Electronic Components Datasheet Search
  English  ▼
ALLDATASHEET.COM

X  

LTC3872ETS8 Datasheet(PDF) 6 Page - Linear Technology

Part # LTC3872ETS8
Description  No RSENSE Current Mode Boost DC/DC Controller
Download  20 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  LINER [Linear Technology]
Direct Link  http://www.linear.com
Logo LINER - Linear Technology

LTC3872ETS8 Datasheet(HTML) 6 Page - Linear Technology

Back Button LTC3872ETS8 Datasheet HTML 2Page - Linear Technology LTC3872ETS8 Datasheet HTML 3Page - Linear Technology LTC3872ETS8 Datasheet HTML 4Page - Linear Technology LTC3872ETS8 Datasheet HTML 5Page - Linear Technology LTC3872ETS8 Datasheet HTML 6Page - Linear Technology LTC3872ETS8 Datasheet HTML 7Page - Linear Technology LTC3872ETS8 Datasheet HTML 8Page - Linear Technology LTC3872ETS8 Datasheet HTML 9Page - Linear Technology LTC3872ETS8 Datasheet HTML 10Page - Linear Technology Next Button
Zoom Inzoom in Zoom Outzoom out
 6 / 20 page
background image
LTC3872
6
3872fa
OPERATIO
Main Control Loop
The LTC3872 is a No RSENSE constant frequency, current
mode controller for DC/DC boost, SEPIC and flyback
converter applications. The LTC3872 is distinguished
from conventional current mode controllers because the
current control loop can be closed by sensing the voltage
drop across the power MOSFET switch or across a discrete
sense resistor, as shown in Figures 1 and 2. This No RSENSE
sensing technique improves efficiency, increases power
density and reduces the cost of the overall solution.
For circuit operation, please refer to the Block Diagram
of the IC and the Typical Application on the front page. In
normal operation, the power MOSFET is turned on when
the oscillator sets the RS latch and is turned off when the
current comparator resets the latch. The divided-down
output voltage is compared to an internal 1.2V reference by
the error amplifier, which outputs an error signal at the ITH
pin. The voltage on the ITH pin sets the current comparator
input threshold. When the load current increases, a fall in
the FB voltage relative to the reference voltage causes the
ITH pin to rise, which causes the current comparator to
trip at a higher peak inductor current value. The average
inductor current will therefore rise until it equals the load
current, thereby maintaining output regulation.
The LTC3872 can be used either by sensing the voltage
drop across the power MOSFET or by connecting the SW
pin to a conventional sensing resistor in the source of the
power MOSFET. Sensing the voltage across the power
MOSFET maximizes converter efficiency and minimizes the
component count; the maximum rating for this pin, 60V,
allows MOSFET sensing in a wide output voltage range.
The RUN/SS pin controls whether the IC is enabled or is in
a low current shutdown state. With the RUN/SS pin below
0.85V, the chip is off and the input supply current is typi-
cally only 10μA. With an external capacitor connected to
the RUN/SS pin an optional external soft-start is enabled.
A 0.7μA trickle current will charge the capacitor, pulling
the RUN/SS pin above shutdown threshold and slowly
ramping RUN/SS to limit the VITH during start-up. Because
the noise on the SW pin could couple into the RUN/SS
pin, disrupting the trickle charge current that charges the
RUN/SS pin, a 1M resistor is recommended to pull-up the
RUN/SS pin when external soft-start is used. When RUN/SS
is driven by an external logic, a minimum of 2.75V logic is
recommended to allow the maximum ITH range.
Light Load Operation
Under very light load current conditions, the ITH pin volt-
age will be very close to the zero current level of 0.85V.
As the load current decreases further, an internal offset at
the current comparator input will assure that the current
comparator remains tripped (even at zero load current) and
the regulator will start to skip cycles, as it must, in order
to maintain regulation. This behavior allows the regulator
to maintain constant frequency down to very light loads,
resulting in low output ripple as well as low audible noise
and reduced RF interference, while providing high light
load efficiency.
Figure 1. SW Pin (Internal Sense Pin)
Connection for Maximum Efficiency
COUT
VSW
VOUT
VIN
GND
L
D
+
NGATE
GND
VIN
SW
3872 F01
LTC3872
COUT
VSW
RSENSE
VOUT
VIN
GND
L
D
+
NGATE
GND
VIN
SW
3872 F02
LTC3872
Figure 2. SW Pin (Internal Sense Pin)
Connection for Sensing Resistor


Similar Part No. - LTC3872ETS8

ManufacturerPart #DatasheetDescription
logo
Linear Technology
LTC3872 LINER-LTC3872 Datasheet
514Kb / 32P
   Wide Input Voltage Range
LTC3872-1 LINER-LTC3872-1 Datasheet
302Kb / 20P
   No RSENSE Current Mode Boost DC/DC Controller
LTC3872-1 LINER-LTC3872-1_15 Datasheet
302Kb / 20P
   No RSENSE Current Mode Boost DC/DC Controller
LTC3872 LINER-LTC3872_15 Datasheet
256Kb / 22P
   No RSENSE Current Mode Boost DC/DC Controller
More results

Similar Description - LTC3872ETS8

ManufacturerPart #DatasheetDescription
logo
Linear Technology
LTC3872 LINER-LTC3872_15 Datasheet
256Kb / 22P
   No RSENSE Current Mode Boost DC/DC Controller
LTC3872-1 LINER-LTC3872-1 Datasheet
302Kb / 20P
   No RSENSE Current Mode Boost DC/DC Controller
LTC3872-1 LINER-LTC3872-1_15 Datasheet
302Kb / 20P
   No RSENSE Current Mode Boost DC/DC Controller
LTC3809 LINER-LTC3809 Datasheet
291Kb / 24P
   No RSENSE?? Low EMI, Synchronous DC/DC Controller
LTC1700 LINER-LTC1700_15 Datasheet
206Kb / 16P
   No RSENSE Synchronous Step-Up DC/DC Controller
LTC1700 LINER-LTC1700 Datasheet
194Kb / 16P
   No RSENSE Synchronous Step-Up DC/DC Controller
LTC3809 LINER-LTC3809_15 Datasheet
296Kb / 24P
   No RSENSE, Low EMI, Synchronous DC/DC Controller
LTC3873-5 LINER-LTC3873-5 Datasheet
169Kb / 16P
   No RSENSETM Constant Frequency Current Mode Boost/Flyback/SEPIC DC/DC Controller
LTC3873 LINER-LTC3873 Datasheet
176Kb / 16P
   No RSENSETM Constant Frequency Current Mode Boost/Flyback/SEPIC DC/DC Controller
LTC1871EMS-7 LINER-LTC1871EMS-7 Datasheet
477Kb / 36P
   Wide Input Range, No RSENSE Current Mode Boost,
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com