TD340

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Standby mode

The TD340 can be put in standby mode under software control. When the STBY pin is driven low, the

MOS drivers are switched off and internal charge pump oscillator is stopped. The 5V regulator, the

watchdog and reset circuits are still active.

There is no pull up/down resistor on the STBY pin. STBY must not be left open.

Power consumption (not including the current drained from the 5V regulator) is reduced to about 200uA.

To achieve this standby current, the 5.6k resistor on the OSC pin has to be disconnected with an external

low power MOS controlled by the STBY signal (see figure 10 for an application example)

Standby mode should be only activated when IN1=IN2=0V and after that the motor is actually stopped

because the four MOS are switched off. On exit from the standby mode, a delay of up to 20ms (depending

upon the bootstrap capacitor value) must be given before applying signals to the IN1 and IN2 inputs to

allow proper startup of the charge pump (it is also true for power-up). Figure 8 shows the voltage across

the Cb bootstrap capacitor at powerup or at standby exit as a function of time.

Figure 8 : Charge pump voltage at startup

Fig. 8a : Cb = 10nF

Fig. 8c : Cb = 100nF

Fig. 8b : Cb = 47nF