Datasheet

Ideal Inductor,
no resistance
Load
Resistance
Load
Capacitance
VIN_B2
High Side FET
Model of Inductor
Equivalent Circuit of Bypass Operation of Buck 2
(Not Applicable to LM10506-B)
SW_B2
V
OUT
Buck2
Ideal Inductor,
no resistance
DCR
100 mMax.
Load
Resistance
Load
Capacitance
VIN_B1
High Side FET
Model of Inductor
Equivalent Circuit of Bypass Operation of Buck 1
SW_B1
V
OUT
Buck1
Bypass FET
FB_B1
DCR
100 mMax.
LM10506
SNVS729E –SEPTEMBER 2011–REVISED MARCH 2013 www.ti.com
Low Dropout Operation
The device can operate at 100% duty cycle (no switching; PMOS switch completely on) for low dropout support.
In this way the output voltage will be controlled down to the lowest possible input voltage. When the device
operates near 100% duty cycle, output voltage ripple is approximately 25 mV.
The minimum input voltage needed to support the output voltage:
V
IN_MIN
=V
OUT
+I
LOAD
*(R
DSON_PFET
+R
IND
), where
• I
LOAD
= Load Current
• R
DSON_PFET
= Drain to source resistance of PFET (high side) switch in the triode region
• R
IND
= Inductor resistance
Out of Regulation
When any of the Buck outputs are taken out of regulation (below 85% of the output level) the device will start a
shutdown sequence and all other outputs will switch off normally. The device will restart when the forced out-of-
regulation condition is removed.
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