TPS737 datasheet(19/50 Pages) TI2

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The TPS737 uses an internal charge pump to develop an internal supply voltage sufficient to drive the gate of

the NMOS pass transistor above VOUT. The charge pump generates approximately 250 μV of switching noise

at approximately 4 MHz; however, charge-pump noise contribution is negligible at the output of the regulator for

most values of IOUT and COUT.

6.3.2 Internal Current Limit

The TPS737 internal current limit helps protect the regulator during fault conditions. Foldback current limit helps

protect the regulator from damage during output short-circuit conditions by reducing current limit when VOUT

drops below 0.5 V. See Figure 5-17 in the Typical Characteristics section.

From Figure 5-17, approximately –0.2 V of VOUT results in a current-limit of 0 mA. Therefore, if OUT is forced

below –0.2 V before EN goes high, the device can possibly not start up. In applications that work with both a

positive and negative voltage supply, the TPS737 must be enabled first.

6.3.3 Enable Pin and Shutdown

The enable pin (EN) is active high and compatible with standard TTL-CMOS levels. VEN below 0.5 V (maximum)

turns the regulator off and drops the GND pin current to approximately 10 nA. When EN is used to shutdown the

regulator, all charge is removed from the pass transistor gate. A VEN above 1.7 V (minimum) turns the regulator

on and the output ramps back up to a regulated VOUT (see Figure 5-39).

When shutdown capability is not required, EN can be connected to VIN. However, the pass transistor can

possibly not be discharged using this configuration, and the pass transistor can be left on (enhanced) for

a significant time after VIN is removed. This scenario can result in reverse current flow (if the IN pin is

low impedance) and faster ramp times upon power up. In addition, for VIN ramp times slower than a few

milliseconds, the output can overshoot upon power up.

Current limit foldback can prevent device start-up under some conditions. See the Internal Current Limit section

for more information.

6.3.4 Reverse Current

The NMOS pass transistor of the TPS737 provides inherent protection against current flow from the output of the

regulator to the input when the gate of the pass transistor is pulled low. To make sure that all charge is removed

from the gate of the pass transistor, the EN pin must be driven low before the input voltage is removed. If the EN

pin is not driven low, the pass transistor can be left on because of stored charge on the gate.

After the EN pin is driven low, no bias voltage is needed on any pin for reverse current blocking. Reverse

current is specified as the current flowing out of the IN pin because of voltage applied on the OUT pin. There is

additional current flowing into the OUT pin as a result of the 80-kΩ internal resistor divider to ground (see Figure

6-1 and Figure 6-2 ).

For the TPS73701, reverse current can flow when VFB is more than 1.0 V above VIN.

6.4 Device Functional Modes

Driving the EN pin over 1.7 V turns on the regulator. Driving the EN pin below 0.5 V causes the regulator to enter

shutdown mode. In shutdown, the current consumption of the device is reduced to 20 nA, typically.

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TPS737

SBVS067W – JANUARY 2006 – REVISED AUGUST 2025

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TPS737 Datasheet(PDF) 19 Page - Texas Instruments