n Wide VIN Range: 4V to 38V
n ±1% 0.6V 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 in Pre-Biased Output
n Optimized for High Step-Down Ratios
n Adjustable Output Voltage Soft-Start or Tracking
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 16-Pin MSOP and 3mm × 3mm QFN Packages
n Distributed Power Systems
n Embedded Computing
n Communications Infrastructure
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
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, 6100678, 6580258, 5847554, 6304066.
Fast, Wide Operating
Range No RSENSE
The LTC®3879 is a synchronous step-down switching
regulator 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. System ﬂex-
ibility is offered through a user-programmable soft-start pin
and independent RUN pin. The voltage ramping soft-start
function can be programmed with a capacitor or made to
track an external reference source.
Operating frequency is set by an external resistor and
compensated for variations in VIN 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.
The current limit is user programmable.
The LTC3879 allows operation from 4V to 38V at the input
and from 0.6V to 90% VIN at the output. The LTC3879 is
available in a small 16-pin thermally enhanced MSOP or
3mm × 3mm QFN packages.
High Efﬁciency Step-Down Converter
4.5V TO 28V
Efﬁciency vs Load Current
VIN = 12V
VOUT = 1.2V
SW FREQ = 400kHz
FIGURE 10 CIRCUIT
LOAD CURRENT (A)