Datasheet

Enable

Chip

VDD

ENABLE

GND

1.5 MΩ

200 kΩ

1 kΩ

300 kΩ

200 Ω

UDG−05061

TPS40190

www.ti.com

SLUS658C –JULY 2005–REVISED JULY 2012

Enable Functionality

The TPS40190 has a dedicated ENABLE pin. This simplifies user level interface design since no multiplexed

functions exist. Another benefit is a true low power shutdown mode of operation. In this state, the BP5 regulator

is turned off. When the ENABLE pin is pulled to GND, the TPS40190 consumes a typical 20-μA of current. A

functionally equivalent circuit to the enable circuitry on the TPS40190 is shown in Figure 4.

Figure 4. TPS40190 ENABLE Pin Internal Circuitry

If the ENABLE pin is left floating, the chip starts automatically. The pin must be pulled to less than 600 mV to

ensure that the TPS40190 is in shutdown mode. Note that the ENABLE pin is relatively high impedance. In some

situations, there could be enough noise nearby to cause the ENABLE pin to swing below the 600 mV threshold

and give erroneous shutdown commands to the rest of the device. There are two solutions to this problem should

it arise.

1. Place a capacitor from ENABLE to GND. A side effect of this is to delay the start of the converter while the

capacitor charges past the enable threshold

2. Place a resistor from VDD to ENABLE. This causes more current to flow in the shutdown mode, but does not

delay converter startup. If a resistor is used, the total current into the ENABLE pin should be limited to no

more than 500 μA.

The ENABLE pin is self-clamping. The clamp voltage can be as low as 1 V with a 1-kΩ ground impedance. Due

to this self-clamping feature, the pull-up impedance on the ENABLE pin should be selected to limit the sink

current to less than 500 μA. Driving the ENABLE pin with a low-impedance source voltage can result in damage

to the device. Because of the self-clamping feature, it requires care when connecting multiple ENABLE pins

together. For enabling multiple TPS4019x devices (TPS40190, TPS40192, TPS40193, TPS40195, TPS40197),

see the Application Report SLVA509.