MAX6699
Detailed Description
The MAX6699 is a precision multichannel temperature
monitor that features one local and four remote temper-
ature-sensing channels with a programmable alert
threshold for each temperature channel and a program-
mable overtemperature threshold for channels 1 and 4
(see Figure 1). Communication with the MAX6699 is
achieved through the SMBus serial interface and a
dedicated alert pin. The alarm outputs, OVERT and
ALERT, assert if the software-programmed temperature
thresholds are exceeded. ALERT typically serves as an
interrupt, while OVERT can be connected to a fan, sys-
tem shutdown, or other thermal-management circuitry.
ADC Conversion Sequence
In the default conversion mode, the MAX6699 starts the
conversion sequence by measuring the temperature on
channel 1, followed by 2, 3, and local channel 4. The
conversion result for each active channel is stored in
the corresponding temperature data register.
In some systems, one of the remote thermal diodes may
be monitoring a location that experiences temperature
changes that occur much more rapidly than in the other
channels. If faster temperature changes must be moni-
tored in one of the temperature channels, the MAX6699
allows channel 1 to be monitored at a faster rate than
the other channels. In this mode (set by writing a 1 to bit
4 of the configuration 1 register), measurements of
channel 1 alternate with measurements of the other
channels. The sequence becomes channel 1, channel
2, channel 1, channel 3, channel 1, etc. Note that the
time required to measure all five channels is consider-
ably greater in this mode than in the default mode.
Low-Power Standby Mode
Standby mode reduces the supply current to less than
15µA by disabling the internal ADC. Enter standby by
setting the STOP bit to 1 in the configuration 1 register.
During standby, data is retained in memory, and the
SMBus interface is active and listening for SMBus com-
mands. The timeout is enabled if a start condition is rec-
ognized on SMBus. Activity on the SMBus causes the
supply current to increase. If a standby command is
received while a conversion is in progress, the conver-
sion cycle is interrupted, and the temperature registers
are not updated. The previous data is not changed and
remains available.
5-Channel Precision Temperature Monitor
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PIN NAME FUNCTION
7 DXP4
Combined Current Source and A/D Positive Input for Channel 4 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave floating or connect to V
CC
if no
remote diode is used. Place a 2200pF capacitor between DXP4 and DXN4 for noise filtering.
8 DXN4
Cathode Input for Channel 4 Remote Diode. Connect the cathode of the channel 1 remote-diode-
connected transistor to DXN4.
9, 10 N.C._ No Connection. Must be connected to ground.
11 OVERT
Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of
channels 1 and 4 exceeds the programmed threshold limit.
12 V
CC
Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
13 ALERT
SMBus Alert (Interrupt), Active-Low, Open-Drain Output. ALERT asserts low when the temperature of
any channel exceeds the programmed ALERT threshold.
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