POWER LOSS (W)
LTC3805-5
Adjustable Frequency
Current Mode Flyback/
Boost/SEPIC DC/DC Controller
FEATURES DESCRIPTION
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V and V Limited Only by External Components The LTC 3805-5 is a current mode DC/DC controller de-
IN OUT
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4.5V Undervoltage Lockout Threshold signed to drive an N-channel MOSFET in flyback, boost
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Adjustable Slope Compensation and SEPIC converter applications. Operating frequency
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Adjustable Overcurrent Protection with Automatic and slope compensation can be programmed by external
Restart resistors. Programmable overcurrent sensing protects
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Adjustable Operating Frequency (70kHz to 700kHz) the converter from overload and short-circuit conditions.
With One External Resistor Soft-start can be programmed using an external capacitor
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Synchronizable to an External Clock and the soft-start capacitor also programs an automatic
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1.5% Reference Accuracy restart feature.
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Only 100mV Current Sense Voltage Drop
The LTC3805-5 provides 1.5% output voltage accuracy
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RUN Pin with Precision Threshold and Adjustable
and consumes only 360A of quiescent current during
Hysteresis
normal operation and only 40A during micropower start-
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Programmable Soft-Start with One External Capacitor
up. Using a 9.5V internal shunt regulator, the LTC3805-5
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Low Quiescent Current: 360A
can be powered from a high V through a resistor or it
IN
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Small 10-Lead MSOP and 3mm 3mm DFN
can be powered directly from a low impedance DC voltage
from 4.7V to 8.8V.
APPLICATIONS
The LTC3805-5 is available in the 10-lead MSOP package
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Automotive Power Supplies
and the 3mm 3mm DFN package.
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Telecom Power Supplies
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered
n trademarks, No R and ThinSOT are trademarks of Linear Technology Corporation.
Isolated Electronic Equipment SENSE
All other trademarks are the property of their respective owners.
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Auxiliary/Housekeeping Power Supplies
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Power over Ethernet
TYPICAL APPLICATION
5V to 12V/1A Boost Converter Efficiency and Power Loss vs Load Current
100 2.5
UPS840
4.3H
V
OUT
V
IN
12V
95 2.0
5V EFFICIENCY
5V
22F 1A
100F
8.5V EFFICIENCY
2 V
CC
RUN GATE
90 1.5
LTC3805-5
1.33k
8.5V LOSS
5V LOSS
I OC
TH
3k
85 1
191k
SSFLT I
SENSE
0.1F
20k
FS FB
80 0.5
SYNC GND
470pF 118k 8m 13.7k
38055 TA01a
75 0
1
0.01 0.1 10
LOAD CURRENT (A)
38055TA01b
38055fe
1
EFFICIENCY (%)LTC3805-5
ABSOLUTE MAXIMUM RATINGS (Note 1)
V to GND
OC, I .................................................... 0.3V to 1V
CC SENSE
Low Impedance Source ........................ 0.3V to 8.8V
Operating Junction Temperature Range
Current Fed ........................................25mA into V *
(Notes 2, 3) ........................................... 55C to 150C
CC
SYNC ........................................................... 0.3V to 6V
Storage Temperature Range ..................65C to 150C
SSFLT........................................................... 0.3V to 5V
Lead Temperature (Soldering, 10 sec)
FB, I , FS ................................................. 0.3V to 3.5V
MSE Package ....................................................300C
TH
RUN ........................................................... 0.3V to 18V
*LTC3805-5 internal clamp circuit regulates V voltage to 9.5V
CC
PIN CONFIGURATION
TOP VIEW
TOP VIEW
SSFLT 1 10 GATE
SSFLT 1 10 GATE
I 2 9 V
TH CC
I 2 9 V
TH CC
11
11
FB 3 8 OC
FB 3 8 OC
RUN 4 7 I
SENSE
RUN 4 7 I
SENSE
FS 5 6 SYNC
FS 5 6 SYNC
MSE PACKAGE
10-LEAD PLASTIC MSOP
DD PACKAGE
T = 125C, = 45C/W
JMAX JA
10-LEAD (3mm 3mm) PLASTIC DFN
EXPOSED PAD (PIN 11) IS GND, MUST BE CONNECTED TO GND
T = 125C, = 45C/W
JMAX JA
EXPOSED PAD (PIN 11) IS GND, MUST BE CONNECTED TO GND
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3805EMSE-5#PBF LTC3805EMSE-5#TRPBF LTDGX 10-Lead Plastic MSOP 40C to 85C
LTC3805IMSE-5#PBF LTC3805IMSE-5#TRPBF LTDGX 10-Lead Plastic MSOP 40C to 125C
LTC3805HMSE-5#PBF LTC3805HMSE-5#TRPBF LTDGX 10-Lead Plastic MSOP 40C to 150C
LTC3805MPMSE-5#PBF LTC3805MPMSE-5#TRPBF LTDGX 10-Lead Plastic MSOP 55C to 150C
LTC3805EDD-5#PBF LTC3805EDD-5#TRPBF LDHB 10-Lead (3mm 3mm) Plastic DFN 40C to 85C
LTC3805IDD-5#PBF LTC3805IDD-5#TRPBF LDHB 10-Lead (3mm 3mm) Plastic DFN 40C to 125C
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 lead based finish parts.
For more information on lead free part marking, go to: