MAX1361 Datasheet, PDF(15/24 Page) Maxim Integrated Products – 4-Channel, 10-Bit, System Monitors with Programmable Trip Window and SMBus Alert Response

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MAX1361 Datasheet, PDF (15/24 Pages) Maxim Integrated Products – 4-Channel, 10-Bit, System Monitors with Programmable Trip Window and SMBus Alert Response

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4-Channel, 10-Bit, System Monitor with Programmable

Trip Window and SMBus Alert Response

return to F/S mode. Use a repeated START condition

(Sr) in place of a STOP condition to leave the bus

active and the mode unchanged.

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

significant 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 I2C 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 0.5ÂµA (external reference mode, typ)

and 300ÂµA (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 VDD 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 60ÂµA (typ) and drops to 6ÂµA (typ) at

1ksps. At 0.1ksps, the average supply current is just

1ÂµA. 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.

Table 3. Reference Voltage and AIN3/REF Format

SEL1

SEL0

INT REF

POWERDOWN

REFERENCE VOLTAGE

VDD

External reference

Internal reference

AIN3/REF

Analog input

Reference input

Analog input

Reference output

INTERNAL

REFERENCE STATE

Always off

Always on

Always off

Always on

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