LT3433
U
U
U
PI FU CTIO S
The time from VSS = 0V to maximum available current can
this pin should be driven above 3V to assure the internal
supply is completely disabled. This pin is typically diode-
connectedtotheconverteroutputtomaximizeconversion
efficiency. This pin must be bypassed with at least a 0.1µF
ceramic capacitor to SGND.
be calculated given a capacitor CSS as:
tSS = (2.7 • 105)CSS or 0.27s/µF
SHDN (Pin 11): Shutdown. If the SHDN pin is externally
pulledbelow0.5V,lowcurrentshutdownmodeisinitiated.
Duringshutdownmode,allinternalfunctionsaredisabled,
and ICC is reduced to 10µA. This pin is intended to receive
a digital input, however, there is a small amount of input
hysteresisbuiltintotheSHDNcircuittohelpassureglitch-
free mode switching. If shutdown is not desired, connect
the SHDN pin to VIN.
V
OUT (Pin 13): Converter Output Pin. This pin voltage is
compared with the voltage on VIN internally to control
operation in single or 2-switch mode. When the ratios of
thetwovoltagesaresuchthata>75%dutycycleisrequired
forregulation,thelowsideswitchisenabled.Drivebiasfor
the low side switch is also derived directly from this pin.
PWRGND (Pin 14): High Current Ground Reference. This
isthecurrentreturnforthelowsideswitchandcorresponds
to the emitter of the low side switch transistor.
VBIAS (Pin 12): Internal Local Supply. Much of the LT3433
circuitry is powered from this supply, which is internally
regulated to 2.5V through an on-board linear regulator.
CurrentdriveforthisregulatorissourcedfromtheVIN pin.
The VBIAS supply is short-circuit protected to 5mA.
SW_L(Pin15):GroundReferencedSwitchOutput.Thispin
is the collector of the low side switch transistor. The low
sideswitchshortstheSW_LpintoPWRGNDwhenenabled.
The series impedance of the ground-referenced switch is
0.6Ω.
The VBIAS supply only sources current, so forcing this pin
abovetheregulatedvoltageallowstheuseofexternalpower
formuchoftheLT3433circuitry.Whenusingexternaldrive,
3433ia
6
Linear [ Linear ]
