Pin Descriptions

MC3PHAC Monolithic Intelligent Motor Controller, Rev. 2

Freescale Semiconductor

7

17

RETRY_TxD

In standalone mode, this pin is an output that drives low to indicate the

parameter mux input pin is reading an analog voltage to specify the time

to wait after a fault before re-enabling the PWM outputs. In PC master

software mode, this pin is an output that transmits UART serial data.

18

RBRAKE

Output which is driven to a logic high whenever the voltage on the dc bus

input pin exceeds a preset level, indicating a high bus voltage. This

signal is intended to connect a resistor across the dc bus capacitor to

prevent excess capacitor voltage.

19

DT_FAULTOUT

In standalone mode, this pin is an output which drives low to indicate the

parameter mux input pin is reading an analog voltage to specify the

dead-time between the on states of the top and bottom PWM signals for

a given motor phase. In PC master software mode, this pin is an output

which goes low whenever a fault condition occurs.

20

VBOOST_MODE

At startup, this input is sampled to determine whether to enter standalone

mode (logic high) or PC master software mode (logic low). In

standalone mode, this pin is also used as an output that drives low to

indicate the parameter mux input pin is reading an analog voltage to

specify the amount of voltage boost to apply to the motor.

21

+5-volt digital power supply to the MC3PHAC

22

Digital power supply ground return for the MC3PHAC

23

FWD

Input which is sampled to determine whether the motor should rotate in

the forward or reverse direction

24

START

Input which is sampled to determine whether the motor should be

running.

25

MUX_IN

In standalone mode, during initialization this pin is an output that is used

to determine PWM polarity and base frequency. Otherwise, it is an

analog input used to read several voltage levels that specify MC3PHAC

operating parameters.

26

SPEED

In standalone mode, during initialization this pin is an output that is used

to determine PWM polarity and base frequency. Otherwise, it is an

analog input used to read a voltage level corresponding to the desired

steady-state speed of the motor.

27

ACCEL

In standalone mode, during initialization this pin is an output that is used

to determine PWM polarity and base frequency. Otherwise, it is an

analog input used to read a voltage level corresponding to the desired

acceleration of the motor.

28

DC_BUS

In standalone mode, during initialization this pin is an output that is used

to determine PWM polarity and base frequency. Otherwise, it is an

analog input used to read a voltage level proportional to the dc bus

voltage.

1. Correct timing of the MC3PHAC is based on a 4.00 MHz crystal or ceramic resonator. Follow the crystal/resonator

manufacturer’s recommendations, as the crystal/resonator parameters determine the external component values required

for maximum stability and reliable starting. The load capacitance values used in the oscillator circuit design should include

all stray capacitances.

Table 2. MC3PHAC Pin Descriptions (Sheet 2 of 2)

Pin

Number

Pin Name

Pin Function