FEATURES
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LTC3407-4
Dual Synchronous, 800mA,
2.25MHz Step-Down
DC/DC Regulator
DESCRIPTION
The LTC
®
3407-4 is a dual, constant frequency, synchro-
nous step down DC/DC converter. Intended for low power
applications, it operates from 2.5V to 5.5V input voltage
range and has a constant 2.25MHz switching frequency,
allowing the use of tiny, low cost capacitors and induc-
tors with a profile ≤1mm. Each output voltage is adjust-
able from 0.6V to 5V. Internal synchronous 0.35Ω, 1.2A
power switches provide high efficiency without the need
for external Schottky diodes.
A user selectable mode input is provided to allow the user
to trade-off noise ripple for low power efficiency. Burst
Mode
®
operation provides high efficiency at light loads,
while pulse-skipping mode provides low noise ripple at
light loads.
To further maximize battery life, the P-channel MOSFETs
are turned on continuously in dropout (100% duty cycle),
and both channels draw a total quiescent current of only
40μA. In shutdown, the device draws <1μA.
The LTC3407-4 is identical to the LTC3407-2 except for
the reduced power-on reset delay time.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo 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 95%
Very Low Quiescent Current: Only 40μA
2.25MHz Constant Frequency Operation
High Switch Current: 1.2A on Each Channel
No Schottky Diodes Required
Low R
DS(ON)
Internal Switches: 0.35Ω
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit Protected
Low Dropout Operation: 100% Duty Cycle
Ultralow Shutdown Current: I
Q
< 1μA
Output Voltages from 5V down to 0.6V
Power-On Reset Output
Externally Synchronizable Oscillator
Small Thermally Enhanced MSOP and 3mm
×
3mm
DFN Packages
APPLICATIONS
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PDAs/Palmtop PCs
Digital Cameras
Cellular Phones
Portable Media Players
PC Cards
Wireless and DSL Modems
TYPICAL APPLICATION
V
IN
*
2.5V TO 5.5V
LTC3407-4 Efficiency/Power Loss Curve
C1
10μF
L2
2.2μH
SW2
C5, 22pF
RUN2
V
IN
RUN1
POR
L1
2.2μH
SW1
C4, 22pF
R5
100k
RESET
EFFICIENCY (%)
V
OUT1
1.8V
800mA
100
90
80
70
60
50
40
30
C2
10μF
20
10
0.01
0.1
POWER LOSS (W)
1
MODE/SYNC
V
OUT2
2.5V
800mA
LTC3407-4
C3
10μF
R4
887k
V
FB2
R3
280k
GND
V
FB1
R2
R1 604k
301k
0.001
C1, C2, C3: TAIYO YUDEN JMK316BJ106ML
L1, L2: MURATA LQH32CN2R2M33
*V
OUT
CONNECTED TO V
IN
FOR V
IN
≤
2.8V
3407 TA01
0
0.1
1
10
100
LOAD CURRENT (mA)
0.0001
1000
34074 TA02
Figure 1. 2.5V/1.8V at 800mA Step-Down Regulators
34074fa
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LTC3407-4
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
Voltages .................................................– 0.3V to 6V
V
FB1
, V
FB2
Voltages .......................... –0.3V to V
IN
+ 0.3V
RUN1, RUN2 Voltages .................................–0.3V to V
IN
MODE/SYNC Voltage....................................–0.3V to V
IN
SW1, SW2 Voltage ........................... –0.3V to V
IN
+ 0.3V
POR
Voltage ................................................. –0.3V to 6V
Ambient Operating Temperature
Range (Note 2)......................................... –40°C to 85°C
Junction Temperature (Note 5) ............................. 125°C
