POWER LOSS (mW)
LTC3873-5
TM
No R Constant
SENSE
Frequency Current Mode
Boost/Flyback/SEPIC
DC/DC Controller
FEATURES DESCRIPTION
n
V and V Limited Only by External Components
The LTC 3873-5 is a constant frequency current mode
IN OUT
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Internal or Programmable External Soft-Start
controller for boost, yback or SEPIC DC/DC converters
n
Constant Frequency 200kHz Operation
designed to drive an N-channel MOSFET for high input
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Adjustable Current Limit
and output voltage converter applications.
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Current Sense Resistor Optional
The LTC3873-5 provides 1.5% output voltage accuracy
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1.5% Voltage Reference Accuracy
and consumes only 300A quiescent current during nor-
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Current Mode Operation for Excellent Line and Load
mal operation and only 50A during micropower start-up.
Transient Response
Using a 9.3V internal shunt regulator, the LTC3873-5 can
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4.1V Undervoltage Threshold for Logic Level
be powered from a high input voltage through a resistor
MOSFET Applications
or it can be powered directly from a low impedance DC
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Low Quiescent Current: 300A
voltage of 9V or less. Soft-start can be programmed using
TM
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Low Pro le (1mm) ThinSOT and (0.75mm)
an external capacitor.
2mm 3mm DFN Package
The LTC3873-5 is available in 8-lead ThinSOT and 2mm
3mm DFN packages.
APPLICATIONS
PARAMETER LTC3873 LTC3873-5
n
Telecom Power Supplies
+
V UV 8.4V 4.1V
CC
n
Automotive Power Supplies
V UV 4V 2.9V
CC
n
PoE Applications
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No R and ThinSOT are trademarks of Linear Technology Corporation.
SENSE
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
High Ef ciency 5V Input, 12V Output Boost Converter Ef ciency and Power Loss vs Load Current
100 10000
1nF
90
4.7nF
80
RUN/SS
11.8k
V
IN
I V
TH CC
70
5V
1000
47pF
10F
LTC3873-5
60
10H
IPRG
50
V
OUT
12V
GND SW
40
12k
2A
100
V NGATE
FB 22F
30
20
108k
38735 TA01a
10
0 10
10 100 1000
I (mA)
OUT
3873 TA01b
38735fb
1
EFFICIENCY (%)LTC3873-5
ABSOLUTE MAXIMUM RATINGS (Note 1)
V to GND Operating Temperature Range (Note 2)
CC
Low Impedance Source ........................... 0.3V to 9V LTC3873E-5 ......................................... 40C to 85C
Current Fed ..........................................25mA Into V LTC3873I-5 ........................................ 40C to 125C
CC
RUN/SS ........................................................ 0.3V to 9V Junction Temperature (Note 3) ............................. 125C
IPRG Voltage .................................0.3V to (V + 0.3V) Storage Temperature Range ................... 65C to 125C
CC
V , I Voltages ....................................... 0.3V to 2.4V Lead Temperature (Soldering, 10 sec)
FB TH
SW Voltage ................................................ 0.3V to 60V TS8 Package .....................................................300C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
GND 1 8 NGATE
IPRG 1 8 SW
V 2 7 V
FB CC
I 2 7 RUN/SS
TH 9
I 3 6 RUN/SS
TH
V 3 6 V
FB CC
IPRG SW
GND 4 5 NGATE 4 5
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
DDB PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
T = 125C, = 230C/W
JMAX JA
T = 125C, = 76C/W
JMAX JA
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3873ETS8-5#PBF LTC3873ETS8-5#TRPBF LTCSP 8-Lead Plastic TSOT-23 40C to 85C
LTC3873ITS8-5#PBF LTC3873ITS8-5#TRPBF LTCSP 8-Lead Plastic TSOT-23 40C to 125C
LTC3873EDDB-5#PBF LTC3873EDDB-5#TRPBF LCSM 8-Lead (3mm 2mm) Plastic DFN 40C to 85C
LTC3873IDDB-5#PBF LTC3873IDDB-5#TRPBF LCSM 40C to 125C
8-Lead (3mm 2mm) Plastic DFN
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3873ETS8-5 LTC3873ETS8-5#TR LTCSP 8-Lead Plastic TSOT-23 40C to 85C
LTC3873ITS8-5 LTC3873ITS8-5#TR LTCSP 8-Lead Plastic TSOT-23 40C to 125C
LTC3873EDDB-5 LTC3873EDDB-5#TR LCSM 8-Lead (3mm 2mm) Plastic DFN 40C to 85C
LTC3873IDDB-5 LTC3873IDDB-5#TR LCSM 40C to 125C
8-Lead (3mm 2mm) Plastic DFN
Consult LTC Marketing for parts speci ed with wider operating temperature ranges. *The temperature grade is identi ed by a label on the shipping container.
For more information on lead free part marking, go to: