LTC3838
Dual, Fast, Accurate Step-
Down DC/DC Controller with
Differential Output Sensing
DescripTion
FeaTures
TheLTC®3838isadual,PolyPhase® synchronousstep-down
DC/DC switching regulator controller. Two independent
channelsdriveallN-channelpowerMOSFETs.Thecontrolled
on-time,valleycurrentmodecontrolarchitectureallowsfor
fast transient response and constant frequency switching
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Wide V Range: 4.5V to 38V, V : 0.6V to 5.5V
IN
OUT
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0.6ꢀ7 Output Voltage Accuracy Over Temperature,
Differential Output Voltage Sensing, Allowing Up to
500mV ꢁine ꢁoss at Remote ꢂround on Cꢃannel 1
17 Output on tꢃe Independent 2nd Cꢃannel
Controlled On-Time, Valley Current Mode Control
FastꢁoadTransientResponse
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in steady-state operation, independent of V , V
and
IN OUT
load current. Its load-release transient detection feature
significantly reduces overshoot at low output voltages.
DetectTransient(DTR)ReducesV
Oversꢃoot
OUT
Frequency Programmable from 200kHz to 2MHz,
Differential output voltage sensing, along with a preci-
sion internal reference, offers an accurate ±±.ꢀ67 output
regulation on Channel 1, even if the remote output ground
deviatesfromlocalgroundby±ꢁ±±mV.Thesecondchannel
caneitherprovideanindependent±17output,ortogether
with the first channel of this controller, serve as one of the
PolyPhase channels for a single-output voltage.
Syncꢃronizable to External Clock
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t
= 30ns, t
= 90ns
ON(MIN)
OFF(MIN)
R
or Inductor DCR Current Sensing
SENSE
Overvoltage Protection and Current Limit Foldback
Power Good Output Voltage Monitor
Output Voltage Tracking and Adjustable Soft Start-Up
Thermally Enhanced 38-Pin (ꢁmm × 6mm) QFN and
TSSOP packages
Theswitchingfrequencycanbeprogrammedfrom2±±kHz
to2MHzwithanexternalresistor,andcanbesynchronizedto
anexternalclock. Verylowt andt timesallowfornear
applicaTions
ON
OFF
±7andnear1±±7dutycycles,respectively.Voltagetrack-
ingsoftstart-upandmultiplesafetyfeaturesareprovided.
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Distributed Power Systems
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Point-of-Load Converters
L, LT, LTC, LTM, PolyPhase, OPTI-LOOP, µModule, Linear Technology and the Linear logo
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Computing Systems
Data Communication Systems
are registered trademarks and No R
and UltraFast are trademarks of Linear Technology
SENSE
Corporation. All other trademarks are the property of their respective owners. Protected by U.S.
Patents, including ꢁ481168, ꢁ846ꢁꢁ4, ꢀꢁ8±2ꢁ8, ꢀ3±4±ꢀꢀ, ꢀ46ꢀꢁ89, ꢀ664ꢀ11.
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Typical applicaTion
1.2V/1.5V, 15A, 350kHz, DCR Sense, Step-Down Converter (Refer to Figure 16 for Full Design)
V
Efficiency/Power ꢁoss
IN
4.5V TO 38V
2.5
2.0
1.5
1.0
0.5
0
100
90
80
70
60
50
40
–
+
–
+
FORCED CONTINUOUS MODE
DISCONTINUOUS MODE
SENSE1
SENSE1
SENSE2
SENSE2
INTV
V
IN
CC
TG1
TG2
LTC3838
EFFICIENCY
SW1
SW2
0.56µH
0.56µH
15k
V
1.5V
15A
V
OUT2
OUT1
1.2V
15A
BOOST1
BOOST2
POWER
LOSS
0.1µF
0.1µF
10k
+
+
DRV
CC2
DRV
CC1
330µF
×2
330µF
×2
BG1
BG2
10k
4.7µF
10k
V
V
= 12V
OUT
PGND
IN
= 1.2V
+
V
V
V
FB2
OUTSENSE1
0.1
1
10
–
OUTSENSE1
LOAD CURRENT (A)
TRACK/SS1 TRACK/SS2
3838 F16b
ITH1
ITH2
115k
3838 TA01a
RT
SGND
3838fb
1
For more information www.linear.com/LTC3838
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