TPSM82480
www.ti.com.cn
ZHCSHU5A –JULY 2017–REVISED MARCH 2018
7.3 Feature Description
7.3.1 Enable / Shutdown (EN)
The device starts operation, when VIN is present and enable (EN) is set High. Since the boundary EN thresholds
are specified with 1.2 V for rising and 0.4 V for falling voltages, the typical values are 0.85 V (rising) and 0.65 V
(falling). The device is disabled by pulling EN Low. Leaving the EN pin floating is not recommended.
7.3.2 Soft Start (SS), Pre-biased Output
The internal soft start circuit controls the output voltage slope during startup. This avoids excessive inrush current
and provides an adjustable controlled output-voltage rise time. The soft start also prevents unwanted voltage
drop from high impedance power sources or batteries.
When EN is set to start device operation, the device starts switching after a delay of typically 200 µs and VOUT
rises with a slope, controlled by the external capacitor which is connected to the SS/TR pin (soft start). Leaving
the SS/TR pin floating or connecting to VIN provides internally set fastest startup with a soft start slope of about
80us. See Application Curves for typical startup operation.
The device can start into a pre-biased output. In this case, the device starts switching, only when the internal set
point for VOUT increases above the pre-biased voltage level.
7.3.3 Tracking (TR)
The device tracks an external voltage applied to the SS/TR pin. The FB voltage tracks the external voltage as
long as it is below about 0.6V. Above 0.6V the device goes to normal operation. If the voltage at the SS/TR pin
decreases below about 0.6V, the FB voltage tracks again this voltage. See Tracking for further details.
7.3.4 Output Voltage Select (VSEL)
A resistive divider (VOUT to FB to AGND) sets the output voltage of the TPSM82480. Providing a logic High
level at the VSEL pin, the RS pin is pulled to ground, so that a resistor, between FB and RS pins is connected in
parallel to the lower resistor of the divider. This sets a different higher output voltage and can be used for
dynamic voltage scaling (see Setting VOUT2 Using the VSEL Feature).
If the VSEL pin is set Low, the device connects an internal pull down resistor to the pin, keeping the internal logic
level Low, even if the pin is floating afterwards. The device disconnects the resistor, if the pin is set to High.
7.3.5 Forced PWM (MODE)
To avoid Power Save Mode (PSM) Operation, the device can be forced to PWM mode operation by pulling the
MODE pin High. In this case the device operates continuously with it's nominal switching frequency and the
minimum peak current can go as low as -500 mA.
If the MODE pin is set Low, the device connects an internal pull down resistor to keep the internal logic level
Low, even if the pin is floating afterwards. The device disconnects the resistor, if the pin is set to High.
7.3.6 Power Good (PG)
The TPSM82480 has a built in power good function. The PG pin goes High, when the output voltage has
reached its nominal value. Otherwise, including when disabled, in UVLO or thermal shutdown, PG is Low. The
PG pin is an open drain output that requires a pull-up resistor and can sink typically 2mA. If not used, the PG pin
can be left floating or grounded.
7.3.7 Thermal Good (TG)
As long as the junction temperature of the TPSM82480 is below the thermal good temperature of typically 120°C,
the logic level at the TG pin is High. If the junction temperature exceeds that temperature, the TG pin goes Low.
This can be used for the system to take action preventing excessive heating or even thermal shutdown. The TG
pin is an open drain output that requires a pull-up resistor and can sink typically 2mA. If not used, the TG pin can
be left floating or grounded.
版权 © 2017–2018, Texas Instruments Incorporated
9