EMC6D102-CZC View Datasheet(PDF) - SMSC -> Microchip

Part Name

Description

MFG CO.

EMC6D102-CZC

Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features

SMSC -> Microchip 

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Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features

Datasheet

Notes:

■ Whenever the programmed number of edges is detected, the edge detection ends and the state

machine is reset. The tachometer reading register is updated with the tachometer count value at

this time. See Note 6.2 below Table 6.2 for the one exception to this behavior.

■ In the case where the programmed number of edges occurs during the stretching time, the

tachometer value is latched when the last required edge is detected. The table below shows the

maximum values that may appear in the reading register.

Table 6.2 Max Tachometer Count Values for Different Stretch Periods

PWM STRETCHING PERIOD

50ms

100ms

200ms

400ms

600ms

800ms

950ms

MAXIMUM TACHOMETER COUNT AT END OF PERIOD

(Note 6.1)

1194h

2328h

4650h

8CA0h

D2F0h

FFFFh (Note 6.2)

FFFFh (Note 6.2)

6.1.4.8

Note 6.1 The maximum tachometer count does not take into account the guard time.

Note 6.2

This max value will be FFFFh if the programmed number of edges is detected when the

count reaches FFFFh or if no edges are detected. If the count reaches FFFFh in Mode 1

or the Max stretch time in Mode 2 and some edges were detected, but less than the

programmed number of edges, the maximum tach count value is determined by the Slow

Interrupt Enable bit located in the TACHx Options registers at offsets 90h to 93h. If slow

interrupt detection is enabled the count will be forced to FFFEh, else the count will be

forced to FFFFh.

Examples of Minimum RPMs Supported

The following tables show minimum RPMs that can be supported with the different parameters. The

first table uses 3 edges and the second table uses 2 edges.

Table 6.3 Minimum RPM Detectable Using 3 Edges – No PWM Stretching

PWM

FREQUENCY

(HZ)

87.7

58.6

44

35.2

PULSE WIDTH AT DUTY CYCLE

(PWM ”ON” TIME)

25%

(MSEC)

2.85

4.27

5.68

7.1

50%

(MSEC)

5.7

8.53

11.36

14.2

100%

(MSEC)

(Note 6.3)

11.36

17

22.64

28.3

MINIMUM RPM AT DUTY CYCLE (Note 6.4)

(30/TTachPulse)

25%

10865

7175

5366

4279

50%

5347

3554

2662

2126

100%

2662

1774

1330

1063

SMSC EMC6D102

41

DATASHEET

Revision 0.4 (04-05-05)

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