LTC3414
4A, 4MHz, Monolithic
Synchronous Step-Down Regulator
DESCRIPTIO
The LTC
®
3414 is a high efficiency monolithic synchro-
nous, step-down DC/DC converter utilizing a constant
frequency, current mode architecture. It operates from an
input voltage range of 2.25V to 5.5V and provides a
regulated output voltage from 0.8V to 5V while delivering
up to 4A of output current. The internal synchronous
power switch with 67mΩ on-resistance increases effi-
ciency and eliminates the need for an external Schottky
diode. Switching frequency is set by an external resistor or
can be synchronized to an external clock. 100% duty cycle
provides low dropout operation extending battery life in
portable systems. OPTI-LOOP
®
compensation allows the
transient response to be optimized over a wide range of
loads and output capacitors.
The LTC3414 can be configured for either Burst Mode
operation or forced continuous operation. Forced continu-
ous operation reduces noise and RF interference while
Burst Mode operation provides high efficiency by reduc-
ing gate charge losses at light loads. In Burst Mode
operation, external control of the burst clamp level allows
the output voltage ripple to be adjusted according to the
requirements of the application.
FEATURES
■
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■
■
■
■
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■
High Efficiency: Up to 95%
4A Output Current
Low Quiescent Current: 64μA
Low R
DS(ON)
Internal Switch: 67mΩ
Programmable Frequency: 300KHz to 4MHz
2.25V to 5.5V Input Voltage Range
±2%
Output Voltage Accuracy
0.8V Reference Allows Low Output Voltage
Selectable Forced Continuous/Burst Mode
®
Operation
with Adjustable Burst Clamp
Synchronizable Switching Frequency
Low Dropout Operation: 100% Duty Cycle
Power Good Output Voltage Monitor
Overtemperature Protected
Available in 20-Lead Exposed TSSOP Package
APPLICATIO S
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Point-of-Load Regulation
Notebook Computers
Portable Instruments
Distributed Power Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP 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, 6724174
TYPICAL APPLICATIO
V
IN
2.7V TO 5.5V
PV
IN
SV
IN
2.2M
294k
RT
22μF
100
95
PGOOD
LTC3414
SW
0.47μH
EFFICIENCY (%)
90
RUN/SS
1000pF
470pF
R
ITH
*
I
TH
PGND
V
OUT
2.5V AT 4A
C
OUT
*
85
80
75
70
65
FORCED
CONTINUOUS
SGND
SYNC/MODE
V
FB
3414 F01a
60
55
50
0.001
0.01
0.1
1.0
LOAD CURRENT (A)
10
3414 F01b
75k
110k
392k
*Burst Mode OPERATION: C
OUT
= 470μF SANYO POSCAP 4TPB470M, R
ITH
= 20k
FORCED CONTINUOUS: C
OUT
= (2) 100μF TDKC4532X5ROJ107M, R
ITH
= 12.1k
Figure 1. 2.5V/4A Step-Down Regulator
3414fb
U
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LTC3414 Efficiency Curve
Burst Mode OPERATION
1
LTC3414
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
PGND 1
RT 2
SYNC/MODE 3
RUN/SS 4
SGND 5
NC 6
PV
IN
7
SW 8
SW 9
PGND 10
21
20 PGND
19 V
FB
18 I
TH
17 PGOOD
16 SV
IN
15 NC
14 PV
IN
13 SW
12 SW
11 PGND
Input Supply Voltage ................................... –0.3V to 6V
I
TH
, RUN/SS, V
FB
,
SYNC/MODE Voltages .................................. –0.3 to V
IN
SW Voltages ................................. –0.3V to (V
IN
+ 0.3V)
Peak SW Sink and Source Current ......................... 9.5A
Operating Temperature Range (Note 2)
E, I Grades .............................................. – 40°C to 85°C
MP Grade ............................................. – 55°C to 125°C
Junction Temperature (Notes 5, 6) ....................... 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC3414EFE
LTC3414IFE
LTC3414MPFE
FE PACKAGE
