MAX8855EVKIT [MAXIM]

Fully Protected Against Overcurrent, Short Circuit, and Overtemperature;


型号：	MAX8855EVKIT
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Fully Protected Against Overcurrent, Short Circuit, and Overtemperature
文件：	总11页 (文件大小：258K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

19-5582; Rev 0; 10/10

MAX8855 Evaluation Kit

Evluates:MAX85

General Description

Features

♦ 2.35V to 3.6V Input Supply Voltage Range

♦ 1.8V at 5A Output (Step-Down Regulator 1)

♦ 1.2V at 5A Output (Step-Down Regulator 2)

The MAX8855 evaluation kit (EV kit) is a fully assembled

and tested circuit board that contains all the compo-

nents necessary to evaluate the performance of the

MAX8855. The device is a high-efficiency dual step-

down regulator. The EV kit is powered from a 2.35V to

3.6V DC supply.

♦ 180° Out-of-Phase Operation Reduces Input

Ripple Current

The EV kit is capable of delivering 1.8V at 5A from out-

put 1 and 1.2V at 5A from output 2. The device switch-

ing frequency is set to 1MHz and the two outputs

switch 180° out-of-phase. High-efficiency, internal dual

nMOS design keeps the board cool under heavy loads.

The voltage-mode control architecture and the high-

bandwidth (> 15MHz typ) voltage-error amplifier allow a

type III compensation scheme to be utilized to achieve

fast response under both line and load transients, and

also allow for ceramic output capacitors.

♦ All-Ceramic-Capacitor Design

♦ High Efficiency

♦ 27mΩ On-Resistance Internal MOSFETs

♦ Fully Protected Against Overcurrent, Short

Circuit, and Overtemperature

♦ REFIN on One Channel for Tracking or External

Reference

Programmable soft-start reduces input inrush current.

Two enable inputs allow the turning on/off of each output

individually, resulting in great flexibility for system-level

designs. A reference input facilitates output-voltage

tracking applications.

♦ Integrated Boost Diodes

♦ Programmable Switching Frequency from 0.5MHz

to 2MHz

♦ Adjustable Outputs from 0.6V to (0.9 x V )

Ordering Information

♦ Individual Enable Inputs and PWRGD Outputs

♦ Low-Cost Solution

PART

TYPE

MAX8855EVKIT+

EV Kit

♦ Fully Assembled and Tested

+Denotes lead(Pb)-free and RoHS-compliant.

Component Suppliers

SUPPLIER

Murata Electronics North America, Inc.

TDK Corp.

PHONE

WEBSITE

www.murata-northamerica.com

www.component.tdk.com

www.tokoam.com

770-436-1300

847-803-6100

847-297-0070

TOKO America, Inc.

Note: Indicate that you are using the MAX8855 when contacting these component suppliers.

Component List

DESIGNATION

QTY

DESCRIPTION

DESIGNATION

QTY

DESCRIPTION

2200pF 10ꢀ, 50V X7R ceramic

capacitor (0402)

TDK C1005X7R1H222K

Murata GRM155R71H222K

22µF 20ꢀ, 6.3V X5R ceramic

capacitors (1206)

TDK C3216X5R0J226M

Murata GRM31CR60J226K

C1, C23

0.22µF 10ꢀ, 16V X5R ceramic

capacitor (0402)

TDK C1005X5R1C224K

0.1µF 10ꢀ, 16V X7R ceramic

capacitors (0402)

TDK C1005X7R1C104K

Murata GRM155R71C104K

C2, C3, C4, C6,

C16, C17, C20

680pF 10ꢀ, 50V X7R ceramic

capacitors (0402)

TDK C1005X7R1H681K

Murata GRM1555R71H681K

Not installed, capacitor

C9, C15

0.022µF 10ꢀ, 25V X7R ceramic

capacitor (0402)

C12

TDK C1005X7R1E223K

________________________________________________________________ Maxim Integrated Products

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX8855 Evaluation Kit

Component List (continued)

DESIGNATION

QTY

DESCRIPTION

DESIGNATION

QTY

DESCRIPTION

47pF 5ꢀ, 50V C0G ceramic

capacitors (0402)

TDK C1005C0G1H470J

Murata GRM1555C1H470J

0.47µH 20ꢀ inductors

TOKO FDV0630-R47M

L1, L2

C10, C14

R1, R19

Not installed, resistors (0402)

0Ω resistor (0402)

560pF 10ꢀ, 50V X7R ceramic

capacitors (0402)

Murata GRM155R71H561K

R3, R4, R5, R12,

R13, R18

C11, C13

C18, C19

10kΩ 1ꢀ resistors (0402)

R7, R10

R8, R9

R11

4.99kΩ 1ꢀ resistor (0402)

8.06kΩ 1ꢀ resistors (0402)

210Ω 1ꢀ resistors (0402)

