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MAX6699UE38+T

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19
SMBus Digital Interface
From a software perspective, the MAX6699 appears as
a series of 8-bit registers that contain temperature-mea-
surement data, alarm threshold values, and control bits.
A standard SMBus-compatible 2-wire serial interface is
used to read temperature data and write control bits
and alarm threshold data. The same SMBus slave
address also provides access to all functions.
The MAX6699 employs four standard SMBus protocols:
write byte, read byte, send byte, and receive byte
(Figure 2). The shorter receive-byte protocol allows
quicker transfers, provided that the correct data regis-
ter was previously selected by a read byte instruction.
Use caution with the shorter protocols in multimaster
systems, since a second master could overwrite the
command byte without informing the first master. Figure
3 is the SMBus write timing diagram, and Figure 4 is
the SMBus read timing diagram.
The remote diode 1 measurement channel provides 11
bits of data (1 LSB = 0.125°C). All other temperature-
measurement channels provide 8 bits of temperature
data (1 LSB = 1°C). The 8 most significant bits (MSBs)
can be read from the local temperature and remote
temperature registers. The remaining 3 bits for remote
diode 1 can be read from the extended temperature
register. If extended resolution is desired, the extended
resolution register should be read first. This prevents
the most significant bits from being overwritten by new
MAX6699
5-Channel Precision Temperature Monitor
_______________________________________________________________________________________ 7
Figure 1. Internal Block Diagram
DXP1
DXN1
DXP2
DXN2
DXP3
DXN3
DXP4
DXN4
INPUT
BUFFER
10/100
µ
A
V
CC
REF
COUNT
COUNTER
COMMAND BYTE
REMOTE TEMPERATURES
LOCAL TEMPERATURES
REGISTER BANK
ALERT THRESHOLD
OVERT THRESHOLD
ALERT RESPONSE ADDRESS
ALARM
ALU
ADC
SMBus
INTERFACE
MAX6699
SCL SDA
OVERT
AVERT
MAX6699
conversion results until they have been read. If the
most significant bits have not been read within an
SMBus timeout period (nominally 37ms), normal updat-
ing continues. Table 1 shows the main temperature
register (high byte) data format, and Table 2 shows the
extended resolution register (low byte) data format.
Diode Fault Detection
If a channel’s input DXP_ and DXN_ are left open, the
MAX6699 detects a diode fault. An open diode fault does
not cause either ALERT or OVERT to assert. A bit in the sta-
tus register for the corresponding channel is set to 1 and
the temperature data for the channel is stored as all 1s
(FFh). It takes approximately 4ms for the MAX6699 to
detect a diode fault. Once a diode fault is detected, the
MAX6699 goes to the next channel in the conversion
sequence. Depending on operating conditions, a shorted
5-Channel Precision Temperature Monitor
8 _______________________________________________________________________________________
Write Byte Format
Read Byte Format
Send Byte Format
Receive Byte Format
Slave Address: equiva-
lent to chip-select line of
a 3-wire interface
Command Byte: selects to
which register you are writing
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
Slave Address: equiva-
lent to chip-select line
Command Byte: selects
from which register you
are reading
Slave Address: repeated
due to change in data-
flow direction
Data Byte: reads from
the register set by the
command byte
Command Byte: sends com-
mand with no data, usually
used for one-shot command
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
S = Start condition Shaded = Slave transmission
P = Stop condition /// = Not acknowledged
S ADDRESS RD ACK DATA /// P
7 bits 8 bits
WRS ACK COMMAND ACK P
8 bits
ADDRESS
7 bits
P
1
ACKDATA
8 bits
ACKCOMMAND
8 bits
ACKWRADDRESS
7 bits
S
S ADDRESS WR ACK COMMAND ACK S ADDRESS
7 bits8 bits7 bits
RD ACK DATA
8 bits
/// P
Figure 2. SMBus Protocols
TEMP (°C) DIGITAL OUTPUT
>127 0111 1111
127 0111 1111
126 0111 1110
25 0001 1001
0.00 0000 0000
<0.00 0000 0000
Diode fault (open) 1111 1111
Diode fault (short) 1111 1111 or 1110 1110
Table 1. Main Temperature Register
(High Byte) Data Format
TEMP (°C) DIGITAL OUTPUT
0 000X XXXX
+0.125 001X XXXX
+0.250 010X XXXX
+0.375 011X XXXX
+0.500 100X XXXX
+0.625 101X XXXX
+0.725 110X XXXX
+0.875 111X XXXX
Table 2. Extended Resolution Temperature
Register (Low Byte) Data Format
diode may or may not cause ALERT or OVERT to assert,
so if a channel will not be used, disconnect its DXP and
DXN inputs.
Alarm Threshold Registers
There are 9 alarm threshold registers that store over-
temperature ALERT and OVERT threshold values.
Seven of these registers are dedicated to store one
local alert temperature threshold limit and six remote
alert temperature threshold limits (see the
ALERT
Interrupt Mode section). The remaining two registers
are dedicated to remote channels 1 and 4 to store
overtemperature threshold limits (see the
OVERT
Overtemperature Alarm section). Access to these regis-
ters is provided through the SMBus interface.
ALERT
Interrupt Mode
An ALERT interrupt occurs when the internal or external
temperature reading exceeds a high-temperature limit
(user programmable). The ALERT interrupt output signal
can be cleared by reading the status register(s) associ-
ated with the fault(s) or by successfully responding to an
alert response address transmission by the master. In
both cases, the alert is cleared, but is reasserted at the
end of the next conversion if the fault condition still
exists. The interrupt does not halt automatic conversions.
The ALERT output is open drain so that multiple devices
can share a common interrupt line. All ALERT interrupts
can be masked using the configuration 3 register. The
POR state of these registers is shown in Table 3.
MAX6699
5-Channel Precision Temperature Monitor
_______________________________________________________________________________________ 9
SMBCLK
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
AB CD
E
FG
HIJ
SMBDATA
t
SU:STA
t
HD:STA
t
LOW
t
HIGH
t
SU:DAT
t
SU:STO
t
BUF
LMK
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 3. SMBus Write Timing Diagram
SMBCLK
AB CD
E
FG H
I
J
K
SMBDATA
t
SU:STA
t
HD:STA
t
LOW
t
HIGH
t
SU:DAT
t
HD:DAT
t
SU:STO
t
BUF
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
L
M
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION
M = NEW START CONDITION
Figure 4. SMBus Read Timing Diagram
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19

MAX6699UE38+T

Mfr. #:
Buy MAX6699UE38+T
Manufacturer:
Maxim Integrated
Description:
Board Mount Temperature Sensors 5Ch Precision Temperature Monitor
Lifecycle:
New from this manufacturer.
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