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°C. 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°C.

Precision Temperature Monitor for

DDR Memory Modules

8

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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 ±2°C over the active and ±3°C monitor ranges

1 = High accuracy ±1°C over the active and ±2°C monitor ranges

2

Wider range

0 = Values lower than 0°C are clamped and represented as binary value 0

1 = Can read temperature below 0°C and set sign bit accordingly

4:3

Temperature resolution

00 = 0.5°C LSB

01 = 0.25°C LSB

10 = 0.125°C LSB

11 = 0.0625°C LSB

15:5

0: Reserved for future use (RFU). Must be zero.