MAX1619 Datasheet, PDF (10/20 Pages) Maxim Integrated Products – Remote/Local Temperature Sensor with Dual- Alarm Outputs and SMBus Serial Interface

Remote/Local Temperature Sensor with Dual-
Alarm Outputs and SMBus Serial Interface
the MAX1619 can be forced to perform A/D conversions
via the one-shot command, despite the RUN/STOP bit
being high.
Activate hardware standby mode by forcing the STBY
pin low. In a notebook computer, this line may be con-
nected to the system SUSTAT# suspend-state signal.
The STBY pin low state overrides any software conversion
command. If a hardware or software standby command
is received while a conversion is in progress, the conver-
sion cycle is truncated, and the data from that conversion
is not latched into either temperature reading register.
The previous data is not changed and remains available.
The OVERT output continues to function in both hard-
ware and software standby modes. If the overtemp lim-
its are adjusted while in standby mode, the digital
comparator checks the new values and puts the OVERT
pin in the correct state based on the last valid ADC con-
version. The last valid ADC conversion may include a
conversion performed using the one-shot command.
Supply-current drain during the 125ms conversion peri-
od is always about 450µA. Slowing down the conversion
rate reduces the average supply current (see Typical
Operating Characteristics). Between conversions, the
instantaneous supply current is about 25µA due to the
current consumed by the conversion rate timer. In
standby mode, supply current drops to about 3µA. At
very low supply voltages (under the power-on-reset
threshold), the supply current is higher due to the
address pin bias currents. It can be as high as 100µA,
depending on ADD0 and ADD1 settings.
SMBus Digital Interface
From a software perspective, the MAX1619 appears as a
set of byte-wide registers that contain temperature data,
alarm threshold values, or control bits. A standard
SMBus 2-wire serial interface is used to read tempera-
ture data and write control bits and alarm threshold data.
Each A/D channel within the device responds to the
same SMBus slave address for normal reads and writes.
The MAX1619 employs four standard SMBus protocols:
Write Byte, Read Byte, Send Byte, and Receive Byte
(Figure 3). The shorter Receive Byte protocol allows
quicker transfers, provided that the correct data register
was previously selected by a Read Byte instruction. Use
caution with the shorter protocols in multi-master sys-
Write Byte Format
S
ADDRESS
WR
ACK
COMMAND
ACK
DATA
ACK
P
7 bits
8 bits
8 bits
1
Slave Address:
equivalent to chip-select
line of a 3-wire interface
Command Byte: selects
which register you are
writing to
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Read Byte Format
S ADDRESS WR ACK COMMAND ACK
S ADDRESS RD ACK DATA
///
P
7 bits
8 bits
7 bits
8 bits
Slave Address:
equivalent to
chip-select line
Command Byte: selects
which register you are
reading from
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
Send Byte Format
Receive Byte Format
S ADDRESS WR ACK COMMAND ACK P
7 bits
8 bits
Command Byte: sends com-
mand with no data; usually
used for one-shot command
S = Start condition Shaded = Slave transmission
P = Stop condition /// = Not acknowledged
Figure 3. SMBus Protocols
S ADDRESS RD ACK DATA ///
P
7 bits
8 bits
Data Byte: reads data from
the register commanded
by the last Read Byte or
Write Byte transmission;
also used for SMBus Alert
Response return address
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