LTC1539 LINER [Linear Technology], LTC1539 Datasheet

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LTC1539

Manufacturer Part Number
LTC1539
Description
Dual High Efficiency, Low Noise, Synchronous Step-Down Switching Regulators
Manufacturer
LINER [Linear Technology]
Datasheet

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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
5V Standby Regulator Active in 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
IN
Range: 3.5V to 36V Operation
V
OUT1
3.5A
APPLICATION
5V
+
M1, M2, M4, M5: Si4412DY
U
MBR140T3
R
0.03
SENSE1
C
220 F
10V
OUT1
10 H
L1
D1
M1
M3*
M2
1000pF
1000pF
U
Figure 1. High Efficiency Dual 5V/3V Step-Down Converter
M3, M6: IRLML2803
0.1 F
C
220pF
C
C
C1A
B1
C1
D
B1
R
10k
, CMDSH-3
C1
BOOST 1
TGL1
TGS1
SW1
BG1
SENSE
SENSE
I
TH1
RUN/SS1
+
1
1
*NOT REQUIRED FOR LTC1538-AUX
Q
C
0.1 F
SS1
Step-Down Switching Regulators
< 200 A
V
PROG1
C
DSC
C
56pF
OSC
V
PROG2
LTC1539
V
IN
SGND
DESCRIPTION
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.
A 5V/20mA regulator, internal 1.19V reference and an
uncommitted comparator remain active when both con-
trollers are shut down. A power-on reset timer (POR) is
included which generates a signal delayed by 65536/f
(typ 300ms) after the controller’s output is within 5% of
the regulated first voltage. Internal resistive dividers pro-
vide 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).
Adaptive Power is a trademark of Linear Technology Corporation.
, LTC and LT are registered trademarks of Linear Technology Corporation.
INTV
PGND
Low Noise, Synchronous
CC
BOLD LINES INDICATE HIGH CURRENT PATHS
®
RUN/SS2
D
1538-AUX/LTC1539 are dual, synchronous step-
SENSE
SENSE
V
BOOST 2
B2
OSENSE2
, CMDSH-3
TGS2
TGL2
SW2
BG2
I
Dual High Efficiency,
TH2
+
C
0.1 F
2
2
SS2
LTC1538-AUX/LTC1539
5V STANDBY
R
10k
+
1000pF
C2
C
1000pF
C
C2
U
B2
, 0.1 F
4.7 F
16V
C
470pF
C2A
M5
M6*
M4
+
D2
MBR140T3
10 H
L2
C
22 F
35V
IN
1538 F01
4
+
V
5.2V TO 28V
IN
R
0.03
SENSE2
C
220 F
10V
V
3.3V
3.5A
TM
OUT
OUT2
output stage
1
CLK

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