L6223 STMicroelectronics, L6223 Datasheet - Page 16

• Manufacturer Part Number: L6223
• Description: DMOS PROGRAMMABLE HIGH SPEED UNIPOLAR STEPPER MOTOR DRIVER
• Manufacturer: STMicroelectronics

L6223
Figure 19: Dot Matrix Printer Motor Driver schematic diagram (See also fig. 10, 16).
External RC Network (pin 14)
The external RC network provides the higher of
the two possible chopping frequencies. The dis-
charge time of the capacitor represents the mini-
mum t
is possible to select a smaller t
Figure 20: Oscillator waveform and timing.
The window must be large enough to mask this
spike, without penalizing excessively the min cur-
rent control. The capacitor C mainly defines the
value of the window. The mathematical formulas
to calculate the approximate values are:
16/33
(ON)
available in closed loop. In open loop it
(ON)
, (see Fig. 20).
The t
supply to the motor, as well as the protection
”window”. This window is necessary to mask the
spike generated at the beginning of each chop-
ping period (see Fig. 21a).
f
t
for R
where R
capacitor discharging.
(osc)
ON(min)
in
= 1/(0.84
(ON)
= 1.2k
= t
in
min defines the min current the IC can
(window)
is the resistor internal to the IC for the
RC)
= 0.84 C R R
for R > 10k
in
/(R+R
in
)