LTC3374IUHFPBF [Linear]
8-Channel Parallelable 1A Buck DC/DCs;
| 型号： | LTC3374IUHFPBF |
| 厂家： | 
Linear |
| 描述： | 8-Channel Parallelable 1A Buck DC/DCs |
| 文件： | 总24页 (文件大小：345K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3374
8-Channel Parallelable
1A Buck DC/DCs
FEATURES
DESCRIPTION
The LTC®3374 is a high efficiency multioutput power sup-
ply IC. The DC/DCs consist of eight synchronous buck
converters (1A each) all powered from independent 2.25V
to 5.5V input supplies.
n
8-Channel Independent Step-Down DC/DCs
n
Master-Slave Configurable for Up to 4A per Output
Rail with a Single Inductor
n
Independent V Supplies for Each DC/DC
IN
(2.25V to 5.5V)
The DC/DCs may be used independently or in parallel to
achievehighercurrentsofupto4Aperoutputwithashared
inductor. The common buck switching frequency may be
programmed with an external resistor, synchronized to an
external oscillator, or set to a default internal 2MHz clock.
The operating mode for all DC/DCs may be programmed
via the MODE pin.
n
n
All DC/DCs Have 0.8V – V Output Range
IN
Precision Enable Pin Thresholds for Autonomous
Sequencing
n
1MHz to 3MHz Programmable/Synchronizable
Oscillator Frequency (2MHz Default)
Die Temperature Monitor Output
Thermally Enhanced 38-Lead QFN (5mm × 7mm)
and TSSOP Packages
n
n
To reduce input noise the buck converters are phased in
90° steps. Precision enable pin thresholds provide reli-
able power-up sequencing. The LTC3374 is available in a
compact 38-lead 5mm × 7mm QFN package as well as a
38-lead TSSOP package.
APPLICATIONS
n
General Purpose Multichannel Power Supplies
Industrial/Automotive/Communications
n
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
8-Channel 1A Multioutput Buck Regulator
V
IN1
BUCK1
0.8V TO V
IN1
UP TO 1A
V
CC
2.7V TO 5.5V
Buck Efficiency vs ILOAD
100
90
80
70
60
50
MASTER
LTC3374
V
IN2
SLAVE
0.8V TO V
UP TO 1A
IN2
BUCK2
EN1
EN2
EN3
EN4
EN5
EN6
EN7
EN8
MASTER
MASTER
SINGLE BUCK
40
DUAL BUCK
•
•
•
TRIPLE BUCK
30
V
IN7
SLAVE
QUAD BUCK
0.8V TO V
UP TO 1A
IN7
BUCK7
20
FORCED CONTINUOUS MODE
V
OSC
= 3.3V, V
= 1.8V
IN
OUT
10
0
f
= 1MHz, L = 3.3µH
PGOOD_ALL
TEMP
0
1000
2000
3000
4000
MODE
LOAD CURRENT (mA)
V
SLAVE
IN8
BUCK8
0.8V TO V
UP TO 1A
IN8
3374 TA01b
SYNC
RT
3374 TA01a
3374f
1
For more information www.linear.com/LTC3374
LTC3374
TABLE OF CONTENTS
Features..................................................... 1
Applications ................................................ 1
Typical Application ........................................ 1
Description.................................................. 1
Absolute Maximum Ratings.............................. 3
Pin Configuration .......................................... 3
Order Information.......................................... 3
Electrical Characteristics................................. 4
Typical Performance Characteristics ................... 6
Pin Functions..............................................11
Block Diagram.............................................13
Operation...................................................14
Buck Switching Regulators..................................... 14
Buck Regulators with Combined Power Stages...... 14
Power Failure Reporting Via PGOOD_ALL Pin........ 15
Temperature Monitoring and Overtemperature
Applications Information ................................17
Buck Switching Regulator Output Voltage
and Feedback Network............................................ 17
Buck Regulators ..................................................... 17
Combined Buck Regulators..................................... 17
Input and Output Decoupling Capacitor Selection... 17
PCB Considerations................................................ 17
Package Description .....................................22
Typical Application .......................................24
Related Parts..............................................24
Protection............................................................... 15
Programming the Operating Frequency.................. 15
3374f
2
For more information www.linear.com/LTC3374
LTC3374
ABSOLUTE MAXIMUM RATINGS (Note 1)
Operating Junction Temperature Range
V
, FB1-8, EN1-8, V , PGOOD_ALL,
IN1-8
CC
(Notes 2, 3)............................................ –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
SYNC, RT, MODE ......................................... –0.3V to 6V
TEMP .................. –0.3V to Lesser of (V + 0.3V) or 6V
PGOOD_ALL
CC
I
...............................................................5mA
PIN CONFIGURATION
TOP VIEW
TOP VIEW
1
2
V
CC
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
TEMP
EN2
EN1
FB1
MODE
EN7
3
38 37 36 35 34 33 32
4
EN8
FB1
1
2
3
4
5
6
7
8
9
31 FB8
5
FB8
V
V
30
29
28
27
26
V
IN8
IN1
IN1
SW1
SW8
SW7
6
V
SW1
SW2
IN8
SW2
7
SW8
SW7
V
V
IN7
IN2
8
V
IN2
FB2
FB3
FB7
39
GND
9
V
FB2
FB3
IN7
25 FB6
24
10
11
12
13
14
15
16
17
18
19
FB7
FB6
39
GND
V
V
IN6
IN3
V
IN3
SW3
23 SW6
22 SW5
V
SW3
IN6
SW4 10
11
SW6
SW5
SW4
V
21
20
V
IN5
IN4
V
IN4
FB4 12
FB5
V
FB4
EN4
IN5
13 14 15 16 17 18 19
FB5
EN5
EN6
RT
EN3
PGOOD_ALL
SYNC
UHF PACKAGE
38-LEAD (5mm × 7mm) PLASTIC QFN
= 150°C, θ = 34°C/W
FE PACKAGE
T
JMAX
JA
38-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
T
= 150°C, θ = 25°C/W
JA
JMAX
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3374EUHF#PBF
LTC3374IUHF #PBF
LTC3374HUHF #PBF
LTC3374EFE #PBF
LTC3374IFEF #PBF
LTC3374HFE #PBF
TAPE AND REEL
PART MARKING*
3374
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3374EUHF#TRPBF
LTC3374IUHF#TRPBF
LTC3374HUHF#TRPBF
LTC3374EFE#TRPBF
LTC3374IFEF#TRPBF
LTC3374HFE#TRPBF
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
38-Lead (5mm × 7mm) Plastic QFN
38-Lead Plastic TSSOP
3374
3374
LTC3374EFE
LTC3374IFE
LTC3374HFE
38-Lead Plastic TSSOP
38-Lead Plastic TSSOP
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 nonstandard 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/
3374f
3
For more information www.linear.com/LTC3374
LTC3374
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). VCC = VIN1-8 = 3.3V, unless otherwise specified.
