the run time in battery-operated systems. Low output
voltages are supported with the 0.6V feedback reference
voltage. The LTC3606B can supply 800mA output current.
The LTC3606B’s programmable average input current limit
is ideal for USB applications and for point-of-load power
supplies because the LTC3606B’s limited input current
will still allow its output to deliver high peak load cur-
rents without collapsing the input supply. The operating
frequency is internally set at 2.25MHz allowing the use of
small surface mount inductors. Internal soft-start reduces
in-rush current during start-up. The LTC3606B is available
in an 8-Lead 3mm
×
3mm DFN package.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and Hot Swap is a 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.
Programmable Average Input Current Limit:
±5% Accuracy
Step-Down Output: Up to 96% Efficiency
Low Noise Pulse-Skipping Operation at Light Loads
Input Voltage Range: 2.5V to 5.5V
Output Voltage Range: 0.6V to 5V
2.25MHz Constant-Frequency Operation
Power Good Output Voltage Monitor
Low Dropout Operation: 100% Duty Cycle
Internal Soft-Start
Current Mode Operation for Excellent Line and Load
Transient Response
±2% Output Voltage Accuracy
Short-Circuit Protected
Shutdown Current ≤ 1μA
Available in Small Thermally Enhanced 8-Lead
3mm
×
3mm DFN Package
APPLICATIONS
n
n
n
n
High Peak Load Current Applications
USB Powered Devices
Supercapacitor Charging
Radio Transmitters and Other Handheld Devices
TYPICAL APPLICATION
Monolithic Buck Regulator with Input Current Limit
V
IN
3.4V
TO 5.5V
C
IN
10μF
PGOOD
499k
1.5μH
V
IN
LTC3606B
RUN
PGOOD
RLIM
GND
1000pF
116k
I
LIM
= 475mA
V
FB
1210k
SW
V
OUT
3.4V AT
800mA
V
OUT
200mV/DIV
V
IN
AC-COUPLED
1V/DIV
I
OUT
500mA/DIV
3606B TA01
GSM Pulse Load
+
2.2mF
2
SuperCap
255k
I
IN
500mA/DIV
1ms/DIV
V
IN
= 5V, 500mA COMPLIANT
I
LOAD
= 0A to 2.2A
3606B TA01b
3606bfb
1
LTC3606B
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
1
2
3
4
9
GND
8 V
FB
7 RUN
6 PGOOD
5 V
IN
GND
RLIM
GND
SW
Input Supply Voltage (V
IN
) ........................... –0.3V to 6V
V
FB
................................................... –0.3V to V
IN
+ 0.3V
RUN, RLIM ....................................... –0.3V to V
IN
+ 0.3V
SW ................................................... –0.3V to V
IN
+ 0.3V
PGOOD............................................. –0.3V to V
IN
+ 0.3V
P-Channel SW Source Current (DC) (Note 2) ..............1A
N-Channel SW Source Current (DC) (Note 2)..............1A
Peak SW Source and Sink Current (Note 2) ............. 2.7A
Operating Junction Temperature Range
(Notes 3, 6, 8) ........................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
Reflow Peak Body Temperature ............................ 260°C
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
ORDER INFORMATION
LEAD FREE FINISH
LTC3606BEDD#PBF
LTC3606BIDD#PBF
TAPE AND REEL
LTC3606BEDD#TRPBF
LTC3606BIDD#TRPBF
PART MARKING*
LFMB
LFMB
PACKAGE DESCRIPTION
8-Lead (3mm
×
3mm) Plastic DFN
8-Lead (3mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–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/
3606bfb
2
LTC3606B
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
UV
I
FB
V
FBREG
V
LINEREG
V
LOADREG
I
S
PARAMETER
V
IN
Operating Voltage Range
V
IN
Undervoltage Lockout
Feedback Pin Input Current
Feedback Voltage
V
FB
Line Regulation
V
FB
Load Regulation
Supply Current
Active Mode (Note 4)
Shutdown
Oscillator Frequency
Peak Switch Current Limit
Input Average Current Limit
LTC3606BE, –40°C < T
J
< 85°C (Note 7)
LTC3606BI, –40°C < T
J
< 125°C (Note 7)
V
IN
= 2.5V to 5.5V (Note 7)
I
LOAD
= 0mA to 800mA (Note 7)
V
FB
= 0.95
×
V
FBREG
V
RUN
= 0V, V
IN
= 5.5V
V
FB
= V
FBREG
V
IN
= 5V, V
FB
< V
FBREG
, Duty Cycle <35%
RLIM = 116k
RLIM = 116k, LTC3606BE
RLIM = 116k, LTC3606BI
l
l
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 5V, unless otherwise noted.
CONDITIONS
l
MIN
2.5
l
l
l
l
TYP
2.1
MAX
5.5
2.5
±30
0.612
0.618
0.25
UNITS
V
V
nA
V
V
%/V
%
V
IN
Low to High
0.588
0.582
0.600
0.600
0.01
0.5
420
650
1
2.7
500
513
523
μA
μA
MHz
mA
mA
mA
mA
Ω
Ω
f
OSC
I
LIM(PEAK)
I
INLIM
1.8
1800
450
437
427
2.25
2400
475
475
475
0.27
0.25
0.01
R
DS(ON)
I
SW(LKG)
t
SOFTSTART
V
RUN
I
RUN
PGOOD
Main Switch On-Resistance (Note 5)
V
IN
= 5V, I
SW
= 100mA
Synchronous Switch On-Resistance (Note 5) V
IN
= 5V, I
SW
= 100mA
Switch Leakage Current
Soft-Start Time
RUN Threshold High
RUN Leakage Current
Power Good Threshold
0V ≤ V
RUN
≤ 5V
Entering Window
V
FB
Ramping Up
V
FB
Ramping Down
Leaving Window
V
FB
Ramping Up
V
FB
Ramping Down
PGOOD Rising and Falling, V
IN
= 5V
8
V
PGOOD
= 5V
V
IN
= 5V, V
RUN
= 0V
V
FB
from 0.06V to 0.54V
l
l
1
1.3
1.2
1
μA
ms
V
μA
%
%
0.3
0.4
0.95
1
0.01
–5
5
–7
7
9
–9
90
15
30
±1
11
–11
%
%
μs
Ω
μA
PGOOD Blanking Power Good Blanking Time
R
PGOOD
I
PGOOD
Power Good Pull-Down On-Resistance
PGOOD Leakage Current
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 LTC3606BE is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3606BI is guaranteed
to meet specified performance over the full –40°C to 125°C operating
junction temperature range.
Note 4:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5:
The 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
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