LTC3872EDDB LINER [Linear Technology], LTC3872EDDB Datasheet

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LTC3872EDDB

Manufacturer Part Number
LTC3872EDDB
Description
No RSENSE Current Mode Boost DC/DC Controller
Manufacturer
LINER [Linear Technology]
Datasheet

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LTC3872EDDB
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APPLICATIO S
FEATURES
TYPICAL APPLICATIO
1.8nF
No Current Sense Resistor Required
V
Constant Frequency 550kHz Operation
Internal Soft-Start and Optional External Soft-Start
Adjustable Current Limit
Pulse Skipping at Light Load
V
±1.5% Voltage Reference Accuracy
Current Mode Operation for Excellent Line and Load
Transient Response
Low Profi le (1mm) SOT-23 and 3mm × 2mm DFN
Packages
Telecom Power Supplies
42V Automotive Systems
24V Industrial Controls
IP Phone Power Supplies
OUT
IN
17.4k
High Effi ciency 3.3V Input, 5V Output Boost Converter
47pF
Range: 2.75V to 9.8V
11k
1%
up to 60V
V
IN
34.8k
1%
I
IPRG
GND
V
TH
FB
U
RUN/SS
LTC3872
1nF
NGATE
V
SW
IN
U
M1
1μH
100μF
D1
×2
3872 TA01
10μF
V
3.3V
V
5V
2A
IN
OUT
DESCRIPTIO
The LTC
boost DC/DC controller that drives an N-channel power
MOSFET and requires very few external components. The
No R
resistor, improves effi ciency and saves board space.
The LTC3872 provides excellent AC and DC load and line
regulation with ±1.5% output voltage accuracy. It incor-
porates an undervoltage lockout feature that shuts down
the device when the input voltage falls below 2.3V.
High switching frequency of 550kHz allows the use of a
small inductor. The LTC3872 is available in an 8-lead low
profi le (1mm) ThinSOT
DFN package.
No R
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6498466, 6611131, 5731694.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
SENSE
SENSE
and ThinSOT are trademarks of Linear Technology Corporation.
®
3872 is a constant frequency current mode
Effi ciency and Power Loss vs Load Current
100
TM
90
80
70
60
50
40
30
20
10
0
architecture eliminates the need for a sense
1
Current Mode Boost
DC/DC Controller
U
10
LOAD CURRENT (mA)
TM
package and 8-pin 3mm × 2mm
100
1000
No R
3872 TA01b
LTC3872
10000
10
0.1
1
0.01
0.001
SENSE
3872fa
1

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LTC3872EDDB Summary of contents

Page 1

FEATURES ■ No Current Sense Resistor Required ■ 60V OUT ■ Constant Frequency 550kHz Operation ■ Internal Soft-Start and Optional External Soft-Start ■ Adjustable Current Limit ■ Pulse Skipping at Light Load ■ V Range: 2.75V to ...

Page 2

... Lead Temperature (Soldering, 10 sec) TS8 Package ......................................................... 300° RUN/ NGATE ORDER PART NUMBER LCGB LTC3872EDDB ● The denotes the specifi cations which apply over the full operating = 25° 4.2V unless otherwise noted. (Note CONDITIONS Typicals 4.2V (Note 4) IN 2.75V ≤ ...

Page 3

ELECTRICAL CHARACTERISTICS temperature range, otherwise specifi cations are at T PARAMETER Oscillator Frequency Normal Operation Gate Drive Rise Time Gate Drive Fall Time Peak Current Sense Voltage Default Internal Soft-Start Time Note 1: Stresses beyond those listed under Absolute Maximum ...

Page 4

LTC3872 W U TYPICAL PERFOR A CE CHARACTERISTICS Shutdown (V) IN 3872 G04 Gate Drive Rise and Fall ...

Page 5

CTIO S (TS8/DD8) IPRG (Pin 1/Pin 4): Current Sense Limit Select Pin. I (Pin 2/Pin 3): It serves as the error amplifi er com- TH pensation point. Nominal voltage range for this pin is 0.7V ...

