EMC2101-R-ACZL-TR datasheet(18/56 Pages) MICROCHIP

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EMC2101

DS20006703A-page 18

 2022 Microchip Technology Inc. and its subsidiaries

4.5.6

DIODE FAULTS

The EMC2101 detects the major types of diode faults;

an open input DP-DN, a short across DP-DN, short to

GND, and short to VDD. For each temperature

measurement made, the device checks for a diode fault

on the external diode.

If an open fault or a short of the DP pin to VDD is

detected, then the temperature data is changed to

+127°C and the Fault bit in the Status Register will be

set. If the high and/or TCRIT limits are set below this

value, and they are not masked, then the ALERT/TACH

pin will be asserted. In addition, the HIGH and TCRIT

status bits will be set accordingly.

If a short between the diode pins or a short to GND is

detected, then the temperature data is changed to

+127.875°C. If the high and/or TCRIT limits are set

below this value, and they are not masked, then the

ALERT/TACH pin will be asserted. In addition, the

HIGH and TCRIT status bits will be set accordingly. The

FAULT bit will not be set.

If the Temperature Filter is enabled and a diode fault

occurs, the diode fault status bit will be set and the

temperature data is updated immediately. The Filter will

stop accumulating data so long as the diode fault

remains in effect.

When a Diode Fault is detected, the ALERT/TACH pin

behavior is still subject to the Fault Queue.

4.6

Fan Control

The EMC2101 includes either a PWM or a linear DAC

based fan driver on the shared FAN pin. Both PWM and

DAC use the Fan Control Look-Up Table and/or Fan

Setting Register interchangeably as well as the

Spin-Up Routine.

In addition, the EMC2101 can monitor the fan speed

using the ALERT/TACH pin.

4.6.1

DAC DRIVER

The Linear DAC driver included in the EMC2101 has

6-bits of resolution based on the supply voltage and is

used for linear drive fan circuits. Its advantages over

PWM drive circuits include reduced circuit complexity

at the expense of reduced effective signal range.

When using the DAC Driver, the pull-up resistor on the

FAN pin should be removed.

The DAC driver output voltage is controlled by either

the Fan Setting Register (see Section 5.18 “Fan

Setting Register”) or the Fan Control Look-Up Table

Registers (see Section 5.22 “Fan Control Look-Up

Table Registers”). It is also controlled by the

POLARITY bit (see Section 5.16 “Fan Configuration

Section 5.19 “PWM Frequency Register”) and PWM

Divider Register (see Section 5.20 “PWM Frequency

Divide Register”) have no effect on the DAC’s output

voltage range, resolution, or response.

4.6.2

PWM DRIVER

The PWM driver included in the EMC2101 has, at

most, 64 steps equaling 1.5% resolution. The effective

resolution, duty cycle, and frequency are all adjustable

based on programmed values. The advantages over

linear drive circuits include a large signal range (0% to

100% duty cycle) at the expense of added complexity

on the drive circuit.

The PWM output is open drain and requires a pull-up

resistor to VDD.

4.6.3

TACH MONITOR

The TACH monitor counts the number of clock pulses

that occur between five edges of the TACH signal. The

monitor assumes that the tachometer signal is always

valid (such as generated from a 4-wire fan or a direct

drive fan) and that the tachometer signal generates 2

TACH pulses per fan revolution.

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