Rainbow Electronics MAX6622 - Manual (Page 8)

MAX6622
conversion results until they have been read. If the most
significant bits have not been read within an SMBus
timeout period (nominally 37ms), normal updating con-
tinues. Table 1 shows the main temperature register
(high byte) data format, and Table 2 shows the extend-
ed resolution register (low byte) data format.
Diode Fault Detection
If a channel’s input DXP_ and DXN_ are left open, the
MAX6622 detects a diode fault. An open diode fault
does not cause either ALERT or OVERT to assert. A bit in
the status register for the corresponding channel is set to
1 and the temperature data for the channel is stored as
all 1s (FFh). It takes approximately 4ms for the MAX6622
to detect a diode fault. Once a diode fault is detected,
the MAX6622 goes to the next channel in the conversion
sequence. Depending on operating conditions, a short-
ed diode may or may not cause
ALERT or OVERT to
assert, so if a channel will not be used, its DXN and DXP
inputs should be left unconnected.
5-Channel Precision Temperature Monitor
8 _______________________________________________________________________________________
Write Byte Format
Read Byte Format
Send Byte Format Receive Byte Format
SLAVE ADDRESS: EQUIVALENT
TO CHIP-SELECT LINE OF A
3-WIRE INTERFACE COMMAND BYTE: SELECTS TO
WHICH REGISTER YOU ARE
WRITING DATA BYTE: DATA GOES INTO THE REGISTER
SET BY THE COMMAND BYTE (TO SET
THRESHOLDS, CONFIGURATION MASKS, AND
SAMPLING RATE)
SLAVE ADDRESS: EQUIVALENT
TO CHIP-SELECT LINE COMMAND BYTE: SELECTS
FROM WHICH REGISTER YOU
ARE READING SLAVE ADDRESS: REPEATED
DUE TO CHANGE IN DATA-
FLOW DIRECTION DATA BYTE: READS FROM
THE REGISTER SET BY THE
COMMAND BYTE
COMMAND BYTE: SENDS COM-
MAND WITH NO DATA, USUALLY
USED FOR ONE-SHOT COMMAND
DATA BYTE: READS DATA FROM
THE REGISTER COMMANDED BY
THE LAST READ BYTE OR WRITE
BYTE TRANSMISSION; ALSO
USED FOR SMBus ALERT
RESPONSE RETURN ADDRESS
S = START CONDITION. SHADED = SLAVE TRANSMISSION.
P = STOP CONDITION. /// = NOT ACKNOWLEDGED.
S ADDRESS RD ACK DATA /// P
7 bits 8 bits
WR S ACK COMMAND ACK P
8 bits
ADDRESS
7 bits
P
1
ACK DATA
8 bits
ACK COMMAND
8 bits
ACK WR ADDRESS
7 bits
S
S ADDRESS WR ACK COMMAND ACK S ADDRESS
7 bits 8 bits 7 bits
RD ACK DATA
8 bits
/// P
Figure 2. SMBus Protocols
TEMP (°C) DIGITAL OUTPUT
> +127 0111 1111
+127 0111 1111
+126 0111 1110
+25 0001 1001
0 0000 0000
< 0 0000 0000
Diode fault (open) 1111 1111
Diode fault (short) 1111 1111 or 1110 1110
Table 1. Main Temperature Register
(High-Byte) Data Format
TEMP (°C) DIGITAL OUTPUT
0 000X XXXX
+0.125 001X XXXX
+0.250 010X XXXX
+0.375 011X XXXX
+0.500 100X XXXX
+0.625 101X XXXX
+0.725 110X XXXX
+0.875 111X XXXX
Table 2. Extended Resolution Temperature
Register (Low-Byte) Data Format