MAX6638 데이터 시트보기 (PDF) - Maxim Integrated

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MAX6638

Temperature Monitor with Dual Serial Interface

Maxim Integrated 

Temperature Monitor with

Dual Serial Interface

The averaging ADC integrates over a 16ms period

(each channel, typical) with excellent noise rejection.

The multiplexer automatically steers bias currents

through the remote and local diodes. The ADC and

associated circuitry measure each diode’s forward volt-

age and compute the temperature based on this volt-

age. Both temperature sensors automatically convert

Table 2. Extended Temperature Data

(RLET1, RRET1, RLET2, RRET2)

FRACTIONAL

TEMPERATURE (°C)

0.000

0.125

0.250

0.375

0.500

0.675

0.750

0.875

DIGITAL OUTPUT (bin)

000X XXXX

001X XXXX

010X XXXX

011X XXXX

100X XXXX

101X XXXX

110X XXXX

111X XXXX

once the conversion process starts, either in free-run-

ning (RUN = 0) or single-shot mode. A BUSY status bit

in the status byte indicates that the device is performing

a new conversion. The results of the previous conver-

sion are always available even when the ADC is busy. If

one of the two temperature sensors is not used, the

MAX6638 still performs both measurements and ignores

the results of the unused channel. When not using the

remote-diode temperature sensor, connect DXP to DXN.

The DXP-DXN differential input voltage range is 0.25V to

0.95V. Excess resistance in series with the remote diode

causes a +0.5°C (typ) error per ohm.

The MAX6638 initiates conversion cycling after POR,

after exiting standby mode from either SMBus channel,

and upon one-shot request from either SMBus channel.

One conversion cycle consists of two ADC conversions

(one for the local temperature, one for the remote tem-

perature), a diagnostic check on the remote tempera-

ture sensor, loading of data into the read registers,

setting diagnostic flags, and setting ALERT1, ALERT2,

and OVERT1, as required. Figure 1 shows the simplified

timing sequence.

ONE CONVERSION CYCLE

ADC LOCAL TEMPERATURE

START CONVERSION

Figure 1. One Complete ADC Conversion Cycle

ADC AND DIAGNOSTIC REMOTE TEMPERATURE

UPDATE REGISTERS DATA AVAILABLE

TIME

START

CRCn

CONVERSION 250

500

750

1000

1250

1500

1750

2000

06h

ONE CONVERSION CYCLE

TIME (ms)

05h

04h

03h

02h

Figure 2. Repeating ADC Conversion Cycles for Various Conversion Rate Settings

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