ZXBM1016

Issue 1 - February 2007

8

www.zetex.com

© Zetex Semiconductors plc 2007

A capacitor is connected from this pin to ground. It is used to store a signal that is proportional

to the commutation period. The stored signal is a representation of the motor speed and is used

Range - Speed range setting pin

The ZXBM1016 is designed to operate over a predefined dynamic range. This will normally be in

excess of 10:1 i.e. the lowest speed will be 1/10 of the full speed. In some instance the speed range

might be 200rpm to 2,000rpm yet in others it could be 1,000 to 10,000rpm. This pin allows the tail-

end current control operation to be tuned to the desired speed range. To do this a resistor is

attached between the range pin and the ThRef pin.

The following graph gives a range of resistor values against the speed range.

Typically a 220k

resistor will cover most mid speed range motors of 600rpm to 6,000rpm,

however a lower value can be used to enable the motor to be run at higher speeds. Conversely a

higher value will be needed for motors running at a lower speed range.

CPWM - Sets PWM frequency

This pin has an external capacitor attached to set the PWM frequency for the phase drive outputs.

A capacitor value of 0.1nF will provide a PWM frequency of typically 25kHz.

FG - Frequency generator (speed)

This is the frequency generator output and is a buffered signal from the Hall sensor.

This is an open collector drive giving an active pull down with the high level being provided by

an external pull up resistor.

Ph1Lo and Ph2Lo - Low-side external H-bridge driver

These pair of outputs drive the low side of the external power device H-bridge that in turn drives

the single phase winding. These outputs provide both the commutation and PWM waveforms.

The outputs are active pull-up and active pull-down to help faster switching off when driving

MOSFET devices with a high gate capacitance. When in the high state the outputs will provide up

to 80mA of drive into the base or gates of external transistors as shown in the typical application

circuit shown on the front page.

When in the low state the active phase drive is again capable of sinking up to 80mA to aid turn

off times during PWM operation. When the phase is inactive the output is held low by a 7.5k

internal pull-down resistor.

0

2000

4000

6000

8000

10000

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

220k

Ω

470k

Ω

120k

Ω

360k

Ω

Speed (rpm)

750k

Ω

μF