LB1695M データシートの表示（PDF） - SANYO -> Panasonic

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LB1695M

DC Fan Motor Driver

SANYO -> Panasonic 

LB1695M

LB1695M Functional Description

1. Hall input circuit

The Hall input circuit is a differential amplifier with a hysteresis of 30 mV (typical). The operating DC level must fall

within the common-mode input voltage range (1.5 V to VCC - 1.8 V). We recommend providing inputs with a swing

of at least three times the hysteresis, i.e. 120 to 160 mV p-p, to prevent noise from interfering with circuit operation.

Insert capacitors in the Hall amplifier IN+ and IN– inputs if capacity is found to be problematic during noise

evaluation.

2. Protection circuits

• Low voltage protection circuit

If the VCC voltage falls below a stipulated level (VLVSD), the sink side output transistor is turned off. This circuit

prevents incorrect operation at low VCC voltages.

• Thermal protection circuit

If the junction temperature exceeds a stipulated temperature (TSD), the sink side output transistor is turned off. This

circuit protects the IC from thermal damage. Applications must be designed so that this circuit only operates in

abnormal conditions.

3. FG output circuit

This circuit outputs signals that are synthesized from the IN1, IN2, and IN3 Hall amplifier input signals and to which

wave shaping has been applied. FG1 has the same frequency as the Hall inputs, and FG2 has a frequency three times

that of the Hall inputs.

4. Forward/reverse control circuit

This IC is designed assuming that applications will not perform motor forward/reverse (F/R) control operations while

the motor is turning. Through currents will flow in the output if the motor direction is switched while the motor is

turning and ASO will become a problem. We recommend performing F/R control operations with the VM power

supply in the off state, i.e. when the motor is stopped.

5. VCC and VM power supplies

If the power supply slew rate at power on is excessive, through currents will flow in the output and ASO will become

a problem. The power supply slew rates must not exceed ∆VCC/∆t = 0.04 V/µs and ∆VM/∆t = 0.16 V/µs. Also, at

power on it is desirable to bring up the VCC voltage first, and then bring up the VM voltage. At power off, it is

desirable to bring down VM first, and then bring down VCC only after the motor has stopped. If VCC is turned off

after VM but while the motor is still turning due to inertia, the VM voltage may rise beyond the voltage handling

capacity of the IC.

6. Power supply stabilization capacitors

If large fluctuation occur in the VCC line, the low-voltage protection circuit may operate incorrectly. Capacitors (with

values of a few µF) must be inserted in the VCC line (between VCC and ground) to stabilize the power supply. Since

large switching current flow in the VM line, fluctuations in the IC VM voltage may occur due to inductances in the

wiring pattern. Capacitors must be inserted in the VM line (between VM and ground) so that incorrect operation and

voltages in excess of the IC voltage handling capacity do not occur. In particular, if the application wiring lines (VM,

VCC, and ground) are long, capacitors adequate to stabilize the power supply lines must be used.

7. Current limiter circuit

When the output current reaches the current set as the output current (the limit value), the current limiter circuit turns

off the sink side output transistor to limit the output current to the limit value. The RF pin is used to detect the output

current. In particular, the output current is detected as a voltage using the Rf resistor, which is inserted between the

RF pin and ground. The current limiter operates when the Rf pin reaches 0.5 V (typical) and thus the output current is

limited to a value of 0.5/Rf.

• Output off time

After the current limiter circuit operates and limits the current by turning off the sink side output transistor, it provides

a fixed off period (referred to as the output off time), after which it turns the transistor back on. As opposed to current

limiter techniques that operated the output in an unsaturated state, the use of an output switching system of this type for

the current limiter has the advantage that ASO during current limiter operation is less likely to be a problem. The

output off time is determined by the charging time of the capacitor connected to the C pin. When the current limiter

operates, the circuit starts to charge the C pin capacitor, and the output off time is the time required to charge the

capacitor to a voltage of 2 V (typical). When the capacitor voltage reaches 2 V, the sink side output is turned on again.

The capacitor charge current is a fixed current determined by the resistor R connected to the R pin. The C charge

No. 5802-5/7

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