step-down DC/DC converter. Intended for low power ap-
plications, it operates from a 2.5V to 5.5V input voltage
range and has a constant 1.5MHz switching frequency,
enabling the use of tiny, low cost capacitors and inductors
1mm or less in height. Each output voltage is adjustable
from 0.6V to 5V. Internal synchronous 0.35Ω, 1A 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 ripple noise for low power efficiency. Burst
Mode
®
operation provides the highest efficiency at light
loads, while Pulse Skip Mode provides the lowest ripple
noise 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.
L,
LT, LTC, LTM and Burst Mode 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%
Low Ripple (35mV
P-P
) Burst Mode Operation;
I
Q
= 40μA
1.5MHz Constant Frequency Operation
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
Optional External Soft-Start
Small Thermally Enhanced MSOP and 3mm
×
3mm
DFN Packages
APPLICATIONS
n
n
n
n
PDAs/Palmtop PCs
Digital Cameras
Cellular Phones
Wireless and DSL Modems
TYPICAL APPLICATION
1mm High 2.5V/1.8V at 600mA Step-Down Regulators
V
IN
= 2.5V
TO 5.5V
10μF
RUN/SS2
MODE/SYNC
LTC3407A
V
OUT2
= 2.5V
AT 600mA
2.2μH
SW2
22pF
SW1
22pF
2.2μH
V
OUT1
= 1.8V
AT 600mA
V
IN
RUN/SS1
POR
100k
EFFICIENCY (%)
RESET
LTC3407A Efficiency/Power Loss Curve
100
90
80
70
60
50
40
30
20
V
IN
= 3.3V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
1
10
100
LOAD CURRENT (mA)
0.0001
1000
3407A TA02
3407A TA01
2.5V
1.8V
1
0.1
POWER LOSS (W)
0.01
0.001
887k
10μF
280k
V
FB2
GND
V
FB1
887k
442k
10μF
10
0
3407afa
1
LTC3407A
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN
Voltage ...................................................– 0.3V to 6V
V
FB1
, V
FB2
Voltages ................................... –0.3V to 1.5V
RUN/SS1, RUN/SS2 Voltages ......................–0.3V to V
IN
MODE/SYNC Voltage....................................–0.3V to V
IN
SW1, SW2 Voltages ......................... –0.3V to V
IN
+ 0.3V
POR
Voltage ................................................. –0.3V to 6V
Operating Temperature Range (Note 2)
LTC3407AE .......................................... –40°C to 85°C
LTC3407AI ......................................... –40°C to 125°C
Junction Temperature (Note 5) ............................. 125°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec)
LTC3407AMSE Only .......................................... 300°C
PIN CONFIGURATION
TOP VIEW
V
FB1
RUN/SS1
V
IN
SW1
GND
1
2
3
4
5
11
10 V
FB2
9 RUN/SS2
8
POR
7 SW2
6 MODE/
SYNC
TOP VIEW
V
FB1
RUN/SS1
V
IN
SW1
GND
1
2
3
4
5
10
9
8
7
6
V
FB2
RUN/SS2
POR
SW2
MODE/
SYNC
11
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
EXPOSED PAD IS PGND (PIN 11)
MUST BE CONNECTED TO GND
T
JMAX
= 125°C,
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
MSE PACKAGE
10-LEAD PLASTIC MSOP
EXPOSED PAD IS PGND (PIN 11)
MUST BE CONNECTED TO GND
T
JMAX
= 125°C,
θ
JA
= 45°C/W,
θ
JC
= 10°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3407AEDD#PBF
LTC3407AIDD#PBF
LTC3407AEMSE#PBF
LTC3407AIMSE#PBF
TAPE AND REEL
LTC3407AEDD#TRPBF
LTC3407AIDD#TRPBF
LTC3407AEMSE#TRPBF
LTC3407AIMSE#TRPBF
PART MARKING*
LCQN
LCQN
LTCRZ
LTCRZ
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead Plastic MSOP
10-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–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/
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
PARAMETER
Operating Voltage Range
Feedback Pin Input Current
Feedback Voltage (Note 3)
Reference Voltage Line Regulation
0°C ≤ T
A
≤ 85°C
–40°C ≤ T
A
≤ 125°C (LTC3407AI)
V
IN
= 2.5V to 5.5V (Note 3)
CONDITIONS
●
●
●
ELECTRICAL CHARACTERISTICS
MIN
2.5
0.588
0.585
TYP
MAX
5.5
30
UNITS
V
nA
V
V
%/V
3407afa
0.6
0.6
0.3
0.612
0.612
0.5
2
LTC3407A
ELECTRICAL CHARACTERISTICS
SYMBOL
ΔV
LOAD REG
I
S
PARAMETER
Output Voltage Load Regulation
Input DC Supply Current
Active Mode
Sleep Mode
Shutdown
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/SS Threshold Low
RUN/SS Threshold High
RUN/SS 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.
Note 2:
The LTC3407AE is 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. The LTC3407AI is guaranteed over the full
–40°C to 125°C temperature range.
