MAX6622
Detailed Description
The MAX6622 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 MAX6622 is
achieved through the SMBus serial interface and a
dedicated alert output. 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 MAX6622 starts the
conversion sequence by measuring the temperature on
channel 1, followed by 2, 3, local channel, and 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 MAX6622
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
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 approximate-
ly 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 stand-
by command is received while a conversion is in
progress, the conversion 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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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 unconnected or connect to V
no remote diode is used. Place a 2200pF capacitor between DXP4 and DXN4 for noise filtering.
Cathode Input for Channel 4 Remote Diode. Connect the cathode of the channel 4 remote-diode-
connected transistor to DXN4.
Standby Input. Drive STBY logic-low to place the MAX6622 in hardware standby mode, or logic-high
for normal operation. Temperature and threshold data are retained in standby mode.
Overtemperature Active-Low, Open-Drain Output. OVERT asserts low when the temperature of
channels 1 and 4 exceed 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
