MC33033

12

MOTOROLA ANALOG IC DEVICE DATA

Figure 20. PWM Timing Diagram

Current Sense

Input

Capacitor CT

Error Amp Out/

PWM Input

Latch “Set”

Inputs

Top Drive

Outputs

Bottom Drive

Outputs

Figure 21. Reference Output Buffers

The NPN circuit is recommended for powering Hall or opto sensors, where the

output voltage temperature coefficient is not critical. The PNP circuit is slightly

more complex, but also more accurate. Neither circuit has current limiting.

To

Control

Circuitry

6.25 V

Sensor

Power

≈5.6 V

MPS

U51A

Vin

14

UVLO

MPS

U01A

Vin

To Control Circuitry

and Sensor Power

6.25 V

UVLO

14

36

REF

7

0.1

REF

7

Load

Figure 22. High Voltage Interface with

NPN Power Transistors

Figure 23. High Voltage Interface with

N–Channel Power MOSFETs

Transistor Q1 is a common base stage used to level shift from VCCtothehigh

motor voltage, VM. The collector diode is required if VCC is present while VM

is low.

Load

Q4

VM

VCC

Q2

Q3

Q1

17

20

1

2

AT

BT

CT

Rotor

Position

Decoder

16

15

VCC = 12 V

1N4744

VM = 170 V

VBoost

1.0 k

5

4

6

2

4.7 k

1.0 M

1

MOC8204

Optocoupler

17

20

1

2

AT

BT

CT

Rotor

Position

Decoder

16

15