TL1963A-XX Datasheet, PDF (2/26 Pages) Texas Instruments – 1.5-A LOW-NOISE FAST-TRANSIENT-RESPONSE LOW-DROPOUT REGULATOR

TL1963A-xx
SLVS719A – JUNE 2008 – REVISED AUGUST 2008 ........................................................................................................................................................ www.ti.com
PIN
NO.
NAME
1
SHDN
2
IN
3
GND
4
OUT
5
ADJ
5
SENSE
TERMINAL FUNCTIONS
DESCRIPTION
Shutdown. The SHDN pin is used to put the TL1963A-xx regulators into a low-power shutdown state. The output
is off when the SHDN pin is pulled low. The SHDN pin can be driven either by 5-V logic or open-collector logic
with a pullup resistor. The pullup resistor is required to supply the pullup current of the open-collector gate,
normally several microamperes, and the SHDN pin current, typically 3 µA. If unused, the SHDN pin must be
connected to V_IN. The device is in the low-power shutdown state if the SHDN pin is not connected.
Input. Power is supplied to the device through the IN pin. A bypass capacitor is required on this pin if the device
is more than six inches away from the main input filter capacitor. In general, the output impedance of a battery
rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits. A bypass
capacitor (ceramic) in the range of 1 µF to 10 µF is sufficient. The TL1963A-xx regulators are designed to
withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reverse input,
which can happen if a battery is plugged in backwards, the device acts as if there is a diode in series with its
input. There is no reverse current flow into the regulator, and no reverse voltage appears at the load. The device
protects both itself and the load.
Ground. The exposed thermal pad is connected to ground and must be soldered to the PCB for rated thermal
performance.
Output. The output supplies power to the load. A minimum output capacitor (ceramic) of 10 µF is required to
prevent oscillations. Larger output capacitors are required for applications with large transient loads to limit peak
voltage transients.
Adjust. For the adjustable TL1963A, this is the input to the error amplifier. This pin is internally clamped to ±7 V.
It has a bias current of 3 µA that flows into the pin. The ADJ pin voltage is 1.21 V referenced to ground, and the
output voltage range is 1.21 V to 20 V.
Sense. For fixed voltage versions of the TL1963A-xx (TL1963A-1.5, TL1963A-1.8, TL1963A-2.5, and
TL1963A-3.3), the SENSE pin is the input to the error amplifier. Optimum regulation is obtained at the point
where the SENSE pin is connected to the OUT pin of the regulator. In critical applications, small voltage drops
are caused by the resistance (R_P) of PC traces between the regulator and the load. These may be eliminated by
connecting the SENSE pin to the output at the load as shown in Figure 32. Note that the voltage drop across the
external PC traces adds to the dropout voltage of the regulator. The SENSE pin bias current is 600 µA at the
rated output voltage. The SENSE pin can be pulled below ground (as in a dual supply system in which the
regulator load is returned to a negative supply) and still allow the device to start and operate.
2
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