TLS205B0

Application Information

Data Sheet

27

Rev. 1.2, 2015-01-15

6.5

Protection Features

The TLS205B0 regulators incorporate several protection features which make them ideal for use in battery-

powered circuits. In addition to normal protection features associated with monolithic regulators like current limiting

and thermal limiting the device is protected against reverse input voltage, reverse output voltage and reverse

voltages from output to input.

Current limit protection and thermal overload protection are intended to protect the device against current overload

conditions at the output of the device. For normal operation the junction temperature must not exceed 125 °C.

The input of the device will withstand reverse voltages of 20 V. Current flowing into the device will be limited to

less than 1 mA (typically less than 100 µA) and no negative voltage will appear at the output. The device will

protect both itself and the load. This provides protection against batteries being plugged backwards.

The output of the TLS205B0 can be pulled below ground without damaging the device. If the input is left open-

circuit or grounded, the output can be pulled below ground by 20 V. Under such conditions the output of the device

cases however where the output is either connected to the SENSE pin (fix voltage variant) or tied either via an

external voltage divider or directly to the ADJ pin (adjustable variant) a small current will be present from this origin.

In the case of the fixed voltage version this current will typically be below 100 µA while for the adjustable version

source the output will source the short circuit current of the device and will protect itself by thermal limiting. In this

case grounding the EN pin will turn off the device and stop the output from sourcing the short-circuit current.

The ADJ pin of the adjustable device can be pulled above or below ground by as much as 7 V without damaging

the device. If the input is grounded or left open-circuit, the ADJ pin will act inside this voltage range like a large

resistor (typically 100 kΩ) when being pulled above ground and like a resistor (typically 5 kΩ) in series with a diode

when being pulled below ground. In situations where the ADJ pin is at risk of being pulled outside its absolute

maximum ratings ±7 V the ADJ pin current must be limited to 1 mA (e.g. in cases where the ADJ pin is connected

to a resistor divider that would pull the ADJ pin above its 7 V clamp voltage). Let’s consider for example the case

where a resistor divider is used to provide a 1.5 V output from the 1.22 V reference and the output is forced to

20 V. The top resistor of the resistor divider must then be chosen to limit the current into the ADJ pin to 1 mA or

less when the ADJ pin is at 7 V. The 13 V difference between output and ADJ pin divided by the 1 mA maximum

current into the ADJ pin requires a minimum resistor value of 13 kΩ.

In circuits where a backup battery is required, several different input/output conditions can occur. The output

voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left

open-circuit. Current flow back into the output will follow the curve as shown in Figure 9 below.

1) typically < 1 µA for the mentioned conditions,

V

2) In case there is no external voltage divider applied i.e. the ADJ pin is directly connected to the output Q and the output is

pulled below ground by 20 V the current flowing out of the ADJ pin will be typically ~ 4 mA. Please ensure in such cases

that the absolute maximum ratings of the ADJ pin are respected.