POWER LOSS (W)
LTC3838-1
Dual, Fast, Accurate
Step-Down DC/DC Controller with
Dual Differential Output Sensing
Fea T Descrip T
n
Wide V Range: 4.5V to 38V, V : 0.6V to 5.5V The LTC 3838-1 is a dual-channel, PolyPhase syn-
IN OUT
n
Two Independent Channels: Dual/Single Output chronous step-down DC/DC switching regulator controller.
n
Output Voltage Regulation Accuracy: 0.67% Two independent channels drive all N-channel power
(V ) and 0.75% (V ) Over Temperature MOSFETs. The controlled on-time, valley current mode
OUT1 OUT2
n
Differential Remote Output Sensing: Up to 500mV control architecture allows for not only fast response to
(V ) and 200mV (V ) Ground Deviations transients without clock delay, but also constant frequency
OUT1 OUT2
n
Controlled On-Time, Valley Current Mode Control switching at steady load condition. Its proprietary load-
n
Fast Load Transient Response Without Clock Delay release transient detection feature (DTR) significantly
n
Detect Transient Release (DTR) Reduces V reduces overshoot at low output voltages.
OUT
Overshoot
A precision internal reference enables accurate differential
n
Frequency Programmable from 200kHz to 2MHz,
output regulation. The dual channels can either provide
Synchronizable to External Clock
two independent output voltages, or be combined into
n
t = 30ns, t = 90ns
ON(MIN) OFF(MIN)
multiphase single-output configuration.
n
R or Inductor DCR Current Sensing
SENSE
n The switching frequency can be programmed from 200kHz
Overvoltage Protection and Current Limit Foldback
n to 2MHz with an external resistor and can be synchronized to
Power Good Output Voltage Monitor
n an external clock. Very low t and t times allow for near
Output Voltage Tracking and Adjustable Soft Start-Up ON OFF
n 0% and near 100% duty cycles, respectively. Voltage track-
Thermally Enhanced 38-Pin (5mm 7mm) QFN Package
ing soft start-up and multiple safety features are provided.
a T
See Table 1 for a comparison of LTC3838, LTC3838-1 and
n
Distributed Power Systems; Power Supply for ASIC
LTC3838-2.
n
Computing, Data Storage, Communication Systems
L, LT, LTC, LTM, PolyPhase, OPTI-LOOP, Module, Linear Technology and the Linear logo are
n registered trademarks of Linear Technology Corporation. All other trademarks are the property
Low Voltage, High Current, and/or High Step-Down Ratio
of their respective owners. Protected by U.S. Patents, including 5481178, 5847554, 6580258,
Converters That Demand Tight Load Transient Regulation 6304066, 6476589, 6774611.
Typical a T
1.2V/1.5V, 15A, 350kHz Step-Down Converter (Refer to Figure 16 for Complete Design)
V
IN
Efficiency/Power Loss
4.5V TO 38V
100 2.5
SENSE1 SENSE2
FORCED CONTINUOUS MODE
+ +
SENSE1 SENSE2 DISCONTINUOUS MODE
90
V INTV
IN CC 2.0
TG1 TG2
LTC3838-1
80
SW1 SW2
0.56H 0.56H 1.5
V V
OUT1 OUT2 EFFICIENCY
1.2V BOOST1 BOOST2 1.5V
70
15A
15A
POWER
0.1F 0.1F 15k
10k 1.0
+ + LOSS
DRV
DRV
CC1 CC2
330F 330F
60
2 2
BG1 BG2
10k/ 10k
4.7F
10k
0.5
15k
PGND EXTV 50
CC
V = 12V
IN
+
+ V = 1.2V
V V OUT
OUTSENSE1 DFB2
40 0
V V
OUTSENSE1
DFB2
0.1 1 10
TRACK/SS1 TRACK/SS2 LOAD CURRENT (A)
ITH1 ITH2 38381 TA01b
115k
RT MODE_PLLIN
SGND CLKOUT
V PHASMD
RNG
RUN1 RUN2
38381 TA01a
38381fa
1
For more information www.linear.com3838-1
EFFICIENCY (%)
ion pplica
ions pplica
ion uresLTC3838-1
a T e Maxi Mu M r a T p c F T
(Note 1)
TOP VIEW
V Voltage ................................................. 0.3V to 40V
IN
BOOST1, BOOST2 Voltages ....................... 0.3V to 46V
SW1, SW2 Voltages ...................................... 5V to 40V
38 37 36 35 34 33 32
INTV , DRV , DRV , EXTV , PGOOD1,
+
CC CC1 CC2 CC V 1 31 TG2
DFB2
PGOOD2, RUN1, RUN2, (BOOST1-SW1),
V 2 30 SW2
RNG
ITH2 BG2
(BOOST2-SW2), MODE/PLLIN Voltages ...... 0.3V to 6V 3 29
+ +
TRACK/SS2 4 28 DRV
CC2
SENSE1 , SENSE2 ,SENSE1 , SENSE2
MODE/PLLIN 5 27 EXTV
CC
Voltages ....................................................... 0.6V to 6V
CLKOUT 6 26 INTV
+ CC
39
V Voltage ............... 0.6V to (INTV + 0.3V)
OUTSENSE1 CC
PGND
SGND 7 25 PGND
+
V Voltage .....................0.6V to V
OUTSENSE1 OUTSENSE1
RT V
8 24
IN
TRACK/SS1, TRACK/SS2 Voltages .............. 0.3V to 5V
PHASMD 9 23 DRV
CC1
+
DTR1, DTR2, PHASMD, RT, V , V , V ,
ITH1 10 22 BG1
RNG DFB2 DFB2
TRACK/SS1 11 21 SW1
ITH1, ITH2 Voltages ................ 0.3V to (INTV + 0.3V)
CC
+
V 12 20 TG1
OUTSENSE1
Operating Junction Temperature Range
13 14 15 16 17 18 19
(Notes 2, 3, 4) ........................................ 40C to 125C
Storage Temperature Range .................. 65C to 150C
UHF PACKAGE
38-LEAD (5mm 7mm) PLASTIC QFN
T = 125C, = 34C/W
JMAX JA
EXPOSED PAD (PIN 39) IS PGND, MUST BE SOLDERED TO PCB
o r D i n F Ma T
(