L6730 datasheet(29/52 Pages) STMICROELECTRONICS

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L6730 - L6730B

Device description

Doc ID 11938 Rev 3

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The phase shift between master and slaves is approximately done 180°.

5.12

Thermal shutdown

When the junction temperature reaches 150°C ±10°C, the device enters in thermal

shutdown.

Both MOSFETs are turned OFF and the soft-start capacitor is rapidly discharged with an

internal switch. The device does not restart until the junction temperature goes down to

120°C and, in any case, until the voltage at the soft-start pin reaches 500 mV.

5.13

Minimum ON-time TON(MIN)

The device can manage minimum ON times lower than 100 ns. This feature comes from the

control topology as well as from the particular L6730/B overcurrent protection system. In a

voltage mode controller, the current does not have to be sensed to perform regulation and,

in the case of L6730/B, it does not have to be sensed for the overcurrent protection either

because valley current protection can operate during the OFF time. The first advantage

related of this feature is the achievement of extremely low conversion ratios. Figure 25

shows a conversion from 14 V to 0.5 V at 820 kHz with a tON of about 50 ns. The ON time is

limited by the MOSFET turn-on and turn-off times.

Figure 24.

Synchronization

PWM SIGNALS

INDUCTOR CURRENTS

L6730 数据表(PDF) 29 Page - STMicroelectronics