LTC3776EUF 查看數據表（PDF） - Linear Technology

零件编号

产品描述 (功能)

生产厂家

LTC3776EUF

Dual 2-Phase, No RSENSE™, Synchronous Controller for DDR/QDR Memory Termination

Linear Technology 

FEATURES

■ No Current Sense Resistors Required

■ Out-of-Phase Controllers Reduce Required

Input Capacitance

■ VOUT2 Tracks 1/2 VREF

■ Symmetrical Source/Sink Output Current

Capability (VOUT2)

■ Spread Spectrum Operation (When Enabled)

■ Wide VIN Range: 2.75V to 9.8V

■ Constant Frequency Current Mode Operation

■ 0.6V ±1.5% Voltage Reference (VOUT1)

■ Low Dropout Operation: 100% Duty Cycle

■ True PLL for Frequency Locking or Adjustment

■ Internal Soft-Start Circuitry

■ Power Good Output Voltage Monitor

■ Output Overvoltage Protection

■ Micropower Shutdown: IQ = 9µA

■ Tiny Low Profile (4mm × 4mm) QFN and Narrow

SSOP Packages

U

APPLICATIO S

■ DDR, DDR II and QDR Memory

■ SSTL, HSTL Termination Supplies

■ Servers, RAID Systems

■ Distributed DC Power Systems

LTC3776

Dual 2-Phase, No RSENSETM,

Synchronous Controller for

DDR/QDR Memory Termination

DESCRIPTIO

The LTC®3776 is a 2-phase dual output synchronous step-

down switching regulator controller for DDR/QDR memory

termination applications. The second controller regulates

its output voltage to 1/2 VREF while providing symmetrical

source and sink output current capability.

The No RSENSE constant frequency current mode architec-

ture eliminates the need for sense resistors and improves

efficiency. Power loss and noise due to the ESR of the

input capacitance are minimized by operating the two

controllers out of phase.

The switching frequency can be programmed up to 750kHz,

allowing the use of small surface mount inductors and ca-

pacitors. For noise sensitive applications, the LTC3776

switching frequency can be externally synchronized from

250kHz to 850kHz, or can be enabled for spread spectrum

operation. Forced continuous operation reduces noise and

RF interference. Soft-start for VOUT1 is provided internally

and can be extended using an external capacitor.

The LTC3776 is available in the tiny thermally enhanced

(4mm × 4mm) QFN package or 24-lead SSOP narrow

package.

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

is a registered trademark 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, 5929620, 6144194, 6580258,

6304066, 6611131, 6498466, patent pending on Spread Spectrum.

TYPICAL APPLICATIO

High Efficiency, 2-Phase, DDR Memory (VDDQ and VTT) Supplies

VIN

3.3V

VIN

SENSE1+ SENSE2+

10µF

×2

1.5µH

TG1

TG2

SW1

SW2

LTC3776

BG1

BG2

1.5µH

PGND

PGND

(VDDQ)VOUT1

2.5V

4A

187k

47µF

470pF

59k

VREF

VFB1

VFB2

ITH1

ITH2

SGND

15k

2200pF

6.2k

VOUT2 (VTT)

1.25V

±4A

47µF

3776 TA01a

Efficiency vs Load Current

100

90

80

70

60

50

40

30

20

10

0

10

FIGURE 14 CIRCUIT

CHANNEL 2 (VIN = 3.3V)

CHANNEL 1 (VIN = 5V)

CHANNEL 1 (VIN = 3.3V)

CHANNEL 2 (VIN = 5V)

100

1000

LOAD CURRENT (mA)

10000

3776 TA01b

3776f

1

Share Link: