POWER LOSS (W)
LTC3838-2
Dual, Fast, Accurate
Step-Down DC/DC Controller with
External Reference Voltage and
Dual Differential Output Sensing
Fea T Descrip T
n
Wide V Range: 4.5V to 38V The LTC 3838-2 is a dual-channel, PolyPhase synchro-
IN
n
V : 0.6V to 5.5V, 0.67% Output Regulation nous step-down DC/DC switching regulator controller. Two
OUT1
Accuracy, with Internal 0.6V V independent channels drive all N-channel power MOSFETs.
REFERENCE
n
V : 0.4V to 5.5V, 4mV Regulation Accuracy, with The two channels can also be combined into a multiphase
OUT2
Differential External V Sensing single output configuration with external reference.
REFERENCE
n
Differential Remote Output Sensing; Up to 500mV
The controlled on-time, valley current mode control architec-
(V ) and 200mV (V ) Ground Deviations
OUT1 OUT2
ture allows for not only fast response to transients without
n
Fast Load Transient Response Without Clock Delay
a clock delay, but also constant frequency switching at a
n
Detect Transient Release (DTR) Reduces V
OUT
steady-load condition. Its proprietary load-release transient
Overshoot
detection feature (DTR) significantly reduces overshoot at
n
Frequency Programmable from 200kHz to 2MHz,
low output voltages.
Synchronizable to External Clock
n The switching frequency can be programmed from 200kHz
t = 30ns, t = 90ns
ON(MIN) OFF(MIN)
n to 2MHz with an external resistor, and can be synchronized
R or Inductor DCR Current Sensing
SENSE
n to an external clock. Very low t and t times allow for near
Overvoltage Protection and Current Limit Foldback ON OFF
n 0% and near 100% duty cycles, respectively. Voltage track-
Power Good Output Voltage Monitor
n ing soft start-up and multiple safety features are provided.
Thermally Enhanced 38-Pin (5mm 7mm) QFN Package
See Table 1 for a comparison of LTC3838, LTC3838-1 and
a T
LTC3838-2.
n
Power for ASICs with Dynamic Voltage Scaling
L, LT, LTC, LTM, PolyPhase, OPTI-LOOP, Module, Linear Technology and the Linear logo are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
n
Low Voltage, High Current, High Step-Down Ratio
of their respective owners. Protected by U.S. Patents, including 5481178, 5847554, 6580258,
6304066, 6476589, 6774611.
Converters That Demand Tight Transient Regulation
Typical a T
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
Efficiency/Power Loss
SENSE1 SENSE2
2.5
+ + 100
SENSE1 SENSE2
FORCED CONTINUOUS MODE
V INTV DISCONTINUOUS MODE
IN
CC
90
TG1 TG2 2.0
LTC3838-2
SW1 SW2
0.56H 0.56H
V V
OUT1 OUT2 80
BOOST1 BOOST2 0.8V TO 2.5V
1.2V
1.5
EFFICIENCY
15A 15A
20k
0.1F 0.1F 70
10k
+ +
DRV DRV POWER
CC1 CC2
330F 330F
1.0
LOSS
2 2
BG1 BG2
60
4.7F 10k 20k
10k
0.4V TO
PGND EXTV
REF2
1.25V 0.5
50
+ +
V = 12V
V V
OUTSENSE1 DFB2 IN
V = 1.2V
V OUT
V
OUTSENSE1 DFB2
40 0
0.1 1 10
TRACK/SS1 TRACK/SS2
LOAD CURRENT (A)
ITH1 ITH2
115k
38382 TA01b
RT MODE/PLLIN
SGND CLKOUT
EXTV PHASMD
CC
RUN1 RUN2
38382 TA01a
38382fa
1
For more information www.linear.com/3838-2
EFFICIENCY (%)
ion pplica
ions pplica
ion uresLTC3838-2
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),
EXTV 2 30 SW2
REF2
(BOOST2-SW2), MODE/PLLIN Voltages ...... 0.3V to 6V
ITH2 3 29 BG2
+ +
SENSE1 , SENSE2 ,SENSE1 , SENSE2
TRACK/SS2 4 28 DRV
CC2
MODE/PLLIN 5 27 EXTV
Voltages ....................................................... 0.6V to 6V
CC
+
CLKOUT INTV
6 26
CC
V , Voltage .............. 0.6V to (INTV + 0.3V) 39
OUTSENSE1 CC
PGND
+ SGND 7 25 PGND
V , Voltage ....................0.6V to V
OUTSENSE1 OUTSENSE1
RT 8 24 V
IN
TRACK/SS1, TRACK/SS2 Voltages .............. 0.3V to 5V
PHASMD 9 23 DRV
CC1
+
DTR1, DTR2, PHASMD, RT, EXTV , V , V ,
REF2 DFB2 DFB2
ITH1 10 22 BG1
ITH1, ITH2 Voltages ................ 0.3V to (INTV + 0.3V)
CC TRACK/SS1 21 SW1
11
+
Operating Junction Temperature Range 20
V 12 TG1
OUTSENSE1
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
(