LT1618
Constant-Current/
Constant-Voltage 1.4MHz
Step-Up DC/DC Converter
FEATURES DESCRIPTIO
Accurate Input/Output Current Control: 5% Over The LT 1618 step-up DC/DC converter combines a tradi-
Temperature tional voltage feedback loop and a unique current feedback
Accurate Output Voltage Control: 1% loop to operate as a constant-current, constant-voltage
Wide V Range: 1.6V to 18V source. This fixed frequency, current mode switcher oper-
IN
1.4MHz Switching Frequency ates from a wide input voltage range of 1.6V to 18V, and
High Output Voltage: Up to 35V the high switching frequency of 1.4MHz permits the use of
Low V Switch: 200mV at 1A tiny, low profile inductors and capacitors. The current
CESAT
Available in (3mm 3mm 0.8mm) 10-Pin DFN and sense voltage is set at 50mV and can be adjusted using the
10-Pin MSOP Packages I pin.
ADJ
U
Available in the 10-Pin (3mm 3mm) Exposed Pad DFN
APPLICATIO S
and 10-pin MSOP packages, the LT1618 provides a com-
plete solution for constant-current applications.
LED Backlight Drivers
, LTC and LT are registered trademarks of Linear Technology Corporation.
USB Powered Boost/SEPIC Converters
Input Current Limited Boost/SEPIC Converters
Battery Chargers
TYPICAL APPLICATIO
USB to 12V Boost Converter
(with Selectable 100mA/500mA Input Current Limit)
L1
D1
10H
0.1
Efficiency Curve
V
IN V
OUT
5V
12V
90
2 7
85
ISN SW
C1
R1
3
4.7F
ISP
909k
LT1618 80
1
8
C2
V FB
IN
4.7F
3.3V
75
9
R2
SHDN
OFF ON
107k
0V
I V
GND
ADJ C
20k 70
4 510
65
3.3V
2k
100mA 500mA
13k
0V
10nF
60
140
0 20 40 60 80 100 120 160
LOAD CURRENT (mA)
C1: TAIYO YUDEN JMK212BJ475 1618 TA01a
1618 TA01b
C2: TAIYO YUDEN EMK316BJ475
D1: ON SEMICONDUCTOR MBR0520
L1: SUMIDA CR43-100
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EFFICIENCY (%)
U
ULT1618
ABSOLUTE AXI U RATI GS (Note 1)
V , SHDN Voltage ................................................... 18V Junction Temperature........................................... 125C
IN
SW Voltage .............................................................. 36V Operating Temperature Range (Note 2) .. 40C to 85C
ISP, ISN Voltage ...................................................... 36V Storage Temperature Range
I Voltage ............................................................... 6V MSOP ............................................... 65C to 150C
ADJ
FB Voltage .............................................................. 1.5V DFN ................................................. 65C to 125C
V Voltage .............................................................. 1.5V Lead Temperature (Soldering, 10 sec) (MSOP) .... 300C
C
UUW
PACKAGE/ORDER I FOR ATIO
TOP VIEW ORDER PART ORDER PART
NUMBER NUMBER
TOP VIEW
FB 1 10 V
C
FB 1 10 V
ISN 2 9 SHDN
C
ISN 2 9
SHDN
LT1618EDD LT1618EMS
11
ISP 3 8 V
IN
ISP 3 8 V
IN
I 4 7 SW
I 4 7 SW
ADJ
ADJ
GND 5 6 NC
GND 5 6 SW
DD PART MS PART
MS PACKAGE
DD PACKAGE 10-LEAD PLASTIC MSOP
MARKING MARKING
10-LEAD (3mm 3mm) PLASTIC DFN
T = 125C, = 160C/W
JMAX JA
T = 125C, = 43C/W, = 3C/W
JMAX JA JC
LAFQ LTNH
EXPOSED PAD (PIN 11) IS GND AND
MUST BE SOLDERED TO PCB
Consult LTC marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25C. V = 1.6V, V = 1.6V, unless otherwise noted.
A IN SHDN
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Voltage 1.6 18 V
Quiescent Current V = 1.6V, Not Switching 1.8 2.7 mA
SHDN
V = 0V 0.1 1 A
SHDN
Reference Voltage Measured at FB Pin 1.250 1.263 1.276 V
1.243 1.263 1.283 V
Reference Voltage Line Regulation 1.6V < V < 18V 0.01 0.03 %/V
IN
FB Pin Bias Current V = 1.263V, V = 1.8V 2 12 nA
FB IN
Error Amplifier Voltage Gain 180 V/V
Error Amplifier Transconductance I = 5A 160 mho
C
Error Amplifier Sink Current V = 1.35V, V = 1V 15 A
FB C
Error Amplifier Source Current V = 1.10V, V = 1V 30 A
FB C
Current Sense Voltage (ISP, ISN) V = 0V, V = 0V 47.5 50 52.5 mV
FB IADJ
ISP, ISN Pin Bias Currents (Note 3) V = 1.85V, V = 1.80V, V = 0V 50 80 A
ISP ISN IADJ
(ISP, ISN) Common Mode Minimum Voltage 1.8 V
Switching Frequency V = 1V 1.25 1.4 1.6 MHz
FB
V = 0V 550 kHz
FB
Maximum Switch Duty Cycle 88 92 %
Switch Current Limit (Note 4) 1.5 2.1 2.8 A
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