Rainbow Electronics MAX6696 - Manual (Page 10)

MAX6695/MAX6696
extended temperature register (11h) (Table 3), which
extends the temperature data to 10 bits + sign and the
resolution to +0.125°C per LSB (Table 4).
When a conversion is complete, the main register and
the extended register are updated almost simultane-
ously. Ensure that no conversions are completed
between reading the main and extended registers so
that when data that is read, both registers contain the
result of the same conversion.
To ensure valid extended data, read extended resolu-
tion temperature data using one of the following
approaches:
• Put the MAX6695/MAX6696 into standby mode by
setting bit 6 of the configuration register to 1. Read
the contents of the data registers. Return to run
mode by setting bit 6 to zero.
• Put the MAX6695/MAX6696 into standby mode by
setting bit 6 of the configuration register to 1. Initiate
a one-shot conversion using Send Byte command
0Fh. When this conversion is complete, read the
contents of the temperature data registers.
Diode Fault Alarm
There is a continuity fault detector at DXP_ that detects
an open circuit between DXP_ and DXN, or a DXP_
short to V
CC
, GND, or DXN. If an open or short circuit
exists, the external temperature register (01h) is loaded
with 1000 0000. Bit 2 (diode fault) of the status registers
is correspondingly set to 1. The ALERT output asserts
for open diode faults but not for shorted diode faults.
Immediately after power-on reset (POR), the status reg-
ister indicates that no fault is present until the end of
the first conversion. After the conversion is complete,
any diode fault is indicated in the appropriate status
register. Reading the status register clears the diode
fault bit in that register, and clears the ALERT output if
set. If the diode fault is present after the next conver-
sion, the status bit will again be set and the ALERT out-
put will assert if the fault is an open diode fault.
Alarm Threshold Registers
Six registers, WLHO, WLLM, WRHA (1 and 2), and
WRLN (1 and 2), store ALERT threshold values. WLHO
and WLLM, are for
internal ALERT high-temperature
and low-temperature limits, respectively. Likewise,
WRHA and WRLN are for
external channel 1 and chan-
nel 2 high-temperature and low-temperature limits,
respectively (Table 5). If either measured temperature
equals or exceeds the corresponding ALERT threshold
value, the ALERT output is asserted. The POR state of
both internal and external ALERT high-temperature limit
registers is 0100 0110 or +70°C.
Dual Remote/Local Temperature Sensors with
SMBus Serial Interface
10 ______________________________________________________________________________________
TEMP ( ° C) DIGITAL OUTPUT
+130.00 0 111 1111
+127.00 0 111 1111
+126.00 0 111 1110
+25.25 0 001 1001
+0.50 0 000 0001
0 0 000 0000
-1 1 111 1111
-55 1 100 1001
Diode fault
(short or open)
1 000 0000
Table 2. Data Format (Two’s Complement)
FRACTIONAL
TEMPERATURE ( ° C)
CONTENTS OF
EXTENDED REGISTER
0 000X XXXX
+0.125 001X XXXX
+0.250 010X XXXX
+0.375 011X XXXX
+0.500 100X XXXX
+0.625 101X XXXX
+0.750 110X XXXX
+0.875 111X XXXX
Table 3. Extended Resolution Register
Note: Extended resolution applies only for conversion rate
control register values of 05h or less.
TEMP ( ° C) INTEGER TEMP FRACTIONAL TEMP
+130.00 0 111 1111 000X XXXX
+127.00 0 111 1111 000X XXXX
+126.5 0 111 1110 100X XXXX
+25.25 0 001 1001 010X XXXX
+0.50 0 000 0000 100X XXXX
0 0 000 0000 000X XXXX
-1 1 111 1111 000X XXXX
-1.25 1111 1111 010X XXXX
-55 1100 1001 000X XXXX
Table 4. Data Format in Extended Mode