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LTC3838-2_15

Description
Dual, Fast, Accurate Step-Down DC/DC Controller with xternal Reference Voltage and Dual Differential Output Sensing
File Size4MB,56 Pages
ManufacturerLinear ( ADI )
Websitehttp://www.analog.com/cn/index.html
Download Datasheet View All

LTC3838-2_15 Overview

Dual, Fast, Accurate Step-Down DC/DC Controller with xternal Reference Voltage and Dual Differential Output Sensing

FEATURES
n
n
LTC3838-2
Dual, Fast, Accurate
Step-Down DC/DC Controller with
External Reference Voltage and
Dual Differential Output Sensing
DESCRIPTION
The LTC
®
3838-2 is a dual-channel, PolyPhase
®
synchro-
nous step-down DC/DC switching regulator controller. Two
independent channels drive all N-channel power MOSFETs.
The two channels can also be combined into a multiphase
single output configuration with external reference.
The controlled on-time, valley current mode control architec-
ture allows for not only fast response to transients without
a clock delay, but also constant frequency switching at a
steady-load condition. Its proprietary load-release transient
detection feature (DTR) significantly reduces overshoot at
low output voltages.
The switching frequency can be programmed from 200kHz
to 2MHz with an external resistor, and can be synchronized
to an external clock. Very low t
ON
and t
OFF
times allow for near
0% and near 100% duty cycles, respectively. Voltage track-
ing soft start-up and multiple safety features are provided.
See Table 1 for a comparison of LTC3838, LTC3838-1 and
LTC3838-2.
L,
LT, LTC, LTM, PolyPhase, OPTI-LOOP, Linear Technology and the Linear logo are registered
trademarks and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents, including 5481178,
5847554, 6580258, 6304066, 6476589, 6774611.
n
n
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n
n
n
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Wide V
IN
Range: 4.5V to 38V
V
OUT1
: 0.6V to 5.5V, ±0.67% Output Regulation
Accuracy, with Internal 0.6V V
REFERENCE
V
OUT2
: 0.4V to 5.5V, ±4mV Regulation Accuracy, with
Differential External V
REFERENCE
Sensing
Differential Remote Output Sensing; Up to ±500mV
(V
OUT1
) and ±200mV (V
OUT2
) Ground Deviations
Fast Load Transient Response Without Clock Delay
Detect Transient Release (DTR) Reduces V
OUT
Overshoot
Frequency Programmable from 200kHz to 2MHz,
Synchronizable to External Clock
t
ON(MIN)
= 30ns, t
OFF(MIN)
= 90ns
R
SENSE
or Inductor DCR Current Sensing
Overvoltage Protection and Current Limit Foldback
Power Good Output Voltage Monitor
Thermally Enhanced 38-Pin (5mm
×
7mm) QFN Package
Power for ASICs with Dynamic Voltage Scaling
Low Voltage, High Current, High Step-Down Ratio
Converters That Demand Tight Transient Regulation
APPLICATIONS
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TYPICAL APPLICATION
V
IN
4.5V TO 38V
1.2V/15A and 0.8V to 2.5V/15A, 350kHz Step-Down Converter (See Figure 16 for Complete Design)
SENSE1
SENSE1
+
V
IN
TG1
V
OUT1
1.2V
15A
330µF
×2
0.56µH
SW1
0.1µF
LTC3838-2
SENSE2
SENSE2
+
INTV
CC
TG2
EFFICIENCY (%)
SW2
0.1µF
10k
0.56µH
20k
V
OUT2
0.8V TO 2.5V
15A
330µF
×2
Efficiency/Power Loss
100
90
80
EFFICIENCY
70
60
50
40
POWER
LOSS
FORCED CONTINUOUS MODE
DISCONTINUOUS MODE
2.5
2.0
POWER LOSS (W)
BOOST1
BOOST2
DRV
CC2
BG2
EXTV
REF2
+
1.5
+
10k
10k
DRV
CC1
4.7µF
BG1
PGND
V
OUTSENSE1
V
OUTSENSE1–
ITH1
RT
SGND
EXTV
CC
RUN1
+
1.0
0.4V TO
1.25V
20k
0.5
V
IN
= 12V
V
OUT
= 1.2V
0.1
1
LOAD CURRENT (A)
10
38382 TA01b
V
DFB2
V
DFB2–
ITH2
+
TRACK/SS1 TRACK/SS2
115k
MODE/PLLIN
CLKOUT
PHASMD
RUN2
0
38382 TA01a
38382f
For more information
www.linear.com/3838-2
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