- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄370297 > G768D ± 3oC remote thermal sensor with one fan control and SMBus interface.|Thermal Sensor / Detector Series PDF資料下載
參數(shù)資料
| 型號： | G768D |
| 英文描述： | ± 3oC remote thermal sensor with one fan control and SMBus interface.|Thermal Sensor / Detector Series |
| 中文描述： | ± 3oC遠程溫度傳感器一個風扇控制和SMBus接口。|熱傳感器/探測器系列 |
| 文件頁數(shù)： | 8/16頁 |
| 文件大?。?/td> | 323K |
| 代理商： | G768D |
Ver: 1.4
May 23, 2003
TEL: 886-3-5788833
http://www.gmt.com.tw
8
G768D
Global Mixed-mode Technology Inc.
Twisted Pair and Shielded Cables
For remote-sensor distances longer than 8 in., or in
particularly noisy environments, a twisted pair is rec-
ommended. Its practical length is 6 feet to 12feet (typi-
cal) before noise becomes a problem, as tested in a
noisy electronics laboratory. For longer distances, the
best solution is a shielded twisted pair like that used
for audio microphones. Connect the twisted pair to
DXP and DXN and the shield to GND, and leave the
shield's remote end unterminated.
Excess capacitance at DX_limits practical remote
sensor distances (see Typical Operating Characteris-
tics), For very long cable runs, the cable's parasitic
capacitance often provides noise filtering, so the
2200pF capacitor can often be removed or reduced in
value. Cable resistance also affects remote-sensor
accuracy; 1
series resistance introduces about + 1°C
error.
Low-Power Standby Mode
Standby mode disables the ADC and reduces the
supply-current drain to less than 10μA. Enter standby
mode via the RUN/STOP bit in the configuration byte
register. In standby mode, all data is retained in mem-
ory, and the SMB interface is alive and listening for
reads and writes. This is valid for temperature sensor
only.
Standby mode is not a shutdown mode. With activity
on the SMBus, extra supply current is drawn (see
Typical
Operating
Characteristics).
standby mode, the G768D can be forced to perform
temperature measurement via the one-shot command,
despite the RUN/STOP bit being high.
In
software
Supply-current drain during the 125ms conversion
period is always about 500μA. Slowing down the con-
version rate reduces the average supply current (see
Typical Operating Characteristics). In between con-
versions, the instantaneous supply current is about
200μA due to the current consumed by the system
resetting circuit.
Fan Controller
Since the fan speed is measured by counting the num-
ber of 32.768KHz cycles between the rising edges of
two fan speed pulses. In this way, we are actually
measuring the period of the fan speed. To avoid the
cost of doing division to obtain the speed, this count
number, N, is used in the PWM control algorithm, thus,
the desired fan speed should be programmed by writ-
ing the corresponding count number. The count num-
ber is given by:
N: Count Number
P: FG pulses number per revolution
P=1
N = 983040 / rpm
P=2
N = 491520 / rpm
P=4
N = 245762 / rpm
Some selected count number for P=2 are listed below
.
Table 2.
Rpm
3000
4000
5000
6000
7000
8000
9000
10000
20000
30000
N
164
123
98
82
70
61
55
49
25
16
To stop the fan, program the fan speed register to 255. This
also makes the fan controller enter power saving mode.
Controlling Fan at Lower Speed
For stably controlling fans at lower rotation speed,
three schemes are recommended as below:
1.Use larger decoupling capacitors between FANVCC
and GND.
2.Shunt a capacitor of 1μF-2μF on FG pin to GND.
3.Use fans with open-collector FG outputs.
When controlling fans under lower rotation speed, the
output voltage of FANVCC would be too low for fan to
generate recognizable FG signals.
Using decouple capacitors on FANVCC and FG is to
increase the SNR on FG pins. While using fans with
open-collector FG outputs can thoroughly solve the
problem, because the logic high level of FG would be
fixed to 5V.
Reset Immunity Negative-Going V
CC
Transients
In addition to issuing a reset to the microprocessor (μP)
during power-up, power-down, and brownout condi-
tions, the G768D is relatively immune to short duration
negative-going V
CC
transients (glitches).
Typically, for the G768D, a V
CC
transient that goes
100mV below the reset threshold and lasts 20μs or
less will not cause a reset pulse. A 0.1μF bypass ca-
pacitor mounted as close as possible to the V
CC
pin
provides additional transient immunity.
相關PDF資料 |
PDF描述 |
|---|---|
| G7881 | Optoelectronic |
| G8342 | Optoelectronic |
| G8796 | Optoelectronic |
| G7J-2A2B-B | |
| G7J-2A2B-P | |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| G770127-1 REV D | 制造商:Amphenol Corporation 功能描述:AMPHENOL CANADA - Rail/Tube |
| G770140-1 REV E | 制造商:Amphenol Corporation 功能描述:AMPHENOL CANADA - Rail/Tube |
| G77015 | 制造商:Glenair Inc 功能描述:1 REPLACEMENT PAD for TG69P |
| G771 | 制造商:GMT 制造商全稱:Global Mixed-mode Technology Inc 功能描述:Two Remote Temperature Sensors with SMBus Serial Interface and System Reset Circuit |
| G772203-1 REV C | 制造商:International Rectifier 功能描述:G772203-1 REV C - Bulk |
發(fā)布緊急采購，3分鐘左右您將得到回復。