step- down DC/DC converter. Intended for medium power
applications, it operates from a 2.63V to 5.5V input voltage
range and has a user configurable operating frequency
up to 4MHz, allowing the use of tiny, low cost capacitors
and inductors 2mm or less in height. The output voltage
is adjustable from 0.8V to 5V. Internal sychronous 0.11Ω
power switches with 1.6A peak current ratings provide
high efficiency. The LTC3411’s current mode architecture
and external compensation allow the transient response
to be optimized over a wide range of loads and output
capacitors.
The LTC3411 can be configured for automatic power sav-
ing Burst Mode operation to reduce gate charge losses
when the load current drops below the level required for
continuous operation. For reduced noise and RF interfer-
ence, the SYNC/MODE pin can be configured to skip pulses
or provide forced continuous operation.
To further maximize battery life, the P-channel MOSFET
is turned on continuously in dropout (100% duty cycle)
with a low quiescent current of 60μA. In shutdown, the
device draws <1μA.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
Small 10-Lead MSOP or DFN Package
Uses Tiny Capacitors and Inductor
High Frequency Operation: Up to 4MHz
High Switch Current: 1.6A
Low R
DS(ON)
Internal Switches: 0.110Ω
High Efficiency: Up to 95%
Stable with Ceramic Capacitors
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit Protected
Low Dropout Operation: 100% Duty Cycle
Low Shutdown Current: I
Q
≤ 1μA
Low Quiescent Current: 60μA
Output Voltages from 0.8V to 5V
Selectable Burst Mode
®
Operation
Synchronizable to External Clock
APPLICATIONS
n
n
n
n
n
Notebook Computers
Digital Cameras
Cellular Phones
Handheld Instruments
Board Mounted Power Supplies
TYPICAL APPLICATION
V
IN
2.63V TO 5.5V
C1
22μF
V
IN
SYNC/MODE
PGOOD
LTC3411
I
TH
13k
1000pF
324k
NOTE: IN DROPOUT, THE OUTPUT TRACKS
THE INPUT VOLTAGE
C1, C2: TAIYO YUDEN JMK325BJ226MM
L1: TOKO A914BYW-2R2M (D52LC SERIES)
SHDN/R
T
SGND
PGND
412k
75
3411 F01
Efficiency vs Load Current
100
95
PV
IN
SV
IN
SW
L1
2.2μH
887k
V
FB
C2
22μF
EFFICIENCY (%)
V
OUT
2.5V/1.25A
90
85
80
V
IN
= 3.3V
V
OUT
= 2.5V
f
O
= 1MHz
Burst Mode OPERATION
1
10
100
LOAD CURRENT (mA)
1000
3411 TA01
70
Figure 1. Step-Down 2.5V/1.25A Regulator
3411fb
1
LTC3411
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PV
IN
, SV
IN
Voltages ..................................... –0.3V to 6V
V
FB
, I
TH
, SHDN/R
T
Voltages ..........–0.3V to (V
IN
+ 0.3V)
SYNC/MODE Voltage .....................–0.3V to (V
IN
+ 0.3V)
SW Voltage ..................................–0.3V to (V
IN
+ 0.3V)
PGOOD Voltage ........................................... –0.3V to 6V
Operating Temperature Range (Note 2)
LTC3411E............................................. –40°C to 85°C
LTC3411I............................................ –40°C to 125°C
Junction Temperature (Notes 5, 8) ....................... 125°C
Storage Temperature Range
DD Package ....................................... –65°C to 125°C
MS Package ...................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
TOP VIEW
SHDN/R
T
SYNC/MODE
SGND
SW
PGND
1
2
3
4
5
10 I
TH
9 V
FB
8 PGOOD
7 SV
IN
6 PV
IN
SHDN/R
T
SYNC/MODE
SGND
SW
PGND
1
2
3
4
5
TOP VIEW
10
9
8
7
6
I
TH
V
FB
PGOOD
SV
IN
PV
IN
DD PACKAGE
10-LEAD (3mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 8°C/W
(EXPOSED PAD MUST BE SOLDERED TO SGND)
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 120°C/W,
θ
JC
= 45°C/W
ORDER INFORMATION
LEAD FREE FINISH
LTC3411EDD#PBF
LTC3411IDD#PBF
LTC3411EMS#PBF
LTC3411IMS#PBF
LEAD BASED FINISH
LTC3411EDD
LTC3411IDD
LTC3411EMS
LTC3411IMS
TAPE AND REEL
LTC3411EDD#TRPBF
LTC3411IDD#TRPBF
LTC3411EMS#TRPBF
LTC3411IMS#TRPBF
TAPE AND REEL
LTC3411EDD#TR
LTC3411IDD#TR
LTC3411EMS#TR
LTC3411IMS#TR
PART MARKING*
LADT
LADT
LTQT
LTQT
PART MARKING*
LADT
LADT
LTQT
LTQT
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead Plastic MSOP
10-Lead Plastic MSOP
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
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.