SYMBOL
PARAMETER
Voltage Range
CONDITIONS
MIN
TYP
MAX
UNITS
l
V
V
V
2.7
5.5
V
VCC
CC
l
l
Undervoltage Threshold on V
V
V
Voltage Falling
Voltage Rising
2.35
2.45
2.45
2.55
2.55
2.65
V
V
VCC_UVLO
CC
CC
CC
I
I
V
V
Input Supply Current
Input Supply Current
All Switching Regulators in Shutdown
At Least 1 Buck Active
8
18
µA
VCC_ALLOFF
CC
VCC
CC
SYNC = 0V, R = 400k, V
= 0.85V
45
200
75
275
µA
µA
T
FB_BUCK
SYNC = 2MHz
f
Internal Oscillator Frequency
Synchronization Frequency
V
V
= V , SYNC = 0V
1.8
1.75
1.8
2
2
2
2.2
2.25
2.2
MHZ
MHz
MHz
OSC
RT
RT
RT
CC
l
l
= V , SYNC = 0V
CC
R
= 400k, SYNC = 0V
f
t
, t > 40ns
LOW HIGH
1
3
MHz
SYNC
l
l
V
SYNC
SYNC Level High
SYNC Level Low
1.2
V
V
0.4
l
V
RT
RT Servo Voltage
R
= 400k
780
800
820
mV
RT
Temperature Monitor
TEMP Voltage at 25°C
Slope
V
150
6.75
165
10
mV
mV/°C
°C
TEMP(ROOM)
V
∆V
/°C
TEMP
TEMP
OT
Overtemperature Shutdown
Overtemperature Hysteresis
Temperature Rising
OT Hyst
1A Buck Regulators
°C
l
V
V
V
Buck Input Voltage Range
Buck Output Voltage Range
Undervoltage Threshold on V
2.25
5.5
V
V
BUCK
V
FB
V
IN
OUT
l
l
V
IN
V
IN
Voltage Falling
Voltage Rising
1.95
2.05
2.05
2.15
2.15
2.25
V
V
IN_UVLO
IN
I
Burst Mode® Operation
V
= 0.85V (Note 4)
18
400
0
50
550
1
µA
µA
µA
µA
VIN_BUCK
FB_BUCK
Forced Continuous Mode Operation
Shutdown Input Current
I
= 0µA, V
= 0V
SW_BUCK
FB_BUCK
All Switching Regulators in Shutdown
At Least One Other Buck Active
Shutdown Input Current
1
2
I
PMOS Current Limit
(Note 5)
2.0
780
–50
100
2.3
2.7
820
50
A
mV
nA
FWD
l
l
V
Feedback Regulation Voltage
Feedback Leakage Current
Maximum Duty Cycle
PMOS On-Resistance
NMOS On-Resistance
PMOS Leakage Current
NMOS Leakage Current
Soft-Start Time
800
FB
I
V
V
= 0.85V
= 0V
FB
FB_BUCK
FB_BUCK
SW_BUCK
SW_BUCK
DMAX
%
R
R
I
I
= 100mA
= 100mA
265
280
mΩ
mΩ
µA
PMOS
NMOS
LEAKP
LEAKN
SS
I
I
t
EN_BUCK = 0
EN_BUCK = 0
–2
–2
2
2
µA
1
92.5
1
ms
%
V
V
Falling PGOOD Threshold Voltage
PGOOD Hysteresis
PGOOD(FALL)
%
PGOOD(HYS)
Buck Regulators Combined
I
I
I
PMOS Current Limit
PMOS Current Limit
PMOS Current Limit
2 Buck Converters Combined (Note 5)
3 Buck Converters Combined (Note 5)
4 Buck Converters Combined (Note 5)
4.6
6.9
9.2
A
A
A
FWD2
FWD3
FWD4
3374f
4
For more information www.linear.com/LTC3374
LTC3374
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). VCC = VIN1-8 = 3.3V, unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Interface Logic Pins (PBGOOD_ALL, MODE)
I
Output High Leakage Current
Output Low Voltage
PGOOD_ALL 5.5V at Pin
PGOOD_ALL 3mA into Pin
MODE
–1
1
µA
V
OH
V
V
V
0.1
0.4
OL
IH
IL
l
l
Input High Threshold
Input Low Threshold
1.2
V
MODE
0.4
V
Interface Logic Pins (EN1, EN2, EN3, EN4, EN5, EN6, EN7, EN8)
l
l
V
V
V
Enable Rising Threshold
Enable Falling Hysteresis
Enable Rising Threshold
Enable Pin Leakage Current
All Regulators Disabled
400
730
60
1200
mV
mV
mV
µA
HI_ALLOFF
EN_HYS
HI
At Least One Regulator Enabled
380
–1
400
420
1
I
EN
EN = V = V = 5.5V
CC IN
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 3: The LTC3374 includes overtemperature protection which protects
the device during momentary overload conditions. Junction temperatures
will exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
may impair device reliability.
Note 2: The LTC3374 is tested under pulsed load conditions such that
T ≈ T . The LTC3374E is guaranteed to meet specifications from
Note 4: Static current, switches not switching. Actual current may be
higher due to gate charge losses at the switching frequency.
Note 5: The current limit features of this part are intended to protect the
IC from short term or intermittent fault conditions. Continuous operation
above the maximum specified pin current rating may result in device
degradation over time.
J
A
0°C to 85°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
LTC3374I is guaranteed over the –40°C to 125°C operating junction
temperature range and the LTC3374H is guaranteed over the –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes; operating lifetime is derated for junction
temperatures greater than 125°C. Note that the maximum ambient
temperature consistent with these specifications is determined by
specific operating conditions in conjunction with board layout, the rated
package thermal impedance and other environmental factors. The junction
temperature (T in °C) is calculated from ambient temperature (T in °C)
J
A
and power dissipation (P in Watts) according to the formula:
D
T = T + (P • θ )
JA
J
A
D
where θ (in °C/W) is the package thermal impedance.
JA
3374f
5
For more information www.linear.com/LTC3374
LTC3374
TYPICAL PERFORMANCE CHARACTERISTICS
VCC Undervoltage Threshold
vs Temperature
Buck VIN Undervoltage Threshold
vs Temperature
VCC Supply Current
vs Temperature
2.70
2.65
2.60
2.55
2.50
2.45
2.40
2.35
2.30
2.30
2.25
2.20
2.15
2.10
2.05
2.00
1.95
1.90
60
55
50
ALL REGULATORS
IN SHUTDOWN
45
40
35
V
RISING
V
RISING
CC
IN
30
25
20
15
10
5
V
FALLING
V
FALLING
CC
IN
V
V
= 5.5V
= 2.7V
V
= 3.3V
CC
CC
CC
0
50 75
–50 –25
0
25
100 125 150
50 75
50 75
25
TEMPERATURE (°C)
–50 –25
0
25
100 125 150
–50 –25
0
100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
3374 G01
3374 G02
3374 G03
VCC Supply Current
vs Temperature
VCC Supply Current
vs Temperature
RT Programmed Oscillator
Frequency vs Temperature
125
100
75
50
25
0
400
2.20
2.15
2.10
2.05
2.00
1.95
1.90
1.85
1.80
AT LEAST ONE BUCK ENABLED
SYNC = 0V
FB = 850mV
AT LEAST ONE BUCK ENABLED
360 SYNC = 2MHz
R
= 402k
RT
320
280
240
200
160
120
80
V
V
= 5.5V
= 3.3V
CC
CC
V
V
= 5.5V
= 2.7V
CC
CC
V
= 3.3V
CC
V
= 2.7V
CC
V
CC
V
CC
V
CC
= 5.5V
= 3.3V
= 2.7V
40
0
50 75
