FEATURES
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LTC3419
Dual Monolithic 600mA
Synchronous Step-Down
Regulator
DESCRIPTION
The LTC
®
3419 is a dual, 2.25MHz, constant-frequency,
synchronous step-down DC/DC converter in a tiny
3mm
×
3mm DFN package. 100% duty cycle provides
low dropout operation, extending battery life in portable
systems. Low output voltages are supported with the 0.6V
feedback reference voltage. Each regulator can supply
600mA output current.
The input voltage range is 2.5V to 5.5V, making it ideal
for Li-Ion and USB powered applications. Supply cur-
rent during operation is only 35μA and drops to <1μA in
shutdown. A user-selectable mode input allows the user
to trade off between high efficiency Burst Mode operation
and pulse-skipping mode.
An internally set 2.25MHz switching frequency allows the
use of tiny surface mount inductors and capacitors. Inter-
nal soft-start reduces inrush current during start-up. Both
outputs are internally compensated to work with ceramic
output capacitors. The LTC3419 is available in a low profile
(0.75mm) 3mm
×
3mm DFN package. The LTC3419 is also
available in a fixed output voltage configuration selected
via internal resistor dividers (see Table 2).
, LT, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5481178, 6127815, 6304066, 6498466, 6580258, 6611131.
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High Efficiency Dual Step-Down Outputs: Up to 96%
600mA Current per Channel at V
IN
= 3V
Only 35μA Quiescent Current During Operation
(Both Channels)
2.25MHz Constant-Frequency Operation
2.5V to 5.5V Input Voltage Range
Low Dropout Operation: 100% Duty Cycle
No Schottky Diodes Required
Internally Compensated for All Ceramic Capacitors
Independent Internal Soft-Start for Each Channel
Available in Fixed Output Versions
Current Mode Operation for Excellent Line and Load
Transient Response
0.6V Reference Allows Low Output Voltages
User-Selectable Burst Mode
®
Operation
Short-Circuit Protected
Ultralow Shutdown Current: I
Q
< 1μA
Available in Small MSOP or 3mm
×
3mm
DFN-8 Packages
APPLICATIONS
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Cellular Telephones
Digital Still Cameras
Wireless and DSL Modems
Portable Media Players
PDAs/Palmtop PCs
TYPICAL APPLICATION
Dual Monolithic Buck Regulator in 8-Lead 3
×
3 DFN
V
IN
2.5V TO 5.5V
10μF
RUN2 V
IN
RUN1
MODE
V
OUT2
1.8V AT
600mA
3.3μH
22pF
LTC3419
SW2
SW1
22pF
3.3μH
V
OUT1
2.5V AT
600mA
Efficiency and Power Loss vs
Output Current
100
90
80
70
EFFICIENCY (%)
60
50
40
30
0.01
0.1
1
POWER LOSS (W)
V
IN
= 3.6V
10
V
FB2
10μF
118k
59k
GND
V
FB1
59k
187k
10μF
3419 TA01
20
10
0
0.1
V
OUT
= 1.2V
V
OUT
= 1.8V
V
OUT
= 2.5V
1
10
100
OUTPUT CURRENT (mA)
0.001
0.0001
1000
3419 TA01b
3419f
1
LTC3419
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (V
IN
) ............................. –0.3 to 6V
V
FB1
, V
FB2
........................................ –0.3V to V
IN
+ 0.3V
RUN1, RUN2, MODE ........................ –0.3V to V
IN
+ 0.3V
SW1, SW2 ....................................... –0.3V to V
IN
+ 0.3V
P-Channel SW Source Current (DC) (Note 2).......800mA
N-Channel SW Source Current (DC) (Note 2) ......800mA
Peak SW Source and Sink Current (Note 2) .............1.3A
Operating Temperature Range (Note 3) .......–40 to 85°C
Junction Temperature (Note 6) ............................. 125°C
Storage Temperature Range...................–65°C to 125°C
Lead Temperature (Soldering, 10 sec)
MSOP Package ................................................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
V
FB1
1
RUN1 2
MODE 3
SW1 4
9
8
7
6
5
V
FB2
RUN2
SW2
V
IN
TOP VIEW
V
FB1
RUN1
MODE
SW1
GND
1
2
3
4
5
10
9
8
7
6
V
FB2
RUN2
SW2
V
IN
GND
DD PACKAGE
8-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 40°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 120°C/W
ORDER PART NUMBER
LTC3419EDD
LTC3419EDD-1
DD PART MARKING
LCQJ
LCWW
ORDER PART NUMBER
LTC3419EMS
LTC3419EMS-1
MS PART MARKING
LTCQK
LTCWX
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/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
UV
I
FB
V
FBREG1
PARAMETER
V
IN
Operating Voltage
V
IN
Undervoltage Lockout
Feedback Pin Input Current
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 3.6V, unless otherwise noted.
