LTC3839
Fast, Accurate, 2-Phase,
Single-Output Step-Down DC/DC
Controller with Differential Output Sensing
DESCRIPTION
FEATURES
The LTC®3839 is a 2-phase, single-output PolyPhase®
synchronous step-down switching regulator controller
that drives all N-channel power MOSFETs. The controlled
on-time,valleycurrentmodecontrolarchitectureallowsfor
fast transient response and constant frequency switching
n
Wide V Range: 4.5V to 38V, V : 0.6V to 5.5V
IN
OUT
n
0.6ꢀ7 Output Voltage Accuracy Over Temperature,
Differential Output Voltage Sensing, Allowing Up to
500mV ꢁine ꢁoss at Remote ꢂround
n
n
n
n
Controlled On-Time, Valley Current Mode Control
FastꢁoadTransientResponse
in steady-state operation, independent of V , V
and
IN OUT
DetectTransient(DTR)ReducesV
Overshoot
load current. Its load-release transient detection feature
significantly reduces overshoot at low output voltages.
OUT
Frequency Programmable from 200kHz to 2MHz,
Synchronizable to External Clock
Differential output voltage sensing, along with a preci-
sion internal reference, offers an accurate ±±.ꢀ67 output
regulation,eveniftheremoteoutputgrounddeviatesfrom
local ground by ±ꢁ±±mV.
n
n
n
n
n
n
n
t
= 30ns, t
= 90ns
ON(MIN)
OFF(MIN)
Up to 12-Phase Operation
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 32-Pin (ꢁmm × ꢁmm) QFN
Package
Theswitchingfrequencycanbeprogrammedfrom2±±kHz
to2MHzwithanexternalresistorandcanbesynchronized
to an external clock. Very low t and t times allow for
ON
OFF
near ±7 and near 1±±7 duty cycles, respectively. Volt-
age tracking soft start-up and multiple safety features are
provided.
APPLICATIONS
L, LT, LTC, LTM, PolyPhase, OPTI-LOOP, Linear Technology and the Linear logo are
registered trademarks and Hot Swap and Stage Shedding are trademarks of Linear Technology
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.
n
Distributed Power Systems
Point-of-Load Converters
n
n
Computing Systems
n
Data Communication Systems
TYPICAL APPLICATION
3.3V/25A Output, 2MHz Step-Down Converter (Refer to Figure 20 for Full Design)
V
IN
Efficiency/Power ꢁoss
4.ꢁV TO 14V
–
+
–
+
1±
8
1±±
9±
8±
6±
ꢀ±
ꢁ±
SENSE1
SENSE1
SENSE2
SENSE2
INTV
V
IN
= ꢁV
DISCONTINUOUS
MODE
V
IN
CC
TG1
TG2
LTC3839
SW1
SW2
FORCED
±.3μH
±.3μH
V
ꢀ
OUT
CONTINUOUS
BOOST1
BOOST2
3.3V
2ꢁA
MODE
±.1μF
±.1μF
4ꢁ.3k
1±k
4
+
DRV
CC2
DRV
CC1
1±±μF
wꢀ
BG1
BG2
4.6μF
2
PGND
LOSS
FORCED CM
MODE/PLLIN
CLKOUT
PHASMD
RUN
LOSS
DCM
+
–
V
V
OUTSENSE
OUTSENSE
±
1±±
±.1
1
1±
TRACK/SS
ITH
LOAD CURRENT (A)
3839 TA±1b
18.6k
DTR
RT
SGND
3839 TA±1a
3839fa
1