Datasheet

TPS77101/115/118/127/128/133/150 WITH RESET OUTPUT
TPS77201/215/218/227/228/233/250 WITH POWER GOOD OUTPUT
150-mA LDO REGULATORS WITH 8-PIN MSOP PACKAGING
SLVS225D – FEBRUARY 2000 – REVISED OCTOBER 2000
15
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
pin functions
enable (EN)
The EN
terminal is an input which enables or shuts down the device. If EN is a logic high, the device will be in
shutdown mode. When EN
goes to logic low, then the device will be enabled.
power good (PG) (TPS772xx)
The PG terminal is an open drain, active high output that indicates the status of V
out
(output of the LDO). When
V
out
reaches 82% of the regulated voltage, PG will go to a high-impedance state. It will go to a low-impedance
state when V
out
falls below 82% (i.e. over load condition) of the regulated voltage. The open drain output of the
PG terminal requires a pullup resistor
.
sense (SENSE)
The SENSE terminal of the fixed-output options must be connected to the regulator output, and the connection
should be as short as possible. Internally, SENSE connects to a high-impedance wide-bandwidth amplifier
through a resistor-divider network and noise pickup feeds through to the regulator output. It is essential to route
the SENSE connection in such a way to minimize/avoid noise pickup. Adding RC networks between the SENSE
terminal and V
out
to filter noise is not recommended because it may cause the regulator to oscillate.
feedback (FB)
FB is an input terminal used for the adjustable-output options and must be connected to an external feedback
resistor divider. The FB connection should be as short as possible. It is essential to route it in such a way to
minimize/avoid noise pickup. Adding RC networks between FB terminal and V
out
to filter noise is not
recommended because it may cause the regulator to oscillate.
reset (RESET
) (TPS771xx)
The RESET
terminal is an open drain, active low output that indicates the status of V
out
. When V
out
reaches 95%
of the regulated voltage, RESET
will go to a high-impedance state after a 220-ms delay. RESET will go to a
low-impedance state when V
out
is below 95% of the regulated voltage. The open-drain output of the RESET
terminal requires a pullup resistor.