CONDITIONS
●
MIN
2.5
●
●
●
●
●
●
●
TYP
2.1
3
MAX
5.5
2.5
±30
5
0.610
0.612
1.606
0.610
0.612
1.836
0.5
UNITS
V
V
nA
μA
V
V
V
V
V
V
%/V
V
IN
Low to High
LTC3419
LTC3419-1
Regulated Feedback Voltage (Channel 1) LTC3419, 0°C < T
A
< 85°C
LTC3419, –40°C < T
A
< 85°C
LTC3419-1, –40°C < T
A
< 85°C
Regulated Feedback Voltage (Channel 2) LTC3419, 0°C < T
A
< 85°C
LTC3419, –40°C < T
A
< 85°C
LTC3419-1, –40°C < T
A
< 85°C
Reference Voltage Line Regulation
V
IN
= 2.5V to 5.5V (Note 7)
0.590
0.588
1.544
0.590
0.588
1.764
0.600
0.600
1.575
0.600
0.600
1.8
0.3
V
FBREG2
ΔV
LINE REG
3419f
2
LTC3419
ELECTRICAL CHARACTERISTICS
SYMBOL
ΔV
LOAD REG
I
S
PARAMETER
Output Voltage Load Regulation
Input DC Supply Current
Active Mode (Note 4)
Sleep Mode
Shutdown
Oscillator Frequency
Peak Switch Current Limit
Channel 1 (600mA)
Channel 2 (600mA)
Channel 1 (Note 5)
Top Switch On-Resistance
Bottom Switch On-Resistance
Channel 2 (Note 5)
Top Switch On-Resistance
Bottom Switch On-Resistance
Switch Leakage Current
Soft-Start Time
RUN Threshold High
RUN Leakage Current
MODE Threshold High
MODE Leakage Current
Output Ripple in Burst Mode Operation
V
OUT
= 1.5V, C
OUT
= 10μF
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 3.6V, unless otherwise noted.
CONDITIONS
I
LOAD
= 0mA to 600mA (Note 7)
V
FB1
= V
FB2
= 0.95
×
V
FBREG
V
FB1
= V
FB2
= 1.05
×
V
FBREG
, V
IN
= 5.5V
RUN1 = RUN2 = 0V, V
IN
= 5.5V
V
FB
= V
FBREG
V
IN
= 3V, V
FB
< V
FBREG
, Duty Cycle < 35%
900
900
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 3.6V, I
SW
= 100mA
V
IN
= 5V, V
RUN
= 0V
V
FB
from 10% to 90% Full Scale
●
●
●
●
●
MIN
TYP
0.5
500
35
0.1
MAX
UNITS
%
700
60
1
2.7
μA
μA
μA
MHz
mA
mA
f
OSC
I
LIM
1.8
2.25
1200
1200
0.4
0.4
0.4
0.4
0.01
R
DS(ON)
0.6
0.6
0.6
0.6
1
1.3
1.2
1
1.2
1
Ω
Ω
Ω
Ω
μA
ms
V
μA
V
μA
mV
P-P
I
SW(LKG)
t
SOFTSTART
V
RUN
I
RUN
V
MODE
I
MODE
V
BURST
0.1
0.4
0.4
0.95
1
0.01
1
0.01
20
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:
Guaranteed by long term current density limitations.
Note 3:
The LTC3419E and LTC3419E-1 are guaranteed to meet specified
performance from 0°C to 85°C. Specifications over the –40°C and 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 4:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5:
The DFN switch on-resistance is guaranteed by correlation to
wafer level measurements.
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 reliability.
Note 7:
The converter is tested in a proprietary test mode that connects
the output of the error amplifier to the SW pin, which is connected to an
external servo loop.
3419f
3
LTC3419
TYPICAL PERFORMANCE CHARACTERISTICS
Burst Mode Operation
SW
2V/DIV
V
OUT
50mV/DIV
AC-COUPLED
I
L
100mA/DIV
3419 G01
T
A
= 25°C, V
IN
= 3.6V, unless otherwise noted.
