MAX1645EVSYSTEM [MAXIM]

Evaluation System for the MAX1645/MAXSMBus ; 评估系统MAX1645 / MAXSMBus\n


型号：	MAX1645EVSYSTEM
厂家：	MAXIM INTEGRATED PRODUCTS
描述：	Evaluation System for the MAX1645/MAXSMBus 评估系统MAX1645 / MAXSMBus\n
文件：	总8页 (文件大小：132K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

19-1306; Rev 0; 3/98

MAXSMBus

2-Wire Interface Board

________________General Description

____________________________Features

ꢀ SMBus-Compatible 2-Wire Interface

ꢀ SMBus Suspend Output

MAXSMBus is an interface between an IBM-compatible

PC and System Management Bus (SMBus™)-

compatible serial-interface devices such as tempera-

ture monitors, voltage regulators, or A/D converters

(ADCs). The MAXSMBus interface board is connected

between the PC parallel port and the device under test,

converting parallel data into 2-wire, open-drain serial

data. The board is provided for use with selected

Maxim products and is not intended to replace com-

mercially available SMBus hardware. MAXSMBus is

shipped with a companion EV kit board, including all

relevant software.

ꢀ Two SMBus Alert Inputs

ꢀ Overvoltage Fault Protection

ꢀ PC Parallel Port Interface

_______________Ordering Information

PART

BOARD TYPE

MAXSMBus

Companion Board for SMBus EV Kits

Maxim SMBus Interface Board

____________________________Component List

___MAXSMBus Functionality Check

Follow these steps to verify that the MAXSMBus inter-

face board is functioning properly. All necessary soft-

ware is supplied on a disk with the companion EV kit.

Instructions for operating the software are included in

the EV kit manual.

DESIGNATION QTY

DESCRIPTION

0.1µF ceramic capacitors

3.3µF, 25V tantalum capacitors

1N5235B zener diode, 6.8V

1N5229B zener diode, 4.3V

1N4148 small-signal diode

DB25 right-angle plug

C1, C2, C3

C4–C9

1) Connect a +9VDC supply (+7V minimum, +20V

maximum) to the MAXSMBus interface board at the

terminals labeled POS9 and GND in the lower left

corner of the board.

Not installed

2) Use a digital voltmeter to verify that the oval pad

labeled POS5 is +5V (+4.75V minimum, +5.25V

maximum). Also verify that the pads labeled

SBDAT1, SBCLK1, SBSUS1, ALERT1, and ALERT2

are above +4V.

2x10 right-angle male header

R1, R2, R3,

R10, R11

47kΩ 5ꢀ resistors

R4–R7

R8, R9

4.7kΩ 5ꢀ resistors

3) If these DC voltages are correct, MAXSMBus pass-

es the functionality test.

1kΩ 5ꢀ resistors

74HC05 hex open-collector inverter

74HC04 hex inverter

_______________Detailed Description

The MAXSMBus interface board provides all of the

interface signals necessary to interface an IBM PC-

compatible computer with an SMBus-compliant device.

A DB25 right-angle plug connects to the computer

(Table 1). The companion board plugs into a 20-pin

dual-row right-angle header at the edge of the board

(Table 2). Alternatively, connection can be made by

soldering wires to the oval pads as appropriate. This

allows the companion board to be placed in an environ-

mental chamber for evaluation over temperature.

74HC08 quad AND gate

74HC74 dual D flip-flop

+5V, 100mA regulator

LM78L05ACM

MAX865EUA (8-pin µMAX)

MAX367CWN (18-pin SO)

PC board

NONE

Refer to the documentation of the companion Maxim EV

kit for quick start and operating instructions.

SMBus is a trademark of Intel Corp.

________________________________________________________________ Maxim Integrated Products

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.

MAXSMBus

2-Wire Interface Board

Power Supply

The interface board is powered by a 78L05 linear regu-

lator. The companion board can draw about 20mA of

+5V power through the circuit protector. Companion

boards that require more power must provide their own

regulator. The unregulated input to the 78L05 is avail-

able on the right-angle header.

Bus Driving Circuitry

A 74HC05 open-drain inverter (U1) is used to pull down

the SMBus interface signals. The 74HC08 (U3),

74HC74 (U4), and 74HC04 (U2) buffer the signal to the

IBM PC and provide the capability to mask the ALERT

interrupts, detect an externally generated start condi-

tion, and capture data sent by an external bus master.

Interface connections are listed in Table 1 and Table 2.

Fault-Protection Circuitry

Overvoltage fault protection is provided by a MAX367

fault protector (U7). If any of the SMBus interface sig-

nals exceed the MAX367’s power-supply rails, the

MAX367 increases its resistance to prevent damage to

the user’s computer. A MAX865 dual charge pump

(U6) and two zener diodes (D1 and D2) provide +7V

and -3V supplies to the MAX367, thus allowing 0V and

+5V signals to pass with a nominal resistance of 100Ω.

