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LTC3415
7A, PolyPhase
Synchronous Step-Down
Regulator
DESCRIPTION
The LTC
®
3415 is a high efficiency, monolithic synchronous
buck regulator using a phase lockable constant frequency,
current mode architecture. PolyPhase
®
operation allows
multiple LTC3415s to run out of phase while using mini-
mal input and output capacitance. The operating supply
range is from 5.5V down to 2.5V, making it suitable for
single Lithium-Ion battery as well as point of load power
supply applications. Burst Mode operation provides high
efficiency at low load currents. 100% duty cycle provides
low dropout operation that extends operating time in bat-
tery-operated systems.
The operating frequency is internally set at 1.5MHz, al-
lowing the use of small surface mount inductors. For
switching-noise sensitive applications, it can be externally
synchronized from 0.75MHz to 2.25MHz. The PHMODE
pin allows user control of the phase of the outgoing clock
signal. The current sense comparator is factory trimmed
for accurate output current sharing. Burst Mode operation
is inhibited during synchronization or when the MODE pin
is pulled low to reduce noise and RF interference.
, LT, LTC, LTM, Burst Mode and PolyPhase are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,
6611131.
High Efficiency: Up to 96%
7A Output Current at V
IN
= 3V
Adjustable Frequency: 1.5MHz Nominal
PolyPhase Operation (Up to 12 Phases)
Spread Spectrum Frequency Modulation
Output Tracking and Margining
±1% Reference Accuracy
2.5V to 5.5V V
IN
Range
Phase Lockable from 0.75MHz to 2.25MHz
Selectable Burst Mode
®
Operation
Low Dropout Operation: 100% Duty Cycle
Low Quiescent Current: 450μA
Current Mode Operation for Excellent Line and Load
Transient Response
Shutdown Mode Draws Only 0.2μA Supply Current
Available in 38-Pin (5mm
×
7mm) QFN Package
APPLICATIONS
n
n
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Point of Load Power Supply
Portable Instruments
Distributed Power Systems
Battery-Powered Equipment
TYPICAL APPLICATION
V
IN
, 2.5V to 5.5V
22μF
x3
Efficiency and Power Loss
100
90
80
EFFICIENCY (%)
10
CLKIN
SV
IN
PV
IN
SW
SW
SW
SW
CLKOUT
PHMODE
PLLLPF
RUN
60k
TRACK
FB
MODE
PGOOD
I
TH
120k
SGND
PGND
LTC3415
EFFICIENCY
70
60
50
40
30
20
10
0
0.01
0.1
1
LOAD CURRENT (A)
POWER LOSS
1
POWER LOSS (W)
SW
V
OUT
1.8V
0.2μH
47μF
x3
0.1
0.01
2.5V
3.3V
5V 0.001
10
3415 TA01B
3415 TA01
Figure 1. High Efficiency Step-Down Converter
3415fa
1
LTC3415
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
CLKOUT
I
THM
SV
IN
PV
IN
PV
IN
RUN
I
TH
31 NC
30 TRACK
29 V
FB
28 PV
IN
27 PV
IN
39
26 SW
25 SW
24 SW
23 SW
22 PGOOD
21 BSEL
20 MGN
13 14 15 16 17 18 19
PGND
PGND
PGND
PGND
PGND
PGND
PGND
SV
IN
, PV
IN
Voltage ....................................... –0.3V to 6V
PLLLPF PGOOD Voltages .............................–0.3V to V
IN
,
CLKIN, PHMODE, MODE Voltages ...............–0.3V to V
IN
CLKOUT Voltage .......................................... –0.3V to 2V
I
TH
, I
THM
, V
FB
, TRACK Voltages ....................–0.3V to V
IN
MGN, BSEL, RUN Voltages ..........................–0.3V to V
IN
SW Voltage (DC) ............................–0.3V to (V
IN
+ 0.3V)
Peak SW Sink and Source Current ............................15A
Operating Ambient Temperature
Range (Note 2)......................................... –40°C to 85°C
Junction Temperature (Note 5) ............................. 125°C
Storage Temperature.............................. –65°C to 125°C
38 37 36 35 34 33 32
NC 1
SGND 2
PLLLPF 3
PV
IN
4
PV
IN
5
SW 6
SW 7
SW 8
SW 9
MODE 10
CLKIN 11
PHMODE 12
UHF PACKAGE
38-LEAD (7mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 34°C/W,
θ
JC
= 1.1°C/W
EXPOSED PAD (PIN 39) IS PGND
MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3415EUHF#PBF
TAPE AND REEL
LTC3415EUHF#TRPBF
PART MARKING
3415
PACKAGE DESCRIPTION
38-Lead (5mm
×
7mm) QFN Package
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
SV
IN
V
FB
ΔV
FB
V
LOADREG
ΔV
PGOOD
R
PGOOD
PARAMETER
Signal Input Voltage Range
Regulated Feedback Voltage
Reference Voltage Line Regulation
Output Voltage Load Regulation
Power Good Range
Power Good Pull-Down Resistance
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V unless otherwise specified.
