MAX1711EVKIT_技术文档

19-1647; Rev 1; 6/00

MAX1711 Voltage Positioning Evaluation Kit

General Description

Features

The MAX1711 evaluation kit (EV kit) demonstrates the

high-power, dynamically adjustable notebook CPU appli-

cation circuit with voltage positioning. Voltage positioning

decreases CPU power consumption and reduces output

capacitance requirements. This DC-DC converter steps

down high-voltage batteries and/or AC adapters, gener-

o Output Voltage Positioned

o Reduces CPU Power Consumption

o Lowest Number of Output Capacitors (only 4)

o High Speed, Accuracy, and Efficiency

o Fast-Response Quick-PWM™ Architecture

o 7V to 24V Input Voltage Range

o 0.925V to 2V Output Voltage Range

o 12A Load-Current Capability (14.1A peak)

o 550kHz Switching Frequency

ating a precision, low-voltage CPU core V rail.

CC

The MAX1711 EV kit provides a digitally adjustable

0.925V to 2V output voltage from a 7V to 24V battery input

range. It delivers sustained output current of 12A and

14.1A peaks, operating at a 550kHz switching frequency,

and has superior line- and load-transient response. The

MAX1711 EV kit is designed to accomplish output voltage

transitions in a controlled amount of time with limited input

surge current.

o Power-Good Output

o 24-Pin QSOP Package

This EV kit is a fully assembled and tested circuit board.

o Low-Profile Components

Ordering Information

o Fully Assembled and Tested

PART

TEMP. RANGE

IC PACKAGE

MAX1711EVKIT

0°C to +70°C

24 QSOP

Quick-PWM is a trademark of Maxim Integrated Products.

Component List

DESIGNATION QTY

DESCRIPTION

DESIGNATION QTY

DESCRIPTION

10µF, 25V ceramic capacitors

Taiyo Yuden TMK432BJ106KM,

Tokin C34Y5U1E106Z, or

United Chemi-Con/Marcon

THCR50E1E106ZT

100mA Schottky diode

Central Semiconductor CMPSH-3

D2

1

C1–C4, C20

5

1A Schottky diode

Motorola MBRS130LT3,

International Rectifier 10BQ040, or

Nihon EC10QS03

D3

1

220µF, 2.5V, 25mΩ low-ESR polymer

capacitors

Panasonic EEFUEOE 221R

C5, C6,

C7, C16

4

1

200mA switching diode

Central Semiconductor CMPD2838

D4

J1

1

10µF, 6.3V ceramic capacitor

Taiyo Yuden JMK325BJ106MN or

TDK C3225X5R1A106M

Scope-probe connector

Berg Electronics 33JR135-1

C8

JU1

1

0

2-pin header

Not installed

C9

1

0

0.1µF ceramic capacitor

JU3–9

0.01µF ceramic capacitor

(not installed)

C10

0.47µH power inductor

Sumida CEP 125 series 4712-T006

L1

1

C11, C12

C13

2

0

1

0.22µF ceramic capacitors

0.1µF ceramic capacitor (not installed)

470pF ceramic capacitor

1µF ceramic capacitor

N-channel MOSFET (SO-8)

International Rectifier IRF7811 or

IRF7811A

N1

1

C14

C15

C18

1000pF ceramic capacitor

N-channel MOSFET (SO-8)

International Rectifier IRF7805 or

IRF7811 or IRF 7811A

N2, N3

2

2A Schottky diode

SGS-Thomson STPS2L25U or

Nihon EC31QS03L

D1

1

________________________________________________________________ Maxim Integrated Products

1

For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.

MAX1711 Voltage Positioning Evaluation Kit

Component Suppliers

Component List (continued)

DESIGNATION QTY

DESCRIPTION

SUPPLIER

Central

PHONE

FAX

N-channel MOSFETs

Motorola 2N7002 or

Central Semiconductor 2N7002

N4, N5

(not installed)