Storage Temperature Range...................– 65°C to 125°C
Lead Temperature (Soldering, 10 sec)
LTC3407EMSE-4 only ....................................... 300°C
Reflow Peak Body Temperature ............................ 260°C
PIN CONFIGURATION
TOP VIEW
V
FB1
RUN1
V
IN
SW1
GND
1
2
3
4
5
11
10 V
FB2
9 RUN2
8
POR
7 SW2
6 MODE/
SYNC
TOP VIEW
V
FB1
RUN1
V
IN
SW1
GND
1
2
3
4
5
10
9
8
7
6
V
FB2
RUN2
POR
SW2
MODE/
SYNC
11
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 11) IS PGND, MUST BE SOLDERED TO GND
MSE PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 11) IS PGND, MUST BE SOLDERED TO GND
ORDER INFORMATION
LEAD FREE FINISH
LTC3407EDD-4#PBF
LTC3407EMSE-4#PBF
TAPE AND REEL
LTC3407EDD-4#TRPBF
LTC3407EMSE-4#TRPBF
PART MARKING
LCJD
LTCJC
PACKAGE DESCRIPTION
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic MSOP
TEMPERATURE RANGE
–40°C to 85°C
–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/
The
l
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 specified. (Note 2)
SYMBOL
V
IN
I
FB
V
FB
ΔV
LINE REG
ΔV
LOAD REG
I
S
PARAMETER
Operating Voltage Range
Feedback Pin Input Current
Feedback Voltage (Note 3)
Reference Voltage Line Regulation
Output Voltage Load Regulation
Input DC Supply Current (Note 4)
Active Mode
Sleep Mode
Shutdown
0°C ≤ T
A
≤ 85°C
–40°C ≤ T
A
≤ 85°C
V
IN
= 2.5V to 5.5V (Note 3)
(Note 3)
V
FB1
= V
FB2
= 0.5V
V
FB1
= V
FB2
= 0.63V, MODE/SYNC = 3.6V
RUN = 0V, V
IN
= 5.5V, MODE/SYNC = 0V
CONDITIONS
●
●
●
ELECTRICAL CHARACTERISTICS
MIN
2.5
0.588
0.585
TYP
MAX
5.5
30
UNITS
V
nA
V
V
%/V
%
0.6
0.6
0.3
0.5
700
40
0.1
0.612
0.612
0.5
950
60
1
μA
μA
μA
34074fa
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LTC3407-4
ELECTRICAL CHARACTERISTICS
SYMBOL
f
OSC
f
SYNC
I
LIM
R
DS(ON)
I
SW(LKG)
POR
PARAMETER
Oscillator Frequency
Synchronization Frequency
Peak Switch Current Limit
Top Switch On-Resistance
Bottom Switch On-Resistance
Switch Leakage Current
Power-On Reset Threshold
Power-On Reset On-Resistance
Power-On Reset Delay
V
RUN
I
RUN
V
MODE
RUN Threshold
RUN Leakage Current
MODE Threshold Low
MODE Threshold High
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. Pins of regulators should not exceed 6V
Note 2:
The LTC3407E-4 is guaranteed to meet specified performance
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
l
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 specified. (Note 2)
CONDITIONS
V
FBX
= 0.6V
V
IN
= 3V, V
FBX
= 0.5V, Duty Cycle <35%
(Note 6)
(Note 6)
V
IN
= 5V, V
RUN
= 0V, V
FBX
= 0V
V
FBX
Ramping Up, MODE/SYNC = 0V
V
FBX
Ramping Down, MODE/SYNC = 0V
●
MIN
1.8
0.95
TYP
2.25
2.25
1.2
0.35
0.30
0.01
8.5
–8.5
100
65536
MAX
2.7
1.6
0.45
0.45
1
UNITS
MHz
MHz
A
Ω
Ω
μA
%
%
200
1.5
1
0.5
V
IN
Ω
Cycles
V
μA
V
V
0.3
0
V
IN
– 0.5
1
0.01
Note 3:
The LTC3407-4 is tested in a proprietary test mode that connects
V
FB
to the output of the error amplifier.
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 T
A
and power dissipation P
D
according to the following formula: T
J
= T
A
+ (P
D
•
θ
JA
).
Note 6:
The DFN switch on-resistance is guaranteed by correlation to
wafer level measurements.
TYPICAL PERFORMANCE CHARACTERISTICS
Burst Mode Operation
SW
5V/DIV
SW
5V/DIV
T
A
= 25°C unless otherwise specified.