Page 6

LTC3872 U OPERATIO Main Control Loop The LTC3872 constant frequency, current SENSE mode controller for DC/DC boost, SEPIC and fl yback converter applications. The LTC3872 is distinguished from conventional current mode controllers because the current control ...

Page 7

U U APPLICATIO S I FOR ATIO Output Voltage Programming The output voltage is set by a resistor divider according to the following formula: ⎛ ⎞ • 1 ⎝ ⎜ ⎠ ...

Page 8

LTC3872 U U APPLICATIO S I FOR ATIO mode gain and avoid subharmonic oscillation recom- mended that the ripple current in the inductor fall in the range of 20% to 40% of the maximum average current. For example, ...

Page 9

U U APPLICATIO S I FOR ATIO the maximum drain current (I D(MAX) thermal resistances (R and R TH(JC) TH(JA threshold MOSFETs should be used when input GS-RATED voltage is high, otherwise if low input voltage operation is ...

Page 10

LTC3872 U U APPLICATIO S I FOR ATIO result, some iterative calculation is normally required to determine a reasonably accurate value. Since the controller is using the MOSFET as both a switching and a sensing element, care should be taken ...

Page 11

U U APPLICATIO S I FOR ATIO where: χ ⎛ ⎞ MAX ( ) = + ⎜ ⎟ • IN PEAK ( ) ⎝ ⎠ – D MAX For the bulk C component, which ...

Page 12

LTC3872 U U APPLICATIO S I FOR ATIO Input Capacitor Selection The input capacitor of a boost converter is less critical than the output capacitor, due to the fact that the inductor is in series with the input and the ...

Page 13

U U APPLICATIO S I FOR ATIO Power MOSFET Selection. 3. The losses in the inductor are simply the DC input cur- rent squared times the winding resistance. Expressing this loss as a function of the output current yields: 2 ...

Page 14

LTC3872 U U APPLICATIO S I FOR ATIO 3. Assuming a MOSFET junction temperature of 125°C, the room temperature MOSFET R than: 1 ≤ • SENSE MAX ( ) χ ⎛ ⎝ ...

Page 15

TYPICAL APPLICATIONS 2.2nF 23.2k 100pF 11. COUPLED STEP FROM 500mA TO 1.5A High Effi ciency 3.3V Input, 12V Output Boost Converter 4.7M 0.1μF I RUN/ IPRG 2.2μH LTC3872 GND SW V NGATE M1 PDS1040 ...

Page 16

LTC3872 TYPICAL APPLICATIONS High Effi ciency 5V Input, 12V Output Boost Converter 4.7M 1nF 2.2nF 11k I RUN/ 100p IPRG LTC3872 GND SW V NGATE FB 11.8k 1% 107k 1% COUT1: TAIYO YUDEN TMK325BJ226MM L1: TOKO D124C ...

Page 17

TYPICAL APPLICATIONS 63.4k 2.2nF 1% V 12.1k 1% Soft-Start RUN/SS 5V/DIV I L 5A/DIV V OUT 20V/DIV 40ms/DIV High Effi ciency 5V Input, 48V Output Boost Converter 1M 0.33μF I RUN/ IPRG IN L1 10μH LTC3872 GND ...

Page 18

LTC3872 PACKAGE DESCRIPTIO 0.61 ±0.05 (2 SIDES) 2.55 ±0.05 1.15 ±0.05 0.25 ± 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS PIN 1 BAR TOP MARK (SEE NOTE 6) 0.200 REF NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE ...

Page 19

PACKAGE DESCRIPTIO 0.52 MAX 3.85 MAX 2.62 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.20 BSC DATUM ‘A’ 0.30 – 0.50 REF NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING ...

Page 20

LTC3872 U TYPICAL APPLICATIO 1.8nF RELATED PARTS PART NUMBER DESCRIPTION ® LT 1619 Current Mode PWM Controller LTC1624 Current Mode DC/DC Controller LTC1700 No R Synchronous Step-Up Controller SENSE LTC1871-7 Wide Input Range Controller LTC1872/LTC1872B SOT-23 Boost Controller LT1930 1.2MHz, ...

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