MAX6636
Detailed Description
The MAX6636 is a precision multichannel temperature
monitor that features one local and six remote tempera-
ture-sensing channels with a programmable alert
threshold for each temperature channel and a program-
mable overtemperature threshold for channels 1, 4, 5,
and 6 (see Figure 1). Communication with the MAX6636
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 MAX6636 starts the
conversion sequence by measuring the temperature on
channel 1, followed by 2, 3, local channel, 4, 5, and 6.
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 MAX6636
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 seven channels is consid-
erably greater in this mode than in the default mode.
Low-Power Standby Mode
Enter software standby mode by setting the STOP bit to
1 in the configuration 1 register. Enter hardware standby
by pulling STBY low. Software standby mode disables
the ADC and reduces the supply current to approxi-
mately 30µA. Hardware standby mode halts the ADC
clock, but the supply current is approximately 350µA.
During either software or hardware standby, data is
retained in memory, and the SMBus interface is active
and listening for SMBus commands. The timeout is
enabled if a START condition is recognized on SMBus.
Activity on the SMBus causes the supply current to
increase. If a standby command is received while a con-
version is in progress, the conversion cycle is interrupt-
7-Channel Precision Temperature Monitor
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Combined Current Source and A/D Positive Input for Channel 5 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave unconnected or connect to V
no remote diode is used. Place a 2200pF capacitor between DXP5 and DXN5 for noise filtering.
Cathode Input for Channel 5 Remote Diode. Connect the cathode of the channel 5 remote-diode-
connected transistor to DXN5.
Cathode Input for Channel 6 Remote Diode. Connect the cathode of the channel 6 remote-diode-
connected transistor to DXN6.
Combined Current Source and A/D Positive Input for Channel 6 Remote Diode. Connect to the anode
of a remote-diode-connected temperature-sensing transistor. Leave unconnected or connect to V
no remote diode is used. Place a 2200pF capacitor between DXP6 and DXN6 for noise filtering.
Active-Low Standby Input. Drive STBY logic-low to place the MAX6636 in standby mode, or logic-high
for operate mode. Temperature and threshold data are retained in standby mode.
Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of
channels 1, 4, 5, and 6 exceeds the programmed threshold limit.
Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.
SMBus Alert (Interrupt), Active-Low, Open-Drain Output. ALERT asserts low when the temperature of
