ML4428
PIN DESCRIPTION
PIN NAME
FUNCTION
PIN NAME
FUNCTION
1
I
SNS
Motor current sense input. Current
limit one-shot is triggered when this
pin is approximately 0.5V.
Drives the external P-channel
transistor driving motor PHI1.
Drives the external P-channel
transistor driving motor PHI2.
Drives the external P-channel
transistor driving motor PHI3.
The resistor/capacitor combination on
this gm amplifier output sets a pole
zero of the speed loop in conjunction
with a gm of 0.230mmho.
A capacitor to ground at this pin sets
the PWM oscillator frequency. A 1nF
capacitor will set the frequency to
approximately 25kHz for PWM speed
control. Grounding this pin selects
linear speed control.
This voltage reference output (6V) can
be used to set the speed reference
voltage.
This voltage input to the amplifier in
the speed loop controls the speed
target of the motor.
Drives the external N-channel
MOSFETs for PHI1.
Drives the external N-channel
MOSFETs for PHI2.
Drives the external N-channel
MOSFETs for PHI3.
The forward/reverse pin controls the
sequence of the commutation states
and thus the direction of motor
rotation. (TTL level)
This logic output indicates the
commutation frequency of the motor
in run mode. (TTL level)
12V power supply.
Timing capacitor for VCO
16 R
VCO
17 C
SNS
The resistor on this pin sets a process
independent current to generate a
repeatable VCO frequency.
This capacitor to ground sets the ON
time of the 6 sense pulses used for
position detection at start-up and at
low speeds. A 5.6nF capacitor will set
the on time to approximately 200µs.
A logic “0” indicates the power supply
is under-voltage. (TTL level)
This resistor sets the minimum VCO
frequency, and thus, the initial on time
of the drive energization at start-up. A
2 M�½ resistor to ground sets the
minimum VCO frequency to
approximately 10Hz, resulting in an
initial drive energization pulse of
100ms in conjunction with 82nF C
VCO
and 10k R
VCO
.
VCO loop filter components.
A capacitor to ground at this gm
amplifier output sets a pole in the
current-mode portion of the speed
loop in conjunction with a gm of
0.230mmho.
Motor Terminal 1
Motor Terminal 2
Motor Terminal 3
A ”0” activates the braking circuit.
(TTL level)
A 50µA current from this pin will
charge a timing capacitor to GND for
fixed OFF-time PWM current control
This resistor sets constant currents on
the device to reduce process
dependence and external components.
A 120k resistor sets the previously
mentioned current levels.
Signal and Power Ground
2
3
4
5
P1
P2
P3
C
SC
18 V
FLT
19 R
INIT
6
C
PWM
20 RC
VCO
21 C
ISC
7
V
REF
8
V
SPEED
22 PHI1
23 PHI2
24 PHI3
25
BRAKE
26 C
IOS
9
N1
10 N2
11 N3
12 F/R
27 R
REF
13 VCO
28 GND
14 V
CC
15 C
VCO
3
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
