EMC2103 datasheet(33/85 Pages) MICROCHIP

33 / 85 page

RPM-Based Fan Controller with Hardware Thermal Shutdown

Datasheet

DS0005250A-page 33

 2013 Microchip Technology Inc.

5.8

Ramp Rate Control

The PWM output drive can be configured with automatic ramp rate control. If the RPM based Fan

Speed Control Algorithm is used, then this ramp rate control is automatically used based on the fan

control derivative option settings. See Section 6.23, "Fan Configuration 2 Register". The user programs

a maximum step size for the PWM setting and an update time. The update time varies from 100ms to

1.6s while the PWM maximum step can vary from 1 PWM count to 31 PWM counts.

When a new PWM is entered, the delta from the next PWM and the previous PWM is determined. If

this delta is greater than the Max Step settings, then the PWM is incrementally adjusted every 100ms

to 1.6s as determined by the Update Time until the target PWM setting is reached. See Figure 5.6.

5.9

Watchdog Timer

The EMC2103 contains an internal Watchdog Timer. Once the device has powered up the watchdog

timer monitors the bus traffic for signs of activity. The Watchdog Timer starts when the internal supply

has reached its operating point. The Watchdog Timer only starts immediately after power-up and once

it has been triggered or deactivated will not restart.

If four (4) seconds elapse without the system host programming the device, then the watchdog will be

triggered and the following will occur:

1. The WATCH status bit will be set.

2. The fan driver will be set to full scale drive. It will remain at full scale drive until one of the three

conditions listed below are met.

If the Watchdog Timer is triggered, the following three operations will disable the timer and return the

device to normal operation. Alternately, if the Watchdog Timer has not yet been triggered performing

any one of the following will disable it.

1. Writing the Fan Setting Register will disable the Watchdog Timer.

2. Enabling the RPM based Fan Speed Control Algorithm by setting the EN_ALGO bit will disable the

Watchdog Timer. The fan driver will be set based on the RPM based Fan Speed Control Algorithm.

Figure 5.6 Ramp Rate Control

EMC2103 Datasheet(PDF) 33 Page - Microchip Technology