CONDITIONS
(Note 3)
V
IN
= 2.5V to 5.5V (Note 3)
Measured in Servo Loop, V
ITH
= 0.3V
Measured in Servo Loop, V
ITH
= 0.9V
1mA Load, V
IN
= 3.3V
l
l
l
MIN
2.375
0.590
TYP
0.596
0.15
0.1
–0.05
MAX
5.5
0.602
0.3
0.2
–0.2
±13
40
UNITS
V
V
%/V
%
%
%
Ω
±7
±10
25
3415fa
2
LTC3415
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V unless otherwise specified.
SYMBOL
I
Q
PARAMETER
Input DC Bias Current
Active Current
Sleep
Shutdown
Switching Frequency
SYNC Capture Range
R
DS(ON)
of P-Channel FET
R
DS(ON)
of N-Channel FET
Peak Current Limit
Undervoltage Lockout Threshold
SW Leakage Current
Internal Soft-Start Delay
Error Amplifier’s Transconductance
Run Input Threshold
PGOOD Falling Edge Delay
Output Voltage Margining Percentage
MGN HI, BSEL LOW
MGN HI, BSEL HI
MGN HI, BSEL = SV
IN
/2
MGN LOW, BSEL LOW
MGN LOW, BSEL HI
MGN LOW, BSEL = SV
IN
/2
RUN = V
IN
RUN = 0V
3
8
13
–3
–8
–13
RUN Rising
RUN Falling
1.7
1.4
1.2
I
SW
= 100mA
I
SW
= 100mA
V
ITH
= 1V (Note 6)
SV
IN
Rising
SV
IN
Falling
V
RUN
= 0V, V
IN
= 5.5V
11
2.05
1.85
CONDITIONS
(Note 4)
V
FB
= 0.57V, MODE = 0V
V
FB
= 0.63V, MODE = V
IN
V
RUN
= 0V
1.3
0.75
32
25
13
2.2
2.0
0.1
140
2
1.5
1.3
35
5
10
15
–5
–10
–15
0.57
0.18
V
IN
– 0.5
V
IN
– 0.5
V
IN
– 0.5
V
FB
Rising
V
FB
Falling
V
FB
Returning to Regulation
7
–7
10
–10
1
13
–13
3
7
12
17
–7
–12
–17
2.2
1.6
1.4
MIN
TYP
1350
450
0.2
1.5
MAX
UNITS
μA
μA
μA
MHz
MHz
mΩ
mΩ
A
V
V
μA
μs
mmho
V
V
μs
%
%
%
%
%
%
V
V
V
V
V
%
%
%
ELECTRICAL CHARACTERISTICS
5
1.7
2.25
40
32
15
2.35
2.15
5
f
OSC
f
SYNC
R
PFET
R
NFET
I
LIMIT
V
UVLO
I
LSW
SS Delay
g
m
RUN
PGOOD Delay
%
MARGINING
TRACK
Tracking Threshold (Rising)
Tracking Threshold (Falling)
Tracking Disable Threshold
V
FB
Slavemode (EA Disable) Threshold
Switch Over Threshold for Internal
Compensation
Output Overvoltage Threshold
Output Undervoltage Threshold
OV/UV Hysteresis
V
FB
Slavemode
I
TH
Internal
OV
UV
V
HYST
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 LTC3415E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
The LTC3415 is tested in a feedback loop that adjusts V
FB
to
achieve a specified error amplifier output voltage (I
TH
).
