Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - voltage regulator - special purpose QSOP 16

General Description

The MAX1917 provides a complete power-manage-

ment solution for DDR memory. It contains a synchro-

nous buck controller and an amplifier to generate

1/2V

DDR

voltage for VTT and VTTR. The VTT and VTTR

voltages are maintained within 1% of 1/2V

DDR

. The

controller operates in synchronous rectification mode to

ensure balanced current sourcing and sinking capabili-

ty of up to 25A. With a shutdown current of less than

5µA, the MAX1917 is the best choice for low-power

notebook applications, as well as servers and desktop

computers. An all N-FET design optimizes efficiency.

The MAX1917 can also be used for generating V

DDR

and as a general-purpose step-down controller with

variable switching frequency as high as 1MHz with few

additional components.

The MAX1917 uses Maxim’s proprietary Quick-PWM™

architecture for fast transient response up to 96% effi-

ciency, and the smallest external components. Output

current monitoring is achieved without sense resistors

by monitoring the bottom FET’s drain-to-source voltage.

The current-limit threshold is programmable through an

external resistor. The MAX1917 comes in a space-sav-

ing 16-pin QSOP package.

Applications

Features

♦ 25A Sourcing and Sinking Current

♦ Automatically Sets VTT to 1/2V

DDR

♦ VTT and VTTR Within 1% of 1/2V

DDR

♦ Smallest Output Capacitors

♦ 4.5V to 14V (or 28V with Resistor-Divider) Input

Voltage Range

♦ 1.5V to 3.6V Input DDR Range

♦ 200kHz/300kHz/400kHz/550kHz Preset Switching

Frequencies

♦ Variable Switching Frequency of Up to 1MHz

♦ Overcurrent Protection Without Current-Sense

Resistor

♦ Internal Soft-Start

♦ VTTR Reference Sources and Sinks Up to 25mA

♦ Quick-PWM Control for Fastest Loop Response

♦ Up to 96% Efficiency

♦ 16-Pin QSOP Package

MAX1917

Tracking, Sinking and Sourcing, Synchronous Buck

Controller for DDR Memory and Termination Supplies

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

MAX1917

(2.5V TO 15V)

POK

VDDR

EN/HSD

POK

DDR

V+

REF

ILIM

FSEL

GND

BST

PGND

VTT

VTTR

OUT

VTTR

(4.5V TO 14V)

Typical Operating Circuit

19-2335; Rev 1; 6/02

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART TEMP RANGE PIN-PACKAGE

MAX1917EEE -40°C to +85°C 16 QSOP

EN/HSD LX

BST

PGND

V+

VTTR

TOP VIEW

MAX1917EEE

QSOP

DDR

POK

FSEL

VTT

ILIM

REF

GND

Pin Configuration

Quick-PWM is a trademark of Maxim Integrated Products, Inc.

DDR Memory Power

Supply

Processor or DSP Core

Supply

AGTL Bus Termination

Supply

Notebook Computers

Desktop Computers

Storage

Networking Systems

Summary of content (18 pages)