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/
3411fb
2
LTC3411
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
I
FB
V
FB
ΔV
LINEREG
ΔV
LOADREG
g
m(EA)
I
S
PARAMETER
Operating Voltage Range
Feedback Pin Input Current
Feedback Voltage
Reference Voltage Line Regulation
Output Voltage Load Regulation
Error Amplifier Transconductance
Input DC Supply Current (Note 4)
Active Mode
Sleep Mode
Shutdown
Shutdown Threshold High
Active Oscillator Resistor
Oscillator Frequency
Synchronization Frequency
Peak Switch Current Limit
Top Switch On-Resistance (Note 6)
Switch Leakage Current
Undervoltage Lockout Threshold
Power Good Threshold
Power Good Pull-Down On-Resistance
R
T
= 324k
(Note 7)
(Note 7)
I
TH
= 1.3
V
IN
= 3.3V
V
IN
= 6V, V
ITH/RUN
= 0V, V
FB
= 0V
V
IN
Ramping Down
V
FB
Ramping Up, SHDN/R
T
= 1V
V
FB
Ramping Down, SHDN/R
T
= 1V
2.375
0.85
0.4
1.6
2
0.11
0.11
0.01
2.5
6.8
–7.6
118
200
0.15
0.15
1
2.625
(Note 3)
V
IN
= 2.7V to 5V
I
TH
= 0.36, (Note 3)
I
TH
= 0.84, (Note 3)
I
TH
Pin Load = ±5μA (Note 3)
V
FB
= 0.75V, SYNC/MODE = 3.3V
V
SYNC/MODE
= 3.3V, V
FB
= 1V
V
SHDN/RT
= 3.3V
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V, R
T
= 324k unless otherwise specified. (Note 2)
CONDITIONS
MIN
2.625
0.784
0.8
0.04
0.02
–0.02
800
240
62
0.1
V
IN
– 0.6
324k
1
350
100
1
V
IN
– 0.4
1M
1.15
4
4
TYP
MAX
5.5
±0.1
0.816
0.2
0.2
–0.2
UNITS
V
μA
V
%/V
%
%
μS
μA
μA
μA
V
Ω
MHz
MHz
MHz
A
Ω
Ω
μA
V
%
%
Ω
V
SHDN/RT
f
OSC
f
SYNC
I
LIM
R
DS(ON)
I
SW(LKG)
V
UVLO
PGOOD
R
PGOOD
Bottom Switch On-Resistance (Note 6) V
IN
= 3.3V
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 LTC3411E is guaranteed to meet specified performance from
0°C to 85°C. Specifications over the –40°C to 85°C operating termperature
range are assured by design, characterization and correlation with
statistical process controls. The LTC3411I is guaranteed to meet specified
performance over the full –40°C to 125°C operating temperature range.
Note 3:
The LTC3411 is tested in a feedback loop which servos V
FB
to the
midpoint for the error amplifier (V
ITH
= 0.6V).
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:
LTC3411DD: T
J
= T
A
+ (P
D
• 43°C/W)
LTC3411MS: T
J
= T
A
+ (P
D
• 120°C/W)
Note 6:
Switch on-resistance is guaranteed by correlation to wafer level
measurements.
Note 7:
4MHz operation is guaranteed by design but not production tested
and is subject to duty cycle limitations (see Applications Information).
Note 8:
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.
3411fb
3
LTC3411
PIN FUNCTIONS
SHDN/R
T
(Pin 1):
Combination Shutdown and Timing
Resistor Pin. The oscillator frequency is programmed by
connecting a resistor from this pin to ground. Forcing
this pin to SV
IN
causes the device to be shut down. In
shutdown all functions are disabled.
SYNC/MODE (Pin 2):
Combination Mode Selection and
Oscillator Synchronization Pin. This pin controls the op-
eration of the device. When tied to SV
IN
or SGND, Burst
Mode operation or pulse skipping mode is selected,
respectively. If this pin is held at half of SV
IN
, the forced
continuous mode is selected. The oscillation frequency
can be syncronized to an external oscillator applied to
this pin. When synchronized to an external clock pulse
skip mode is selected.
SGND (Pin 3):
The Signal Ground Pin. All small signal
components and compensation components should be
connected to this ground (see Board Layout Consider-
ations).
SW (Pin 4):
The Switch Node Connection to the Inductor.
This pin swings from PV
IN
to PGND.
PGND (Pin 5):
Main Power Ground Pin. Connect to the
(–) terminal of C
OUT
, and (–) terminal of C
IN
.
PV
IN
(Pin 6):
Main Supply Pin. Must be closely decoupled
to PGND.
SV
IN
(Pin 7):
The Signal Power Pin. All active circuitry
is powered from this pin. Must be closely decoupled to
SGND. SV
IN
must be greater than or equal to PV
IN
.
PGOOD (Pin 8):
The Power Good Pin. This common drain
logic output is pulled to SGND when the output voltage is
not within ±7.5% of regulation.
V
FB
(Pin 9):
Receives the feedback voltage from the ex-
ternal resistive divider across the output. Nominal voltage
for this pin is 0.8V.
I
TH
(Pin 10):
Error Amplifier Compensation Point. The
current comparator threshold increases with this control
voltage. Nominal voltage range for this pin is 0V to 1.5V.
PCB设计
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