MAX1989MEE+ Maxim Integrated Products, MAX1989MEE+ Datasheet - Page 10

• Manufacturer Part Number: MAX1989MEE+
• Description: IC TEMP SENSOR REMOTE 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1989MEE+

• Function: Thermometer, Thermostat
• Topology: ADC, Comparator, Multiplexer, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -55°C ~ 125°C, External Sensor
• Output Type: I²C™/SMBus™
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -55°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Full Temp Accuracy: +/- 3.5 C, +/- 5 C
• Digital Output - Bus Interface: Serial (2-Wire)
• Digital Output - Number Of Bits: 7 bit + Sign
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 55 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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.
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.
From a software perspective, the MAX1668/MAX1805/
MAX1989 appear 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 temperature data and write control bits and
alarm threshold data. Each A/D channel within the
devices responds to the same SMBus slave address for
normal reads and writes.
The MAX1668/MAX1805/MAX1989 employ 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 instruc-
Multichannel Remote/Local
Temperature Sensors
Write Byte Format
Read Byte Format
Send Byte Format
S = Start condition
P = Stop condition
Figure 3. SMBus Protocols
10
S
S
S
______________________________________________________________________________________
ADDRESS
Slave Address: equiva-
lent to chip-select line
ADDRESS
7 bits
7 bits
Slave Address: equiva-
lent to chip-select line of
a 3-wire interface
ADDRESS
7 bits
WR
Shaded = Slave transmission
/// = Not acknowledged
WR
SMBus Digital Interface
ACK
ACK
WR
Command Byte: sends com-
mand with no data
COMMAND
8 bits
Command Byte: selects
which register you are
reading from
COMMAND
8 bits
ACK
ACK
Command Byte: selects which
register you are writing to
ACK
COMMAND
P
8 bits
S
tion. Use caution with the shorter protocols in multimaster
systems, since a second master could overwrite the com-
mand byte without informing the first master.
The temperature data format is 7 bits plus sign in two’s-com-
plement form for each channel, with each data bit represent-
ing 1°C (Table 2), transmitted MSB first. Measurements are
offset by +0.5°C to minimize internal rounding errors; for
example, +99.6°C is reported as +100°C.
Ten (six for MAX1805) registers store alarm threshold
data, with high-temperature (T
ture (T
measured temperature equals or exceeds the corre-
sponding alarm threshold value, an ALERT interrupt is
asserted.
The power-on-reset (POR) state of all T
the MAX1668 and MAX1805 is full scale (0111 1111, or
+127°C). The POR state of the channel 1 T
of the MAX1989 is 0110 1110 or +110°C, while all other
channels are at +127°C. The POR state of all T
isters is 1100 1001 or -55°C.
Receive Byte Format
S
Slave Address: repeated
due to change in data-
flow direction
ADDRESS
7 bits
LOW
ADDRESS
ACK
7 bits
) registers for each A/D channel. If either
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
RD
DATA
Alarm Threshold Registers
8 bits
RD
ACK
Data Byte: This command only
works immediately following a
Read Byte. Reads data from the
register commanded by that last
Read Byte; also used for SMBus
Alert Response return address
ACK
HIGH
Data Byte: reads from
the register set by the
command byte
DATA
8 bits
DATA
8 bits
ACK
) and low-tempera-
HIGH
HIGH
///
///
registers of
LOW
register
P
1
P
reg-
P