Datasheet > 34712

34712

更新时间： 2024-02-17 08:46:21

品牌	Logo	应用领域
飞思卡尔 - FREESCALE		开关双倍数据速率
页数	文件大小	规格书
23页	473K
描述
3.0A 1.0MHz Fully Integrated DDR Switch-Mode Power Supply

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数据手册

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34712 数据手册

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

INTRODUCTION

In modern microprocessor/memory applications, address

commands and control lines require system level termination

to a voltage (V_TT) equal to 1/2 the memory supply voltage

(V_DDQ). Having the termination voltage at midpoint, the power

supply insures symmetry for switching times. Also, a

continuous current. It provides protection against output over

current, overvoltage, undervoltage, and overtemperature

conditions. It also protects the system from short circuit

events. It incorporates a power-good output signal to alert the

host when a fault occurs.

reference voltage (V_REF) that is free of any noise or voltage

variations is needed for the DDR SDRAM input receiver,

V_REFis also equal to 1/2 V_DDQ. Varying the V_REFvoltage will

effect the setup and hold time of the memory. To comply with

DDR requirements and to obtain best performance, V_TTand

V_REFneed to be tightly regulated to track 1/2 V_DDQacross

voltage, temperature, and noise margins. V_TTshould track

any variations in the DC V_REFvalue (V_TT= V_REF+/- 40 mV),

(See Figure 4) for a DDR system level diagram.

For boards that support the Suspend-To-RAM (S3) and

the Suspend-To-Disk (S5) states, the 34712 offers the STBY

and the SD pins respectively. Pulling any of these pins low,

puts the IC in the corresponding state.

By integrating the control/supervisory circuitry along with

the Power MOSFET switches for the buck converter into a

space-efficient package, the 34712 offers a complete, small-

size, cost-effective, and simple solution to satisfy the needs

of DDR memory applications.

The 34712 supplies the V_TTand a buffered V_REFoutput.

To ensure compliance with DDR specifications, the V_DDQline

is applied to the VREFIN pin and divided by 2 internally

through a precision resistor divider. This internal voltage is

then used as the reference voltage for the V_TToutput. The

same internal voltage is also buffered to give the V_REF

voltage at the VREFOUT pin for the application to use without

the need for an external resistor divider. The 34712 provides

the tight voltage regulation and power sequencing/tracking

required along with handling the DDR peak transient current

requirements. Buffering the V_REFoutput helps its immunity

against noise and load changes.

Besides DDR memory termination, the 34712 can be used

to supply termination for other active buses and graphics card

memory. It can be used in Netcom/Telecom applications like

servers. It can also be used in desktop motherboards, game

consoles, set top boxes, and high end high definition TVs.

DDQ

The 34712 utilizes a voltage mode synchronous buck

switching converter topology with integrated low R_DS(ON)

(45 mΩ) N-channel power MOSFETs to provide a V_TTvoltage

with an accuracy of less than ±2.0 %. It has a programmable

switching frequency that allows for flexibility and optimization

over the operating conditions and can operate at up to

1.0 MHz to significantly reduce the external components size

and cost. The 34712 can sink and source up to 3.0 A of

REF

BUS

DDR Memory Input Receiver

DDR Memory Controller

Figure 4. DDR System Level Diagram

FUNCTIONAL PIN DESCRIPTION

REFERENCE VOLTAGE INPUT (VREFIN)

FREQUENCY ADJUSTMENT INPUT (FREQ)

The 34712 will track 1/2 the voltage applied at this pin.

The buck converter switching frequency can be adjusted

by connecting this pin to an external resistor divider between

VDDI and GND pins. The default switching frequency (FREQ

pin connected to ground, GND) is set at 1.0 MHz.

REFERENCE VOLTAGE OUTPUT (VREFOUT)

This is a buffered reference voltage output that is equal to

1/2 V_REFIN. It has a 10.0 mA current drive capability. This

output is used as the V_REFvoltage rail and should be filtered

against any noise. Connect a 0.1 µF, 6 V low ESR ceramic

filter capacitor between this pin and the GND pin and

between this pin and V_DDQrail. V_REFOUTis also used as the

reference voltage for the buck converter error amplifier.

SIGNAL GROUND (GND)

Analog ground of the IC. Internal analog signals are

referenced to this pin voltage.

34712

Analog Integrated Circuit Device Data

Freescale Semiconductor

1...7 8 91011 12 13...23

中文翻译

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与34712相关器件

型号	品牌	获取价格	描述	数据表
347120002	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120003	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120101	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120103	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120300	ITT	获取价格	THUMB/PUSHWHEEL SWITCH-4SWITCHES, BINARY CODED HEXADECIMAL, 0.1A, 28VDC, PANEL MOUNT
347120301	ITT	获取价格	THUMB/PUSHWHEEL SWITCH-4SWITCHES, BINARY CODED HEXADECIMAL, 0.1A, 28VDC, PANEL MOUNT
347120302	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120303	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120N00	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S
347120N01	ITT	获取价格	Thumb/Pushwheel Switch, 4 Switches, Binary Coded Hexadecimal, 16 Positions, 0.1A, 28VDC, S

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