Locked Rotor timing capacitor (CONT).

As these threshold voltages are nominally set to

as follows:

T

C

I

LCK

LCKC

lock

=

×

2

T=

C

I

on

LCK

LCKC

T

C

I

LCK

LCKD

off

=

- Sets PWM frequency

- external PWM input

This pin has an external capacitor attached to set the

PWM frequency for the Phase drive outputs. A

capacitor value of 0.15nF will provide a PWM

frequency of typically 24kHz.

following equation:

T=

(V

- V

)

C

I

(V

V

)

C

I

lock

THH

THL

PWMC

THH

THL

PWMD

×

+

−×

discharge currents.

As these threshold voltages are nominally set to

as follows:

T

C

I

C

I

PWM

PWMC

PWMD

=+

externally derived PWM signal to control the motor

speed. The signal should have a VOL <1V and a VOH

>2V. A standard TTL or CMOS digital signal is ideal.

When driving from an external PWM source no

SPD pin should be left open circuit.

9. PH2

- External transistor driver

10. PH1

- External transistor driver

These are the Phase drive outputs and are open

darlington emitter followers designed to provide up to

80mA of drive to external transistors as shown in the

Application circuits following. The external transistors

in turn drive the fan motor windings.

ZXBM2001

ZXBM2002 ZXBM2003

SEMICO NDUC TORS

ISSUE 4 - OCTOBER 2004

6