LTC3838-1_15 Datasheet, PDF (1/52 Pages) Linear Technology – Dual, Fast, Accurate Step-Down DC/DC Controller with Dual Differential Output Sensing

LTC3838-1
Dual, Fast, Accurate
Step-Down DC/DC Controller with
Dual Differential Output Sensing
FEATURES
n _{Wide VIN Range: 4.5V to 38V, VOUT: 0.6V to 5.5V}
n _{Two Independent Channels: Dual/Single Output}
n _{Output Voltage Regulation Accuracy: ±0.67%}
(V_OUT1) and ±0.75% (V_OUT2) Over Temperature
n _{Differential Remote Output Sensing: Up to ±500mV}
(V_OUT1) and ±200mV (V_OUT2) Ground Deviations
n _{Controlled On-Time, Valley Current Mode Control}
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 _{Output Voltage Tracking and Adjustable Soft Start-Up}
n _{Thermally Enhanced 38-Pin (5mm × 7mm) QFN Package}
APPLICATIONS
n _{Distributed Power Systems; Power Supply for ASIC}
n _{Computing, Data Storage, Communication Systems}
n _{Low Voltage, High Current, and/or High Step-Down Ratio}
Converters That Demand Tight Load Transient Regulation
DESCRIPTION
The LTC^®3838-1 is a dual-channel, PolyPhase^® syn-
chronous step-down DC/DC switching regulator controller.
Two independent channels drive all N-channel power
MOSFETs. The controlled on-time, valley current mode
control architecture allows for not only fast response to
transients without clock delay, but also constant frequency
switching at steady load condition. Its proprietary load-
release transient detection feature (DTR) significantly
reduces overshoot at low output voltages.
A precision internal reference enables accurate differential
output regulation. The dual channels can either provide
two independent output voltages, or be combined into
multiphase single-output configuration.
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/1.5V, 15A, 350kHz Step-Down Converter (Refer to Figure 16 for Complete Design)
V_IN
4.5V TO 38V
V_OUT1
1.2V
15A
330µF ⁺
×2
0.56µH
10k
10k
0.1µF
SENSE1^–
SENSE1⁺
SENSE2^–
SENSE2⁺
V_IN
INTV_CC
TG1
TG2
LTC3838-1
SW1
SW2
BOOST1
BOOST2
DRV_CC1
DRV_CC2
BG1
4.7µF
PGND
BG2
EXTV_CC
V_OUTSENSE1+
V_{OUTSENSE1–}
V_DFB2+
V_DFB2–
TRACK/SS1 TRACK/SS2
0.1µF
0.56µH
15k ₊
10k/ 10k
15k
V_OUT2
1.5V
15A
330µF
×2
115k
ITH1
RT
SGND
V_RNG
RUN1
ITH2
MODE_PLLIN
CLKOUT
PHASMD
RUN2
38381 TA01a
For more information www.linear.com3838-1
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)
38381 TA01b
38381f
1