10Ω 1ꢀ resistor (0402)

20kΩ 1ꢀ resistors (0402)

49.9Ω 1ꢀ resistor (1206)

Dual step-down regulator

(32 TQFN-EP*)

Maxim MAX8855ETJ+

47µF 20ꢀ, 6.3V X5R ceramic

capacitors (1206)

TDK C3216X5R0J476M

Murata GRM31CR60J476K

1000pF 10ꢀ, 50V X7R ceramic

capacitors (0402)

TDK C1005X7R1H102K

Murata GRM155R71H102K

R14, R15

R16

C21, C22

FSYNC

JU1, JU3

JU2

Not installed, BNC connector

3-pin headers

Evluates:MAX85

—

Shunts, 2-position

2-pin header

—

PCB: MAX8855 EVALUATION KIT+

*EP = Exposed pad.

5) Connect the positive lead of a voltmeter to the

OUT1 pad and the negative lead of the voltmeter to

the PGND1 pad of the EV kit.

Quick Start

Recommended Equipment

• MAX8855 EV kit

6) Connect the positive lead of the other voltmeter to

the OUT2 pad and the negative lead of the volt-

meter to the PGND2 pad of the EV kit.

• Adjustable DC power supply capable of supplying

3.6V at up to 7A

• Two electronic loads capable of sinking 5A (e.g.,

HP 6060B)

7) Connect the positive lead of a 5A electronic load to

the OUT1 pad and the negative lead of the elec-

tronic load to the PGND1 pad of the EV kit.

• Two voltmeters (DMM)

8) Connect the positive lead of the second 5A elec-

tronic load to the OUT2 pad and the negative lead

of the electronic load to the PGND2 pad of the EV

kit.

Procedure

The EV kit is fully assembled and tested. Follow these

steps to verify board operation. Do not turn on the

power supply until all connections are completed:

9) Turn on the power supply.

1) Set the DC power supply in the 2.35V to 3.6V range

and turn off the power supply.

10) Verify that V

is 1.8V throughout the 2.35V to

OUT1

3.6V input voltage range.

2) Connect the positive lead of the power supply to

the IN pad and the negative pad to the PGND pad

of the EV kit.

11) Verify that V

is 1.2V throughout the 2.35V to

OUT2

3.6V input voltage range.

12) Turn on both electronic loads. Repeat steps 10 and 11.

3) Verify that JU1 and JU2 do not have a shunt installed.

4) Verify that a shunt is across pins 1 and 2 of jumper

JU3.

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

0V and V

- 1.6V to the REFIN pad to set the FB1 reg-

Detailed Description

ulation voltage. To use the internal 0.6V reference,

place a shunt on JU3 pins 1-2 to connect REFIN to SS1

(see Table 3). When the IC is shut down, REFIN is

pulled to GND through an internal 335Ω.

The MAX8855 EV kit evaluates the MAX8855 dual step-

down regulator. The regulator switching frequency is

set to 1MHz by default and can be adjusted from

0.5MHz to 2MHz. The EV kit is designed to operate

from a DC power supply that can provide 2.35V to 3.6V

and 7A of current.

If additional filtering is required, a 0.22µF capacitor can

be added (C5).

Regulator 1 (OUT1) is configured as a step-down regu-

lator set to 1.8V and can provide 5A of current.

Regulator 2 (OUT2) is configured as a step-down regu-

lator set to 1.2V and can provide 5A of current.

Tracking

The EV kit can be configured as a tracking circuit (com-

monly used in DDR supply applications). To configure

the EV kit for tracking, install resistors R1 and R19.

These resistors form a voltage-divider that sets the

tracking ratio. Remove R6 so OUT1 regulates to the

REFIN voltage. Set jumper JU3 to pins 2-3. Refer to the

MAX8855 IC data sheet for more information on track-

ing circuits and component selection.

The EV kit output voltages are adjustable from a mini-

mum of 0.6V to a maximum of 0.9 x V . Refer to the

Setting the Output Voltage section of the MAX8855 IC

data sheet to set other output voltages in this range for

OUT1

and V

OUT2

Sequencing

To enable sequencing on the EV kit, place a shunt on

pins 1-2 of JU1. In this configuration, OUT1 remains

disabled until OUT2 is enabled and reaches regulation.

When OUT1 is disabled, OUT2 shuts down at the same

time. Refer to the MAX8855 IC data sheet for more

information on sequencing.

Enable (EN1 and EN2)

The EV kit provides separate enable inputs, EN1 and

EN2, to individually control or sequence the output volt-

ages. The enable signals EN1 and EN2 are pulled up to

by resistors R3 and R18, respectively. To enable

OUT1, remove the shunt from JU1; to disable OUT1,

place the shunt on JU1 pins 2-3. To enable OUT2,

remove the shunt from JU2; to disable OUT2, place the

shunt on JU2 pins 1-2.