●
●
●
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
MODE/SYNC = 0V (Note 3)
(Note 4)
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
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
TYP
0.5
600
40
0.1
MAX
UNITS
%
800
60
1
1.8
1.25
0.45
0.45
1
μA
μA
μA
MHz
MHz
A
Ω
Ω
μA
%
%
f
OSC
f
SYNC
I
LIM
R
DS(ON)
I
SW(LKG)
POR
1.2
0.75
1.5
1.5
1
0.35
0.30
0.01
8.5
–8.5
100
65,536
200
1.5
2
1
0.5
V
IN
Ω
Cycles
V
V
μA
V
V
0.3
1
0.01
0
V
IN
– 0.5
Note 3:
The LTC3407A 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
V
OUT
50mV/DIV
SW
5V/DIV
V
OUT
10mV/DIV
Pulse Skipping Mode
I
L
200mA/DIV
2μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 50mA
CIRCUIT OF FIGURE 3
3407 G01
I
L
100mA/DIV
1μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 50mA
CIRCUIT OF FIGURE 3
3407 G02
3407afa
3
LTC3407A
TYPICAL PERFORMANCE CHARACTERISTICS
Load Step
V
OUT1
200mV/DIV
V
OUT2
100mV/DIV
V
IN
2V/DIV
V
OUT1
1V/DIV
I
L
500mA/DIV
20μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 50mA TO 600mA
CIRCUIT OF FIGURE 3
3407 G03
T
A
= 25°C unless otherwise specified.
Soft Start
I
L
500mA/DIV
I
LOAD
500mA/DIV
1ms/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 500mA
CIRCUIT OF FIGURE 4
3407 G04
Efficiency vs Input Voltage
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10 V
OUT
= 1.8V
CIRCUIT OF FIGURE 3
0
4
2
3
5
INPUT VOLTAGE (V)
1mA
10mA
FREQUENCY (MHz)
100mA
600mA
1.70
1.65
1.60
1.55
1.50
1.45
1.40
1.35
6
3407A G05
Oscillator Frequency
vs Temperature
1.8
OSCILLATOR FREQUENCY (MHz)
1.7
1.6
1.5
1.4
1.3
1.2
Oscillator Frequency
vs Supply Voltage
1.30
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
2
3
4
SUPPLY VOLTAGE (V)
5
6
3407A G07
3407A G06
Reference Voltage
vs Temperature
0.615
0.610
REFERENCE VOLTAGE (V)
0.605
0.600
0.595
0.590
0.585
–50 –25
500
V
IN
= 3.6V
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
3407A G08
4
V
IN
(V)
5
6
7
3407A G09
100
–50 –25
MAIN SWITCH
SYNCHRONOUS SWITCH
0
25 50 75 100 125 150
TEMPERATURE (°C)
3407A G10
3407afa
4
LTC3407A
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
100
90
80
EFFICIENCY (%)
70
EFFICIENCY (%)
60
50
40
30
20
10 V
OUT
= 2.5V Burst Mode OPERATION
CIRCUIT OF FIGURE 3
0
10
100
1
LOAD CURRENT (mA)
2.7V
4.2V
3.3V
100
90
80
V
OUT
ERROR(%)
70
60
50
40
30
20
10 V
IN
= 3.6V, V
OUT
= 1.8V
NO LOAD ON OTHER CHANNEL
0
10
100
1
LOAD CURRENT (mA)
PULSE SKIP MODE
Burst Mode OPERATION
T
A
= 25°C unless otherwise specified.
Efficiency vs Load Current
4
3
2
Load Regulation
1 Burst Mode OPERATION
0
–1
–2
–3
–4
V
IN
= 3.6V, V
OUT
= 1.8V
NO LOAD ON OTHER CHANNEL
1
10
100
LOAD CURRENT (mA)
1000
3407A G13
PULSE SKIP MODE
1000
3407A G11
1000
3407A G12
Efficiency vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1
V
OUT
= 1.2V Burst Mode OPERATION
10
100
LOAD CURRENT (mA)
1000
3407A G14
Efficiency vs Load Current
100
0.5
3.3V
2.7V
4.2V
V
OUT
ERROR (%)
0.4
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
V
OUT
= 1.5V Burst Mode OPERATION
1
10
100
LOAD CURRENT (mA)
1000
3407A G15
Line Regulation
V
OUT
= 1.8V
I
OUT
= 200mA
3.3V
2.7V
4.2V
EFFICIENCY (%)
90
80
70
60
50
40
30
20
10
0
–0.4
–0.5
2
3
4
V
IN
(V)
5
6
3407A G16
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.
RUN/SS1 (Pin 2):
Regulator 1 Enable and Soft-Start Input.
Forcing this pin to V
IN
enables regulator 1, while forcing it
to GND causes regulator 1 to shut down. Connect external
RC-network with desired time-constant to enable soft-start
feature. 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):
Main Ground. Connect to the (–) terminal
of C
OUT
, and (–) terminal of C
IN
.
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.
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