MAX1361 Datasheet, PDF (18/24 Pages) Maxim Integrated Products – 4-Channel, 10-Bit, System Monitors with Programmable Trip Window and SMBus Alert Response

4-Channel, 10-Bit, System Monitor with Programmable
Trip Window and SMBus Alert Response
R/W
START
ADDRESS
FROM THE MASTER
1
ACK
1, CH ADD, 10b/12b
1,1 RESULT (2 MSBs)
ACK
RESULT (8 LSBs)
ACK
t_ACQ
CONVERSION 1
t_ACQ
1, CH ADD, 10b/12b, 1,1
RESULT (2 MSBs)
ACK
RESULT N (8 LSBs)
ACK
t_ACQ
CONVERSION N
t_ACQ
Figure 13. Example of Scan-Mode Conversions Using the External Clock, SCAN = 0,0 and 0,1
contains D7–D0. To read the next conversion result,
issue an ACK. To stop reading, issue a NACK.
When the MAX1361/MAX1362 receive a NACK, they
release SDA allowing the master to generate a STOP or
a repeated START condition.
Monitor Mode
Monitor-Mode Overview
The MAX1361/MAX1362 automatically monitor up to four
input channels. For systems with limited I²C bandwidth,
monitor mode allows the µC to set a window by
programming lower and upper thresholds during initial-
ization, and only intervening if the MAX1361/MAX1362
detect an alarm condition. This allows an interrupt-driven
approach as an alternative to continuously polling the
ADC with the µC. Monitor mode reduces processor over-
head and conserves I²C bandwidth.
The following shows an example of events in monitor
mode:
1) Fault condition(s) detected, INT asserted.
2) Host µC services interrupt and send SMBus alert to
identify the alarming device. The MAX1361/
MAX1362 respond with the I²C slave address,
pending arbitration rules. (See the SMBus Alert sec-
tion.)
3) The MAX1361/MAX1362 release the INT.
4) Host-µC reads the alarm-status register, latched-
fault register, and current-conversion results to
determine the alarming channel(s) and course of
action.
5) Host µC services alarm(s); adjusts system parame-
ters as needed and/or adjust lower and upper
thresholds.
6) Clears the alarm register. See the Configuring
Monitor Mode section.
7) Monitor mode resumes.
8) If there is still an active fault, the device asserts INT
again. See step 1.
Writing SCAN1 and SCAN0 bits = [1,0] in the configura-
tion byte activates monitor mode. The MAX1361/
MAX1362 scan from channels 0 up to the channel
selected by [CS1:CS0] at a rate determined by the
scan delay bits. The MAX1361/MAX1362 compare the
conversion results with the lower and upper thresholds
for each channel. When any conversion exceeds the
threshold, the MAX1361/MAX1362 assert an interrupt
by pulling INT low (if enabled). The MAX1361/
MAX1362 set the corresponding flag bit in the alarm-
status register and write conversion results to the
latched-fault register to record the event causing the
alarm condition.
INT active state is randomly delayed with respect to the
conversion. Depending on the number of channels
scanned and the position in the channel scan
sequence, the maximum possible delay for asserting
INT is five conversion periods (34µs typ, delay = 0,0,0).
Configuring Monitor Mode
To write monitoring setup data, set the monitor-setup bit
(bit 0 in setup byte) to 1 to extend writing up to 104 bits
(13 bytes) of monitoring setup data. The number of bits
written to the MAX1361/MAX1362 depends on whether
the part is in single-ended or differential mode and
whether the upper channel limit is set by [CS1:CS0]
(Table 9).
Terminate writing at any time by using a STOP or
repeated START condition. Previous monitoring setup
data not overwritten remains valid.
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