LTC3838-2_15 Datasheet, PDF (1/56 Pages) Linear Technology – Dual, Fast, Accurate Step-Down DC/DC Controller with xternal Reference Voltage and Dual Differential Output Sensing

LTC3838-2
Dual, Fast, Accurate
Step-Down DC/DC Controller with
External Reference Voltage and
Dual Differential Output Sensing
FEATURES
n _{Wide VIN Range: 4.5V to 38V}
n _{VOUT1: 0.6V to 5.5V, ±0.67% Output Regulation}
Accuracy, with Internal 0.6V V_REFERENCE
n _{VOUT2: 0.4V to 5.5V, ±4mV Regulation Accuracy, with}
Differential External V_REFERENCE Sensing
n _{Differential Remote Output Sensing; Up to ±500mV}
(V_OUT1) and ±200mV (V_OUT2) Ground Deviations
n _{Fast Load Transient Response Without Clock Delay}
n _{Detect Transient Release (DTR) Reduces VOUT}
Overshoot
n _{Frequency Programmable from 200kHz to 2MHz,}
Synchronizable to External Clock
n _{tON(MIN) = 30ns, tOFF(MIN) = 90ns}
n _{RSENSE or Inductor DCR Current Sensing}
n _{Overvoltage Protection and Current Limit Foldback}
n _{Power Good Output Voltage Monitor}
n _{Thermally Enhanced 38-Pin (5mm × 7mm) QFN Package}
APPLICATIONS
n _{Power for ASICs with Dynamic Voltage Scaling}
n _{Low Voltage, High Current, High Step-Down Ratio}
Converters That Demand Tight Transient Regulation
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.
TYPICAL APPLICATION
1.2V/15A and 0.8V to 2.5V/15A, 350kHz Step-Down Converter (See Figure 16 for Complete Design)
V_IN
4.5V TO 38V
V_OUT1
1.2V
15A
330µF ⁺
×2
0.56µH
10k
10k
0.1µF
115k
SENSE1^–
SENSE1⁺
SENSE2^–
SENSE2⁺
V_IN
INTV_CC
TG1
TG2
LTC3838-2
SW1
SW2
BOOST1
BOOST2
DRV_CC1
BG1
4.7µF
PGND
DRV_CC2
BG2
EXTV_REF2
V_OUTSENSE1+
V_{OUTSENSE1–}
V_DFB2+
V_DFB2–
TRACK/SS1 TRACK/SS2
ITH1
ITH2
0.1µF
0.4V TO
1.25V
RT
SGND
EXTV_CC
RUN1
MODE/PLLIN
CLKOUT
PHASMD
RUN2
38382 TA01a
0.56µH
20₊k
10k 20k
V_OUT2
0.8V TO 2.5V
15A
330µF
×2
Efficiency/Power Loss
100
2.5
FORCED CONTINUOUS MODE
DISCONTINUOUS MODE
90
2.0
80
EFFICIENCY
70
60
1.5
POWER
LOSS
1.0
50
40
0.1
0.5
V_IN = 12V
V_OUT = 1.2V
0
1
10
LOAD CURRENT (A)
38382 TA01b
38382f
For more information www.linear.com/3838-2
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