L6728AH

Output voltage setting and protections

Doc ID 15726 Rev 1

13/33

8

Output voltage setting and protections

L6728AH is capable to precisely regulate an output voltage as low as 0.8 V. In fact, the

device comes with a fixed 0.8 V internal reference that guarantee the output regulated

voltage to be within ±1% tolerance over line and temperature variations (excluding output

resistor divider tolerance, when present).

FB pin and ground. Referring to Figure 1, the steady state DC output voltage will be:

L6728AH monitors the voltage at VSEN pin and compares it to internal reference voltage in

order to provide under voltage and overvoltage protections as well as PGOOD signal.

According to the level of VSEN, different actions are performed from the controller:

●

PGOOD

If the voltage monitored through VSEN exits from the PGOOD window limits, the device

de-asserts the PGOOD signal still continuing switching and regulating. PGOOD is

asserted at the end of the soft-start phase.

●

Under voltage protection

If the voltage at VSEN pin drops below UV threshold, the device turns off both HS and

●

Overvoltage protection

If the voltage at VSEN pin rises over OV threshold (1 V typ), overvoltage protection

turns off HS MOSFET and turns on LS MOSFET. The LS MOSFET will be turned off as

recover. Notice that, even if the device is latched, the device still controls the LS

MOSFET and can switch it on whenever VSEN rises above 0.4 V.

●

Feedback disconnection protection

In order to provide load protection even if VSEN pin is not connected, a 100 nA bias

current is always sourced from this pin. If VSEN pin is not connected, this current will

permanently pull it up causing the device to detect an OV: thus LS will be latched on

preventing output voltage from rising out of control.

V

OUT

V

REF

1

R

FB

R

OS

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