MPZ2012S221A datasheet(11/56 Pages) STMICROELECTRONICS

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Figure 6. Power-up/down procedure

EN (t)

VCC (t)

SW (t)

IVIN (t)

VEN,Rising = 1.2 V

VWAKE UP, Rising ≈ 0.5 V

VVCC = 3.3 V

ISHTDWN = 2 µA

IS_OPVIN

VEN, Falling =1.0 V

IS_OPVIN

ISHDWN = 2 µA

VWAKE UP, Falling ≈0.4 V

When the voltage applied on the EN pin rises over VWAKEUP THR, RISING, the device powers up the internal circuit

increasing the current consumption.

As soon as the voltage rises over VENTHR, RISING, the device starts the switching activities as described in

Section 5.1.2 Soft-start.

Once the voltage becomes lower than VEN THR, FALLING, the device interrupts the switching activities.

As soon as the voltage becomes lower than VWAKEUP THR.FALLING, the device powers down the internal circuit

reducing the current consumption.

The pin is VIN compatible.

Please refer to Table 6. Electrical characteristics for the reported thresholds.

5.1.2

Soft-start

The soft-start (SS) limits the inrush current surge and makes the output voltage increase monotonically.

The device implements the soft-start phase ramping the internal reference with very small steps. Once the SS

ends the error amplifier reference is switched to the internal value of 0.85 V coming directly from the band gap

cell.

The soft-start duration is fixed and has a typical value of 1.3 ms.

L6983I

Primary side

DS14040 - Rev 1

page 11/56

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