LM3880 datasheet(5/20 Pages) NSC

5 / 20 page

Enable Combinations

EN_DCDC

EN_LILO

EN_LDO

Function

No Outputs

Linear Regulator enabled only (EN_LDO), supply from V

IN_LDO,

OUT_MAX = 300 mA

Linear Regulator enabled only LILO supplies from V

IN_LDO,

OUT_MAX = 50 mA, VIN_LDO > = VOUT_LILO

DC-DC converter enabled only

Linear Regulator & DCDC enabled

1) V

IN_LILO < VOUT_LILO + 150 mV (typ.), the small NMOS device is active

MAX = 50 mA) and supplied by VIN_LDO.

2) If V

IN_LILO > VOUT_LILO + 250 mV (typ.), the large NMOS device is active

MAX = 350 mA) and supplied by VIN_LILO. Maxium current of DC-DC when

EN_LILO = High is 250 mA (Note A & B)

DC-DC converter and linear regulator active.

Linear regulator starts after DC-DC converter.

Note A: The LILO is turned on via a small NMOS device supplied by V

IN_LDO . The maximum current is 50 mA when this small

NMOS is ON. If higher current > 50 mA is desired the following condition must be done: EN_DC = HIGH .

Note B: When the switcher is enabled, a transition occurs from the small NMOS to a larger NMOS. The transition occurs when

IN_LILO > VOUT_LILO + 250 mV. If VIN_LILO < VOUT_LILO + 150 mV, the LILO switches back to small NMOS (Switcher EN = low).

30025532

FIGURE 3. Mode Transition

LM3880 Datasheet(PDF) 5 Page - National Semiconductor (TI)