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3374 G05
–50 –25
0
25
100 125 150
–25
50 75
TEMPERATURE (°C)
–50
0
25
100 125
150
TEMPERATURE (°C)
3374 G04
3374 G06
Default Oscillator Frequency
vs Temperature
Oscillator Frequency vs VCC
2.20
2.15
2.10
2.05
2.00
1.95
1.90
1.85
1.80
2.20
2.15
2.10
2.05
2.00
1.95
1.90
1.85
1.80
V
= V
CC
RT
V
= V
CC
RT
R
= 402k
RT
V
CC
V
CC
V
CC
= 5.5V
= 3.3V
= 2.7V
50 75
TEMPERATURE (°C)
4.3 4.7
(V)
–50 –25
0
25
100 125 150
2.7 3.1 3.5 3.9
5.1 5.5
V
CC
3374 G07
3374 G08
3374f
6
For more information www.linear.com/LTC3374
LTC3374
TYPICAL PERFORMANCE CHARACTERISTICS
VTEMP vs Temperature
Enable Threshold vs Temperature
Oscillator Frequency vs RT
1400
1200
1000
800
600
400
200
0
900
850
800
750
700
650
600
550
500
450
400
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 3.3V
ALL REGULATORS DISABLED
CC
V
= 3.3V
CC
EN RISING
EN FALLING
ACTUAL V
TEMP
IDEAL V
20
TEMP
–200
0
40
60
80 100 120 140
125
100
450 500
–50
50
250 300 350 400
550 600 650 700 750 800
–25
0
25
75
150
TEMPERATURE (°C)
TEMPERATURE (°C)
R
RT
(kΩ)
3374 G10
3374 G11
3374 G09
Enable Pin Precision Threshold
vs Temperature
Buck VIN Supply Current
vs Temperature
Buck VIN Supply Current
vs Temperature
420
415
410
405
400
395
390
385
380
50
40
30
20
10
0
550
500
450
Burst Mode OPERATION
FB = 850mV
FORCED CONTINUOUS MODE
FB = 0V
V
IN
= 5.5V
400
350
V
V
= 3.3V
IN
= 2.25V
IN
EN RISING
300
250
200
V
IN
= 5.5V
EN FALLING
V
IN
= 2.25V
150
100
50
V
IN
= 3.3V
0
50 75
TEMPERATURE (°C)
–50 –25
0
25
100 125 150
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3374 G14
3374 G12
3374 G13
PMOS Current Limit
vs Temperature
VOUT vs Temperature
1.88
1.86
1.84
1.82
1.80
1.78
1.76
1.74
1.72
2.6
2.5
2.4
2.3
2.2
2.1
2.0
FORCED CONTINUOUS MODE
LOAD = 0mA
V
IN
= 3.3V
V
IN
= 5.5V
V
= 2.25V
IN
V
IN
= 3.3V
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3374 G16
3374 G15
3374f
7
For more information www.linear.com/LTC3374
LTC3374
TYPICAL PERFORMANCE CHARACTERISTICS
1A Buck Efficiency vs ILOAD
PMOS RDS(ON) vs Temperature
NMOS RDS(ON) vs Temperature
100
90
600
550
500
450
400
350
300
250
200
600
550
500
450
400
350
300
250
200
Burst Mode OPERATION
80
70
FORCED
60
50
CONTINUOUS
V
IN
= 2.25V
V
IN
= 2.25V
MODE
V
IN
= 3.3V
V
IN
= 3.3V
40
30
20
10
0
V
OSC
L = 2.2µH
= 1.8V
OUT
f
= 2MHz
V
IN
= 5.5V
V
IN
= 5.5V
V
IN
V
IN
V
IN
= 2.25V
= 3.3V
= 5.5V
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3374 G17
1
10
100
1000
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3374 G18
LOAD CURRENT (mA)
3374 G19
1A Buck Efficiency vs ILOAD
2A Buck Efficiency vs ILOAD
2A Buck Efficiency vs ILOAD
100
90
100
90
100
90
Burst Mode
OPERATION
Burst Mode
OPERATION
Burst Mode
OPERATION
80
80
80
70
70
70
FORCED
FORCED
FORCED
60
50
CONTINUOUS
60
50
60
50
CONTINUOUS
CONTINUOUS
MODE
MODE
MODE
40
30
20
10
0
40
30
20
10
0
40
30
20
10
0
V
OSC
L = 2.2µH
V
V
V
= 1.8V
V
= 2.5V
V
OSC
L = 2.2µH
V
V
V
= 2.5V
OUT
OUT
OUT
OSC
f
= 2MHz
f
= 2MHz
f
= 2MHz
L = 2.2µH
= 2.25V
= 3.3V
= 5.5V
V
V
V
= 2.7V
= 3.3V
= 5.5V
= 2.7V
= 3.3V
= 5.5V
IN
IN
IN
IN
IN
IN
IN
IN
IN
1
10
100
1000
1
10
100
1000
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3374 G21
3374 G20
3374 G22
3A Buck Efficiency vs ILOAD
3A Buck Efficiency vs ILOAD
100
100
90
90
80
70
80
Burst Mode
OPERATION
Burst Mode
OPERATION
70
FORCED
60
50
60
50
FORCED
CONTINUOUS
MODE
CONTINUOUS
MODE
40
30
20
10
0
40
30
20
10
0
V
f
= 2.5V
V
f
= 1.8V
OUT
OSC
OUT
OSC
= 2MHz
= 2MHz
L = 2.2µH
L = 2.2µH
V
V
V
= 2.7V
= 3.3V
= 5.5V
V
V
V
= 2.25V
= 3.3V
= 5.5V
IN
IN
IN
IN
IN
IN
1
10
100
1000
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3374 G24
3374 G23
3374f
8
For more information www.linear.com/LTC3374
LTC3374
TYPICAL PERFORMANCE CHARACTERISTICS
1A Buck Efficiency vs Frequency
(Forced Continuous Mode)
4A Buck Efficiency vs ILOAD
4A Buck Efficiency vs ILOAD
100
90
100
90
100
90
80
70
60
50
40
30
20
10
0
V
= 2.25V
V
V
= 3.3V
IN
IN
80
80
Burst Mode
OPERATION
Burst Mode
OPERATION
= 5.5V
70
70
IN
60
50
60
50
FORCED
CONTINUOUS
MODE
FORCED
CONTINUOUS
40
30
20
10
0
40
30
20
10
0
MODE
V
= 1.8V
V
= 2.5V
OUT
OSC
OUT
OSC
f
= 2MHz
f
= 2MHz
L = 2.2µH
L = 2.2µH
V
I
OSC
= 1.8V
= 100mA
= 2MHz
OUT
L
V
V
V
= 2.25V
= 3.3V
= 5.5V
V
V
V
= 2.7V
= 3.3V
= 5.5V
IN
IN
IN
IN
IN
IN
f
L = 3.3µH
2.2 2.4 2.6 2.8
FREQUENCY (MHz)
1
10
100
1000
1
10
100
1000
1
1.2 1.4 1.6
3
1.8
2
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3374 G25
3374 G26
3374 G27
1A Buck Efficiency vs Frequency
(Forced Continuous Mode)
1A Buck Efficiency vs ILOAD
1A Buck Regulator Load Regulation
(Forced Continuous Mode)
(Across Operating Frequency)
100
90
100
90
80
70
60
50
40
30
20
10
0
1.820
1.816
1.812
1.808
1.804
1.800
1.796
1.792
1.788
1.784
1.780
I
= 100mA
f
= 2MHz
L
OSC
L = 2.2µH
I
= 500mA
= 20mA
L
80
Burst Mode
OPERATION
FORCED
I
V
V
V
= 5.5V
70
L
IN
CONTINUOUS
MODE
60
50
= 3.3V
IN
V
V
= 1.8V
= 3.3V
= 1MHz
OUT
IN
40
30
20
10
0
= 2.25V
IN
f
OSC
L = 3.3µH
V
V
f
= 1.8V
f
= 2MHz
OUT
IN
OSC
OSC
= 3.3V
L = 2.2µH
f = 3MHz
OSC
DROPOUT
= 2MHz
L = 3.3µH
L = 1µH
1
10
100
1000
1
1.2 1.4 1.6 1.8
2
2.2 2.4 2.6 2.8
3
1
10
100
1000
I
(mA)
FREQUENCY (MHz)
LOAD CURRENT (mA)
L
3374 G29
3374 G30
3374 G28
4A Buck Regulator Load Regulation
(Forced Continuous Mode)
1A Buck Regulator Line Regulation
(Forced Continuous Mode)
1.820
1.820
f
= 2MHz
f
= 2MHz
OSC
OSC
L = 2.2µH
1.816 L = 2.2µH
1.815
1.810
1.805
1.800
1.795
1.790
1.785
1.780
1.812
V
V
= 5.5V
= 3.3V
1.808
1.804
1.800
1.796
1.792
1.788
1.784
1.780
IN
IN
I
= 100mA
L
I
= 500mA
L
V
= 2.25V
IN
DROPOUT
1
10
100
1000
2.25 2.75 3.25 3.75 4.25 4.75 5.25
(V)
I
(mA)
V
IN
L
3374 G31
3374 G32
3374f
9
For more information www.linear.com/LTC3374