20-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 21), MUST BE SOLDERED TO PCB
T
JMAX
= 125°C,
θ
JA
= 38°C/W,
θ
JC
= 10°C/W
Order Options
Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
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
V
IN
I
FB
V
FB
ΔV
FB
V
LOADREG
ΔV
PGOOD
R
PGOOD
I
Q
PARAMETER
Input Voltage Range
Feedback Pin Input Current
Regulated Feedback Voltage
Reference Voltage Line Regulation
Output Voltage Load Regulation
Power Good Range
Power Good Resistance
Input DC Bias Current
Active Current
Sleep
Shutdown
Switching Frequency
Switching Frequency Range
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
RUN Threshold
CONDITIONS
●
ELECTRICAL CHARACTERISTICS
MIN
2.25
0.784
0.780
TYP
(Note 3)
E, I Grade (Note 3)
MP Grade
V
IN
= 2.7V to 5.5V (Note 3)
Measured in Servo Loop, V
ITH
= 0.36V
Mesured in Servo Loop, V
ITH
= 0.84V
●
●
●
●
0.800
0.800
0.04
0.02
–0.02
±7.5
120
250
64
0.02
1.00
MAX
5.5
0.2
0.816
0.816
0.2
0.2
–0.2
±9
200
330
100
1
1.12
4
4
100
100
2.25
1.0
0.8
UNITS
V
μA
V
V
%V
%
%
%
Ω
μA
μA
μA
MHz
MHz
MHz
mΩ
mΩ
A
V
μA
V
f
OSC
f
SYNC
R
PFET
R
NFET
I
LIMIT
V
UVLO
I
LSW
V
RUN
(Note 4)
V
FB
= 0.75V, V
ITH
= 1.2V
V
FB
= 1V, V
ITH
= 0V, V
SYNC/MODE
= 0V
V
RUN
= 0V
R
OSC
= 294k
0.88
0.3
0.3
I
SW
= 300mA
I
SW
= –300mA
6
1.75
V
RUN
= 0V, V
IN
= 5.5V
0.5
67
50
8
2.00
0.1
0.65
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 LTC3414E 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. The LTC3414I is guaranteed over the full
–40°C to 85°C operating temperature range. The LTC3414MP is
guaranteed over the full –55°C to 125°C operating tempaerature range.
Note 3:
The LTC3414 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 P
D
as follows: T
J
=T
A
+ (P
D
)(38°C/W)
Note 6:
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 reliabability.
3414fb
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W W
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LTC3414
TYPICAL PERFOR A CE CHARACTERISTICS
V
REF
vs Temperature, V
IN
= 3.3V
0.800
90
80
0.799
ON-RESISTANCE (mΩ)
ON-RESISTANCE (mΩ)
V
REF
(V)
0.798
0.797
0.796
0.795
–40 –20
0
20 40 60 80 100 120 140
TEMPERATURE (°C)
3414 G01
Switch Leakage vs Input Voltage
20
18
SWITCH LEAKAGE CURRENT (nA)
T
A
= 25°C
16
FREQUENCY (kHz)
12
10
8
6
4
2
0
2.25
NFET
PFET
FREQUENCY (kHz)
14
2.75 3.25 3.75 4.25 4.75
INPUT VOLTAGE (V)
Frequency vs Temperature
1090
1070
1050
FREQUENCY (kHz)
MINIMUM PEAK INDUCTOR CURRENT (A)
V
IN
= 3.3V
R
OSC
= 294k
QUIESCENT CURRENT (μA)
1030
1010
990
970
950
930
910
–40 –20
0
20 40 60 80
TEMPERATURE (°C)
100 120
3414 G07
U W
5.25
3414 G04
Switch On-Resistance vs
Input Voltage
120
T
A
= 25°C
PFET
Switch On-Resistance vs
Temperature, V
IN
= 3.3V
100
80
PFET
60
40
20
NFET
70
60
50
40
30
20
10
NFET
0
2.25 2.75 3.25 3.75 4.25 4.75 5.25
INPUT VOLTAGE (V)
5.75
0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
3414 G03
3414 G02
Frequency vs R
OSC
7000
6000
5000
4000
3000
2000
1000
0
25 125 225 325 425 525 625 725 825 925
R
OSC
(k)
3414 G05
Frequency vs Input Voltage
V
IN
= 3.3V
T
A
= 25°C
1040
1020
1000
980
960
940
920
900
2.25
R
OSC
= 294k
T
A
= 25°C
2.75 3.25 3.75 4.25 4.75
INPUT VOLTAGE (V)
5.25
3414 G06
DC Supply Current vs Input
Voltage
350
300
ACTIVE
250
200
150
100
SLEEP
50
0
2.25
T
A
= 25°C
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
Minimum Peak Inductor Current
vs Burst Clamp Voltage
V
IN
= 3.3V
T
A
= 25°C
2.75
3.25 3.75 4.25 4.75
INPUT VOLTAGE (V)
5.25
3414 G08
0
0.1
0.2 0.3 0.4 0.5 0.6 0.7
BURST CLAMP VOLTAGE (V)
0.8
3414 G09
3414fb
3
LTC3414
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Load Current, Burst
