Datasheet

TPS62120
TPS62122
www.ti.com SLVSAD5 –JULY 2010
POWER GOOD OUTPUT
The Power Good Output is an open drain output available in TPS62120. The circuit is active once the device is
enabled. It is driven by an internal comparator connected to the FB voltage and internal reference. The PG
output provides a high level (open drain high impedance) once the feedback voltage exceeds typical 95% of its
nominal value. The PG output is driven to low level once the feedback voltage falls below typ. 90% of its nominal
value. The PG output is high (high impedance) with an internal delay of typically 2µs. A pullup resistor is needed
to generate a high level and limit the current into the PG pin to 0.5mA. The PG pin can be connected via an pull
up resistors to a voltage up to 5.5V
The PG output is pulled low if the device is enabled but the input voltage is below the undervoltage lockout
threshold UVLO or the device is turned into shutdown mode.
SGND OPEN DRAIN OUTPUT
This is an NMOS open drain output with a typical R
DS(on)
of 370Ω and can be used to discharge the output
capacitor. The internal NMOS connects SGND pin to GND once the device is in shutdown mode or V
IN
falls
below the UVLO threshold during operation. SGND becomes high impedance once the device is enabled and V
IN
is above the UVLO threshold. If SGND is connected to the output, the output capacitor is discharged through
SGND.
SHORT-CIRCUIT PROTECTION
The TPS6212X integrates a high-side MOSFET switch current limit I
LIMF
to protect the device against short
circuit. The current in the high-side MOSFET switch is monitored by current limit comparator and once the
current reaches the limit of I
LIMF
, the high-side MOSFET switch is turned off and the low-side MOSFET switch is
turned on to ramp down the inductor current. The high-side MOSFET switch is turned on again once the zero
current comparator trips and the inductor current has become zero. In this case, the output current is limited to
half of the high-side MOSFET switch current limit ½ I
LIMF
.
THERMAL SHUTDOWN
As soon as the junction temperature, T
J
, exceeds 150°C (typical) the device goes into thermal shutdown. In this
mode, the high-side and low-side MOSFETs are turned-off. The device continues its operation when the junction
temperature falls below the thermal shutdown hysteresis.
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Product Folder Link(s): TPS62120 TPS62122