516-435-1110

516-435-1824

0

Semiconductor

Dale-Vishay

Fairchild

402-564-3131

408-721-2181

402-563-6418

408-721-1635

R1

R2

1

0

1

20Ω 5% resistor

Not installed

International

Rectifier

310-322-3331

310-322-3332

R3

1MΩ 5% resistor

100kΩ 5% resistor

100kΩ 1% resistor

140kΩ 1% resistor

1kΩ 5% resistor

100Ω 5% resistor

R4

Kemet

408-986-0424

602-303-5454

847-843-7500

714-373-7939

619-661-6835

617-259-0300

708-956-0666

408-573-4150

847-390-4373

408-432-8020

408-986-1442

602-994-6430

847-843-2798

714-373-7183

619-661-1055

617-259-9442

708-956-0702

408-573-4159

847-390-4428

408-434-0375

R6

Motorola

Nihon

R9

R10

R11

Panasonic

Sanyo

0.005Ω 1%, 1W resistor

Dale WSL-2512-R005F

SGS-Thomson

Sumida

Taiyo Yuden

TDK

R12

1

R13

R14

1

1MΩ 1% resistor

10kΩ 1% resistor

DIP-10 dip switch

SW1

Tokin

Momentary switch, normally open

Digi-Key P8006/7S

Note: Please indicate that you are using the MAX1711 when

contacting these component suppliers.

SW2

U1

1

0

MAX1711EEG (24-pin QSOP)

5) Turn on battery power prior to +5V bias power; oth-

erwise, the output UVLO timer will time out and the

FAULT latch will be set, disabling the regulator until

+5V power is cycled or shutdown is toggled (press

the RESET button).

U2

Exclusive-OR gate (5-Pin SSOP)

Toshiba TC4S30F

(not installed)

None

1

Shunt (JU1)

MAX1711 PC board

MAX1711 data sheet

6) Observe the output with the DMM and/or oscillo-

scope. Look at the LX switching-node and MOSFET

gate-drive signals while varying the load current.

Recommended Equipment

• 7V to 24V, >20W power supply, battery, or notebook

AC adapter

• DC bias power supply, 5V at 100mA

• Dummy load capable of sinking 14.1A

• Digital multimeter (DMM)

• 100MHz dual-trace oscilloscope

Quick Start

1) Ensure that the circuit is connected correctly to the

supplies and dummy load prior to applying power.

Detailed Description

This 14A buck-regulator design is optimized for a

550kHz frequency and output voltage settings around

1.6V. At V

= 1.6V, inductor ripple is approximately

OUT

35%, with a resulting pulse-skipping threshold at rough-

ly I = 2.2A.

LOAD

Setting the Output Voltage

Select the output voltage using the D0–D4 pins. The

MAX1711 uses an internal 5-bit DAC as a feedback

resistor voltage divider. The output voltage can be digi-

tally set from 0.925V to 2V using the D0–D4 inputs.

Switch SW1 sets the desired output voltage. See Table 1.

2) Ensure that the shunt is connected at JU1 (SHDN =

V

).

CC

3) Set switch SW1 per Table 1 to achieve the desired

output voltage.

4) Connect +5V or ground to the AC Present pad to dis-

able the transition detector circuit. See the Dynamic

Output Voltage Transitions section for more informa-

tion regarding the transition detector circuit.

2

_______________________________________________________________________________________

MAX1711 Voltage Positioning Evaluation Kit

tial output voltage 20mV high, and R12 (5mΩ) causes

Table 1. MAX1710/1711 Output Voltage

Adjustment Settings

the output voltage to drop with increasing load (60mV

or about 4% of 1.6V at 12A).

OUTPUT

VOLTAGE (V)

Setting the output voltage high allows a larger step-

down when the output current increases suddenly, and

regulating at the lower output voltage under load allows

a larger step-up when the output current suddenly

decreases. Allowing a larger step size means that the

output capacitance can be reduced and the capaci-

tor’s ESR can be increased. If voltage positioning is not

used, one additional output capacitor is required to

meet the same transient specification.

D4

D3

D2

D1

D0

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

2.00

1.95

1.90

1.85

1.80

1.75

Reduced power consumption at high load currents is an

additional benefit of voltage positioning. Because the

output voltage is reduced under load, the CPU draws

less current. This results in lower power dissipation in

the CPU, though some extra power is dissipated in R12.

For a 1.6V, 12A nominal output, reducing the output

voltage 2.75% (1.25% - 4%) gives an output voltage of

1.556V and an output current of 11.67A. So the CPU

power consumption is reduced from 19.2W to 18.16W.

The additional power consumption of R12 is 5mΩ ·

11.7A²= 0.68W, and the overall power savings is 19.2 –

(18.16 + 0.68) = 0.36W. In effect, 1W of CPU dissipation

is saved and the power supply dissipates much of the

savings, but both the net savings and the transfer of dis-

sipation away from the hot CPU are beneficial.

