down switching regulator controller for high current
distributed power systems, digital signal processors, and
other telecom and industrial DC/DC power supplies. It uses
a constant frequency voltage mode architecture combined
with very low offset, high bandwidth error amplifiers and
a remote output sense differential amplifier for excellent
transient response and output regulation.
The controller incorporates lossless inductor DCR current
sensing to maintain current balance between phases and to
provide overcurrent protection. The chip operates from a
V
CC
supply between 3V and 5.5V and is designed for step-
down conversion from V
IN
between 3V and 24V to output
voltages between 0.6V and V
CC
– 0.5V.
The TRACK/SS pins provide programmable soft-start or
tracking functions. Inductor current reversal is disabled
during soft-start to safely power prebiased loads. The con-
stant operating frequency can be synchronized to an exter-
nal clock or linearly programmed from 250kHz to 1.25MHz.
Up to six LTC3860 controllers can operate in parallel for
1-, 2-, 3-, 4-, 6- or 12-phase operation.
The LTC3860 is available in a 32-pin 5mm
×
5mm QFN
package.
L,
LT, LTC, LTM, PolyPhase, µModule, Linear Technology and the Linear logo 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
6144194, 5055767
n
n
n
n
n
n
n
n
Constant Frequency Voltage Mode Control with
Accurate Current Sharing
±0.75% 0.6V Voltage Reference
Differential Remote Output Voltage Sense Amplifier
Multiphase Capability—Up to 12-Phase Operation
Programmable Current Limit
Safely Powers a Pre-Biased Load
Programmable or PLL-Synchronizable Switching
Frequency Up to 1.25MHz
Lossless Current Sensing Using Inductor DCR or
Precision Current Sensing with Sense Resistor
Fast and Accurate True Operational Error Amplifiers
V
CC
Range: 3V to 5.5V
V
IN
Range: 3V to 24V
Power Good Output Voltage Monitor
Output Voltage Tracking Capability
Programmable Soft-Start
Available in a 32- Pin 5mm
×
5mm QFN Package
applicaTions
n
n
n
n
High Current Distributed Power Systems
Digital Signal Processor and ASIC Supplies
Telecom Systems
Industrial Power Supplies
Typical applicaTion
PWM1
V
IN
V
CC
470µF
PWM1
VINSNS
V
CC
FREQ
FB2
I
LIM2
LTC3860
FB1
COMP1,2
SS1,2
VSNSOUT
VSNSN
VSNSP
SGND
V
CC
1µF
V
OUT
1nF
20k
20k
220
33pF
0.1µF
12.7k
RUN1,2
I
LIM1
ISNS1P
ISNS1N
ISNS2N
ISNS2P
50k
0.22µF
0.22µF
PWM2
V
CC
100pF
LTC4449
IN
GND
V
LOGIC
TG
V
CC
TS
BOOST
BG
0.22µF
V
IN
TG1
SW1
BG1
2.32k
V
OUT
1.2V
330µF 50A
4
2.32k
0.3µH
3860 TA01
0.3µH
V
IN
LTC4449
IN
GND
V
LOGIC
TG
V
CC
TS
BOOST
BG
0.22µF
TG2
SW2
BG2
PWM2
I
AVG
CLKIN
220pF
3860f
LTC3860
absoluTe maximum raTings
(Note 1)
pin conFiguraTion
TRACK/SS1
PWMEN1
PWMEN2
TOP VIEW
PGOOD1
VINSNS
SGND
SGND
I
AVG
PWM1
24 RUN1
23 I
LIM1
22 ISNS1P
33
SGND
21 ISNS1N
20 ISNS2N
19 ISNS2P
18 I
LIM2
17 RUN2
9 10 11 12 13 14 15 16
CLKIN
TRACK/SS2
CLKOUT
PHSMD
PGOOD2
PWM2
FREQ
V
CC
Voltage .................................................. –0.3V to 6V
VINSNS Voltage ......................................... –0.3V to 30V
VSNSN Voltage ............................................ –0.3V to 2V
RUN Voltage ................................................ –0.3V to 6V
ISNS1P , ISNS1N,
ISNS2P , ISNS2N ...........................–0.3V to (V
CC
+ 0.1V)
All Other Voltages .........................–0.3V to (V
CC
+ 0.3V)
Operating Junction Temperature Range (Note 3)
LTC3860E............................................. –40°C to 85°C
LTC3860I............................................ –40°C to 125°C
Storage Temperature Range................... –65°C to 125°C
32 31 30 29 28 27 26 25
V
CC
1
FB1 2
COMP1 3
VSNSOUT 4
VSNSN 5
VSNSP 6
COMP2 7
FB2 8
UH PACKAGE
32-LEAD (5mm 5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W
EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB
orDer inFormaTion
LEAD FREE FINISH
LTC3860EUH#PBF
LTC3860IUH#PBF
TAPE AND REEL
LTC3860EUH#TRPBF
LTC3860IUH#TRPBF
PART MARKING*
3860
3860
PACKAGE DESCRIPTION
32-Lead (5mm
×
5mm) Plastic QFN
32-Lead (5mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°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.
