1

LTC3701

3701fa

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

2-Phase, Low Input Voltage,

Dual Step-Down DC/DC Controller

The LTC

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 460

µA 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.

s

Out-of-Phase Controllers Reduce Required

Input Capacitance

s

True PLL for Frequency Locking or Frequency

Adjustment

s

Operating Frequency Range: 300kHz to 750kHz

s

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

at Light Loads

s

Output Overvoltage Protection

s

Low Quiescent Current: 460

µA

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

Figure 1. High Efficiency 2-Phase 550kHz Dual Step-Down Converter

Efficiency vs Load Current

+

SGND

PLLLPF

PGATE1

PGND

PGATE2

PGOOD

EXTCLK/MODE

1

3

2

4

6

5

7

8

16

15

14

13

12

11

10

9

LTC3701

220pF

220pF

10k

10k

D1, D2: IR10BQ015

L1, L2: LQN6C-4R7

M1, M2: FDC638P

78.7k

80.6k

100k

169k

L1

4.7

µH

47

µF

10

µF

47

µF

0.03

Ω

0.03

Ω

L2

4.7

µH

D1

M1

M2

D2

3701 F01a

2.5V

2A

2.5V TO 9.8V

1.8V

2A

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode is a registered trademark of Linear Technology Corporation.

LOAD CURRENT (mA)

60

80

100

50

70

90

1

100

1000

10000

3701 F01b

40

10