L6730 datasheet(19/52 Pages) STMICROELECTRONICS

19 / 52 page

L6730 - L6730B

Device description

Doc ID 11938 Rev 3

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protection on page 21) but not enter into HICCUP mode. The soft-start phase ends when

VSS reaches 3.5 V. After that the over current-protection triggers the HICCUP mode

(L6730). With the L6730B there is the possibility to set the HICCUP mode or the constant

current mode after the soft-start acting on the multifunction pin CC/O/U. With the L6730 the

low-side MOSFET(s) management after soft-start phase depends on the S/O/U pin state

(see related section). If the sink mode is enabled the converter can sink current after soft-

start (see Figure 11) while, if the sink mode is disabled the converter never sinks current

(see Figure 12).

During normal operation, if any under voltage is detected on one of the two supplies (VCC,

VIN), the SS pin is internally shorted to GND by an internal switch so the SS capacitor is

rapidly discharged. Two different turn-on UVLO thresholds can be set: 4.2 V for 5 V BUS

and 8.6 V for 12 V BUS.

Figure 11.

Sink mode enabled: Inductor current during and after soft-start (L6730)

VOUT

VSS

VCC

L6730 Datasheet(PDF) 19 Page - STMicroelectronics