EMC2103 datasheet(32/85 Pages) MICROCHIP

32 / 85 page

RPM-Based Fan Controller with Hardware Thermal Shutdown

Datasheet

 2013 Microchip Technology Inc.

DS0005250A-page 32

5.7

Spin Up Routine

The EMC2103 also contains programmable circuitry to control the spin up behavior of the fan driver

to ensure proper fan operation. The Spin Up Routine is initiated under the following conditions when

the Tach Period Measurement method of tach measurement is used. This applies to either the RPM

based Fan Speed Control Algorithm mode or the Direct Setting mode (with or without the Look Up

Table).

1. The TACH Target Register value changes from a value of FFh to a value that is less than the Valid

TACH Count.

2. The RPM based Fan Speed Control Algorithm’s measured TACH Reading Register value is greater

than the Valid TACH Count setting.

When the Spin Up Routine is operating, the fan driver is set to full scale (optional) for one quarter of

the total user defined spin up time. For the remaining spin up time, the fan driver output is set a a user

defined level (30% through 65% drive).

After the Spin Up Routine has finished, the EMC2103 measures the TACH signal. If the measured

TACH Reading Register value is higher than the Valid TACH Count Register setting, the FAN_SPIN

status bit is set and the Spin Up Routine will automatically attempt to restart the fan.

Figure 5.5 shows an example of the Spin Up Routine in response to a programmed fan speed change

based on the first condition above.

Figure 5.5 Spin Up Routine

EMC2103 Datasheet(PDF) 32 Page - Microchip Technology