Consult LTC Marketing for information on non-standard 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/
elecTrical characTerisTics
SYMBOL
V
CC
V
IN
I
Q
PARAMETER
Input Voltage Range
V
IN
Range
Input Voltage Supply Current
Normal Operation
Shutdown Mode
UVLO
RUN Input Threshold
RUN Input Pull-Up Current
Undervoltage Lockout Threshold
Soft-Start Pin Output Current
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
= 25°C. V
CC
= 5V, V
RUN1,2
= 5V, V
FREQ
= V
CLKIN
= 0V, V
FB
= 0.6V, f
OSC
= 0.6MHz
unless otherwise specified.
CONDITIONS
l
MIN
3.0
3
l
TYP
MAX
5.5
24
UNITS
V
V
mA
µA
mA
V
mV
µs
V
mV
µA
3860f
V
CC
= 5V
V
RUN1,2
= 5V
V
RUN1,2
= 0V
V
CC
< V
UVLO
V
RUN
Rising
V
RUN
Hysteresis
V
RUN1,2
= TBDV
V
CC
Rising
V
CC
Hysteresis
V
SS
= 0V
14
3.5
1.95
2.25
250
1.5
l
50
2.45
V
RUN
I
RUN
V
UVLO
I
SS
100
2.5
3.0
LTC3860
elecTrical characTerisTics
SYMBOL
t
SS(INTERNAL)
V
FB
∆V
FB
/∆V
CC
I
LIMIT
Power Good
V
FB(OV)
V
FB(UV)
V
PGOOD(ON)
Error Amplifier
I
FB
I
OUT
A
V(OL)
SR
f
0dB
A
V
V
OS
SR
f
0dB
V
OUT(MAX)
V
ISENSE(MAX)
A
V(ISENSE)
V
CM(ISENSE)
I
ISENSE
V
MM
f
OSC
FB Pin Input Current
COMP Pin Output Current
Open-Loop Voltage Gain
Slew Rate
COMP Unity-Gain Bandwidth
Diffierential Amplifier Voltage Gain
Input Referred Offset
Slew Rate
Bandwidth
Maximum Output Voltage
Maximum Differential Current Sense
Voltage (V
ISNSP
-V
ISNSN
)
Voltage Gain
Input Common Mode Range
SENSE Pin Input Current
Current Sense Mismatch
Oscillator Frequency
V
CM
= 1.5V
Channel 1 to Channel 2
V
CLKIN
= 0V
V
FREQ
= 0V
V
FREQ
= 5V
V
CLKIN
= 5V
R
FREQ
< 24.9k
R
FREQ
= 30.1k
R
FREQ
= 54.9k
R
FREQ
= 75.0k
Maximum Frequency
Minimum Frequency
I
FREQ
t
CLKIN(HI)
FREQ Pin Output Current
CLKIN Pulse Width High
V
FREQ
= 0.8V
V
CLKIN
= 0V to 5V
1.25
19
100
20
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
= 25°C. V
CC
= 5V, V
RUN1,2
= 5V, V
FREQ
= V
CLKIN
= 0V, V
FB
= 0.6V, f
OSC
= 0.6MHz
unless otherwise specified.
