EMC2104 datasheet(35/101 Pages) SMSC

35 / 101 page

Dual RPM-Based PWM Fan Controller with Hardware Thermal Shutdown

Datasheet

SMSC EMC2104

Revision 1.74 (05-08-08)

DATASHEET

APPLICATION NOTE: Disabling the Watchdog will not automatically set the fan drive. This must be done manually

(or via the Look Up Table).

5.10

Fault Queue

The EMC2104 contains a programmable fault queue on all fault conditions except a FAN_SHORT or

TSD condition (including all temperature high, low, and tcrit limits as well as the hardware set thermal

limit). The fault queue defines how many consecutive out-of-limit conditions must be reported before

the corresponding status bit is set (and the ALERT# pin asserted).

APPLICATION NOTE: With the exception of the Tcrit limit, the fault queue is not applied to the internal diode

measurement.

5.11

Temperature Monitoring

The EMC2104 can monitor the temperature of up to four (4) externally connected diodes as well as

the internal or ambient temperature. Each channel is configured with the following features enabled or

disabled based on user settings and system requirements.

APPLICATION NOTE: When measuring an Intel 45nm CPU, the reported temperature will have an error of

approximately 1.5°C at 100°C. This error is related to a non-perfect ideality factor of the CPU

diode and is proportional to the diode temperature.

5.11.1

Dynamic Averaging

The EMC2104 supports dynamic averaging. When enabled, this feature changes the conversion time

for all channels based on the selected conversion rate. This essentially increases the averaging factor

as shown in Table 5.4. The benefits of Dynamic Averaging are improved noise rejection due to the

longer integration time as well as less random variation on the temperature measurement.

5.11.2

Resistance Error Correction

The EMC2104 includes active Resistance Error Correction to remove the effect of up to 100 ohms of

series resistance. Without this automatic feature, voltage developed across the parasitic resistance in

the remote diode path causes the temperature to read higher than the true temperature is. The error

induced by parasitic resistance is approximately +0.7°C per ohm. Sources of parasitic resistance

include bulk resistance in the remote temperature transistor junctions, series resistance in the CPU,

and resistance in the printed circuit board traces and package leads. Resistance error correction in the

EMC2104 eliminates the need to characterize and compensate for parasitic resistance in the remote

diode path.

Table 5.4 Dynamic Averaging Behavior

CONVERSION RATE

AVERAGING FACTOR (RELATIVE TO 11-BIT CONVERSI0N)

DYNAMIC AVERAGING

ENABLED

DYNAMIC AVERAGING

DISABLED

1 / sec

2 / sec

4 / sec

8 / sec

EMC2104 Datasheet(PDF) 35 Page - SMSC Corporation

EMC2104 Datasheet(HTML) 35 Page - SMSC Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL