LTC3709 Datasheet, PDF (1/24 Pages) Linear Technology – Fast 2-Phase, No RSENSE Synchronous DC/DC Controller with Tracking/Sequencing

LTC3709
Fast 2-Phase, No R_SENSE^TM,
Synchronous DC/DC Controller
with Tracking/Sequencing
FEATURES
DESCRIPTIO
■ _PolyPhase^TM _{Valley Current Mode Controller}
■ _{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}
■ _{Programmable Soft-Start and Operating Frequency}
■ _{Output Overvoltage Protection}
■ _{Optional Short-Circuit Shutdown Timer}
■ _{32-Lead (5mm × 5mm) QFN Package}
U
APPLICATIO S
■ _{Notebook Computers}
■ _{Power Supply for DSP, ASIC, Graphic Processors}
The LTC^®3709 is a single output, dual phase, 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. An internal phase-locked loop allows the LTC3709
to be synchronized to an external clock.
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-
complished using an external timing capacitor.
Fault protection is provided by an output overvoltage com-
parator and an optional short-circuit shutdown timer. The
current limit level is user programmable. A wide supply
range allows voltages as high as 31V to step down to 0.6V.
, 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.
TYPICAL APPLICATIO
High Efficiency Dual Phase 1.5V/30A Step-Down Converter
5V
4.7µF
10Ω
324k
1µF
47.5k
10k
100k
0.1µF
3.32k
100nF
680pF
20k
10k
15k
V_CC DRV_CC I_ON
TRACK
TG1
V_RNG
FCB
BOOST1
PGOOD
SW1
SENSE1⁺
RUN/SS
BG1
EXTLPF SENSE1^–
INTLPF
PGND1
I_TH LTC3709
SGND
V_FB
DIFFOUT
V_OS–
V_OS+
TG2
BOOST2
SW2
SENSE2⁺
BG2
SENSE2^–
PGND2
1µF
1µF
PGND1
PGND2
0.22µF
HAT2168H
10µF
35V
×3
1.22µH
HAT2165H
V_IN
4.5V TO 28V
0.22µF
HAT2168H
HAT2165H
V_IN
1.22µH
V_OUT
1.5V
30A
+ 330µF
2.5V
×4
Efficiency and Power Loss
100
10
V_IN = 12V
95
9
90
8
EFFICIENCY
85
7
80
6
75
5
70
4
65
3
POWER LOSS
60
2
55
1
50
0.01
0.1
1
10
LOAD CURRENT (A)
0
100
3709 TA01b
3709 TA01a
3709f
1