Software Description
Configuration/Setup Bytes (Write Cycle)
A write cycle begins with the bus master issuing a
START condition followed by 7 address bits and a write
bit (R/W = 0). If the address byte is successfully
received, the MAX1361/MAX1362 (slave) issue an ACK.
The master then writes to the slave. If the most signifi-
cant bit (MSB) is 1, the slave recognizes the received
byte as the setup byte (Table 4). If the MSB is 0, the
slave recognizes that byte as the configuration byte
(Table 2). Write to the configuration byte before writing
to the setup byte (Figure 8). If enabling RESET in the
setup byte, rewrite the configuration byte after writing
the setup byte, since RESET clears the contents of the
configuration byte back to the power-up state.
When the monitor-setup bit of the setup byte is set to 1,
writing extends up to 13 bytes to clock in monitor-setup
data. Terminate writing monitor-setup data at any time
by issuing a STOP or repeated START condition. If the
slave receives a byte successfully, it issues an ACK
(Figure 9).
Note: When operating in HS mode, a STOP condition
returns the bus into F/S mode (see the
HS I
2
C Mode
section).
Automatic Shutdown
AutoShutdown occurs between conversions when the
MAX1361/MAX1362 are idle. When operating in exter-
nal clock mode, issue a STOP, NACK, or repeated
START condition to place the devices in idle mode and
benefit from automatic shutdown. A STOP condition is
not necessary in internal clock mode for automatic
shutdown because power-down occurs once all con-
versions are complete. Shutdown reduces supply cur-
rent to less than 0.5µA (external reference mode, typ)
and 300µA (internal reference mode, typ).
When idle, the MAX1361/MAX1362 continuously wait
for a START condition followed by their slave address.
Upon reading a valid address byte, the MAX1361/
MAX1362 power up. The internal reference requires
10ms to wake up. Therefore, power up the internal ref-
erence 10ms prior to conversion or leave the reference
continuously powered. Wake-up is transparent when
using an external reference or V
DD
as the reference.
Automatic shutdown results in dramatic power savings,
particularly at slow conversion rates with internal clock.
For example, using an external reference at a conver-
sion rate of 10ksps, the average supply current for the
MAX1361 is 60µA (typ) and drops to 6µA (typ) at
1ksps. At 0.1ksps, the average supply current is just
1µA. Table 3 shows AIN3/REF configuration and refer-
ence power-down state.
Scan Modes
SCAN1 and SCAN0 of the configuration byte set the
scan-mode configuration. When configuring AIN3/REF
for reference input or output (SEL0 = 1), AIN3/REF is
excluded from a multichannel scan. The scanned
results write to memory in the same order as the con-
version. Start a conversion sequence by initiating a
read with the desired scan mode. Read the results from
memory in the order they were converted (see the
Reading a Conversion (Read Cycle)
section).
Selecting channel scan mode [0,0] starts converting
from channel 0 up to the channel chosen by CS1, CS0.
Selecting channel scan mode [0,1] converts the chan-
nel selected by CS1, CS0 eight times and returns eight
consecutive results.
Selecting monitor mode [1,0] initiates a continuous con-
version scan sequence from channel 0 to the channel
selected by CS1, CS0. See the
Monitor Mode
section
for more details.
Selecting channel scan mode [1,1] performs a single
conversion on the channel selected by CS1, CS0 and
returns the result.
MAX1361/MAX1362
4-Channel, 10-Bit, System Monitor with Programmable
Trip Window and SMBus Alert Response
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