參數(shù)資料
型號(hào): ADM1027ARQZ-RL7
廠商: ON Semiconductor
文件頁數(shù): 15/56頁
文件大?。?/td> 1822K
描述: IC REMOTE THERMAL CTLR 24QSOP
產(chǎn)品變化通告: MFG CHG Notification ADI to ON Semi
Product Discontinuation Notice 25/Aug/2008
Product Obsolescence 30/Sept/2009
標(biāo)準(zhǔn)包裝: 1,000
系列: dBCool®
功能: 風(fēng)扇控制,溫度監(jiān)控器
傳感器類型: 內(nèi)部和外部
感應(yīng)溫度: 0°C ~ 105°C,外部傳感器
精確度: ±1°C
拓?fù)洌?/td> ADC,比較器,風(fēng)扇速度計(jì)數(shù)器,多路復(fù)用器,寄存器庫
輸出類型: SMBus?
輸出警報(bào):
輸出風(fēng)扇:
電源電壓: 3 V ~ 5.5 V
工作溫度: 0°C ~ 105°C
安裝類型: 表面貼裝
封裝/外殼: 24-SSOP(0.154",3.90mm 寬)
供應(yīng)商設(shè)備封裝: 24-QSOP
包裝: 帶卷 (TR)
REV. A
ADM1027
15
If a discrete transistor is used, the collector will not be grounded,
and should be linked to the base. If a PNP transistor is used, the
base is connected to the D input and the emitter to the D+
input. If an NPN transistor is used, the emitter is connected to
the D input and the base to the D+ input. Figure 14 shows
how to connect the ADM1027 to an NPN or PNP transistor for
temperature measurement. To prevent ground noise from inter-
fering with the measurement, the more negative terminal of the
sensor is not referenced to ground, but is biased above ground
by an internal diode at the D input.
To measure DV
be
, the sensor is switched between operating cur-
rents of I and N I. The resulting waveform is passed through a
65 kHz low-pass filter to remove noise, and to a chopper-stabilized
amplifier that performs the functions of amplification and recti-
fication of the waveform to produce a dc voltage proportional to
DV
be
. This voltage is measured by the ADC to give a temperature
output in 10-bit, twos complement format. To further reduce
the effects of noise, digital filtering is performed by averaging the
results of 16 measurement cycles. A remote temperature measure-
ment takes nominally 25.5 ms. The results of remote temperature
measurements are stored in 10-bit, twos complement format,
as illustrated in Table III. The extra resolution for the temperature
measurements is held in the Extended Resolution Register 2
(Reg. 0x77). This gives temperature readings with a resolution
of 0.25
o
C.
Table III. Temperature Data Format*
Temperature
Digital Output (10-Bit)
128rC
1000 0000 00
125rC
1000 0011 00
100rC
1001 1100 00
75rC
1011 0101 00
50rC
1100 1110 00
25rC
1110 0111 00
10
o
C
1111 0110 00
0rC
0000 0000 00
+10.25rC
0000 1010 01
+25.5rC
0001 1001 10
+50.75rC
0011 0010 11
+75rC
0100 1011 00
+100rC
0110 0100 00
+125rC
0111 1101 00
+127rC
0111 1111 00
*Bold denotes 2 LSBs of measurement in Extended Resolution
Register 2 (Reg. 0x77) with 0.25
o
C resolution.
ADM1027
2N3904
NPN
D+
D
Figure 14a. Measuring Temperature Using an
NPN Transistor
2N3906
PNP
ADM1027
D+
D
Figure 14b. Measuring Temperature Using a
PNP Transistor
NULLING OUT TEMPERATURE ERRORS
As CPUs run faster, it is getting more difficult to avoid high
frequency clocks when routing the D/D+ traces around a system
board. Even when recommended layout guidelines are followed,
there may still be temperature errors attributed to noise being
coupled onto the D+/D lines. High frequency noise generally
has the effect of giving temperature measurements that are too
high by a constant amount. The ADM1027 has temperature
offset registers at addresses 0x70, 0x71, and 0x72 for the Remote 1,
Local, and Remote 2 temperature channels. By doing a one-time
calibration of the system, you can determine the offset caused
by system board noise and null it out using the offset registers.
The offset registers automatically add a twos complement 8-bit
reading to every temperature measurement. The LSB adds a 1rC
offset to the temperature reading so the 8-bit register effectively
allows temperature offsets of up to 127rC with a resolution of
1rC. This ensures that the readings in the temperature measure-
ment registers are as accurate as possible.
TEMPERATURE OFFSET REGISTERS
Reg. 0x70 Remote 1 Temperature Offset = 0x00 (0rC default)
Reg. 0x71 Local Temperature Offset = 0x00 (0rC default)
Reg. 0x72 Remote 2 Temperature Offset = 0x00 (0rC default)
Rev. 3 | Page 15 of 56 | www.onsemi.com
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