1.70

1.65

1.60

1.55

1.50

1.45

1.40

1.35

1.30

Shutdown

1.275

1.250

1.225

1.200

1.175

1.150

1.125

1.100

1.075

1.050

1.025

1.000

0.975

0.950

0.925

Shutdown

Dynamic Output Voltage Transitions

If the DAC inputs (D0–D4) are changed, the output volt-

age will change accordingly. However, under some cir-

cumstances, the output voltage transition may be slow-

er than desired. All transitions to a higher voltage will

occur very quickly, with the circuit operating at the cur-

rent limit set by the voltage at the ILIM pin. Transitions

to a lower output voltage require the circuit or the load

to sink current. If SKIP is held low (PFM mode), the cir-

cuit won’t sink current, so the output voltage will

decrease only at the rate determined by the load cur-

rent. This is often acceptable, but some applications

require output voltage transitions to be completed with-

in a set time limit.

Powering CPUs with Intel’s Geyserville technology is

such an application. The specification requires that out-

put voltage transitions occur within 100µs after a DAC

code change. This fast transition timing means that the

regulator circuit must sink as well as source current.

Voltage Positioning

The MAX1711 EV kit uses voltage positioning to mini-

mize the output capacitor requirements of the Intel

Coppermine CPU’s transient voltage specification

(-7.5% to +7.5%). The output voltage is initially set

slightly high (1.25%) and then allowed to regulate lower

as the load current increases. R13 and R14 set the ini-

The simplest way of meeting this requirement is to use

the MAX1711’s fixed-frequency PWM mode (set SKIP

high), allowing the regulator to sink or source currents

equally. This EV kit is shipped with SKIP set high.

Although this results in a V

quiescent current to

DD

20mA or more, depending on the MOSFETs and

_______________________________________________________________________________________

3

MAX1711 Voltage Positioning Evaluation Kit

switching frequency used, it is often an acceptable

choice. A similar but more clever approach is to use

PWM mode only during transitions. This approach

allows the regulator to sink current when needed and to

operate with low quiescent current the rest of the time,

but it requires that the system know when the transitions

will occur. Any system with a changing output voltage

must know when its output voltage changes occur.

Usually, it is the system that initiates the transition, either

by driving the DAC inputs to new levels or by selecting

new DAC inputs with a digital mux. While it is possible

for the regulator to recognize transitions by watching for

DAC code changes, the glue logic needed to add that

feature to existing controllers is unnecessarily compli-

cated (refer to the MAX1710/MAX1711 data sheet,

Figure 10). It is easier to use the chipset signal that

selects DAC codes at the mux, or some other system

signal to inform the regulator that a code change is

occurring.

Accurate measurement of output ripple and load-tran-

sient response invariably requires that ground clip

leads be completely avoided and that the probe hat be

removed to expose the GND shield, so the probe can

be plugged directly into the jack. Otherwise, EMI and

noise pickup will corrupt the waveforms.

Most benchtop electronic loads intended for power-

supply testing are unable to subject the DC-DC con-

verter to ultra-fast load transients. Emulating the supply

current di/dt at the CPU VCORE pins requires at least

10A/µs load transients. One easy method for generat-

ing such an abusive load transient is to solder a MOS-

FET, such as an MTP3055 or 12N05 directly across the

scope-probe jack. Then drive its gate with a strong

pulse generator at a low duty cycle (10%) to minimize

heat stress in the MOSFET. Vary the high-level output

voltage of the pulse generator to adjust the load current.

To determine the load current, you might expect to

insert a meter in the load path, but this method is pro-

hibited here by the need for low resistance and induc-

tance in the path of the dummy-load MOSFET. There

are two easy alternative methods for determining how

much load current a particular pulse-generator ampli-

tude is causing. The first and best is to observe the

inductor current with a calibrated AC current probe,

such as a Tektronix AM503. In the buck topology, the

load current is equal to the average value of the induc-

tor current. The second method is to first put on a static

dummy load and measure the battery current. Then,

connect the MOSFET dummy load at 100% duty

momentarily, and adjust the gate-drive signal until the

battery current rises to the appropriate level (the MOS-

FET load must be well heatsinked for this to work with-

out causing smoke and flames).

