LTC3823
Fast No RSENSETM Step-Down
Synchronous DC/DC Controller
with Differential Output Sensing,
Tracking and PLL
FEATURES
DESCRIPTION
n Wide VIN Range: 4.5V to 36V
n ±0.67%, 0.6V Reference Voltage
n Output Voltage Tracking Capability
n True Remote Sensing Differential Amplifier
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: 30μA
n Power Good Output Voltage Monitor Tracks the
Reference Input Pin
n Available in (5mm × 5mm) 32-Lead QFN and
28-Lead SSOP Narrow Packages
APPLICATIONS
n Distributed Power Systems
n Server Power Supplies
The LTC®3823 is a synchronous step-down switching regu-
lator controller with true remote differential output sensing
and output voltage up/down tracking capability. Its advanced
functions and high accuracy reference are ideal for powering
high performance server, ASIC and computer memory
systems.
The LTC3823 uses a constant on-time, valley current
mode control architecture to deliver very low duty fac-
tors without requiring a sense resistor. The operating
frequency is selected by an external resistor and is com-
pensated 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 compara-
tor and input undervoltage lockout. The regulator current
limit is user programmable. A wide supply range allows
voltages as high as 36V to be stepped down to as low as
a 0.6V output. When using remote sense, output voltages
up to 3.3V can be developed, and up to 90% of VIN without
remote sense. Power supply sequencing is accomplished
using an external soft-start timing capacitor.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No RSENSE is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5481178, 5847554,
6580258, 6304066, 6476589, 6774611.
TYPICAL APPLICATION
0.01μF
10k
0.1μF
1000pF 10k
VOUT
9.5k
3k
High Efficiency Step-Down Converter
PGOOD
ION
68k
VIN
PLLFLTR
PLLIN
TRACK/SS
ITH
LTC3823
TG
SW
BOOST
SGND
RUN
VON
VRNG
VDIFFOUT
INTVCC
DRVCC
BG
SENSE+
SENSE–
Si4884
1.8μH
0.22μF
+
CMDSH-3
Si4874
10μF
B340A
PGND
VFB
VOUTSENSE+
VOUTSENSE–
3823 TA01a
VIN
10μF 5V TO 28V
35V
s3
VOUT
2.5V
10A
180μF
4V
s2
Efficiency and Power Loss
vs Load Current
97
10
96
VIN = 5V
VOUT = 2.5V
95 FIGURE 12 CIRCUIT
94
EFFICIENCY
1
93
92
POWER LOSS
91
90
0.1
89
88
87
0.1
1
LOAD CURRENT (A)
0.01
10
3823 TA01b
3823fd
1
