Datasheet

SW
VIN
GND
BOOT
FB
COMP
TPS54340
EN
RT/CLK
Cpole
Czero
Rcomp
RT
Coneg
Lo
Cboot
Cin
R1
R2
Cd
VIN
VONEG
+
+
GND
VOPOS
Copos
+
TPS54340
SLVSBK0B –OCTOBER 2012–REVISED MARCH 2014 www.ti.com
8.4 Device Functional Modes
8.4.1 Operation with V
IN
< 4.5 V (Minimum V
IN
)
The device is recommended to operate with input voltages above 4.5 V. The typical VIN UVLO threshold is 4.3 V
and the device may operate at input voltages down to the UVLO voltage. At input voltages below the actual
UVLO voltage, the device will not switch. If EN is externally pulled up to V
IN
or left floating, when V
IN
passes the
UVLO threshold the device will become active. Switching is enabled the soft start sequence is initiated. The
TPS54340 will start at the soft start time determined by the internal soft start time.
8.4.2 Operation with EN Control
The enable threshold voltage is 1.2 V typical. With EN held below that voltage the device is disabled and
switching is inhibited even if V
IN
is above its UVLO threshold. The IC quiescent current is reduced in this state. If
the EN voltage is increased above the threshold while V
IN
is above its UVLO threshold, the device becomes
active. Switching is enabled, and the soft start sequence is initiated. The TPS54340 will start at the soft start time
determined by the internal soft start time.
8.4.3 Alternate Power Supply Topologies
8.4.3.1 Inverting Power
The TPS54340 can be used to convert a positive input voltage to a split rail positive and negative output voltage
by using a coupled inductor. Idea applications are amplifiers requiring a split rail positive and negative voltage
power supply. For a more detailed example see SLVA369.
Figure 34. TPS54340 Split Rail Power Supply
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