G768D Datasheet, PDF (2/16 Pages) Global Mixed-mode Technology Inc – Two Remote Temperature Sensors and One Fan Controller with SMBus Serial Interface and System Reset Circuit

Global Mixed-mode Technology Inc.
G768D
It uses LDO method and an on-chip MOSFET to con-
trol the fan speed to ±2% of the programmed speed.
The desired fan speed is also programmed via
SMBus^TM. The actual fan speed and fan status can be
read via the SMBus^TM. Short-circuit protection is im-
plemented to prevent damages to the fan and this IC
itself. The accepted frequency of fan rotation pulses is
100~1000Hz, which corresponds to 3,000 to 30,000
rpm for a typical fan that produces two pulses per
revolution. The G768D also turns on the fans by hard-
ware watchdog system. The fan controller would fully
turn on the fan when any of the following conditions
happens.
1.when either of the remote temperature is higher than
its own T_MAX.
2.when either of these two remote diodes is open.
3.when both remote diodes are short.
The G768D also contains a microprocessor (µP) su-
pervisory circuit used to monitor the power supplies in
µP and digital systems. They provide excellent circuit
reliability and low cost by eliminating external compo-
nents and adjustments when used with 5V-powered
circuits. This circuit asserts a reset signal whenever
the V_CC supply voltage declines below a preset
threshold, keeping it asserted for at least 140ms after
V_CC has risen above the reset threshold. The G768D
has an active-low RESET output. The reset com-
parator is designed to ignore fast transients on V_CC.
Reset threshold of this circuit is set to 4.4V typical.
The G768D is available in a small, 16-pin SSOP sur-
face-mount package.
Typical Operating Circuit
IN
FAN1
FG
1µF ^FANVCC
FG
TH_SHUT
VCC
2N3904
2200pF
DXP1
DXN
G768D
SMBCLK
SMBDATA
ALERT
CLK
2N3904
DXP2
2200pF
10µF
10k EACH
SMBCLK
SMBDATA
INTERRUPT TO µC
CLOCK 32.768kHz
RESET
µP
RESET
GND
Ver: 1.2
Apr 03, 2002
TEL: [phone]
http://www.gmt.com.tw
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