Rainbow Electronics MAX1617A - Manual (Page 14)

MAX1617A
Remote/Local Temperature Sensor
with SMBus Serial Interface
14 ______________________________________________________________________________________
The address pin states are checked at POR and SPOR
only, and the address data stays latched to reduce qui-
escent supply current due to the bias current needed
for high-Z state detection.
The MAX1617A also responds to the SMBus Alert
Response slave address (see the
Alert Response
Address section).
POR and UVLO
The MAX1617A has a volatile memory. To prevent ambig-
uous power-supply conditions from corrupting the data in
memory and causing erratic behavior, a POR voltage
detector monitors V
CC and clears the memory if V CC falls
below 1.7V (typical, see Electrical Characteristics table).
When power is first applied and V CC rises above 1.75V
(typical), the logic blocks begin operating, although reads
and writes at V
CC levels below 3V are not recommended.
A second V CC comparator, the ADC UVLO comparator,
prevents the ADC from converting until there is sufficient
headroom (V
CC = 2.8V typical).
The SPOR software POR command can force a power-on
reset of the MAX1617A registers via the serial interface.
Use the SEND BYTE protocol with COMMAND = FCh.
This is most commonly used to reconfigure the slave
address of the MAX1617A “on the fly,” where external
hardware has forced new states at the ADD0 and ADD1
address pins prior to the software POR. The new address
takes effect less than 100µs after the SPOR transmission
stop condition.
Power-Up Defaults:
•
Interrupt latch is cleared.
•
Address select pins are sampled.
•
ADC begins auto-converting at a 0.25Hz rate.
•
Command byte is set to 00h to facilitate quick
remote Receive Byte queries.
•
T HIGH and T LOW registers are set to max and min
limits, respectively.
Table 8. RLTS and RRTE Temp Register Update Timing Chart
n/a (0.25Hz)
NEW CONVERSION RATE
(CHANGED VIA WRITE TO
WCRW)
Power-on reset Auto-Convert
OPERATING MODE CONVERSION INITIATED BY:
156ms max
TIME UNTIL RLTS AND RRTE
ARE UPDATED
156ms max n/a
1-shot command, while idling
between automatic conversions
Auto-Convert
When current conversion is
complete (1-shot is ignored)
20sec
n/a
0.0625Hz Rate timer Auto-Convert
1-shot command that occurs
during a conversion
Auto-Convert
10sec
5sec
0.125Hz
0.25Hz Rate timer Auto-Convert
2.5sec
1.25sec
0.5Hz
1Hz Rate timer Auto-Convert
Rate timer Auto-Convert
Rate timer Auto-Convert
625ms
312.5ms
2Hz
4Hz Rate timer Auto-Convert
237.5ms
156ms
8Hz
n/a STBY pin Hardware Standby
Rate timer Auto-Convert
Rate timer Auto-Convert
156ms
156ms
n/a
n/a 1-shot command Software Standby
RUN/STOP bit Software Standby
Table 9. Slave Address Decoding (ADD0
and ADD1)
Note: High-Z means that the pin is left unconnected and floating.
0011 001 High-Z GND
0011 000
ADDRESS
0101 001 GND High-Z
0011 010 V CC GND
0101 011 V CC High-Z
0101 010
1001 101 High-Z V CC
1001 100
GND GND
GND V CC
High-Z High-Z
1001 110 V CC V CC
ADD0 ADD1