LTC3374
TYPICAL PERFORMANCE CHARACTERISTICS
4A Buck Regulator No-Load
Start-Up Transient (Forced
Continuous Mode)
1A Buck Regulator No-Load
Start-Up Transient (Burst Mode
Operation)
1A Buck Regulator, Transient
Response (Burst Mode Operation)
V
OUT
V
V
OUT
OUT
100mV/DIV
500mV/DIV
500mV/DIV
AC-COUPLED
INDUCTOR
CURRENT
200mA/DIV
INDUCTOR
CURRENT
500mA/DIV
INDUCTOR
CURRENT
500mA/DIV
0mA
EN 2V/DIV
EN 2V/DIV
3374 G35
3374 G34
3374 G33
50µs/DIV
V
IN
= 3.3V
200µs/DIV
V
IN
= 3.3V
200µs/DIV
LOAD STEP = 100mA TO 700mA
V
V
= 3.3V
IN
OUT
= 1.8V
1A Buck Regulator, Transient
Response (Forced Continuous
Mode)
4A Buck Regulator, Transient
Response (Forced Continuous
Mode)
4A Buck Regulator, Transient
Response (Burst Mode Operation)
V
OUT
100mV/DIV
V
V
OUT
OUT
AC-COUPLED
100mV/DIV
100mV/DIV
AC-COUPLED
AC-COUPLED
INDUCTOR
CURRENT
200mA/DIV
INDUCTOR
CURRENT
1A/DIV
INDUCTOR
CURRENT
1A/DIV
0mA
0mA
0mA
3374 G36
3374 G37
3374 G38
50µs/DIV
50µs/DIV
50µs/DIV
LOAD STEP = 100mA TO 700mA
LOAD STEP = 400mA TO 2.8A
LOAD STEP = 400mA TO 2.8A
V
IN
V
OUT
= 3.3V
V
V
= 3.3V
V
V
= 3.3V
IN
OUT
IN
OUT
= 1.8V
= 1.8V
= 1.8V
3374f
10
For more information www.linear.com/LTC3374
LTC3374
PIN FUNCTIONS (QFN/TSSOP)
FB1(Pin1/Pin4):BuckRegulator1FeedbackPin.Receives
feedbackbyaresistordividerconnectedacrosstheoutput.
FB4 (Pin 12/Pin 15): Buck Regulator 4 Feedback Pin.
Receives feedback by a resistor divider connected across
theoutput. ConnectingFB4toV combinesbuckregula-
IN4
V
(Pin 2/Pin 5): Buck Regulator 1 Input Supply. Bypass
IN1
tor 4 with buck regulator 3 for higher current. Up to four
to GND with a 10µF or larger ceramic capacitor.
converters may be combined in this way.
SW1(Pin3/Pin6):BuckRegulator1SwitchNode.External
inductor connects to this pin.
EN4 (Pin 13/Pin 16): Buck Regulator 4 Enable Input.
Active high.
SW2(Pin4/Pin7):BuckRegulator2SwitchNode.External
inductor connects to this pin.
EN3 (Pin 14/Pin 17): Buck Regulator 3 Enable Input.
Active high.
V
(Pin 5/Pin 8): Buck Regulator 2 Input Supply. Bypass
IN2
PGOOD_ALL (Pin 15/Pin 18): PGOOD Status Pin. Open-
drain output. When the regulated output voltage of any
enabled switching regulator is more than 7.5% below its
programmed level, this pin is driven LOW. When all buck
regulators are disabled PGOOD_ALL is driven LOW.
to GND with a 10µF or larger ceramic capacitor. May be
drivenbyanindependentsupplyormustbeshortedtoV
IN1
when buck regulator 2 is combined with buck regulator 1
for higher current.
FB2(Pin6/Pin9):BuckRegulator2FeedbackPin.Receives
SYNC(Pin16/Pin19):OscillatorSynchronizationPin.Driv-
ing SYNC with an external clock signal will synchronize all
switcherstotheappliedfrequency.Theslopecompensation
is automatically adapted to the external clock frequency.
The absence of an external clock signal will enable the
frequency programmed by the RT pin. SYNC should be
held at ground if not used. Do not float.
feedbackbyaresistordividerconnectedacrosstheoutput.
Connecting FB2 to V combines buck regulator 2 with
IN2
buck regulator 1 for higher current. Up to four converters
may be combined in this way.
FB3 (Pin 7/Pin 10): Buck Regulator 3 Feedback Pin.
Receives feedback by a resistor divider connected across
theoutput. ConnectingFB3toV combinesbuckregula-
IN3
RT (Pin 17/Pin 20): Oscillator Frequency Pin. This pin
provides two modes of setting the switching frequency.
ConnectingaresistorfromRT togroundwillsettheswitch-
ing frequency based on the resistor value. If RT is tied to
tor 3 with buck regulator 2 for higher current. Up to four
converters may be combined in this way.
V
(Pin8/Pin11):BuckRegulator3InputSupply.Bypass
IN3
to GND with a 10µF or larger ceramic capacitor. May be
V
the internal 2MHz oscillator will be used. Do not float.
CC
drivenbyanindependentsupplyormustbeshortedtoV
IN2
EN6 (Pin 18/Pin 21): Buck Regulator 6 Enable Input.
Active high.
when buck regulator 3 is combined with buck regulator 2
for higher current.
EN5 (Pin 19/Pin 22): Buck Regulator 5 Enable Input.
Active high.
SW3 (Pin 9/Pin 12): Buck Regulator 3 Switch Node.
External inductor connects to this pin.
FB5 (Pin 20/Pin 23): Buck Regulator 5 Feedback Pin.
SW4 (Pin 10/Pin 13): Buck Regulator 4 Switch Node.
External inductor connects to this pin.
Receives feedback by a resistor divider connected across
theoutput. ConnectingFB5toV combinesbuckregula-
IN5
V
(Pin 11/Pin 14): Buck Regulator 4 Input Supply.
tor 5 with buck regulator 4 for higher current. Up to four
IN4
Bypass to GND with a 10µF or larger ceramic capacitor.
converters may be combined in this way.
May be driven by an independent supply or must be
shorted to V when buck regulator 4 is combined with
IN3
buck regulator 3 for higher current.
3374f
11
For more information www.linear.com/LTC3374
LTC3374
PIN FUNCTIONS (QFN/TSSOP)
V
(Pin 21/Pin 24): Buck Regulator 5 Input Supply.
V
(Pin 30/Pin 33): Buck Regulator 8 Input Supply.
IN5
IN8
Bypass to GND with a 10µF or larger ceramic capacitor.
Bypass to GND with a 10µF or larger ceramic capacitor.
May be driven by an independent supply or must be
May be driven by an independent supply or must be
shorted to V when buck regulator 5 is combined with
shorted to V when buck regulator 8 is combined with
buck regulator 7 for higher current.
IN4
IN7
buck regulator 4 for higher current.
SW5 (Pin 22/Pin 25): Buck Regulator 5 Switch Node.
FB8 (Pin 31/Pin 34): Buck Regulator 8 Feedback Pin.
External inductor connects to this pin.
Receives feedback by a resistor divider connected across
theoutput. ConnectingFB8toV combinesbuckregula-
IN8
SW6 (Pin 23/Pin 26): Buck Regulator 6 Switch Node.