Pulse Skip Mode Operation
100
SW
2V/DIV
V
OUT
50mV/DIV
AC-COUPLED
I
L
100mA/DIV
EFFICIENCY (%)
90
80
70
60
50
5μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 5mA
3419 G02
Efficiency vs Input Voltage
I
OUT
= 100mA
I
OUT
= 1mA
I
OUT
= 600mA
I
OUT
= 10mA
I
OUT
= 0.1mA
40
V
OUT
= 1.8V
30
3.0
3.5
2.5
2μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 25mA
4.0
V
IN
(V)
4.5
5.0
5.5
3419 G03
Reference Voltage
vs Temperature
1.5
1.0
V
FB
(% ERROR)
0.5
0
–0.5
–1.0
–1.5
–50
FREQUENCY (MHz)
2.6
2.5
Oscillator Frequency
vs Temperature
60
Supply Current
vs Temperature
I
LOAD
= 0A
RUN1 = RUN2 = V
IN
50
2.3
2.2
V
IN
= 2.7V
2.1
2.0
1.9
–25
0
50
25
75
TEMPERATURE (°C)
100
125
1.8
–50
–25
25
75
0
50
TEMPERATURE (°C)
100
125
10
–50
–25
25
0
50
TEMPERATURE (°C)
75
100
3419 G06
SUPPLY CURRENT (μA)
2.4
V
IN
= 4.2V
V
IN
= 3.6V
40
V
IN
= 5.5V
30
V
IN
= 2.7V
20
3419 G04
3419 G05
Switch Leakage vs Input Voltage
3.0
2.5
LEAKAGE CURRENT (nA)
2.0
R
DS(ON)
(Ω)
MAIN SWITCH
1.5
1.0
0.5
0
2.5
SYNCHRONOUS
SWITCH
0.50
0.45
0.40
Switch On-Resistance vs
Input Voltage
0.6
Switch On-Resistance vs
Temperature
0.5
MAIN SWITCH
R
DS(ON)
(Ω)
MAIN SWITCH
0.35
0.30
0.25
0.20
2.5
0.4
0.3
SYNCHRONOUS SWITCH
0.2
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
–25
25
75
0
50
TEMPERATURE (°C)
100
125
SYNCHRONOUS
SWITCH
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
3419 G07
3.0
3.5
4.0 4.5
V
IN
(V)
5.0
5.5
6.0
0.1
–50
3419 G08
3419 G09
3419f
4
LTC3419
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
90
80
70
EFFICIENCY (%)
EFFICIENCY (%)
60
50
40
30
20
10
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1000
3419 G10
T
A
= 25°C, V
IN
= 3.6V, unless otherwise noted.
Efficiency vs Load Current
100
90
80
70
60
50
40
30
20
10
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1000
3419 G11
Efficiency vs Load Current
100
90
80
70
EFFICIENCY (%)
60
50
40
30
20
10
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1000
3419 G12
V
OUT
= 1.2V
0
0.1
10
100
1
OUTPUT CURRENT (mA)
V
OUT
= 1.8V
0
0.1
10
100
1
OUTPUT CURRENT (mA)
V
OUT
= 2.5V
0
0.1
10
100
1
OUTPUT CURRENT (mA)
Efficiency vs Load Current
100
90
80
V
OUT
ERROR (%)
70
EFFICIENCY (%)
60
50
40
30
20
10
0
0.1
V
OUT
= 1.8V
10
100
1
OUTPUT CURRENT (mA)
1000
3419 G13
Load Regulation
3.0
2.5
2.0
V
OUT
ERROR (%)
V
OUT
= 1.2V
V
OUT
= 1.8V
V
OUT
= 2.5V
2.0
1.5
1.0
0.5
0
–0.5
–1.0
Load Regulation
V
OUT
= 1.8V
Burst Mode OPERATION
PULSE SKIP MODE
1.5
Burst Mode OPERATION
1.0
0.5
0
–0.5
–1.0
0
100
200
400
300
LOAD CURRENT (mA)
500
600
3419 G14
Burst Mode OPERATION
PULSE SKIP MODE
0
100
300
200
400
LOAD CURRENT (mA)
500
600
3419 G15
Line Regulation
0.6
0.4
V
OUT
ERROR (%)
0.2
0
–0.2
–0.4
–0.6
2.5
I
L
500mA/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA
RUN
2V/DIV
Start-Up from Shutdown
RUN
2V/DIV
Start-Up from Shutdown
V
OUT
1V/DIV
V
OUT
1V/DIV
I
LOAD
500mA/DIV
250μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 0A
3419 G17
250μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
R
LOAD
= 3Ω
3419 G18
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
3419 G16
3419f
5
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