LTC3709
TM
SENSE
Fast 2-Phase, No R
,
Synchronous DC/DC Controller
with Tracking/Sequencing
U
FEATURES
DESCRIPTIO
PolyPhaseTM Valley Current Mode Controller
TheLTC®3709isasingleoutput,dualphase,synchronous
step-down switching regulator. The controller uses a
constant on-time, valley current control architecture to
deliver very low duty cycles without requiring a sense
resistor. Operating frequency is selected by an external
resistor and is compensated for variations in input supply
voltage.Aninternalphase-lockedloopallowstheLTC3709
to be synchronized to an external clock.
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■
Synchronizable to an External Clock with PLL
■
Coincident or Ratiometric Tracking
■
Sense Resistor Optional
■
2% to 90% Duty Cycle at 200kHz
■
tON(MIN) < 100ns
■
True Remote Sensing Differential Amplifier
■
High Efficiency at Both Light and Heavy Loads
■
Power Good Output Voltage Monitor
0.6V ±1% Reference
Adjustable Current Limit
A TRACK pin is provided for tracking or sequencing the
output voltage among several LTC3709 chips or an
LTC3709 and other DC/DC regulators. Soft-start is ac-
■
■
■
Programmable Soft-Start and Operating Frequency
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
32-Lead (5mm ×U5mm) QFN Package
complished using an external timing capacitor.
■
■
■
Faultprotectionisprovidedbyanoutputovervoltagecom-
parator and an optional short-circuit shutdown timer. The
current limit level is user programmable. A wide supply
rangeallowsvoltagesashighas31Vtostepdownto0.6V.
, LTC and LT are registered trademarks of Linear Technology Corporation.
No RSENSE and PolyPhase are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6476589, 6144194, 5847554, 6177678,
6304066, 6580258, 6674274, 6462525, 6593724.
APPLICATIO S
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Notebook Computers
Power Supply for DSP, ASIC, Graphic Processors
■
U
TYPICAL APPLICATIO
High Efficiency Dual Phase 1.5V/30A Step-Down Converter
1µF
PGND1
1µF
5V
PGND2
4.7µF
324k
10Ω
V
IN
4.5V TO 28V
10µF
35V
×3
1µF
V
DRV
I
47.5k
10k
CC
CC ON
TG1
Efficiency and Power Loss
HAT2168H
HAT2165H
TRACK
RNG
FCB
V
100
95
90
85
80
75
70
65
60
55
50
10
9
8
7
6
5
4
3
2
1
0
0.22µF
V
= 12V
IN
BOOST1
SW1
SENSE1
1.22µH
100k
+
0.1µF
PGOOD
EFFICIENCY
RUN/SS
BG1
–
EXTLPF
INTLPF
SENSE1
3.32k
PGND1
100nF
680pF
LTC3709
I
TH
V
IN
20k
HAT2168H
HAT2165H
SGND
TG2
BOOST2
SW2
POWER LOSS
0.22µF
10k
1.22µH
V
1.5V
30A
OUT
V
FB
+
DIFFOUT
SENSE2
15k
0.01
0.1
1
10
100
BG2
–
–
LOAD CURRENT (A)
330µF
2.5V
×4
+
V
V
OS
SENSE2
PGND2
+
3709 TA01b
OS
3709 TA01a
3709f
1