Rainbow Electronics MAX6649 - Manual (Page 11)

MAX6646/MAX6647/MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
______________________________________________________________________________________ 11
Slave Addresses
The MAX6646/MAX6647/MAX6649 have fixed slave
addresses (see Table 9). All devices also respond to the
SMBus alert response slave address (see the Alert
Response Address section).
POR and UVLO
To prevent ambiguous 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 2.0V (typ). When
power is first applied and V CC rises above 2.0V (typ),
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 = 2.7V typ).
Power-Up Defaults
Power-up defaults include:
• Interrupt latch is cleared.
• ADC begins autoconverting at a 4Hz rate.
• Command byte is set to 00h to facilitate quick local
temperature receive byte queries.
• Local (internal) T HIGH limit is set to +85°C.
• Local (internal) T LOW limit is set to 0°C.
• Remote (external) T HIGH limit is set to +85°C
(MAX6649)/+95°C (MAX6646/MAX6647)
• OVERT (internal) limit is set to +85°C
• OVERT (external) limit is set to +85°C (MAX6649)/
+125°C (MAX6646/MAX6647)
DATA
CONVERSION
RATE (Hz)
00h 0.0625
01h 0.125
02h 0.25
03h 0.5
04h 1
05h 2
06h 4
07h 4
08h-FFh Reserved
Table 8. Conversion-Rate Control Byte
(04h)
BIT NAME
POR
STATE
FUNCTION
7 (MSB) BUSY 0 A/D is busy converting when 1.
6 LHIGH 0
Local (internal) high-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
5 LLOW 0
Local (internal) low-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
4 RHIGH 0
Remote (external) high-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
3 RLOW 0
Remote (external) low-temperature alarm has tripped when 1; cleared by POR or readout of the
status byte if the fault condition no longer exists.
2 FAULT 0
A 1 indicates DXN and DXP are either shorted or open; cleared by POR or readout of the status
byte if the fault condition no longer exists.
1 EOT 0 A 1 indicates the remote (external) junction temperature exceeds the external OVERT threshold.
0 IOT 0 A 1 indicates the local (internal) junction temperature exceeds the internal OVERT threshold.
Table 7. Status Register Bit Assignments (02h)
PART SLAVE ADDRESS
MAX6646 1001 101
MAX6647 1001 110
MAX6649 1001 100
Table 9. Slave Addresses