LM3880 Datasheet, PDF (5/20 Pages) National Semiconductor (TI) – Power Sequencer

Enable Combinations
EN_DCDC
0
0
EN_LILO
0
0
EN_LDO
0
1
0
1
0
1
0
0
1
1
0
1
1
1
Function
No Outputs
Linear Regulator enabled only (EN_LDO), supply from V_{IN_LDO},
I_{OUT_MAX} = 300 mA
Linear Regulator enabled only LILO supplies from V_{IN_LDO},
I_{OUT_MAX} = 50 mA, V_{IN_LDO} > = V_{OUT_LILO}
DC-DC converter enabled only
Linear Regulator & DCDC enabled
1) V_{IN_LILO} < V_{OUT_LILO} + 150 mV (typ.), the small NMOS device is active
(I_MAX = 50 mA) and supplied by V_{IN_LDO}.
2) If V_{IN_LILO} > V_{OUT_LILO} + 250 mV (typ.), the large NMOS device is active
(I_MAX = 350 mA) and supplied by V_{IN_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
V_{IN_LILO} > V_{OUT_LILO} + 250 mV. If V_{IN_LILO} < V_{OUT_LILO} + 150 mV, the LILO switches back to small NMOS (Switcher EN = low).
FIGURE 3. Mode Transition
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