Datasheet

TPS62125
SLVSAQ5C –MARCH 2012–REVISED DECEMBER 2013 www.ti.com
ENABLE COMPARATOR (EN / EN_hys)
The EN pin is connected to an On/Shutdown detector (ON/SD) and an input of the Enable Comparator. With a
voltage level of 0.4V or less at the EN pin, the ON/SD detector turns the device into Shutdown mode and the
quiescent current is reduced to typically 350nA. In this mode the EN comparator as well the entire internal-control
circuitry are switched off. A voltage level of typ. 900mV (rising) at the EN pin triggers the ON/Shutdown detector
and activates the internal reference VREF (Typ.1.2V), the EN comparator and the UVLO comparator. In
applications with slow rising voltage levels at the EN pin, the quiescent current profile before this trip point needs
to be considered, see Figure 27. Once the ON/SD detector has tripped, the quiescent current consumption of the
device is typ. 6µA. The TPS62125 starts regulation once the voltage at the EN pin trips the threshold V
EN_TH ON
(typ. 1.2V) and the input voltage is above the UVLO threshold. It enters softstart and ramps up the output
voltage. For proper operation, the EN pin must be terminated and must not be left floating. The quiescent current
consumption of the TPS62125 is typ. 13µA under no load condition (not switching). See Figure 25. The DC/DC
regulator stops operation once the voltage on the EN pin falls below the threshold V
EN_TH OFF
(typ. 1.15V) or the
input voltage falls below UVLO threshold. The enable comparator features a built in hysteresis of typ. 50mV. This
hysteresis can be increased with an external resistor connected to pin EN_hys. See more details in application
information section.
POWER GOOD OUTPUT / OUTPUT DISCHARGE (PG)
The Power Good Output (PG pin) is an open drain output. The circuit is active once the device is enabled. It is
driven by an internal comparator connected to the FB pin voltage and an 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 FB pin voltage falls below typ. 90% of its nominal value
V
REF_FB
. The PG output goes high (high impedance) with a delay of typically 2µs. A pull up resistor is needed to
generate a high level. The PG pin can be connected via a pull up resistors to a voltage up to 10V. This pin can
also be used to discharge the output capacitor. See section Application Information for more details.
The PG output is pulled low if the voltage on the EN pin falls below the threshold V
EN_TH OFF
or the input voltage
is below the undervoltage lockout threshold UVLO.
SHORT-CIRCUIT PROTECTION
The TPS62125 integrates a high-side MOSFET switch current limit, I
LIMF
, to protect the device against a short
circuit. The current in the high-side MOSFET switch is monitored by a 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
, typ. 300mA.
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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