Note 4:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5:
T
J
is calculated from the ambient temperature T
A
and power
dissipation as follows: LTC3415: T
J
= T
A
+ P
D
(34°C/W).
Note 6:
Current Limit is measured with internal servo loop while forcing
V
ITH
= 1V.
Note 7:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
3415fa
3
LTC3415
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency and Power Loss vs
Load Current (3 Operating Modes)
(Reference Figure 13)
100
90
80
70
V
OUT
= 1.8V
V
IN
= 3.3V
SUPPLY CURRENT (mA)
1
10
1.6
1.4
Supply Current vs V
IN
40
35
R
DSON
vs V
IN
PFET
60
50
40
30
20
10
0
0.001
% (Burst)
% (PSKIP)
% (FC)
W (Burst)
W (PSKIP)
W (FC)
0.01
0.1
1
LOAD CURRENT (A)
0.1
1.0
0.8
0.6
0.4
0.2
V
O
= 1.2V BURST MODE
ON-RESISTANCE (mΩ)
1.2
V
O
= 1.2V PULSE SKIP
30
25
NFET
20
15
10
5
0
2.25
POWER LOSS (mW)
EFFICIENCY (%)
0.01
0.001
10
0
2.5
3
3.5
4
4.5
INPUT VOLTAGE (V)
5
5.5
3415 G03
3415 G01
3.25
4.25
INPUT VOLTAGE (V)
5.25
3415 G04
R
DSON
vs Temperature
40
0.5
0.4
Load Regulation
(Reference Figure 13)
FC MODE
V
IN
= 3.3V
V
OUT
= 1.8V
Load Step
(Reference Figure 13)
V
OUT
(AC)
100mV/
DIV
35
POWER PMOS
LOAD REGULATION (%)
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
R
DSON
(mΩ)
30
I
L
5A/
DIV
I
OUT
5A/DIV
40μs/DIV
FORCED CONTINUOUS
I
LOAD
= 0.1A TO 5A
3415 G08
25
POWER NMOS
20
15
–100
–0.5
V
IN
= 3.3V
V
OUT
= 1.8V
0
1
2
3
4
5
6
LOAD CURRENT (A)
7
8
–50
100
0
50
TEMPERATURE (°C)
150
3415 G05
3415 G06
Oscillator Frequency
vs Temperature
2.0
Efficiency and Power Loss vs Load
Current Force Continuous Mode
100
90
V
OUT
= 1.8V
10
OSCILLATOR FREQUENCY (MHz)
1.8
EFFICIENCY (%)
80
70
60
50
40
30
POWER LOSS
0.1
POWER LOSS (mW)
EFFICIENCY
1
1.6
1.4
1.2
20
10
1.0
–100
–50
0
50
100
TEMPERATURE (°C)
150
3415 G11
0
0.01
0.1
1
LOAD CURRENT (A)
2.5V
3.3V
5V 0.01
10
3415 G02
3415fa
4
LTC3415
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency and Power Loss
Burst Mode Operation
100
90
80
EFFICIENCY (%)
Efficiency and Power Loss
Pulse-Skip Mode Operation
10
100
90
V
OUT
= 1.8V
EFFICIENCY
POWER LOSS (mW)
V
OUT
= 1.8V
EFFICIENCY
10
60
50
40
30
20
10
0
0.01
0.1
1
LOAD CURRENT (A)
POWER LOSS
0.1
EFFICIENCY (%)
70
1
80
POWER LOSS (mW)
70
60
50
40
30
20
10
0
0.01
0.1
1
LOAD CURRENT (A)
1
0.1
POWER LOSS
2.5V
3.3V
5V 0.01
10
3415 G10
0.01
2.5V
3.3V
5V 0.001
10
3415 G09
Output Tracking
V
OUT2
=
3.3V/7A
500mV/DIV
LEAKAGE CURRENT (nA)
Switch Leakage Current
vs Input Voltage
200
175
150
125
100
75
50
25
0
2.5
3
SYNCHRONOUS
SWITCH
4
3.5
4.5
5
INPUT VOLTAGE (V)
5.5
6
MAIN SWITCH
V
OUT1
=
1.8V/14A
500mV/DIV
500μs/DIV
3415 G07
3415 G12
3415fa
5
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