Datasheet

UC3717A
The θ
JA
of the UC3717AN plastic package can be re-
duced by soldering the GND pins to a suitable copper
area of the printed circuit board or to an external heat
sink. Due to different lead frame design, θ
JA
of the ce-
ramic J package cannot be similarly reduced.
The diagram of Figure 11 shows the maximum package
power P
TOT
and the θ
JA
as a function of the side " l " of
two equal square copper areas having a thickness of 35µ
(see Figure 10).
During soldering the pins’ temperature must not exceed
260°C and the soldering time must not be longer than 12
seconds.
The printed circuit copper area must be connected to
electrical ground.
APPLICATIONS
A typical chopper drive for a two phase bipolar perma-
nent magnet or hybrid stepping motor is shown in Figure
12. The input can be controlled by a microprocessor,
TTL, LS, or CMOS logic.
The timing diagram in Figure 13 shows the required sig-
nal input for a two phase, full step stepping sequence.
Figure 14 shows the required input signal for a one
phase-two phase stepping sequence called half-step-
ping.
The circuit of Figure 15 provides the signal shown in Fig-
ure 13, and in conjunction with the circuit shown in Fig-
ure 12 will implement a pulse-to-step two phase, full
step, bi-directional motor drive.
The schematic of Figure 16 shows a pulse to half step
circuit generating the signal shown in Figure 14. Care
has been taken to change the phase signal the same
time the current inhibit is applied. This will allow the cur-
rent to decay faster and therefore enhance the motor
performance at high step rates.
Figure 10. Example of P.C. Board Copper
Area which is used as Heatsink.
MOUNTING INSTRUCTIONS
Figure 12. Typical Chopper Drive for a Two
Phase Permanent Magnet Motor.
Figure 11. Maximum Package Power and Junction
to Ambient Thermal Resistance vs Side "
l
".
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