Bus Monitoring Circuitry

Flip-flop U4A detects the start condition (falling edge of

SMBDATA when SMBCLK is high). Flip-flop U4B

detects the falling SMBCLK edge when enabled, and

U1F holds SMBCLK low until the software releases it.

To advance to the next data bit, the software uses U1A

to assert and then release SMBCLK. A logic high at the

input of U1A also resets flip-flop U4B. Because the IBM

PC parallel port has a limited number of inputs, the

start-detect circuit and the two alert inputs share a sin-

gle interrupt input. The source of the interrupt is distin-

guished using U3A, U3B, and U3C.

________________________________________________________Troubleshooting Guide

SYMPTOM

CAUSE

SOLUTION

Verify that the cable is a 25-pin parallel port I/O extension cable

with a plug on one end and a socket on the other end.

Verify that the cable is connected to a printer port, not a floppy

disk, SCSI, or serial communications port.

Board not connected to

parallel printer port

Can’t Find the Interface Board

Check power connections on the interface board.

Board is connected to cor- Check clock and data signal connections.

Clock or Data Stuck Low

rect port, but SMBus is not Try operating the interface board without the companion Maxim

functioning

evaluation kit—this should cause the address-not-acknowledged

symptom described below.

Verify that the companion board is connected to the MAXSMBus

interface board.

Verify that the companion board is powered.

If the companion offers a choice of addresses, confirm that the soft-

ware and hardware addresses match. Some devices only read the

address select pins at device power-up.

SMBus is OK, but no

response at expected

SMBus address

Address Not Acknowledged

Conflict with local printer

driver

Disable print manager in Windows printer control panel. Disable

printer driver.

Erratic Operation

1) Use computer with commercially available BIOS.

2) Make a bootable floppy disk, remove unnecessary device dri-

vers from A:config.sys, and boot system from floppy.

Operating system conflict

_______________________________________________________________________________________

MAXSMBus

2-Wire Interface Board

Table 1. DB25 Connector Signals

NAME

FUNCTION

SPARE OUTPUT A

Spare output

When high, drives SMBCLK signal low

SMBCLK_OUT

When high, drives SMBDATA signal low

When high, drives SMBSUS signal low

SMBDATA_OUT

SMBUS_OUT

LOOPBACK

Loopback connection for port verification

When high, allows ALERT1 to trigger INT low

When high, allows ALERT2 to trigger INT low

When high, allows a start condition to trigger INT low

MASK_ALERT1

MASK_ALERT2

MASK_START

When high, enables slave / bus monitor circuitry. This circuit waits until SMBCLK

is pulled low, and then it holds SMBCLK until the software resets it.

CAPTURE_ENABLE

INT

Active low interrupt input

When high, indicates that SMBDATA is low

When high, indicates that SMBCLK is low

Loopback connection for port verification

Spare output

SMBDATA_IN

SMBCLK_IN

LOOPBACK

SPARE OUTPUT B

When low, indicates that interface board is holding SMBCLK low

Not used

HOLDING_CLOCK

UNUSED

GND

Not used

18–25

Signal ground return

_______________________________________________________________________________________

MAXSMBus

2-Wire Interface Board

Table 2. Right-Angle Header P1 Signals

NAME

DUT +5V

GND

FUNCTION

+5V at 20mA power supply to Maxim companion board

Signal ground return

DUT SDA

GND

SMBDATA interface signal

Signal ground return

GND

Signal ground return

GND

Signal ground return

DUT SCL

GND

SMBCLK interface signal

Signal ground return

DUTSMBSUS

GND

SMBSUS interface signal

Signal ground return

DUTSMBALERT

GND

Primary ALERT interface signal

Signal ground return

DUTALERT2

GND

Secondary ALERT interface signal

Signal ground return

SPARE OUTPUT A

GND

Spare output from pin 1 of the DB25 connector

Signal ground return

SPARE OUTPUT B

GND

Spare output from pin 14 of the DB25 connector

Signal ground return

GND

Signal ground return

RAW POWER

Unregulated, unprotected power-supply input to MAXSMBus interface board

Note: Odd-numbered pins are on the outer row. Even-numbered pins are on the inner row. All right-angle header signals pass through

the MAX367 circuit protector, except 20.

_______________________________________________________________________________________

MAXSMBus

2-Wire Interface Board

Figure 1. MAXSMBus Schematic

_______________________________________________________________________________________

MAXSMBus

2-Wire Interface Board

Figure 1. MAXSMBus Schematic (continued)

_______________________________________________________________________________________

MAXSMBus

2-Wire Interface Board

1.0"

Figure 2. MAXSMBus Component Placement Guide

Figure 3. MAXSMBus PC Board Layout—Component Side

_______________________________________________________________________________________

MAXSMBus

2-Wire Interface Board

1.0"

Figure 4. MAXSMBus PC Board Layout—Solder Side

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.

8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Printed USA

is a registered trademark of Maxim Integrated Products.

MAX1645EVSYSTEM [MAXIM]

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