MAX1619 View Datasheet(PDF) - Maxim Integrated

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MAX1619

Remote/Local Temperature Sensor with Dual Alarm Outputs and SMBus Serial Interface

Maxim Integrated 

Remote/Local Temperature Sensor with Dual-

Alarm Outputs and SMBus Serial Interface

Table 6. Status-Byte Bit Assignments

BIT

7

(MSB)

6

5

4

3

2

1

0

(LSB)

NAME

BUSY

RFU

RFU

RHIGH*

RLOW*

OPEN*

OVER

RFU

FUNCTION

A high indicates that the ADC is busy

converting.

Reserved for future use.

Reserved for future use.

A high indicates that the remote high-

temperature alarm has activated.

A high indicates that the remote low-

temperature alarm has activated.

A high indicates a remote-diode conti-

nuity (open-circuit) fault.

This bit follows the state of the OVERT

pin exactly, in real time (unlatched).

Reserved for future use.

Table 7. Conversion-Frequency Control

Byte

DATA

00h

01h

02h

03h

04h

05h

06h

07h

08h to

FFh

CONVERSION

FREQUENCY

(Hz)

0.0625

0.125

0.25

0.5

1

2

4

8

RFU

AVERAGE SUPPLY

CURRENT

(µA typ, at VCC = 3.3V)

30

33

35

48

70

128

225

425

—

*The HIGH and LOW temperature alarm flags stay high until

cleared by POR or until status register is read.

Write-Once Protection

Write-once protection allows the host BIOS code to

configure the MAX1619 in a particular way, and then

protect that configuration against data corruption in the

host that might cause spurious writes to the MAX1619.

In particular, write protection allows a foolproof over-

temperature override that forces the fan on 100% via

OVERT independent of the host system. The write-pro-

tection bit (bit 4), once set high, can’t be reset to low

except by a hardware power-on reset. A SPOR (soft-

ware POR) will not reset this bit.

Status Byte Functions

The status byte register (Table 6) indicates which (if

any) temperature thresholds have been exceeded. This

byte also indicates whether or not the ADC is converting

and whether there is an open circuit in the remote diode

DXP–DXN path. The status byte is cleared by any suc-

cessful read of the status byte, unless the fault persists.

The status of bit1 (OVER) follows the state of OVERT

exactly. Note that the ALERT interrupt latch is not auto-

matically cleared when the status flag bit is cleared.

When autoconverting, if the THIGH and TLOW limits are

close together, it’s possible for both high-temp and low-

temp status bits to be set, depending on the amount of

time between status read operations (especially when

converting at the fastest rate). In these circumstances, it’s

best not to rely on the status bits to indicate reversals in

long-term temperature changes. Instead, use a current

temperature reading to establish the trend direction.

Conversion Rate Byte

The conversion rate register (Table 7) programs the time

interval between conversions in free-running autoconvert

mode. This variable rate control reduces the supply cur-

rent in portable-equipment applications. The conversion

rate byte’s POR state is 02h (0.25Hz). The MAX1619

looks only at the 3 LSB bits of this register, so the upper 5

bits are “don’t care” bits, which should be set to zero. The

conversion rate tolerance is ±25% at any rate setting.

Valid A/D conversion results for both channels are avail-

able one total conversion period (125ms nominal, 156ms

maximum) after initiating a conversion, whether conver-

sion is initiated via the RUN/STOP bit, hardware STBY

pin, one-shot command, or initial power-up. Changing the

conversion rate can also affect the delay until new results

are available (Table 8).

Manufacturer and Device ID Codes

Two ROM registers provide manufacturer and device ID

codes (Table 4). Reading the manufacturer ID returns

4Dh, which is the ASCII code “M” (for Maxim). Reading

the device ID returns 04h, indicating a MAX1619 device.

If READ WORD 16-bit SMBus protocol is employed

(rather than the 8-bit READ BYTE), the least significant

byte contains the data and the most significant byte con-

tains 00h in both cases.

Slave Addresses

The MAX1619 appears to the SMBus as one device

having a common address for both ADC channels. The

device address can initially be set to one of nine differ-

ent values by pin-strapping ADD0 and ADD1 so that

more than one MAX1619 can reside on the same bus

without address conflicts (Table 9).

14 ______________________________________________________________________________________

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