External inductor connects to this pin.
tor 8 with buck regulator 7 for higher current. Up to four
converters may be combined in this way.
V
(Pin 24/Pin 27): Buck Regulator 6 Input Supply.
IN6
EN8 (Pin 32/Pin 35): Buck Regulator 8 Enable Input.
Active high.
Bypass to GND with a 10µF or larger ceramic capacitor.
May be driven by an independent supply or must be
shorted to V when buck regulator 6 is combined with
EN7 (Pin 33/Pin 36): Buck Regulator 7 Enable Input.
Active high.
IN5
buck regulator 5 for higher current.
FB6 (Pin 25/Pin 28): Buck Regulator 6 Feedback Pin.
MODE (Pin 34/Pin 37): Logic Input. MODE enables Burst
Mode functionality for all the buck switching regulators
when the pin is set low. When the pin is set high, all the
buck switching regulators will operate in forced continu-
ous mode.
Receives feedback by a resistor divider connected across
theoutput. ConnectingFB6toV combinesbuckregula-
IN6
tor 6 with buck regulator 5 for higher current. Up to four
converters may be combined in this way.
FB7 (Pin 26/Pin 29): Buck Regulator 7 Feedback Pin.
V
(Pin 35/Pin 38): Internal Bias Supply. Bypass to GND
CC
Receives feedback by a resistor divider connected across
with a 10µF or larger ceramic capacitor.
theoutput. ConnectingFB7toV combinesbuckregula-
IN7
TEMP (Pin 36/Pin 1): Temperature Indication Pin. TEMP
outputs a voltage of 150mV (typical) at room tempera-
ture.TheTEMPvoltagewillchangeby6.75mV/°C(typical)
giving an external indication of the LTC3374 internal die
temperature.
tor 7 with buck regulator 6 for higher current. Up to four
converters may be combined in this way.
V
(Pin 27/Pin 30): Buck Regulator 7 Input Supply.
IN7
Bypass to GND with a 10µF or larger ceramic capacitor.
May be driven by an independent supply or must be
EN2 (Pin 37/Pin 2): Buck Regulator 2 Enable Input.
Active high.
shorted to V when buck regulator 7 is combined with
IN6
buck regulator 6 for higher current.
EN1 (Pin 38/Pin 3): Buck Regulator 1 Enable Input.
Active high.
SW7 (Pin 28/Pin 31): Buck Regulator 7 Switch Node.
External inductor connects to this pin.
GND (Exposed Pad Pin 39/Exposed Pad Pin 39): Ground.
The exposed pad must be connected to a continuous
ground plane on the printed circuit board directly under
the LTC3374 for electrical contact and rated thermal
performance.
SW8 (Pin 29/Pin 32): Buck Regulator 8 Switch Node.
External inductor connects to this pin.
3374f
12
For more information www.linear.com/LTC3374
LTC3374
BLOCK DIAGRAM (Pin numbers reflect QFN package)
TOP LOGIC
V
35
PGOOD_ALL
15
CC
SYNC 16
RT 17
REF, CLK
8 PGOOD
BANDGAP,
OSCILLATOR,
UV, OT
TEMP 36
TEMP MONITOR
34 MODE
V
2
3
1
30
V
IN8
IN1
SW1
FB1
29 SW8
31 FB8
32 EN8
BUCK REGULATOR 1
1A
BUCK REGULATOR 8
1A
EN1 38
MASTER/SLAVE LINES
MASTER/SLAVE LINES
V
5
4
6
27
V
IN7
IN2
SW2
FB2
28 SW7
26 FB7
33 EN7
BUCK REGULATOR 2
1A
BUCK REGULATOR 7
1A
EN2 37
MASTER/SLAVE LINES
MASTER/SLAVE LINES
V
8
9
7
24
V
IN6
IN3
SW3
FB3
23 SW6
25 FB6
18 EN6
BUCK REGULATOR 3
1A
BUCK REGULATOR 6
1A
EN3 14
MASTER/SLAVE LINES
MASTER/SLAVE LINES
V
IN4
11
21
V
IN5
SW4 10
FB4 12
EN4 13
22 SW5
20 FB5
19 EN5
BUCK REGULATOR 4
1A
BUCK REGULATOR 5
1A
MASTER/SLAVE LINES
GND (EXPOSED PAD)
39
3374 BD
3374f
13
For more information www.linear.com/LTC3374
LTC3374
OPERATION
Buck Switching Regulators
The buck switching regulators are phased in 90° steps to
reduce noise and input ripple. The phase step determines
the fixed edge of the switching sequence, which is when
the PMOS turns on. The PMOS off (NMOS on) phase
is subject to the duty cycle demanded by the regulator.
Bucks 1 and 2 are set to 0°, bucks 3 and 4 are set to 90°,
bucks 5 and 6 are set to 180°, and bucks 7 and 8 are set
to 270°. In shutdown all SW nodes are high impedance.
The LTC3374 contains eight monolithic 1A synchronous
buck switching regulators. All of the switching regula-
tors are internally compensated and need only external
feedback resistors to set the output voltage. The switch-
ing regulators offer two operating modes: Burst Mode
operation (when the MODE pin is set low) for higher
efficiencyatlightloadsandforcedcontinuousPWM mode
(when the MODE pin is set high) for lower noise at light
loads. The MODE pin collectively sets the operating mode
for all enabled buck switching regulators. In Burst Mode
operation at light loads, the output capacitor is charged
to a voltage slightly higher than its regulation point. The
regulator then goes into sleep mode, during which time
the output capacitor provides the load current. In sleep
most of the regulator’s circuitry is powered down, helping
conserve input power. When the output capacitor droops
below its programmed value, the circuitry is powered on
and another burst cycle begins. The sleep time decreases
as load current increases. In Burst Mode operation, the
regulator will burst at light loads whereas at higher loads
itwilloperateatconstantfrequencyPWM modeoperation.
In forced continuous mode, the oscillator runs continu-
ously and the buck switch currents are allowed to reverse
under very light load conditions to maintain regulation.
This mode allows the buck to run at a fixed frequency with
minimal output ripple.
The buck regulator enable pins may be tied to V
volt-
OUT
ages, through a resistor divider, to program power-up
sequencing.
Buck Regulators with Combined Power Stages
Up to four adjacent buck regulators may be combined
in a master-slave configuration by connecting their SW
pins together, connecting their V pins together, and
IN
connecting the higher numbered bucks’ FB pin(s) to the
input supply. The lowest numbered buck is always the
master. In Figure 1, buck regulator 1 is the master. The
feedback network connected to the FB1 pin programs
the output voltage to 1.2V. The FB2 pin is tied to V
,
IN1-2
which configures buck regulator 2 as the slave. The SW1
and SW2 pins must be tied together, as must the V
IN1
and V pins. The slave buck control circuitry draws no
IN2
current. The enable of the master buck (EN1) controls the
V
IN
L1
V
OUT
1.2V
2A
V
SW1
IN1
Each buck switching regulator has its own V , SW, FB
IN
C
OUT
BUCK REGULATOR 1
(MASTER)
and EN pins to maximize flexibility. The enable pins have
two different enable threshold voltages that depend on
the operating state of the LTC3374. With all regulators
disabled,theenablepinthresholdissetto730mV(typical).
Once any regulator is enabled, the enable pin thresholds
of the remaining regulators are set to a bandgap-based
400mV and the EN pins are each monitored by a precision
comparator. This precision EN threshold may be used to
provide event-based sequencing via feedback from other
previously enabled regulators. All buck regulators have
forward and reverse-current limiting, soft-start to limit
inrushcurrentduringstart-up,andshort-circuitprotection.
