0.002
1.015
100
0.01
3.7
1
V
IN
= 3V to 42V
2.0
I
SW1
= 1A
I
SW1
= 1A
Percentage of V
FB1
, V
FB1
Falling
Percentage of V
FB1
, V
FB1
Rising
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2.7
0.1
240
170
89
104
92
107
0.8
0.13
95
110
0.3
6
3.1
%
%
%
V
μA
μA
1.5
2.4
For more information
www.linear.com/LT8603
3
8603f
LT8603
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, EN/UVLO = 3V unless otherwise noted. (Note 2)
PARAMETER
Channel 2
Feedback Voltage FB2
Input Current FB2
FB2 Line Regulation
SW2 Peak Current Limit (Note 3)
SW2 Leakage Current
SW2 Top On-Resistance
SW2 Bottom On-Resistance
Lower FB2 Power Good Threshold
Upper FB2 Power Good Threshold
Power Good Threshold Hysteresis
PG2 Output Voltage Low
PG2 Leakage Current
TRKSS2 Pull-Up Current
Channel 3
PV
IN3
Operating Voltage
PV
IN3
Undervoltage Lockout
Feedback Voltage FB3
FB3 Line Regulation
Input Current FB3
SW3 Leakage Current
SW3 Peak Current Limit (Note 3)
SW3 PMOS On-Resistance
SW3 NMOS On-Resistance
Lower FB3 Power Good Threshold
Upper FB3 Power Good Threshold
Power Good Threshold Hysteresis
PG3 Output Voltage Low
PG3 Leakage Current
RUN3 Threshold Voltage
RUN3 Input Current
Soft-Start Time
I
PG3
= 350μA
PG3 = 5V, FB3 = 0.8V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
0.985
–100
TYP
1
0.002
MAX
1.015
100
0.01
5.3
1
UNITS
V
nA
%/V
A
μA
mΩ
mΩ
V
IN
= 3V to 42V
3.2
I
SW2
= 1A
I
SW2
= 1A
Percentage of V
FB2
, V
FB2
Falling
Percentage of V
FB2
, V
FB2
Rising
I
PG2
= 350μA
PG2 = 5V, FB2 = 1V
TRKSS2 = 0.2V
PV
IN3
Falling
PV
IN3
Falling
V
IN
= 3V to 42V
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4.0
0.1
150
100
89
104
92
107
0.8
0.13
95
110
0.3
6
3.1
5.5
%
%
%
V
μA
μA
V
V
mV
%/V
nA
μA
A
mΩ
mΩ
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1.5
2.6
2.4
2.35
788
–100
0.1
2.6
3.2
150
100
800
0.002
2.6
812
0.01
100
1
3.8
I
SW3
= 1A
I
SW3
= 1A
Percentage of V
FB3
, V
FB3
Falling
Percentage of V
FB3
, V
FB3
Rising
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89
104
92
107
0.2
0.13
95
110
0.3
6
1.25
100
1.3
%
%
%
V
μA
V
nA
ms
1.15
–100
0.7
1.20
1
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8603f
For more information
www.linear.com/LT8603
LT8603
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, EN/UVLO = 3V unless otherwise noted. (Note 2)
PARAMETER
Channel 4
Feedback Voltage FB4
FB4 Line Regulation
Input Current FB4
Soft-Start Time
Current Comparator Limit Threshold
Current Comparator Input Common Mode Range
ISP4, ISN4 Input Currents, Sleep
ISP4, ISN4 Input Currents, Active
ISP4, ISN4 Input Currents
GATE4 High Side PMOS On-Resistance
GATE4 Low Side NMOS On-Resistance
FB4 Power Good Threshold
Power Good Threshold Hysteresis
PG4 Output Voltage Low
PG4 Leakage Current
Power-On Reset
POR Delay Time
RST
Output Voltage Low
RST
Pull-Up Current
RST
Leakage Current
POREN Threshold
POREN Pull-Up Current
POREN = 0V
CPOR = 1000pF
I
RST
= 100μA
POR Timed Out,
RST
= 0V
POR Timed Out,
RST
= 6V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
788
–100
TYP
800
0.002
MAX
812
0.01
100
UNITS
mV
%/V
nA
ms
mV
V
nA
μA
mA
Ω
Ω
V
IN
= 3.2V to 42V
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1
V
ISP4
to V
ISN4
, V
CM
= 2V to 42V
V
ISP4
= V
ISN4
= 2V to 42V, FB4 = 1V, SYNC = 0V
V
ISP4
= V
ISN4
= 2V to 42V, FB4 = 0V, SYNC = 0V
V
ISP4
= V
ISN4
= –42V
34
7
2.5
1.25
Percentage of V
FB4
, V
FB4
Falling
I
PG4
= 350μA
PG4 = 5V, FB4 = 0.8V
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43
2
50
57
42
200
44
10
89
92
0.2
0.13
95
0.3
6
%
%
V
μA
ms
V
μA
nA
V
μA
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35.2
0.1
20
39.4
0.2
100
–100
1.15
0.6
1.2
1.0
1.25
1.4
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 LT8603E is guaranteed to meet performance specifications
from 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT8603I is guaranteed to meet performance specifications from –40°C
to 125°C junction temperature. High junction temperatures degrade
operating lifetimes. Operating lifetime is derated at junction temperatures
above 125°C.
Note 3:
Current limit is assured by design and/or correlation to static test.
Slope compensation reduces current limit at higher duty cycles.
Note 4:
Measurement made using the circuit titled, “Details of Front Page
Application” in the Typical Applications section.
Note 5:
This IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum junction temperature will
reduce lifetime.
For more information
www.linear.com/LT8603
5
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