L7983 datasheet(19/43 Pages) STMICROELECTRONICS

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In case of overvoltage detection (OVP), the RST pin is asserted low. A 2% hysteresis (typ.) is required before

releasing RST.

Figure 17. Output voltage and RST behavior

VTHR

VTHR-HYST

VOUT

RST

A built-in 2 ms typ. delay is always implemented before releasing RST.

5.5

VCC and switchover

The internal LDO (low drop-out) linear regulator is turned on when VIN is higher than the VINH threshold and EN

pin is detected above VWAKEUPH. The output voltage is available on pin VCC, which must be properly bypassed to

GND by 470 nF ceramic capacitor. No external load is expected on VCC pin.

The switchover function is enabled in case VBIAS is detected higher than the SWO threshold (refer to Table 7).

When this occurs, the internal LDO power supply is switched from VIN to VBIAS, so increasing the power

conversion efficiency. This is the typical case when VBIAS is connected to the regulator output.

If the programmed output voltage is lower than the SWO threshold and no auxiliary rail lower than VIN is

available, VBIAS must be connected to GND (refer to Figure 29, Figure 35 and Figure 41 for no load input current

in typical application conditions).

5.6

Fault management

The L7983 fault management is continuously monitoring the inductor current, the output voltage and the device

junction temperature.

Furthermore, thanks to the input UVLO (undervoltage lock-out) circuitry, the switching activity is guaranteed only

with the proper VIN level. All the protections are auto-recovery.

L7983

VCC and switchover

DS13354 - Rev 1

page 19/43

L7983 Datasheet(PDF) 19 Page - STMicroelectronics