Ver 1.0
Dec 11, 2001
TEL: 886-3-5788833
http://www.gmt.com.tw
4
Global Mixed-mode Technology Inc.
G766
Pin Description
PIN
NAME
FUNCTION
1
ADD0
SMBus Slave Address Select pin
2
ADD1
SMBus Address Select pin (Table 8). ADD0 and ADD1 are sampled upon power-up. Excess capaci-
tance (>50pF) at the address pins when floating may cause address-recognition problems.
3
GND
Ground
4
DXN
Combined Current Sink and A/D Negative Input.
5
DXP
Combined Current Source and A/D Positive Input for remote-diode channel. Do not leave DXP float-
ing; tie DXP to DXN if no remote diode is used. Place a 2200pF capacitor between DXP and DXN for
noise filtering.
6
Vcc
Supply Voltage Input , 3V to 5.5V. Bypass to GND with a 0.1µF capacitor. A 200
Ω series resistor is
recommended but not required additional noise filtering.
7
STBY
Hardware Standby Input. Temperature and comparison threshold data are retained in standby mode.
Low = standby mode, high = operate mode.
8
SMBCLK
SMBus Serial-Clock Input
9
SMBDATA SMBus Serial-Data Input / Output, open drain
10
ALERT
SMBus Alert (interrupt) Output, open drain
Detailed Description
The G766 (patents pending) is a temperature sensor
designed to work in conjunction with an external mi-
crocontroller (µC) or other intelligence in thermostatic,
process-control, or monitoring applications. The µC is
typically a power-management or keyboard controller,
generating SMBus serial commands by “bit-banging”
general-purpose input-output (GPIO) pins or via a
dedicated SMBus interface block.
Essentially an 8-bit serial analog-to digital converter
(ADC) with a sophisticated front end, the G766 con-
tains a switched current source, a multiplexer, an ADC,
an SMBus interface, and associated control logic (Fig-
ure 1). Temperature data from the ADC is loaded into
two data registers, where it is automatically compared
with data previously stored in four over/under-tem-
perature alarm registers.
ADC and Multiplexer
The ADC is an averaging type that integrates over a
60ms period (typical), with excellent noise rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes, measures their
forward voltages, and computes their temperatures.
Both channels are automatically converted once the
conversion process has started, either in free-running
or single-shot mode. If one of the two channels is not
used, the device still performs both measurements,
and the user can simply ignore the results of the un-
used channel.
The worst-case DXP-DXN differential input voltage
range is 0.25V to 0.95V.
Excess resistance in series with the remote diode
causes about +1/2°C error per ohm. Likewise, 200µV
of offset voltage forced on DXP-DXN causes about
1°C error.
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