PARAMETER
Internal Soft-Start Time
Regulated Feedback Voltage
Regulated Feedback Voltage Line
Dependence
I
LIM
Pin Output Current
PGOOD/V
FB
Overvoltage Threshold
PGOOD/V
FB
Undervoltage Threshold
PGOOD Pull-Down Resistance
V
FB
= 600mV
Sourcing
Sinking
–100
1
5
75
45
20
V
VSNSN
= 0V
V
VSNSN
= 0V
l
CONDITIONS
0°C to 85°C T
J
–40°C to 125°C T
J
3.0V < V
CC
< 5.5V
V
ILIM
= 0.8V
V
FB
Falling
V
FB
Rising
V
FB
Falling
V
FB
Rising
MIN
595.5
594
TYP
2
600
600
0.05
MAX
604.5
606
0.2
22
UNITS
ms
mV
mV
%/V
µA
mV
mV
mV
mV
Ω
nA
mA
mA
dB
V/µs
MHz
l
18
20
645
660
540
555
15
650
530
670
550
60
100
Differential Amplifier
1.005
–2
45
20
4
50
18.5
–0.3
100
–2.75
2.75
V
CC
+ 0.1
1
0.995
2
V/V
mV
V/µs
MHz
V
mV
V/V
V
nA
mV
Current Sense Amplifier
Oscillator and Phase-Locked Loop
l
l
360
540
400
600
200
300
800
1.2
440
660
kHz
kHz
kHz
kHz
kHz
MHz
0.25
21
MHz
MHz
µA
ns
3860f
LTC3860
elecTrical characTerisTics
SYMBOL
t
CLKIN(LO)
R
CLKIN
V
CLKIN
V
FREQ
V
OL(CLKOUT)
V
OH(CLKOUT)
θ
2
-θ
1
θ
CLKOUT
-θ
1
PARAMETER
CLKIN Pulse Width Low
CLKIN Pull-Up Resistance
CLKIN Input Threshold
FREQ Input Threshold
V
CLKIN
Falling
V
CLKIN
Rising
V
CLKIN
= 0V
V
FREQ
Falling
V
FREQ
Rising
I
LOAD
= –500µA
I
LOAD
= 500µA
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
J
= 25°C. V
CC
= 5V, V
RUN1,2
= 5V, V
FREQ
= V
CLKIN
= 0V, V
FB
= 0.6V, f
OSC
= 0.6MHz
unless otherwise specified.
CONDITIONS
V
CLKIN
= 0V to 5V
MIN
100
13
1.2
2
1.5
2.5
0.2
V
CC
– 0.2
180
180
120
60
90
240
l
l
TYP
MAX
UNITS
ns
kΩ
V
V
V
V
V
V
Deg
Deg
Deg
Deg
Deg
Deg
V
CLKOUT Low Output Voltage
CLKOUT High Output Voltage
Channel 1-to-Channel 2 Phase Relationship V
PHSMD
= 0V
V
PHSMD
= Float
V
PHSMD
= V
CC
CLKOUT-to-Channel 1 Phase Relationship
V
PHSMD
= 0V
V
PHSMD
= Float
V
PHSMD
= V
CC
I
LOAD
= 500µA
I
LOAD
= –500µA
4.5
PWM/PWMEN Outputs
PWM
PWM Output High Voltage
PWM Output Low Voltage
PWM Output Current in Hi-Z State
PWM Maximum Duty Cycle
PWMEN
PWMEN Output High Voltage
I
LOAD
= 1mA
l
0.5
±5
91.5
4.5
V
µA
%
V
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:
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
)
Note 3:
The LTC3860E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3860I is guaranteed
over the full –40°C to 125°C operating junction temperature range. The
maximum ambient temperature is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
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