Pulse-Skipping Mode
Load Step
V
OUT
200mV/DIV
I
L
500mA/DIV
I
LOAD
500mA/DIV
V
OUT
20mV/DIV
V
OUT
20mV/DIV
I
L
200mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA
2μs/DIV
34073 G01
I
L
200mA/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 20mA
1μs/DIV
34073 G02
V
IN
= 3.6V
10μs/DIV
V
OUT
= 1.8V
I
LOAD
= 80mA ~ 800mA
34074 G03
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LTC3407-4
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Input Voltage
100
95
90
LOAD = 800mA
LOAD = 1mA
FREQUENCY (MHz)
EFFICIENCY (%)
85
80
75
70
65
60
55
50
2
3
V
OUT
= 1.8V
Burst Mode OPERATION
4
5
INPUT VOLTAGE (V)
6
34074 G04
Oscillator Frequency vs
Temperature
2.5
V
IN
= 3.6V
FREQUENCY DEVIATION (%)
10
8
2.4
6
4
2
0
–2
–4
–6
–8
2.0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
–10
Oscillator Frequency Deviation
vs Supply Voltage
LOAD = 100mA
LOAD = 10mA
2.3
2.2
2.1
2
3
4
SUPPLY VOLTAGE (V)
5
6
34074 G06
34074 G05
Reference Voltage vs
Temperature
0.615
0.610
REFERENCE VOLTAGE (V)
0.605
0.600
0.595
0.590
0.585
–50 –25
V
IN
= 3.6V
500
450
R
DS(ON)
vs Input Voltage
550
500
450
R
DS(ON)
(mΩ)
R
DS(ON)
(mΩ)
400
350
300
250
200
SYNCHRONOUS
SWITCH
MAIN
SWITCH
400
350
300
250
200
150
R
DS(ON)
vs Temperature
V
IN
= 2.7V
V
IN
= 4.2V
V
IN
= 3.6V
50
25
75
0
TEMPERATURE (°C)
100
125
1
2
3
4
V
IN
(V)
5
6
7
34074 G08
100
–50 –25
MAIN SWITCH
SYNCHRONOUS SWITCH
0
25 50 75 100 125 150
TEMPERATURE (°C)
34074 G09
34074 G07
Efficiency vs Load Current
100
95
90
EFFICIENCY (%)
85
80
75
70
65
60
1
V
OUT
= 2.5V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
10
100
LOAD CURRENT (mA)
1000
LTC1273/75/76 • F25
Efficiency vs Load Current
100
4
3
Load Regulation
V
IN
= 3.6V
V
IN
= 2.7V
V
OUT
ERROR (%)
V
IN
= 4.2V
EFFICIENCY (%)
90
Burst Mode
OPERATION
2
1
0
Burst Mode
OPERATION
80
PULSE-SKIPPING
MODE
70
V
IN
= 3.6V, V
OUT
= 1.8V
NO LOAD ON OTHER CHANNEL
1
10
100
LOAD CURRENT (mA)
1000
34074 G11
PULSE-SKIPPING
MODE
–1
–2
–3
–4
1
V
IN
= 3.6V, V
OUT
= 1.8V
NO LOAD ON OTHER CHANNEL
10
100
LOAD CURRENT (mA)
1000
34074 G12
60
34074fa
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LTC3407-4
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
70
V
OUT
= 1.5V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
1
10
100
LOAD CURRENT (mA)
1000
34074 G14
Efficiency vs Load Current
100
0.8
0.6
90
EFFICIENCY (%)
V
IN
= 3.6V
V
IN
= 2.7V
V
OUT
ERROR (%)
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
Line Regulation
V
OUT
= 1.8V
I
OUT
= 200mA
T
A
= 25°C
V
IN
= 3.6V
V
IN
= 2.7V
V
IN
= 4.2V
80
V
IN
= 4.2V
V
OUT
= 1.2V
10 Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
0
1
10
100
LOAD CURRENT (mA)
60
1000
34074 G13
2
3
4
V
IN
(V)
5
6
34074 G15
PIN FUNCTIONS
V
FB1
(Pin 1):
Output Feedback. Receives the feedback volt-
age from the external resistive divider across the output.
Nominal voltage for this pin is 0.6V.
RUN1 (Pin 2):
Regulator 1 Enable. Forcing this pin to V
IN
enables regulator 1, while forcing it to GND causes regulator
1 to shut down. This pin must be driven; do not float.
V
IN
(Pin 3):
Main Power Supply. Must be closely decoupled
to GND.
SW1 (Pin 4):
Regulator 1 Switch Node Connection to the
Inductor. This pin swings from V
IN
to GND.
GND (Pin 5):
Ground. This pin is not connected internally.
Connect to PCB ground for shielding.
MODE/SYNC (Pin 6):
Combination Mode Selection and
Oscillator Synchronization. This pin controls the opera-
tion of the device. When tied to V
IN
or GND, Burst Mode
operation or pulse-skipping mode is selected, respectively.
Do not float this pin. The oscillation frequency can be
synchronized to an external oscillator applied to this pin
and pulse-skipping mode is automatically selected.
SW2 (Pin 7):
Regulator 2 Switch Node Connection to the
Inductor. This pin swings from V
IN
to GND.
POR
(Pin 8):
Power-On Reset . This common-drain logic
output is pulled to GND when the output voltage is not
within ±8.5% of regulation and goes high after 29ms when
both channels are within regulation.
RUN2 (Pin 9):
Regulator 2 Enable. Forcing this pin to V
IN
enables regulator 2, while forcing it to GND causes regulator
2 to shut down. This pin must be driven; do not float.
V
FB2
(Pin 10):
Output Feedback. Receives the feedback
voltage from the external resistive divider across the output.
Nominal voltage for this pin is 0.6V.
Exposed Pad (GND) (Pin 11):
Power Ground. Connect to
the (–) terminal of C
OUT
, and (–) terminal of C
IN
. Must be
connected to electrical ground on PCB.
34074fa
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