LTC3770_15 Datasheet, PDF (1/24 Pages) Linear Technology – Fast No RSENSE Step-Down Synchronous Controller with Margining, Tracking and PLL

FEATURES
n _{Wide VIN Range: 4V to 32V}
n _{±0.67% 0.6V Reference Voltage}
n _{Output Voltage Tracking Capability}
n _{Programmable Margining}
n _{Sense Resistor Optional}
n _{True Current Mode Control}
n _{2% to 90% Duty Cycle at 200kHz}
n _{tON(MIN) ≤ 100ns}
n _{Phase-Locked Loop Frequency Synchronization}
n _{Powerful Dual N-Channel MOSFET Driver}
n _{Adjustable Cycle-by-Cycle Current Limit}
n _{Adjustable Switching Frequency}
n _{Programmable Soft-Start}
n _{Current Foldback Protection (Disabled at Start-Up)}
n _{Output Overvoltage Protection}
n _{Micropower Shutdown: IQ < 30μA}
n _{Power Good Output Voltage Monitor}
Tracks the Reference Input Pin
n _{Available in (5mm × 5mm) QFN and 28-Lead}
SSOP Packages
APPLICATIONS
n _{Distributed Power Systems}
n _{Server Power Supply}
LTC3770
Fast No R_SENSE^TM Step-Down
Synchronous Controller with
Margining, Tracking and PLL
DESCRIPTION
The LTC^®3770 is a synchronous step-down switching
regulator controller with output voltage up/down tracking
capability and voltage margining. Its advanced functions
and high accuracy reference are ideal for powering
high performance server, ASIC and computer memory
systems.
The LTC3770 uses a constant on-time, valley current
mode control architecture to deliver very low duty factors
without requiring a sense resistor. The operating frequency
is selected by an external resistor and is compensated for
variations in input supply voltage. An internal phase-locked
loop allows the IC to be synchronized to an external
clock.
Fault protection is provided by an overvoltage comparator
and input undervoltage lockout. The regulator current
limit is user programmable. A wide supply range allows
voltages as high as 32V to be stepped down to as low as
a 0.6V output. Power supply sequencing is accomplished
using an external soft-start timing capacitor.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
R_SENSE is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 5481178, 5487554, 6580258, 6304066, 6476589,
6774611.
TYPICAL APPLICATION
High Efficiency Step-Down Converter
0.01μF
10k
0.1μF
1000pF ^10k
V_OUT
10k
82k
PGOOD I_ON
MARGIN _VIN
PLLFLTR _TG
PLLIN
SW
TRACK/SS
I_TH
BOOST
LTC3770
SGND
RUN
V_ON
V_RNG
INTV_CC
DRV_CC
BG
SENSE⁺
V_{REFOUTSENSE–}
V_REFIN
MPGM
PGND
V_FB
68k
0.22μF
Si4884
1.8μH
CMDSH-3
V_IN
10μF ^{5V TO 28V}
35V
x3
V_OUT
2.5V
+
10A
180μF
4V
x2
Si4874
B340A
4.7μF
95.3k
30.1k
3770 TA01
Efficiency and Power Loss vs Load Current
100
V_IN = 5V
95 VOUT = 2.5V
90
EFFICIENCY
85
80
75
70
POWER LOSS
65
60
55
50
0.01
0.1
1
LOAD CURRENT (A)
10
1
0.1
0.01
10
3770 TA01b
3770fc
1