PAGE 1
9-2335; Rev 1; 6/02 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies Applications DDR Memory Power Supply Processor or DSP Core Supply AGTL Bus Termination Supply Notebook Computers Desktop Computers Storage Networking Systems Features ♦ 25A Sourcing and Sinking Current ♦ Automatically Sets VTT to 1/2VDDR ♦ VTT and VTTR Within 1% of 1/2VDDR ♦ Smallest Output Capacitors ♦ 4.5V to 14V (or 28V with Resistor-Divider) Input Voltage Range ♦ 1.5V to 3.
PAGE 2
MAX1917 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies ABSOLUTE MAXIMUM RATINGS V+ to GND ..............................................................-0.3V to +15V EN/HSD to GND .....................................................-0.3V to +16V VL to GND ................................................................-0.3V to +6V PGND to GND .......................................................-0.3V to +0.3V VTT, DDR, POK to GND .....................
PAGE 3
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies (V+ = 12V, VEN/HSD = VDDR = 2.5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0, ILIM = VL, PGND = LX = POK = GND, BST = VL. Specifications are for TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise specified.) PARAMETER Thermal Shutdown CONDITIONS MIN Rising temperature, typical hysteresis = 15°C TYP MAX UNITS +160 °C 1.
PAGE 4
MAX1917 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies ELECTRICAL CHARACTERISTICS (continued) (V+ = 12V, VEN/HSD = VDDR = 2.5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0, ILIM = VL, PGND = LX = POK = GND, BST = VL. Specifications are for TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise specified.) PARAMETER Logic VL Level CONDITIONS FSEL = VL MIN TYP MAX VL - 0.
PAGE 5
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies (V+ = 12V, VEN/HSD = VDDR = 2.5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0, ILIM = VL, PGND = LX = POK = GND, BST = VL. Specifications are for TA = -40°C to +85°C, unless otherwise specified.) (Note 2) PARAMETER Reference UVLO CONDITIONS V+ = VL = 5V MIN TYP MAX UNITS 1.5 1.7 V 0 1.8 V 49.5 50.
PAGE 6
ELECTRICAL CHARACTERISTICS (continued) (V+ = 12V, VEN/HSD = VDDR = 2.5V, CVL = 4.7µF, CVTTR = 1µF, CREF = 0.22µF, VFSEL = 0, ILIM = VL, PGND = LX = POK = GND, BST = VL. Specifications are for TA = -40°C to +85°C, unless otherwise specified.) (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS POK Output Low Level ISINK = 2mA 0.4 %VDDR /2 %VDDR /2 V POK Output High Leakage VPOK = 5.
PAGE 7
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies FREQUENCY vs. INPUT VOLTAGE 500 IOUT = 0.1A 450 534 532 530 528 526 400 524 350 CIRCUIT OF FIGURE 3 5 7 9 11 13 15 -40 -20 40 60 80 LOAD REGULATION WITHOUT DROOP RESISTOR MAX1917 toc10 1.32 1.7 1.5 1.3 1.1 0.9 1.29 VIN = 5V VIN = 12V 1.28 1.27 1.26 1.25 5 7 9 11 13 9 11 13 15 1.29 VIN = 5V 1.27 1.25 1.23 VIN = 2.5V 1.21 1.19 1.17 1.22 15 7 VIN = 12V 1.31 1.
PAGE 8
Typical Operating Characteristics (continued) (V+ = 12V, VOUT = 1.25V, TA = +25°C, unless otherwise noted.) INDUCTOR PEAK AND VALLEY CURRENT vs. INPUT VOLTAGE AT CURRENT LIMIT CURRENT LIMIT vs.
PAGE 9
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies ILIM 1-SHOT FSEL VTT ON TIME COMPUTE Q TRIG 5µA BST S TON TRIG POK DH Q Q R 1-SHOT Σ LX DDR VL DL EN/HSD PGND VTT V+ VL 5V REF 2V REF REF GND MAX1917 VTTR _______________________________________________________________________________________ 9 MAX1917 Functional Diagram
PAGE 10
MAX1917 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies Detailed Description fS = Internal Linear Regulator (VL) An internal regulator produces the 5V supply (VL) that powers the PWM controller, MOSFET driver, logic, reference, and other blocks within the IC. This 5V lowdropout (LDO) linear regulator supplies up to 35mA for MOSFET gate-drive and external loads. For supply voltages between 4.5V and 5.5V, connect VL to V+.
PAGE 11
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies Overcurrent Protection The current-limit circuit employs a unique “valley” current-sensing algorithm that uses the on-state resistance of the low-side MOSFET as a current-sensing element. If the current-sense signal is greater than the currentlimit threshold, the PWM is not allowed to initiate a new cycle.
PAGE 12
MAX1917 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies high-side FET from turning on until DL is fully off. There must be a low-resistance, low-inductance path from the DL driver to the MOSFET gate in order for the adaptive dead-time circuit to work properly. Otherwise, the sense circuitry in the MAX1917 interprets the MOSFET gate as off while there is actually still charge left on the gate.
PAGE 13
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies VL R2 5.1kΩ VL R3 20kΩ 2.5V 3 POK 5.5V TO 14V 10 V+ 2 VDDR C9 0.47µF/25V C8 0.47µF/10V SHDN Q3 2N7002K VL 1 7 5 POK VL V+ DDR BST MAX1917 DH EN/HSD LX REF DL ILIM PGND FSEL VTT GND VTTR 11 D1 CMPSH-3 14 C3 4.7µF 10V C4 0.47µF 10V 15 C2 2 x 330µF 6V C1 1µF 6.3V VIN Q1 IRF7463 2mΩ 16 2.5V 12 1.25V AT 7A VOUT L1 0.
PAGE 14
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies MAX1917 Typical Application Circuits (continued) R2 10kΩ VL Q3 Si1029X SHDN VL R3 20kΩ` 2.5V 3 POK 5.5V TO 14V V+ 10 2 VDDR C9 0.47µF/25V 1 7 VL C8 0.47µF/10V 5 POK VL V+ BST MAX1917 DDR EN/HSD REF DH LX DL ILIM PGND 6 FSEL VTT 11 14 15 D1 CMPSH-3 C3 2.2µF 10V C4 0.22µF 10V C1 1µF 6.3V C2 330µF 6V Q1 IRF7811W 1.25V AT 3.5A 16 2.5V 12 L1 1.
PAGE 15
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies Firmly establish the input voltage range and maximum load current before choosing a switching frequency and inductor operating point (ripple current ratio). The primary design trade-off is in choosing a good switching frequency and inductor operating point, and the following four factors dictate the rest of the design: 1) Input Voltage Range.
PAGE 16
MAX1917 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies The actual microfarad capacitance value required relates to the physical size needed to achieve low ESR, as well as to the chemistry of the capacitor technology. As a result, the capacitor is usually selected by ESR and voltage rating rather than by capacitance value (this is true of tantalums, OS-CONs, POSCAPs, and other electrolytics).
PAGE 17
Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies ILOAD = ILIMIT(HIGH) + (LIR / 2) (ILOAD(MAX)) where I LIMIT(HIGH) is the maximum valley current allowed by the current-limit circuit, including threshold tolerance and on-resistance variation. If short-circuit protection without overload protection is enough, a normal ILOAD value can be used for calculating component stresses.
PAGE 18
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) QSOP.EPS MAX1917 Tracking, Sinking and Sourcing, Synchronous Buck Controller for DDR Memory and Termination Supplies Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.