the critical temperature register is likely to be higher than
that of the alarm-upper-boundary register. As a result,
when the temperature is above the critical temperature,
it is likely that it is above the alarm-upper-boundary as
well. In interrupt mode, EVENT asserts when the temper-
ature crosses the alarm upper boundary.
If the EVENT output is cleared and the temperature
continues to increase until it crosses the critical temper-
ature threshold, EVENT asserts again. Because the
temperature is greater than the critical temperature
threshold, a clear event command does not clear the
EVENT output. Once the temperature drops below the
critical temperature, EVENT deasserts immediately.
If the EVENT output is not cleared before the tempera-
ture goes above the critical temperature threshold,
EVENT remains asserted. Attempting a clear event
command has no effect until the temperature drops
below the critical temperature, at which point EVENT
deasserts immediately because of the earlier clear
event command. If no clear event command is attempt-
ed, EVENT remains asserted after the temperature
drops below the critical temperature. At this point, a
clear event command deasserts EVENT.
Detailed Register Descriptions
Capability Register (Read Only)
[Address = 00h, POR = 0017h]
This register indicates the capabilities of the thermal
sensor, including accuracy, temperature range, and
resolution. See Table 3 for register details.
Configuration Register (Read/Write)
[Address = 01h, POR = 0000h]
This register controls the various features of EVENT
functionality, and controls the bit for thermal-sensor
shutdown mode. See Table 4 for register details.
Hysteresis
When enabled, hysteresis is applied to temperature varia-
tions around trigger points. For example, consider the
behavior of the alarm window bit (bit 14 of the tempera-
ture register) when the hysteresis is set to 3癈. As the
temperature rises, bit 14 is set to 1 (temperature is above
the alarm window) when the temperature register con-
tains a value that is greater than the value in the alarm
temperature upper boundary register. If the temperature
decreases, bit 14 remains set until the measured temper-
ature is less than or equal to the value in the alarm tem-
perature upper boundary register minus 3癈.
Precision Temperature Monitor for
DDR Memory Modules
8  _______________________________________________________________________________________
Table 3. Capability Register (Read Only)
Bit 15   Bit 14   Bit 13   Bit 12   Bit 11   Bit 10    Bit 9    Bit 8    Bit 7    Bit 6    Bit 5    Bit 4    Bit 3    Bit 2    Bit 1    Bit 0
BIT
DEFINITION (DESCRIPTIONS IN BOLD TYPE APPLY TO THE MAX6604)
0
Basic capability
1: Has alarm and critical trips capability
1
Accuracy
0 = Default accuracy ?癈 over the active and ?癈 monitor ranges
1 = High accuracy ?癈 over the active and ?癈 monitor ranges
2
Wider range
0 = Values lower than 0癈 are clamped and represented as binary value 0
1 = Can read temperature below 0癈 and set sign bit accordingly
4:3
Temperature resolution
00 = 0.5癈 LSB
01 = 0.25癈 LSB
10 = 0.125癈 LSB
11 = 0.0625癈 LSB
15:5
0: Reserved for future use (RFU). Must be zero.