400k
800k
EN1
FB1
V
IN
SW2
V
IN2
BUCK REGULATOR 2
(SLAVE)
V
IN
EN2
FB2
3374 F01
Figure 1. Buck Regulators Configured as Master-Slave
3374f
14
For more information www.linear.com/LTC3374
LTC3374
OPERATION
operation of the combined bucks; the enable of the slave
regulator (EN2) must be tied to ground.
Thetemperaturemaybereadbackbytheuserbysampling
theTEMPpinanalogvoltage.Thetemperature,T,indicated
by the TEMP pin voltage is given by:
Any combination of 2, 3, or 4 adjacent buck regulators
may be combined to provide either 2A, 3A, or 4A of aver-
age output load current. For example, buck regulator 1
and buck regulator 2 may run independently, while buck
regulators 3 and 4 may be combined to provide 2A, while
buck regulators 5 through 8 may be combined to provide
4A. Buck regulator 1 is never a slave, and buck regulator
8 is never a master. 15 unique output power stage con-
figurationsarepossibletomaximizeapplicationflexibility.
VTEMP + 19mV
T =
•1°C
(1)
6.75mV
Iftemperaturemonitoringfunctionalityisnotdesired,then
the user may shut down the temperature monitor in order
tolowerquiescentcurrent(15µAtypical)bytyingTEMPto
V . In this case all enabled buck switching regulators are
CC
still shut down when the die temperature reaches 165°C
(typical) and remain in shutdown until the die tempera-
ture falls to 155°C (typical). If none of the buck switching
regulators are enabled, then the temperature monitor is
also shut down to further reduce quiescent current.
Power Failure Reporting Via PGOOD_ALL Pin
Power failure conditions are reported back via the
PGOOD_ALL pin. All buck switching regulators have an
internalpowergood(PGOOD)signal.Whentheregulated
output voltage of an enabled switcher rises above 93.5%
ofitsprogrammedvalue,thePGOODsignalwilltransition
high. When the regulated output voltage falls below
92.5% of its programmed value, the PGOOD signal is
pulled low. If any internal PGOOD signal stays low for
greater than 100µs, then the PGOOD_ALL pin is pulled
low, indicating to a microprocessor that a power failure
fault has occurred. The 100µs filter time prevents the pin
from being pulled low due to a transient.
Programming the Operating Frequency
Selectionoftheoperatingfrequencyisatrade-offbetween
efficiency and component size. High frequency operation
allows the use of smaller inductor and capacitor values.
Operation at lower frequencies improves efficiency by
reducing internal gate charge losses but requires larger
inductance values and/or capacitance to maintain low
output voltage ripple.
The operating frequency for all of the LTC3374 regulators
is determined by an external resistor that is connected
between the RT pin and ground. The operating frequency
can be calculated by using the following equation:
An error condition that pulls the PGOOD_ALL pin low
is not latched. When the error condition goes away, the
PGOOD_ALL pin is released and is pulled high if no other
error condition exists. If no buck switching regulators are
enabled, then PGOOD_ALL will be pulled low.
8•1011 •ΩHz
fOSC
=
(2)
RT
Temperature Monitoring and Overtemperature
Protection
While the LTC3374 is designed to function with operat-
ing frequencies between 1MHz and 3MHz, it has safety
clamps that will prevent the oscillator from running faster
than4MHz(typical)orslowerthan250kHz(typical). Tying
To prevent thermal damage to the LTC3374 and its sur-
rounding components, the LTC3374 incorporates an
overtemperature (OT) function. When the LTC3374 die
temperature reaches 165°C (typical) all enabled buck
switchingregulatorsareshutdownandremaininshutdown
until the die temperature falls to 155°C (typical).
the RT pin to V sets the oscillator to the default internal
CC
operating frequency of 2MHz (typical).
3374f
15
For more information www.linear.com/LTC3374
LTC3374
OPERATION
The LTC3374’s internal oscillator can be synchronized
through an internal PLL circuit, to an external frequency
by applying a square wave clock signal to the SYNC pin.
During synchronization, the top MOSFET/turn-on of buck
switching regulators 1 and 2 are locked to the rising edge
of the external frequency source. All other buck switching
regulators are locked to the appropriate phase of the ex-
ternal frequency source (see Buck Switching Regulators).
The synchronization frequency range is 1MHz to 3MHz.
requires a certain number of periods to gradually settle
until the frequency at SW matches the frequency and
phase of SYNC.
When the external clock is removed the LTC3374 needs
approximately 5µs to detect the absence of the external
clock. During this time, the PLL will continue to provide
clock cycles before it recognizes the lack of a SYNC input.
Once the external clock removal has been identified, the
oscillator will gradually adjust its operating frequency to
match the desired frequency programmed at the RT pin.
SYNC should be connected to ground if not used.
After detecting an external clock on the first rising edge of
the SYNC pin, the PLL starts up at the current frequency
being programmed by the RT pin. The internal PLL then
3374f
16
For more information www.linear.com/LTC3374
LTC3374
APPLICATIONS INFORMATION
Buck Switching Regulator Output Voltage
and Feedback Network
Theinputsupplyneedstobedecoupledwitha22µFcapaci-
tor while the output needs to be decoupled with a 47µF
capacitor for a 2A combined buck regulator. Likewise for
3Aand4Aconfigurationstheinputandoutputcapacitance
must be scaled up to account for the increased load. Refer
to the Capacitor Selection section for details on selecting
a proper capacitor.
The output voltage of the buck switching regulators is
programmed by a resistor divider connected from the
switching regulator’s output to its feedback pin and is
given by V
= V (1 + R2/R1) as shown in Figure 2.
OUT
FB
Typical values for R1 range from 40k to 1M. The buck
regulator transient response may improve with optional
capacitor C that helps cancel the pole created by the
In many cases, any extra unused buck converters may be
used to increase the efficiency of the active regulators.
In general the efficiency will improve for any regulators
running close to their rated load currents. If there are
unused regulators, the user should look at their specific
applications and current requirements to decide whether
to add extra stages.
FF
feedback resistors and the input capacitance of the FB
pin. Experimentation with capacitor values between 2pF
and 22pF may improve transient response.
V
OUT
+
BUCK
SWITCHING
REGULATOR
C
FF
C
R2
OUT
Input and Output Decoupling Capacitor Selection
FB
The LTC3374 has individual input supply pins for each
(OPTIONAL)
R1
buck switching regulator and a separate V pin that
CC
supplies power to all top level control and logic. Each of
these pins must be decoupled with low ESR capacitors
to GND. These capacitors must be placed as close to
the pins as possible. Ceramic dielectric capacitors are a
good compromise between high dielectric constant and
stability versus temperature and DC bias. Note that the
capacitance of a capacitor deteriorates at higher DC bias.
It is important to consult manufacturer data sheets and
obtain the true capacitance of a capacitor at the DC bias
voltage it will be operated at. For this reason, avoid the
use of Y5V dielectric capacitors. The X5R/X7R dielectric
capacitors offer good overall performance.
3374 F02
Figure 2. Feedback Components
Buck Regulators
All eight buck regulators are designed to be used with
inductors ranging from 1µH to 3.3µH depending on the
lowest switching frequency that the buck regulator must
operate at. To operate at 1MHz a 3.3µH inductor should
be used, while to operate at 3MHz a 1µH inductor may be
used. Table 1 shows some recommended inductors for
the buck regulators.
The input supply voltage Pins 2/5, 5/8, 8/11, 11/14, 21/24,
24/27, 27/30, 30/33, and 35/38 (QFN/TSSOP packages)
all need to be decoupled with at least 10µF capacitors.
The input supply needs to be decoupled with a 10µF
capacitor while the output needs to be decoupled with a
22µF capacitor. Refer to the Capacitor Selection section
for details on selecting a proper capacitor.