Switching Frequency and

Synchronization (FSYNC)

The enable inputs can also be driven from an external

logic signal. With the JU1 and JU2 shunts removed,

connect the EN1 signal to pin 2 of JU1, and the EN2

signal to pin 2 of JU2. The device enable pins are

active-high and TTL compatible.

The EV kit operates from an internal 0.5MHz to 2MHz

switching frequency set by R5. The EV kit’s switching

frequency is set to 1MHz by default. To change the

switching frequency, replace R5 with a resistor value

calculated as shown in the Setting the Switching

Frequency section of the MAX8855 IC data sheet.

Power-Good Outputs (PWRGD_)

Regulator 1 and 2 provide power-good output signals

that indicate when the corresponding output is in regu-

lation. PWRGD1 and PWRGD2 are open-drain outputs

The EV kit can also be synchronized to an external

clock from 250kHz to 2.5MHz by connecting the clock

to the FSYNC BNC input. The external clock must have

a duty cycle between 10ꢀ and 90ꢀ to ensure the regu-

lators operate 180° out-of-phase.

that are pulled up to V

by a 20kΩ resistor. The

power-good, open-drain output for regulator 1

(PWRGD1) is high impedance when V ≥ 0.54V

REFIN

Thermal-Overload Protection

Thermal-overload protection limits the total power dissi-

pation of the device. Internal thermal sensors monitor

the internal die temperature of each regulator. When this

temperature exceeds +165°C, the corresponding regu-

lator is shut down, allowing the IC to cool. The thermal

sensor turns the regulator on after the junction tempera-

ture cools by 20°C. In a continuous thermal-overload

condition, this results in a pulsed output.

and V

≥ 0.9 x V

. PWRGD1 is low when V

FB1

REFIN REFIN

< 0.54V, EN1 is low, V

or V

is below V

, the

IN1

UVLO

thermal-overload protection is activated, or when V

FB1

< 0.9 x V

REFIN

PWRGD2 is high impedance when V

≥ 0.54V and

SS2

≥ 0.9 x V . PWRGD2 is low when V

< 0.54V,

FB2

SS2

EN2 is low, V or V

is below V , the thermal-over-

UVLO

IN2

load protection is activated, or when V

< 0.9 x V

FB2

SS2

External Reference Input (REFIN)

The EV kit provides an option for an external reference

input. To use an external reference, remove the shunt

from JU3 and connect an external reference between

Current Limit

The EV kit provides both peak and valley current limits

to achieve robust short-circuit protection.

_______________________________________________________________________________________

MAX8855 Evaluation Kit

single input supply between 2.35V and 3.6V. VDL can

optionally be powered separately from the power input.

When powering VDL separately, remove resistor R2

and connect a 2.35V to 3.6V supply to the VDL pad on

the EV kit.

VDL Supply

VDL is the low-side gate-drive supply for the device.

The high-side gate drive (BST_) and the IC supply volt-

age (V ) are also derived from VDL. In the EV kit’s

default configuration, VDL is connected to IN through

the 0Ω resistor R2, allowing the EV kit to operate from a

Table 1. Jumper JU1 Functions

Table 3. Jumper JU3 Functions

SHUNT

LOCATION

REFIN CONNECTED

SHUNT

LOCATION

FUNCTION

EN1 CONNECTED TO

REGULATOR 1

Internal reference

(0.6V)

Not installed

(default)

Pulled up to V

through R3

1-2 (default)

2-3

SS1

Enabled

OUT2 through R1

OUT1 tracks V

OUT2

Sequencing: OUT1 is

enabled when OUT2

is in regulation

1-2

2-3

PWRGD2

GND

External reference

(0V to V - 1.6V)

connected to REFIN

pad

Not installed

—

Disabled

Evluates:MAX85

Table 2. Jumper JU2 Functions

SHUNT

LOCATION

EN2 CONNECTED TO

REGULATOR 2

Not installed

(default)

Pulled up to V

through R18

Enabled

1-2

GND

Disabled

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Figure 1. MAX8855 EV Kit Schematic

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Figure 2. MAX8855 EV Kit Component Placement Guide—Component Side

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Figure 3. MAX8855 EV Kit PCB Layout—Component Side

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Figure 4. MAX8855 EV Kit PCB Layout—Layer 2

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Figure 5. MAX8855 EV Kit PCB Layout—Layer 3

_______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Figure 6. MAX8855 EV Kit PCB Layout—Solder Side

10 ______________________________________________________________________________________

MAX8855 Evaluation Kit

Evluates:MAX85

Revision History

REVISION REVISION

PAGES

CHANGED

DESCRIPTION

NUMBER

DATE

10/10

Initial release

—

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.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11

Maxim is a registered trademark of Maxim Integrated Products, Inc.

MAX8855EVKIT [MAXIM]

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