Mode Operation
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
0.001
0.01
0.1
1
LOAD CURRENT (A)
10
3414 G10
V
IN
= 3.3V
V
IN
= 5V
EFFICIENCY (%)
60
50
40
30
20
10
0
0.001
EFFICIENCY (%)
Efficiency vs Input Voltage
98
96
94
92
EFFICIENCY (%)
90
88
86
84
82
80
78
2.5
3.0
4.0
4.5
3.5
INPUT VOLTAGE (V)
5.0
5.5
3414 G13
I
OUT
= 1A
V
OUT
= 2.5V
T
A
= 25°C
L = 0.2μH
85
80
75
70
300 800 1300 1800 2300 2800 3300 3800
FREQUENCY (kHz)
3414 G14
I
OUT
= 4A
ΔV
OUT
/V
OUT
(%)
EFFICIENCY (%)
Burst Mode Operation
OUTPUT
VOLTAGE
20mV/DIV
OUTPUT
VOLTAGE
100mV/DIV
INDUCTOR
CURRENT
500mA/DIV
V
IN
= 3.3V, V
OUT
= 2.5V
LOAD = 250mA
4
U W
T
A
= 25°C
Efficiency vs Load Current,
Forced Continuous
100
90
80
70
V
OUT
= 2.5V
T
A
= 25°C
V
IN
= 3.3V
V
IN
= 5V
100
95
90
85
80
75
70
65
60
55
0.01
0.1
1
LOAD CURRENT (A)
10
3414 G11
Efficiency vs Load Current
Burst Mode OPERATION
T
A
= 25°C
FORCED
CONTINUOUS
V
IN
= 3.3V
V
OUT
= 2.5V
0.01
0.1
1
LOAD CURRENT (A)
10
3414 G12
50
0.001
Efficiency vs Frequency
100
L = 1μH
95
L = 0.47μH
90
–0.10
–0.15
–0.20
–0.25
–0.30
V
IN
= 3.3V
V
OUT
= 2.5V
T
A
= 25°C
0
–0.05
Load Regulation
V
IN
= 3.3V
V
OUT
= 2.5V
T
A
= 25°C
0
0.5
1.0
1.5 2.0 2.5 3.0
LOAD CURRENT (A)
3.5
4.0
3414 G15
Load Step Transient Forced
Continuous
INDUCTOR
CURRENT
2A/DIV
10μs/DIV
3414 G16
20μs/DIV
V
IN
= 3.3V, V
OUT
= 2.5V
LOAD STEP = 0A TO 4A
3414 G17
3414fb
LTC3414
TYPICAL PERFOR A CE CHARACTERISTICS
Load Step Transient Burst Mode
Operation
OUTPUT
VOLTAGE
100mV/DIV
V
RUN
OUTPUT
VOLTAGE
INDUCTOR
CURRENT
2A/DIV
V
IN
= 3.3V, V
OUT
= 2.5V
LOAD STEP = 250mA TO 4A
PI FU CTIO S
PGND (Pins 1, 10, 11, 20):
Power Ground. Connect this
pin closely to the (–) terminal of C
IN
and C
OUT
.
RT (Pin 2):
Oscillator Resistor Input. Connecting a resistor
to ground from this pin sets the switching frequency.
SYNC/MODE (Pin 3):
Mode Select and External Clock
Synchronization Input. To select Forced Continuous, tie to
SV
IN
. Connecting this pin to a voltage between 0V and 1V
selects Burst Mode operation with the burst clamp set to
the pin voltage.
RUN/SS (Pin 4):
Run Control and Soft-Start Input. Forcing
this pin below 0.5V shuts down the LTC3414. In shutdown
all functions are disabled. Less than 1μA of supply current
is consumed. A capacitor to ground from this pin sets the
ramp time to full output current.
SGND (Pin 5):Signal
Ground. All small signal components
and compensation components should connect to this
ground, which in turn connects to PGND at one point.
NC (Pin 6):
Open. No internal connection.
PV
IN
(Pins 7, 14):
Power Input Supply. Decouple this pin
to PGND with a capacitor.
SW (Pins 8, 9, 12, 13):
Switch Node Connection to
Inductor. This pin connects to the drains of the internal
main and synchronous power MOSFET switches.
NC (Pin 15):
Open. No internal connection.
SV
IN
(Pin 16):
Signal Input Supply. Decouple this pin to
SGND with a capacitor.
PGOOD (Pin 17):
Power Good Output. Open drain logic
output that is pulled to ground when the output voltage is
not within
±7.5%
of regulation point.
I
TH
(Pin 18):
Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is from 0.2V to
1.4V with 0.4V corresponding to the zero-sense voltage
(zero current).
V
FB
(Pin 19):
Feedback Pin. Receives the feedback voltage
from a resistive divider connected across the output.
Exposed Pad (Pin 21):
Should be connected to SGND and
soldered to the PCB.
U W
Start-Up Transient
INDUCTOR
CURRENT
2A/DIV
20μs/DIV
3414 G18
1ms/DIV
V
IN
= 3.3V, V
OUT
= 2.5V
LOAD = 4A
3414 G19
U
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3414fb
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