PCB Considerations
Combined Buck Regulators
When laying out the printed circuit board, the following
list should be followed to ensure proper operation of the
LTC3374:
A single 2A buck regulator is available by combining two
adjacent 1A buck regulators together. Likewise a 3A or 4A
buck regulator is available by combining any three or four
adjacent buck regulators respectively. Tables 2, 3, and 4
show recommended inductors for these configurations.
1. Theexposedpadofthepackage(Pin39)shouldconnect
directlytoalargegroundplanetominimizethermaland
electrical impedance.
3374f
17
For more information www.linear.com/LTC3374
LTC3374
APPLICATIONS INFORMATION
Table 1. Recommended Inductors for 1A Buck Regulators
PART NUMBER
L (µH)
1.0
1
MAX I (A)
MAX DCR (mΩ)
MANUFACTURER
Vishay
SIZE IN mm (L × W × H)
3 × 3.6 × 1.2
DC
IHLP1212ABER1R0M-11
1239AS-H-1R0N
3
38
65
2.5
3.5
2.6
3
Toko
2.5 × 2.0 × 1.2
4 × 4 × 2.1
XFL4020-222ME
2.2
2.2
2.2
3.3
3.3
23.5
84
CoilCraft
Toko
1277AS-H-2R2N
3.2 × 2.5 × 1.2
3 × 3.6 × 1.2
IHLP1212BZER2R2M-11
XFL4020-332ME
46
Vishay
2.8
2.7
38.3
61
CoilCraft
Vishay
4 × 4 × 2.1
IHLP1212BZER3R3M-11
3 × 3.6 × 1.2
Table 2. Recommended Inductors for 2A Buck Regulators
PART NUMBER
L (µH)
1.0
1
MAX I (A)
MAX DCR (mΩ)
MANUFACTURER
CoilCraft
SIZE IN mm (L × W × H)
4 × 4 × 2.1
DC
XFL4020-102ME
74437324010
5.1
9
11.9
27
Wurth Elektronik
CoilCraft
4.45 × 4.06 × 1.8
4 × 4 × 2.1
XAL4020-222ME
FDV0530-2R2M
IHLP2020BZER2R2M-11
XAL4030-332ME
FDV0530-3R3M
2.2
2.2
2.2
3.3
3.3
5.6
5.3
5
38.7
15.5
37.7
28.6
34.1
Toko
6.2 × 5.8 × 3
Vishay
5.49 × 5.18 × 2
4 × 4 × 3.1
5.5
4.1
CoilCraft
Toko
6.2 × 5.8 × 3
Table 3. Recommended Inductors for 3A Buck Regulators
PART NUMBER
L (µH)
1.0
1
MAX I (A)
MAX DCR (mΩ)
MANUFACTURER
CoilCraft
Toko
SIZE IN mm (L × W × H)
4 × 4 × 2.1
DC
XAL4020-102ME
FDV0530-1R0M
XAL5030-222ME
IHLP2525CZER2R2M-01
74437346022
8.7
8.4
9.2
8
14.6
11.2
14.5
20
6.2 × 5.8 × 3
2.2
2.2
2.2
3.3
3.3
CoilCraft
Vishay
5.28 × 5.48 × 3.1
6.86 × 6.47 × 3
7.3 × 6.6 × 2.8
5.28 × 5.48 × 3.1
7.1 × 6.5 × 3
6.5
8.7
7.3
20
Wurth Elektonik
CoilCraft
TDK
XAL5030-332ME
SPM6530T-3R3M
23.3
27
Table 4. Recommended Inductors for 4A Buck Regulators
PART NUMBER
L (µH)
1.2
1
MAX I (A)
MAX DCR (mΩ)
MANUFACTURER
CoilCraft
TDK
SIZE IN mm (L × W × H)
5.28 × 5.48 × 3.1
7.1 × 6.5 × 3
DC
XAL5030-122ME
SPM6530T-1R0M120
XAL5030-222ME
SPM6530T-2R2M
IHLP2525EZER2R2M-01
XAL6030-332ME
FDVE1040-3R3M
12.5
14.1
9.2
8.4
13.6
8
9.4
7.81
14.5
19
2.2
2.2
2.2
3.3
3.3
CoilCraft
TDK
5.28 × 5.48 × 3.1
7.1 × 6.5 × 3
20.9
20.81
10.1
Vishay
6.86 × 6.47 × 5
6.36 × 6.56 × 3.1
11.2 × 10 × 4
CoilCraft
Toko
9.8
3374f
18
For more information www.linear.com/LTC3374
LTC3374
APPLICATIONS INFORMATION
2. All the input supply pins should each have a decoupling
capacitor.
and parasitic coupling. Due to the large voltage swing
of the switching nodes, high input impedance sensitive
nodes, such as the feedback nodes, should be kept far
away or shielded from the switching nodes or poor
performance could result.
3. Theconnectionstotheswitchingregulatorinputsupply
pins and their respective decoupling capacitors should
be kept as short as possible. The GND side of these
capacitors should connect directly to the ground plane
of the part. These capacitors provide the AC current
to the internal power MOSFETs and their drivers. It is
importanttominimizeinductancefromthesecapacitors
5. The GND side of the switching regulator output capaci-
torsshouldconnectdirectlytothethermalgroundplane
of the part. Minimize the trace length from the output
capacitor to the inductor(s)/pin(s).
to the V pins of the LTC3374.
IN
6. Inacombinedbuckregulatorapplicationthetracelength
of switch nodes to the inductor must be kept equal to
ensure proper operation.
4. TheswitchingpowertracesconnectingSW1,SW2,SW3,
SW4, SW5, SW6, SW7, and SW8 to their respective
inductors should be minimized to reduce radiated EMI
3.3V TO 5.5V
3.0V TO 5.5V
2.5V TO 5.5V
2.25V TO 5.5V
V
V
IN8
2.25V TO 5.5V
2.25V TO 5.5V
2.25V TO 5.5V
2.25V TO 5.5V
IN1
2.2µH
1.02M
324k
2.2µH
2.2µH
2.2µH
2.2µH
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
1.8V
1A
3.3V
1A
SW1
FB1
SW8
FB8
22µF
22µF
22µF
22µF
22µF
22µF
22µF
22µF
806k
649k
V
V
IN7
IN2
2.2µH
1.5V
1A
3.0V
1A
SW2
FB2
SW7
FB7
1.0M
365k
715k
806k
LTC3374
V
V
IN6
IN3
2.2µH
1.2V
1A
2.5V
1A
SW3
FB3
SW6
FB6
1.02M
475k
232k
464k
V
V
IN5
IN4
2.2µH
1.0V
1A
2.0V
1A
SW4
FB4
SW5
FB5
1.0M
665k
255k
1.02M
EN1
EN2
EN3
EN4
EN5
EN6
EN7
EN8
SYNC
MODE
RT
V
2.7V TO 5.5V
CC
10µF
MICROPROCESSOR
CONTROL
PGOOD_ALL
TEMP
MICROPROCESSOR
CONTROL
402k
EXPOSED PAD
3374 F03
Figure 3. Detailed Front Page Application
3374f
19
For more information www.linear.com/LTC3374
LTC3374
APPLICATIONS INFORMATION
V
IN
5.5V TO 36V
C
IN
22µF
V
INTV
CC
IN
100k
2.2µF
D1
PGOOD
INTV
CC
PGND
TG
PLLIN/MODE
MTOP
I
LIM
0.1µF
LTC2955TS8-1
LTC3891
L1
R
SENSE
7mΩ
V
IN
EN
RUN
BOOST
8µH
5V
6A
MICROPROCESSOR
KILL
INT
PB
SW
FREQ
CONTROL
C
470pF
MBOT
OUT
BG
34.8k
330µF
ITH
TMR GND ON
+
SENSE
0.1µF
1nF
–
SENSE
TRACK/SS
SGND
100k
EXTV
CC
V
FB
1M
MTOP, MBOT: Si7850DP
SGND
19.1k
L1 COILCRAFT SER1360-802KL
C
: SANYO 10TPE330M
OUT
D1: DFLS1100
V
IN1
V
IN8
