MC3479FN Datasheet, PDF (5/10 Pages) ON Semiconductor – Stepper Motor Driver

MC3479
APPLICATION INFORMATION
General
The MC3479 integrated circuit is designed to drive a
stepper positioning motor in applications such as disk drives
and robotics. The outputs can provide up to 350 mA to each
of two coils of a two−phase motor. The outputs change state
with each low−to−high transition of the clock input, with the
new output state depending on the previous state, as well as
the input conditions at the logic controls.
Outputs
The outputs (L1−L4) are high current outputs (see
Figure 5), which when connected to a two−phase motor,
provide two full−bridge configurations (L3 and L4 are not
shown in Figure 5). The polarities applied to the motor coils
depend on which transistor (Q_H or Q_L) of each output is on,
which in turn depends on the inputs and the decoding
circuitry.
3.0 V
Clk
0
PW_CLKH
1.5 V
t_PCD
PW_CLKL
L1 − L4
Outputs
3.0 V
F/HS,
CW/CCW
Inputs ₀
Phase A
Output
6.0 V
t_su t_h
1.5 V
t_PHLA
t_PLHA
1.5 V
Figure 4. Clock Timing (Refer to Figure 2)
Note: t_r, t_f (10% to 90%) for
input signals are p 10 ns.
V_M
V_D
B/S
R_B
I_BS
I′_BS
Current
Drivers
and
Logic
Q_H
Q_H
Motor Coil
L1
Q_L
L2
Q_L
Parasitic
Diodes
To L3, L4
Transistors
Logic Decoding
Circuit
CW / CCW
OIC
F/HS
Clk
Inputs
Figure 5. Output Stages
The maximum sink current available at the outputs is a
function of the resistor connected between Pin 6 and ground
(see section on Bias/Set operation). Whenever the outputs
are to be in a high impedance state, both transistors (Q_H and
Q_L of Figure 5) of each output are off.
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