MAX6581TG9A+【PDF 8/27 页】IC TEMP SENSOR 8-CH PREC 24-TQFN

8

Maxim Integrated

?癈 Accurate 8-Channel Temperature Sensor

MAX6581

Detailed Description

The MAX6581 is a precision multichannel temperature

monitor that features one local and seven remote tem-

perature-sensing channels with a programmable alert

threshold for each temperature channel and a program-

mable overtemperature threshold for channels 17 (see

Figure 1). Communication with the MAX6581 is achieved

through the SMBus serial interface and a dedicated alert

pin (ALERT). The alarm outputs, (OVERT and ALERT)

assert if the software-programmed temperature thresh-

olds are exceeded. ALERT also asserts if the measured

temperature falls below the ALERT low limits. ALERT

typically serves as an interrupt, while OVERT can be

connected to a fan, system shutdown, or other thermal-

management circuitry.

ADC Conversion Sequence

The MAX6581 starts the conversion sequence by

measuring the temperature on channel 1, followed by 2,

local channel, 37. The conversion result for each active

channel is stored in the corresponding temperature data

register. No conversion is performed on any channel that

does not have a diode.

Low-Power Standby Mode

Enter software-standby mode by setting the STOP

bit to 1 in the Configuration register. Enter hardware-

standby by pulling STBY low. Software-standby mode

disables the ADC and reduces the supply current to

approximately 4FA. During either software or hardware

standby, data is retained in memory. During hardware

standby, the SMBus interface is inactive. During software

standby, the SMBus interface is active and listening for

commands. The timeout is enabled if a START condition

is recognized on SMBus. Activity on the SMBus causes

the supply current to increase. If a standby command is

received while a conversion is in progress, the conver-

sion cycle is interrupted, and the temperature registers

are not updated. The previous data is not changed and

remains available.

Operating-Current Calculation

The MAX6581 operates at different operating-current

levels depending on how many external channels are in

use and how many of those are in resistance cancella-

tion (RC) mode. The average operating current is:

N

R

AV

CC1

CC2

N

R

N

R

N 1

2 N

I

N

2 N

1

N

2 N

1

+

?/DIV>

=

+

?/DIV>

+ ?/DIV>

+

+ ?/DIV>

+

where:

N

= the number of remote channels that are operating

in normal mode.

N

R

= the number of remote channels that are in RC

mode.

I

AV

= the average operating power-supply current over a

complete series of conversions.

I

CC1

= the average operating power-supply current

during a conversion in normal mode.

I

CC2

= the average operating power-supply current

during a conversion in RC mode.

Pin Description (continued)

NAME

FUNCTION

21

GND

Ground

23

DXP1

Combined Current Source and ADC Positive Input for Channel 1 Remote Diode. Connect DXP1 to

the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP1 unconnected

or connect to DXN1 if a remote diode is not used. Connect a 100pF capacitor between DXP1 and

DXN1 for noise filtering.

24

DXN1

Cathode Input for Channel 1 Remote Diode. Connect the cathode of the channel 1 remote-diode-

connected transistor to DXN1. If the channel 1 remote transistor is a substrate pnp (e.g., on a CPU

die), connect the base of the pnp to DXN1. Leave DXN1 unconnected or connect to DXP1 if a

remote diode is not used. Connect a 100pF capacitor between DXP1 and DXN1 for noise filtering.

EP

Exposed Pad. Connect EP to GND.

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