For easy modification, the MAX1711 EV kit is designed

to use an external chipset signal to indicate DAC code

transitions (install U2, R2, C10, C13; short JU9 and cut

JU10). This signal connects to the EV kit’s AC Present

pad and should have 5V logic levels. Logic edges on

AC Present are detected by exclusive-OR gate U2,

which generates a 60µs pulse on each edge (deter-

mined by R2 and C10). These pulses drive SKIP, allow-

ing the regulator to sink current during transitions.

Because U2 is powered by V

(5V), the signal con-

CC

nected to AC Present must have 5V logic levels so that

U2’s output pulses will be symmetric for positive- and

negative-going transitions. If the signal that’s available

to drive AC Present has a different logic level, either

level-shift the signal or lift U2’s supply pin and power it

from the appropriate supply rail.

In addition to controlling SKIP, the pulses from U2 have

two other functions, which are optional. U2’s output dri-

ves the gates of two small-signal MOSFETs, N4 and N5

(not installed). N4 is used to temporarily reduce the cir-

cuit’s current limit, in effect soft-starting the regulator.

This reduces the battery surge current, which otherwise

would discharge (upward transitions) or charge (down-

ward transitions) the regulator input (battery) at a rate

determined by the regulator’s maximum current limit. N5

pulls down on PGOOD during transitions, indicating that

the output voltage is in transition.

Efficiency Measurements and

Effective Efficiency

Testing the power conversion efficiency POUT/PIN fair-

ly and accurately requires more careful instrumentation

than might be expected. One common error is to use

inaccurate DMMs. Another is to use only one DMM,

and move it from one spot to another to measure the

various input/output voltages and currents. This second

error usually results in changing the exact conditions

applied to the circuit due to series resistance in the

ammeters. It’s best to get four 3-1/2 digit, or better,

DMMs that have been recently calibrated, and monitor

Load-Transient Measurement

One interesting experiment is to subject the output to

large, fast load transients and observe the output with

an oscilloscope. This necessitates careful instrumenta-

tion of the output, using the supplied scope-probe jack.

V

, V

, I

, and I

simultaneously, using

LOAD

BATT

OUT BATT

separate test leads directly connected to the input and

output PC board terminals. Note that it’s inaccurate to

test efficiency at the remote V

and ground termi-

OUT

4

_______________________________________________________________________________________

MAX1711 Voltage Positioning Evaluation Kit

nals, because doing this incorporates the parasitic

resistance of the PC board output and ground buses in

the measurement (a significant power loss).

cy is the efficiency required of a nonvoltage-positioned

circuit to equal the total dissipation of a voltage-posi-

tioned circuit for a given CPU operating condition.

Calculate effective efficiency as follows:

Remember to include the power consumed by the +5V

bias supply when making efficiency calculations:

• Start with the efficiency data for the positioned circuit

(V , I , V

, I

).

IN IN OUT OUT

V

×I

OUT LOAD

Efficiency =

• Model the load resistance for each data point

(R = V / I ).

(V

×I

)+(5V ×I

)

BIAS

BATT BATT

LOAD

OUT OUT

The choice of MOSFET has a large impact on efficiency

performance. The International Rectifier MOSFETs

used were of leading-edge performance for the 12A

application at the time this kit was designed. However,

the pace of MOSFET improvement is rapid, so the lat-

est offerings should be evaluated.

• Calculate the output current that would exist for each

data point in a nonpositioned application (I

R

LOAD

= V / R

NP

, where V = 1.6V in this example).

NP

LOAD

✕

• Effective efficiency = (V

I

) / (V

I ) = cal-

IN

NP

IN

culated nonpositioned power output divided by the

measured voltage-positioned power input.

Once the actual efficiency data has been obtained,

some work remains before an accurate assessment of

a voltage-positioned circuit can be made. As dis-

cussed in the Voltage Positioning section, a voltage-

positioned power supply can dissipate additional

power while reducing system power consumption. For

this reason, we use the concept of effective efficiency,

which allows the direct comparison of a positioned

and nonpositioned circuit’s efficiency. Effective efficien-

• Plot the efficiency data point at the current I

.

NP

The effective efficiency of the voltage-positioned circuit

will be less than that of the nonpositioned circuit at light

loads where the voltage-positioned output voltage is

higher than the nonpositioned output voltage. It will be

greater than that of the nonpositioned circuit at heavy

loads where the voltage-positioned output voltage is

lower than the nonpositioned output voltage.

