ADM1032ARMZ-2R datasheet(14/18 Pages) ONSEMI

Part #	ADM1032ARMZ-2R

Description	짹1??Remote and Local System Temperature Monitor

Download	18 Pages

Scroll/Zoom	100%

Manufacturer	ONSEMI [ON Semiconductor]

Direct Link	http://www.onsemi.com

Logo

14 / 18 page

ADM1032

http://onsemi.com

14

In this respect, the ADM1032 differs from and improves

upon competitive devices that output zero if the external

sensor goes short−circuit. These devices can misinterpret a

genuine 0

°C measurement as a fault condition.

When the D+ and D− lines are shorted together, an

ALERT is always generated. This is because the remote

value register reports a temperature value of −128

°C. Since

the ADM1032 performs a less−than or equal−to comparison

with the low limit, an ALERT is generated even when the

low limit is set to its minimum of −128

°C.

Applications Information — Factors Affecting

Accuracy

Remote Sensing Diode

The ADM1032 is designed to work with substrate

transistors built into processors’ CPUs or with discrete

transistors. Substrate transistors are generally PNP types

with the collector connected to the substrate. Discrete types

can be either a PNP or an NPN transistor connected as a

diode (base shorted to collector). If an NPN transistor is

used, the collector and base are connected to D+ and the

emitter to D−. If a PNP transistor is used, the collector and

base are connected to D− and the emitter to D+. Substrate

transistors are found in a number of CPUs. To reduce the

error due to variations in these substrate and discrete

transistors, a number of factors should be taken into

consideration:

1. The ideality factor, nf, of the transistor. The

ideality factor is a measure of the deviation of the

thermal diode from the ideal behavior. The

ADM1032 is trimmed for an nf value of 1.008.

The following equation can be used to calculate

the error introduced at a temperature T

°C when

using a transistor whose nf does not equal 1.008.

Consult the processor data sheet for nf values.

(eq. 2)

DT +

nnatural * 1.008

1.008

273.15 Kelvin ) T

This value can be written to the offset register and

is automatically added to or subtracted from the

temperature measurement.

2. Some CPU manufacturers specify the high and

low current levels of the substrate transistors. The

high current level of the ADM1032, IHIGH, is 230

mA and the low level current, ILOW, is 13 mA. If

the ADM1032 current levels do not match the

levels of the CPU manufacturers, then it can

become necessary to remove an offset. The CPU’s

data sheet advises whether this offset needs to be

removed and how to calculate it. This offset can be

programmed to the offset register. It is important

to note that if accounting for two or more offsets is

needed, then the algebraic sum of these offsets

must be programmed to the offset register.

If a discrete transistor is being used with the ADM1032,

the best accuracy is obtained by choosing devices according

to the following criteria:

• Base−emitter voltage greater than 0.25 V at 6 mA, at

the highest operating temperature.

• Base−emitter voltage less than 0.95 V at 100 mA, at the

lowest operating temperature.

• Base resistance less than 100 W.

• Small variation in hFE (say 50 to 150) that indicates

tight control of VBE characteristics.

Transistors such as 2N3904, 2N3906, or equivalents in

SOT−23 packages are suitable devices to use.

Thermal Inertia and Self−Heating

Accuracy depends on the temperature of the

remote−sensing diode and/or the internal temperature

sensor being at the same temperature as that being measured,

and a number of factors can affect this. Ideally, the sensor

should be in good thermal contact with the part of the system

being measured, for example, the processor. If it is not, the

thermal inertia caused by the mass of the sensor causes a lag

in the response of the sensor to a temperature change. In the

case of the remote sensor, this should not be a problem, since

it is either a substrate transistor in the processor or a small

package device, such as the SOT−23, placed in close

proximity to it.

The on−chip sensor, however, is often remote from the

processor and is only monitoring the general ambient

temperature around the package. The thermal time constant

of the SOIC−8 package in still air is about 140 seconds, and

if the ambient air temperature quickly changed by 100

°, it

would take about 12 minutes (five time constants) for the

junction temperature of the ADM1032 to settle within 1

° of

this. In practice, the ADM1032 package is in electrical and

therefore thermal contact with a printed circuit board and

can also be in a forced airflow. How accurately the

temperature of the board and/or the forced airflow reflect the

temperature to be measured also affects the accuracy.

Self−heating due to the power dissipated in the ADM1032

or the remote sensor causes the chip temperature of the

device or remote sensor to rise above ambient. However, the

current forced through the remote sensor is so small that

self−heating is negligible. In the case of the ADM1032, the

worst−case condition occurs when the device is converting

at 16 conversions per second while sinking the maximum

current of 1 mA at the ALERT and THERM output. In this

case, the total power dissipation in the device is about

11 mW. The thermal resistance,

qJA, of the SOIC−8 package

is about 121

°C/W.

In practice, the package has electrical and therefore

thermal connection to the printed circuit board, so the

temperature rise due to self−heating is negligible.

Similar Part No. - ADM1032ARMZ-2R

Manufacturer	Part #	Datasheet	Description
ON Semiconductor	ADM1032ARMZ-2R	237Kb / 18P	1C Remote and Local System Temperature Monitor Supports SMBus Alert April, 2012 ??Rev. 12
ON Semiconductor	ADM1032ARMZ-2R	214Kb / 18P	Local System Temperature Monitor October, 2013 ??Rev. 13

More results

Similar Description - ADM1032ARMZ-2R

Manufacturer	Part #	Datasheet	Description
Analog Devices	ADM1032	167Kb / 12P	-1C Remote and Local System Temperature Monitor REV. 0
ON Semiconductor	ADM1032ARMZ-1	203Kb / 18P	1C Remote and Local System Temperature Monitor October, 2013 ??Rev. 13
	ADM1032ARM-REEL	203Kb / 18P	1C Remote and Local System Temperature Monitor October, 2013 ??Rev. 13
	ADM1032	237Kb / 18P	1C Remote and Local System Temperature Monitor Supports SMBus Alert April, 2012 ??Rev. 12
	ADM1032ARZ-1RL7	214Kb / 18P	Local System Temperature Monitor October, 2013 ??Rev. 13
Texas Instruments	THMC10	374Kb / 22P	[Old version datasheet] REMOTE/LOCAL TEMPERATURE MONITOR WITH SMBus INTERFACE
	THMC10	269Kb / 20P	[Old version datasheet] REMOTE/LOCAL TEMPERATURE MONITOR WITH SMBus INTERFACE
	THMC50	437Kb / 32P	[Old version datasheet] REMOTE/LOCAL TEMPERATURE MONITOR AND FAN CONTROLLER WITH SMBus INTERFACE
	TMP421-Q1	1Mb / 38P	[Old version datasheet] Remote and Local Temperature Sensor
	THMC50	537Kb / 34P	[Old version datasheet] REMOTE/LOCAL TEMPERATURE MONITOR AND FAN CONTROLLER WITH SMBus INTERFACE

More results

ADM1032ARMZ-2R Datasheet(PDF) 14 Page - ON Semiconductor

ADM1032ARMZ-2R Datasheet(HTML) 14 Page - ON Semiconductor

Similar Part No. - ADM1032ARMZ-2R

Similar Description - ADM1032ARMZ-2R

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Datasheet Download

Link URL