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
2.2µH
2.2µH
2.2µH
2.2µH
2.2µH
1.2V
1A
1.2V
1A
SW1
FB1
SW8
FB8
22µF
22µF
324k
649k
324k
649k
V
V
IN7
IN2
2.2µH
2.5V
1A
2.5V
1A
SW2
FB2
SW7
FB7
22µF
22µF
22µF
22µF
22µF
22µF
665k
309k
665k
309k
LTC3374
V
V
IN6
IN3
2.2µH
1.8V
1A
1.8V
1A
SW3
FB3
SW6
FB6
590k
475k
590k
475k
V
V
IN5
IN4
2.2µH
1.6V
1A
1.6V
1A
SW4
FB4
SW5
FB5
511k
511k
511k
511k
MICROPROCESSOR
CONTROL
MODE
SYNC
V
CC
10µF
EN1
EN2
EN3
EN4
EN5
EN6
EN7
EN8
RT
PGOOD_ALL
TEMP
MICROPROCESSOR
CONTROL
402k
EXPOSED PAD
3374 F04
Figure 4. Buck Regulators with Sequenced Start-Up Driven from a High Voltage Upstream Buck Converter
3374f
20
For more information www.linear.com/LTC3374
LTC3374
APPLICATIONS INFORMATION
2.7V TO 5.5V
V
IN1
V
IN6
10µF
2.5V
4A
10µF
2.2µH
665k
SW1
SW2
SW3
SW4
2.2µH
SW8
SW7
SW6
1.2V
3A
100µF
68µF
324k
649k
FB1
FB6
309k
V
V
IN7
IN2
10µF
10µF
FB2
FB7
LTC3374
V
IN3
V
IN8
10µF
10µF
10µF
10µF
FB3
FB8
V
IN4
V
IN5
2.2µH
1.6V
1A
SW5
22µF
10µF
511k
511k
FB4
FB5
EN2
EN3
EN4
EN7
EN8
V
CC
PGOOD_ALL
TEMP
MICROPROCESSOR
CONTROL
EN1
EN5
MICROPROCESSOR
CONTROL
EN6
SYNC
MODE
RT
402k
EXPOSED PAD
3374 F05
Figure 5. Combined Buck Regulators with Common Input Supply
3374f
21
For more information www.linear.com/LTC3374
LTC3374
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UHF Package
38-Lead Plastic QFN (5mm × 7mm)
(Reference LTC DWG # 05-08-1701 Rev C)
0.70 ± 0.05
5.50 ± 0.05
5.15 0.05
4.10 ± 0.05
3.15 0.05
3.00 REF
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
5.5 REF
6.10 ± 0.05
7.50 ± 0.05
RECOMMENDED SOLDER PAD LAYOUT
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
PIN 1 NOTCH
R = 0.30 TYP OR
0.35 × 45° CHAMFER
0.75 ± 0.05
3.00 REF
5.00 ± 0.10
37 38
0.00 – 0.05
0.40 ±0.10
PIN 1
TOP MARK
1
2
(SEE NOTE 6)
5.15 0.10
5.50 REF
7.00 ± 0.10
3.15 0.10
(UH) QFN REF C 1107
0.200 REF 0.25 ± 0.05
R = 0.125
TYP
R = 0.10
TYP
0.50 BSC
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE
OUTLINE M0-220 VARIATION WHKD
2. DRAWING NOT TO SCALE
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
3. ALL DIMENSIONS ARE IN MILLIMETERS
3374f
22
For more information www.linear.com/LTC3374
LTC3374
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
FE Package
38-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1772 Rev C)
Exposed Pad Variation AA
4.75 REF
9.60 – 9.80*
(.378 – .386)
4.75
(.187)
REF
38
20
6.60 0.10
4.50 REF
2.74 REF
SEE NOTE 4
6.40
2.74
REF (.252)
(.108)
0.315 0.05
BSC
1.05 0.10
0.50 BSC
RECOMMENDED SOLDER PAD LAYOUT
1
19
1.20
(.047)
MAX
4.30 – 4.50*
(.169 – .177)
0.25
REF
0° – 8°
0.50
(.0196)
BSC
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
0.05 – 0.15
(.002 – .006)
0.17 – 0.27
FE38 (AA) TSSOP REV C 0910
(.0067 – .0106)
TYP
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS 4. RECOMMENDED MINIMUM PCB METAL SIZE
2. DIMENSIONS ARE IN
FOR EXPOSED PAD ATTACHMENT
MILLIMETERS
(INCHES)
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.150mm (.006") PER SIDE
3. DRAWING NOT TO SCALE
3374f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTC3374
TYPICAL APPLICATION
Combined Bucks with 3MHz Switch Frequency and Sequenced Power Up
2.25V TO 5.5V
3.3V TO 5.5V
V
V
IN8
IN1
10µF
10µF
FB8
10µF
10µF
V
FB2
V
IN2
IN7
1µH
3.3V
2A
V
SW7
SW8
IN3
FB3
10µF
1µH
47µF
1.02M
324k
SW1
SW2
SW3
FB7
2V
3A
68µF
649k
LTC3374
FB1
V
2.5V TO 5.5V
IN6
432k
FB6
10µF
10µF
2.25V TO 5.5V
V
V
IN5
IN4
10µF
1µH
1µH
1.2V
1A
2.5V
2A
SW4
FB4
SW5
SW6
22µF
47µF
324k
649k
1.02M
475k
FB5
RT
V
2.7V TO 5.5V
CC
10µF
PGOOD_ALL
267k
MICROPROCESSOR
CONTROL
TEMP
SYNC
MODE
EN1
EN2
EN3
EN6
EN8
EN4
EN5
EN7
EXPOSED PAD
3374 TA02
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
2
2
LTC3589
8-Output Regulator with Sequencing and I C
Triple I C Adjustable High Efficiency Step-Down DC/DC Converters: 1.6A, 1A, 1A.
High Efficiency 1.2A Buck-Boost DC/DC Converter, Triple 250mA LDO Regulators.
Pushbutton On/Off Control with System Reset, Flexible Pin-Strap Sequencing
2
Operation. I C and Independent Enable Control Pins, Dynamic Voltage Scaling and
Slew Rate Control. Selectable 2.25MHz or 1.12MHz Switching Frequency, 8µA
Standby Current, 40-Pin 6mm × 6mm × 0.75mm QFN.
LTC3675
7-Channel Configurable High Power PMIC
Four Monolithic Synchronous Buck DC/DCs (1A/1A/500mA/500mA). Buck DC/DCs
Can Be Paralleled to Deliver Up to 2× Current with a Single Inductor. Independent
2
1A Boost and 1A Buck-Boost DC/DCs, Dual String I C Controlled 40V LED Driver.
2
I C Programmable Output Voltage, Operating Mode, and Switch Node Slew Rate
2
for All DC/DCs. I C Read Back of DC/DC, LED Driver, Fault Status, Pushbutton
On/Off/Reset, Always-On 25mA LDO. Low Quiescent Current: 16µA (All DC/DCs
Off), 4mm × 7mm × 0.75mm 44-Lead QFN Package.
LTC3375
8-Channel Programmable Configurable 1A DC/DC
8 × 1A Synchronous Buck Regulators. Can Connect Up to Four Power Stages in
Parallel to Make a Single Inductor, High Current Output (4A Maximum), 15 Output
Configurations Possible, 7mm × 7mm QFN-48 Package
3374f
LT 0513 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTC3374
LINEAR TECHNOLOGY CORPORATION 2013
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