EMC2103 datasheet(67/85 Pages) MICROCHIP

67 / 85 page

RPM-Based Fan Controller with Hardware Thermal Shutdown

Datasheet

 2013 Microchip Technology Inc.

DS0005250A-page 67

The Look Up Table Registers hold the 40 entries of the Look Up Table that controls the drive of the

PWM. As the temperature channels are updated, the measured value for each channel is compared

against the respective entries in the Look Up Table and the associated drive setting is loaded into an

internal shadow register and stored.

The bit weighting for temperature inputs represents °C and is compared against the measured data.

Note that the LUT entry does not include a sign bit. The Look Up Table does not support negative

temperature values and the MSBit should not be set for a temperature input.

Each temperature channel threshold shares the same hysteresis value. When the measured

temperature for any of the channels meets or exceeds the programmed threshold, the drive setting

associated with that threshold is used. The temperature must drop below the threshold minus the

hysteresis value before the drive setting will be set to the previous value.

If the RPM based Fan Speed Control Algorithm is used, the TACH Target is updated after every

conversion. It is always set to the minimum TACH Target that is stored by the Look Up Table. The

PWM duty cycle is updated based on the RPM based Fan Speed Control Algorithm configuration

settings.

If the RPM based Fan Speed Control Algorithm is not used, then the PWM duty cycle is updated after

every conversion. It is set to the maximum duty cycle that is stored by the Look Up Table.

52h

R/W

LUT Ext

Diode 1

Setting 1

7Fh

(127°C)

53h

R/W

LUT Ext

Diode 2

Setting 1

7Fh

(127°C)

54h

R/W

LUT Temp 3

Setting 1

7Fh

(127°C)

55h

R/W

LUT Temp 4

Setting 1

7Fh

(127°C)

. . .

74h

R/W

LUT Drive

Setting 8

‘0’

4096

2048

1024

512

256

128

92h

‘1’

128

75h

R/W

LUT Ext

Diode 1

Setting 8

7Fh

(127°C)

76h

R/W

LUT Ext

Diode 2

Setting 8

7Fh

(127°C)

77h

R/W

LUT Temp 3

Setting 8

7Fh

(127°C)

78h

R/W

LUT Temp 4

Setting 8

7Fh

(127°C)

79h

R/W

LUT Temp

Hysteresis

0Ah

Table 6.50 Look Up Table Registers (continued)

ADDR

R/W

RPM /

PWM

DEFAULT

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