LTC1438 LINER [Linear Technology], LTC1438 Datasheet
LTC1438
Manufacturer Part Number
LTC1438
Description
Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators
Manufacturer
LINER [Linear Technology]
Datasheet
1.LTC1438.pdf
(32 pages)
Available stocks
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Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
LTC1438CG
Manufacturer:
LT
Quantity:
1 120
Part Number:
LTC1438CG
Manufacturer:
LT/凌特
Quantity:
20 000
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Manufacturer:
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Part Number:
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Part Number:
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LINEAR/凌特
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FEATURES
APPLICATIONS
TYPICAL
Maintains Constant Frequency at Low Output Currents
Dual N-Channel MOSFET Synchronous Drive
Programmable Fixed Frequency (PLL Lockable)
Wide V
Ultrahigh Efficiency
Very Low Dropout Operation: 99% Duty Cycle
Low Dropout, 0.5A Linear Regulator for VPP
Generation or Low Noise Audio Supply
Built-In Power-On Reset Timer
Programmable Soft Start
Low-Battery Detector
Remote Output Voltage Sense
Foldback Current Limiting (Optional)
Pin Selectable Output Voltage
Logic-Controlled Micropower Shutdown: I
Output Voltages from 1.19V to 9V
Available in 28- and 36-Lead SSOP Packages
Notebook and Palmtop Computers, PDAs
Portable Instruments
Battery-Operated Devices
DC Power Distribution Systems
V
OUT1
3.5A
5V
IN
Range: 3.5V to 36V Operation
+
M1, M2, M4, M5: Si4412DY
APPLICATION
MBR140T3
R
0.03
SENSE1
C
220 F
10V
OUT1
10 H
L1
D1
U
M1
M3*
M2
1000pF
1000pF
0.1 F
C
220pF
C
C
M3, M6: IRLML2803
C1A
B1
C1
Figure 1. High Efficiency Dual 5V/3V Step-Down Converter
U
D
B1
R
10k
, CMDSH-3
C1
BOOST 1
TGL1
TGS1
SW1
BG1
SENSE
SENSE
I
TH1
RUN/SS1
+
–
1
1
C
0.1 F
SS1
*NOT REQUIRED FOR LTC1438
V
Q
PROG1
C
DSC
< 30 A
Step-Down Switching Regulators
C
56pF
OSC
V
PROG2
LTC1439
V
IN
SGND
INTV
The LTC
down switching regulator controllers which drive external
N-channel power MOSFETs in a phase-lockable fixed
frequency architecture. The Adaptive Power
selectively drives two N-channel MOSFETs at frequencies
up to 400kHz while reducing switching losses to maintain
high efficiencies at low output currents.
An auxiliary 0.5A linear regulator using an external PNP
pass device provides a low noise, low dropout voltage
source. A secondary winding feedback control pin (SFB1)
guarantees regulation regardless of load on the main
output by forcing continuous operation.
An additional comparator is available for use as a low
battery detector. A power-on reset timer (POR) is included
which generates a signal delayed by 65536/f
300ms) after the output is within 5% of the regulated
output voltage. Internal resistive dividers provide pin
selectable output voltages with remote sense capability on
one of the two outputs.
The operating current levels are user-programmable via
external current sense resistors. Wide input supply range
allows operation from 3.5V to 30V (36V maximum).
DESCRIPTION
Adaptive Power is a trademark of Linear Technology Corporation.
PGND
CC
, LTC and LT are registered trademarks of Linear Technology Corporation.
BOLD LINES INDICATE HIGH CURRENT PATHS
RUN/SS2
D
SENSE
SENSE
V
Low Noise, Synchronous
BOOST 2
B2
OSENSE2
, CMDSH-3
TGS2
TGL2
SW2
BG2
I
TH2
+
–
C
0.1 F
2
2
®
SS2
1438/LTC1439 are dual, synchronous step-
Dual High Efficiency,
R
10k
+
1000pF
C2
C
1000pF
C
C2
B2
, 0.1 F
4.7 F
16V
C
470pF
U
C2A
M5
LTC1438/LTC1439
M6*
M4
D2
MBR140T3
10 H
L2
1438 F01
+
+
R
0.03
SENSE2
C
22 F
35V
C
220 F
10V
V
3.3V
3.5A
IN
OUT
OUT2
4
V
5.2V TO 28V
TM
IN
output stage
CLK
(typ
1
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