_______________________________________________________________________________________

5

MAX1711 Voltage Positioning Evaluation Kit

Jumper and Switch Settings

Table 2. Jumper JU1 Functions

(Shutdown Mode)

Table 4. Jumper JU6 Functions

(Fixed/Adjustable Current-Limit Selection)

SHUNT

LOCATION

MAX1711

SHUNT

LOCATION

CURRENT-LIMIT

THRESHOLD

SHDN PIN

ILIM PIN

OUTPUT

MAX1711 enabled

Shutdown mode,

Installed

Connected to V

CC

100mV

Connected to

Installed

V

CC

Connected to GND via an

external resistor divider,

R6/R9. Refer to the Pin

Description ILIM section in

the MAX1711 data sheet for

more information.

Connected to

GND

Adjustable

between 50mV

and 200mV

Not Installed

V

OUT

= 0

Not Installed

Table 3. Jumpers JU3/JU4/JU5 Functions

(Switching-Frequency Selection)

SHUNT LOCATION

FREQUENCY

(kHz)

TON PIN

JU3

JU4

JU5

Table 5. Jumpers JU9/JU10 Functions

(FBS and FB Integrator Disable Selection)

Not

Connected

Installed

200

400

550

300

Installed Installed to V

CC

SHUNT LOCATION

Not

Installed

Not

Connected

SKIP PIN

Installed

Installed to REF

JU9

JU10

Installed

Not Installed Connected to V

CC

Not

Connected

to GND

Installed

Not

Installed Installed

Not Installed

Installed

Connected to the output of U2

Not Not

Installed Installed Installed

Floating

IMPORTANT: Don’t change the operating frequency without

first recalculating component values because the frequency

has a significant effect on the peak current-limit level, MOSFET

heating, preferred inductor value, PFM/PWM switchover point,

output noise, efficiency, and other critical parameters.

Table 6. Troubleshooting Guide

SYMPTOM

POSSIBLE PROBLEM

SOLUTION

Power-supply sequencing: +5V

bias supply was applied first.

Circuit won’t start when power is applied.

Press the RESET button.

Replace the MOSFET.

Output overvoltage due to

shorted high-side MOSFET.

Output overvoltage due to load

recovery overshoot.

Reduce the inductor value, raise the switching

frequency, or add more output capacitance.

Circuit won’t start when RESET is pressed,

+5V bias supply cycled.

Overload condition.

Remove the excessive load.

Troubleshoot the power stage. Are the DH and DL

Broken connection, bad MOSFET,

or other catastrophic problem.

gate-drive signals present? Is the 2V V

sent?

pre-

REF

Add a bulk electrolytic bypass capacitor across

the benchtop power supply, or substitute a real

battery.

On-time pulses are erratic or have

unexpected changes in period.

VBATT power source has poor

impedance characteristic.

6

_______________________________________________________________________________________

MAX1711 Voltage Positioning Evaluation Kit

Figure 1. MAX1711 Voltage Positioning EV Kit Schematic

_______________________________________________________________________________________

7

MAX1711 Voltage Positioning Evaluation Kit

Figure 1. MAX1711 Voltage Positioning EV Kit Schematic (continued)

8

_______________________________________________________________________________________

MAX1711 Voltage Positioning Evaluation Kit

1.0"

Figure 2. MAX1711 Voltage Positioning EV Kit Component

Placement Guide—Component Side

Figure 3. MAX1711 Voltage Positioning EV Kit Component

Placement Guide—Solder Side

1.0"

Figure 4. MAX1711 Voltage Positioning EV Kit PC Board

Layout—Component Side

Figure 5. MAX1711 Voltage Positioning EV Kit PC Board

Layout—Internal GND Plane (Layer 2)

_______________________________________________________________________________________

9

MAX1711 Voltage Positioning Evaluation Kit

1.0"

Figure 7. MAX1711 Voltage Positioning EV Kit PC Board

Layout—Solder Side

Figure 6. MAX1711 Voltage Positioning EV Kit PC Board

Layout—Internal GND Plane (Layer 3)

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Printed USA

is a registered trademark of Maxim Integrated Products.


型号：	MAX1711EVKIT
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Voltage-Positioning Evaluation Kit for the MAX1711 电压定位评估板MAX1711\n
文件：	总10页 (文件大小：266K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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