M54687FP View Datasheet(PDF) - Renesas Electronics
Part Name
Description
Manufacturer
M54687FP Datasheet PDF : 9 Pages
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M54687FP
(3) Speed Control Method III (to increase the precision of forward rotation and reverse rotation)
RS1 RT1
RT2 RS2
M
PSC1 O1
O2 PSC2 VR
VCC
R
L
S
L-G
P-G
Control signal
The above two applications cannot make fine adjustments in forward rotation and reverse rotation (because the external
resistance is shared with the forward rotation and reverse rotation).
Fine adjustments can be made for each of forward rotation and reverse rotation if the external circuit is set as shown in
the drawing above.
This external circuit is also available to change the speed of forward and reverse rotation.
The control method adopts the same formula as formula (1).
However, the following relations must be satisfied:
RT+RS→RS1 or RS2
RT→RT1 or RT2
CAUTIONS
(1) Oscillation may take place with the setting of RT>K•Ra. Set
R ≤ K•Ra.
(2) Add a capacitor of 0.1µF to the portion between PSCs to reduce brush noise of the motor.
(3) Add a capacitor of 10µF to the portion between VCC and GND to reduce brush noise and back electromotive noise of
the motor.
(4) At a low temperature, RT>K•Ra is set due to temperature characteristics of resistance Ra of the motor. When
oscillation takes place, use resistance with a temperature coefficient for RT.
(5) When the supply voltage is low, note that saturation of the output transistor of the IC may prevent the rotating speed
for control. Taking into account motor noise etc., set constants in the following range.
2.0V
=
VCC
VCC
-
-
(EC+Ia • Ra)
{RT • IB + Vref(1+
RT
RS
)+
RT
K
• Ia}
When the back electromotive force is large with the brakes applied, for example, malfunction may occur in internal
parasitic Di. If flyback current of 1A or more flows, add Schottky Di to the portion between the output and the GND.
When the IC is used at a high speed for PWM etc., note that switching of output results in delay of approx. 10µs.
Rev.1.0, Sep.19.2003, page 7 of 8
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