2-Phase, Low Input Voltage,
Dual Step-Down DC/DC Controller
s Out-of-Phase Controllers Reduce Required
s True PLL for Frequency Locking or Frequency
s Operating Frequency Range: 300kHz to 750kHz
s Wide VIN Range: 2.5V to 10V
s Constant Frequency Current Mode Architecture
s Low Dropout: 100% Duty Cycle
s Power Good Output Voltage Monitor
s Internal Soft-Start Circuitry
s Selectable Burst Mode®/Pulse Skipping Operation
at Light Loads
s Output Overvoltage Protection
s Low Quiescent Current: 460µA
s 0.8V ±2% Voltage Reference
s Small 16-Lead Narrow SSOP Package
s One or Two Lithium-Ion Powered Applications
s Notebook and Handheld Computers
s Personal Digital Assistants
s Portable Instruments
s Distributed DC Power Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
The LTC®3701 is a 2-phase dual constant frequency cur-
rent mode step-down DC/DC controller providing excellent
load and line regulation. Power loss and noise due to ESR
of the input capacitor are minimized by operating the two
controller output stages out-of-phase.
The LTC3701 provides a 0.8V ±2% voltage reference and
consumes only 460µA of quiescent current. To further
maximize the life of a battery source, the external
P-channel MOSFET is turned on continuously in dropout
(100% duty cycle).
Switching frequency is internally set at 550kHz, allowing
the use of small inductors and capacitors. For noise sen-
sitive applications, the LTC3701 can be externally syn-
chronized using its phase-locked loop. The frequency can
also be externally set from 300kHz to 750kHz by applying
a voltage to the PLLLPF pin. Burst Mode operation is inhib-
ited during synchronization or when the EXTCLK/MODE
pin is pulled low to reduce noise and RF interference.
The LTC3701 contains independent internal soft-start
circuitry for each controller. Other features include a
power good output voltage monitor and output overvolt-
age and short-circuit protection.
The LTC3701 is available in a small footprint 16-lead nar-
row SSOP package.
4 SGND LTC3701 PGND 13
2.5V TO 9.8V
D1, D2: IR10BQ015 L1, L2: LQN6C-4R7 M1, M2: FDC638P
Figure 1. High Efficiency 2-Phase 550kHz Dual Step-Down Converter
Efficiency vs Load Current
VIN = 4.2V VIN = 3.3V
VIN = 6V
70 VIN = 8.4V
VOUT = 2.5V
10 100 1000
LOAD CURRENT (mA)