Rainbow-electronics MAX17000 Manual de usuario descargar pdf (Pagina 16)

MAX17000

Complete DDR2 and DDR3 Memory

Power-Management Solution

16 ______________________________________________________________________________________

Detailed Description

The MAX17000 complete DDR solution comprises a

step-down controller, a source-sink LDO regulator, and a

reference buffer. Maxim’s proprietary Quick-PWM pulse-

width modulator in the MAX17000 is specifically

designed for handling fast load steps while maintaining a

relatively constant operating frequency and inductor

operating point over a wide range of input voltages. The

Quick-PWM architecture circumvents the poor load-tran-

sient timing problems of fixed-frequency current-mode

PWMs, while also avoiding the problems caused by

widely varying switching frequencies in conventional con-

stant-on-time and constant-off-time PWM schemes.

Figure 1 is the MAX17000 standard application circuit

and Figure 2 is the MAX17000 functional diagram.

The MAX17000 includes a ±2A source-sink LDO regu-

lator for the memory termination rail. The source-sink

regulator features a dead band that either sources or

sinks, ideal for the fast-changing short-period loads

presenting in memory termination applications. This

feature also reduces the VTT output capacitance

requirement down to 1μF, though load-transient

response can still require higher capacitance values

between 10μF and 20μF.

The reference buffer sources and sinks ±3mA, generating

a reference rail for use in the memory controller and

memory devices.

TON

ON/OFF

BST

7V TO 20V

VDDQ

+1.8V OR 1.5V

PGND1

CSL

SENSE

FBA

FBB

VTTI

VTT

VTTR

0.33μF

PGND2

VTTI

VTTR

VTTS

+5V

SLP_S3#

VTT

+1V TO + 2.5V

VTT = VDDQ/2

STDBY

SHDN

SKIP

REFIN

PGOOD2

+5V

PGOOD1

AGND

FB OPTIONS:

1. CONNECT FB TO 5V FOR FIXED +1.8V.

2. CONNECT FB TO GND FOR FIXED +1.5V.

3. USE FB RESISTOR-DIVIDER FOR ADJUSTABLE

OUTPUT VOLTAGES.

TON

CSH

5V V

OVP

AGND

PGND

BST

0.1μF

100kΩ

10Ω

VDD

1μF

VCC

1μF

AGND

PGND

AGND

PGND

OUT

MAX17000

VTTR = VDDQ/2

Figure 1. MAX17000 Standard Application Circuit

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 30 31

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