LTC3878_15 Datasheet, PDF (1/26 Pages) Linear Technology – Fast, Wide Operating Range No RSENSE Step-Down DC/DC Controller

Features
n _{Wide VIN Range: 4V to 38V}
n _{±1% 0.8V Voltage Reference}
n _{Extremely Fast Transient Response}
n _{tON(MIN): 43ns}
n _{No RSENSE™ Valley Current Mode Control}
n _{Stable with Low ESR Ceramic COUT}
n _{Supports Smooth Start-Up Into Pre-Biased Output}
n _{Optimized for High Step-Down Ratios}
n _{Pin Compatible with the LTC1778 (No EXTVCC Pin)}
n _{Power Good Output Voltage Monitor}
n _{Dual N-Channel MOSFET Synchronous Drive}
n _{Adjustable Switching Frequency}
n _{Programmable Current Limit with Foldback}
n _{Output Overvoltage Protection}
n _{Small 16-Pin Narrow SSOP Package}
Applications
n _{Distributed Power Systems}
n _{Embedded Computing}
n _{Communications Infrastructure}
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. No R_SENSE is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6100678, 6580258, 5847554, 6304066.
LTC3878
Fast, Wide Operating Range
No R_SENSE Step-Down
DC/DC Controller
Description
The LTC^®3878 is a synchronous step-down switching
DC/DC controller optimized for high switching frequency
and fast transient response. The constant on-time valley
current mode architecture allows for a wide input range,
including very low duty factor operation. No external sense
resistor or slope compensation is required. The LTC3878
is pin compatible with the LTC1778 in applications that do
not use EXTV_CC while offering better efficiency. Consult
with the factory to verify compatibility.
Operating frequency is set by an external resistor and
compensated for variations in V_IN to offer excellent line
stability. Discontinuous mode operation provides high
efficiency during light load conditions. A forced continu-
ous control pin allows the user to reduce noise and RF
interference. Safety features include output overvoltage
protection and programmable current limit with foldback.
Soft-start capability for supply sequencing is accomplished
through an external timing capacitor. The current limit is
user programmable.
The LTC3878 allows operation from 4V to 38V at the input
and from 0.8V to 90% V_IN at the output. The LTC3878 is
available in a small 16-pin narrow SSOP package.
Typical Application
High Efficiency Step-Down Converter
0.1µF
I_ON
RUN/SS V_IN
220pF
12.1k
TG
LTC3878
I_TH
SW
SGND BOOST
FCB
INTV_CC
BG
PGOOD PGND
V_RNG
V_FB
432k
RJK0305
0.56µH
0.22µF
4.7µF
RJK0330
5.11k
10k
V_IN
4.5V TO 28V
10µF
V_OUT
1.2V
15A
330µF
s2
3878 TA01a
Efficiency vs Load Current
100
90 DISCONTINUOUS
MODE
80
70
60
CONTINUOUS
MODE
50
40
30
20
10
0
0.01
V_IN = 12V
V_OUT = 1.2V
SW FREQ = 400kHz
FIGURE 7 CIRCUIT
0.1
1
10
LOAD CURRENT (A)
100
3878 G07
3878fa