Datasheet

EN
ip
i
h
VIN
R1
R2
PVIN
EN
ip
i
h
PVIN
R1
R2
EN
ip
i
h
VIN
R1
R2
TPS54120
SBVS180C –JANUARY 2012–REVISED JUNE 2012 www.ti.com
DEVICE ENABLE AND UNDERVOLTAGE LOCKOUT ADJUSTMENT
SWITCHER ENABLE AND UNDERVOLTAGE LOCKOUT
The EN pin is used to turn the switcher on and off. When the EN pin voltage exceeds the threshold voltage, the
device begins operating. If the EN pin voltage is pulled below the threshold voltage, the regulator stops switching
and enters a low I
Q
state.
The EN pin has an internal pull-up current source; float or drive the EN pin to enable the device. If an application
requires control of the EN pin, use an open-drain or open-collector output logic to interface with the pin.
The TPS54120 implements internal UVLO circuitry on the VIN pin. The device is disabled when the VIN pin
voltage falls below the internal VIN UVLO threshold. The internal VIN UVLO threshold has a hysteresis of 150
mV.
If an application requires either a higher UVLO threshold on the VIN pin, or a secondary UVLO on the PVIN pin
in split-rail applications, then the EN pin can be configured as shown in Figure 30, Figure 31, or Figure 32. When
using the external UVLO function, it is recommended to set the hysteresis to be greater than 500 mV.
Figure 30. Adjustable VIN Under Voltage Lock Out
Figure 31. Adjustable PVIN Under Voltage Lock Out, VIN ≥ 4.5V
Figure 32. Adjustable VIN and PVIN Under Voltage Lock Out
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