TA7267BP

2007-2-28

7

Notes When Using The TA7267BP

The full bridge driver, TA7267BP, is an IC specifically developed to control rotation switching in brush motors. This

IC has been carefully designed and strengthened to withstand counter−electromotive force or start up rush current,

which are problems in driving brush motors.

However, as with other power ICs, application circuits must be designed not to apply surge voltage or excess

current that exceeds the standard values.

In addition, when designing PCBs, make sure the wiring pattern does not cause oscillation, which can result in

equipment malfunction or destruction of the IC.

The following are notes on TA7267BP use. These should be reflected at the design stage.

1.

Maximum voltage and current

The maximum supply voltage (pins (6) and (7)) for TA7267BP is 25 V.

Operating supply voltage is in the range of 6

∼ 18 V. No voltage exceeding this range should be applied to

pins (6) or (7).

The maximum current is 1.0 A (AVE.) or 3.0 A (PEAK). The circuit should be designed so that rush

current at startup does not exceed peak current, and average current at steady operation does not exceed

1.0 A.

2.

External diodes

As the block diagram shows, TA7267BP has internal diodes. The lower two diodes, which are the IC’s

internal parasitic diodes, have a relatively large capacitance. However, when a motor with a large

reactance such as a core motor is driven, the upper two diodes may be damaged by the motor’s

counter−electromotive force.

In such a case, connect external diodes in parallel.

The lower diodes should not be subjected to high current. Therefore, in such cases as brake operation,

external diodes should be connected.

3.

PCB design

The following points concern the TA7267BP pattern design around the power supply line (pins (6) and

(7)) and the pattern design of the GND (pin (4)).

a. Ensure that the bypass capacitor between pin (6), pin (7), and GND does not share impedance with

other lines.

b. The GND line should not be shared by other circuits.

c. The capacitance of the bypass capacitor should be as large as possible.

4.

Oscillation remedies

To prevent noise from sparks when using brush motors, a capacitor may be connected between both pins.

When using TA7267BP, the capacitor is connected between output pins (3) and (5). This may cause

oscillation.

Therefore, avoid connecting the capacitor where possible. If connection is necessary to overcome noise,

connect resistors in series as shown in the technical data.

The values for the capacitor and resistors must be determined according to the motor. However,

recommended values are about 0.1 μF and 33 Ω.