Datasheet
SGLS243A − APRIL 2004 − REVISED JUNE 2008
6
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
low noise antiringing switch
An antiringing switch is implemented in order to reduce the EMI radiated from the converter during
discontinuous conduction mode (DCM). In DCM, the inductor current ramps to zero before the end of each
switching period. The internal load comparator turns off the low side switch at that instant thus preventing the
current flowing backward through the inductance which increases the efficiency. An antiringing switch across
the inductor prevents parasitic oscillation caused by the residual energy stored in the inductance (see
Figure 12).
NOTE:
The antiringing switch is only activated in the fixed output voltage versions. It is not enabled for the
adjustable output voltage version TPS62000.
soft start
As the enable pin (EN) goes high, the soft-start function generates an internal voltage ramp. This causes the
start-up current to slowly rise preventing output voltage overshoot and high inrush currents. The soft-start
duration is typical 1 ms (see Figure 13). When the soft-start function is completed, the error amplifier is
connected directly to the internal voltage reference.
enable
Logic low on EN forces the TPS6200x into shutdown. In shutdown, the power switch, drivers, voltage reference,
oscillator, and all other functions are turned off. The supply current is reduced to less than 1 µA in the shutdown
mode.
undervoltage lockout
An undervoltage lockout circuit provides the save operation of the device and it prevents the converter from
turning on when the voltage on V
IN
is less than 1.6 V typical.
power good comparator
The power good (PG) comparator has an open drain output capable of sinking typically 10 µA. The PG is only
active when the device is enabled (EN = high). When the device is disabled (EN = low), the PG pin is high
impedance.
The PG output is only valid after a 100 µs delay after the device is enabled and the supply voltage is greater
than 1.2 V. This is only important in cases where the pullup resistor of the PG pin is connected to an external
voltage source, which might cause an initial spike (false high signal) within the first 100 µs after the input voltage
exceeds 1.2 V. This initial spike can be filtered with a small R-C filter to avoid false power good signals during
start-up.
If the PG pin is connected to the output of the TPS62000 with a pullup resistor, no initial spike (false high signal)
occurs and no precautions have to be taken during start-up.
The PG pin becomes active high when the output voltage exceeds typically 94.5% of its nominal value. Leave
the PG pin unconnected when not used.
no load operation
In case the converter operates in the forced PWM mode and there is no load connected to the output, the
converter regulates the output voltage by allowing the inductor current to reverse for a short period of time.