Application information

STLQ50XX

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Application information

The STLQ50 is a BiCMOS linear regulator specifically designed for operating in

environment with very low power consumption constraints. The very low quiescent current

of 3 µA is obtained with use of CMOS technology that makes the device suitable for those

application that have very long stand-by time. The very low power consumption allows

extending the battery life and the tiny packages (SOT323-5L or SOT23-5L) fulfil the space

saving requirements of battery powered equipments. Moreover the STLQ50 provides wide

input voltage operation from 2.5 V up to 12 V.

The P-MOS pass element allows also a very good drop-out figure: 0.7 V at full load and at

125 °C without affecting the consumption characteristics.

7.1

External components

The typical application schematic of STLQ50 is shown in Figure 1 - Figure 2, a 1 µF input

and output capacitors placed close to the device are needed in order to provide proper

operation. The device is stable with electrolytic and ceramic output capacitors having values

higher than 1 µF (see figure typical characteristics for stability details).

In the adjustable version (STLQ50) the output voltage is programmed using an external

resistor divider as shown in Figure 2. The output voltage can be adjusted from 1.22 to 11 V

and it can be calculated using the following formula:

divider current at least. Lower value resistors will improve the noise performances but the

quiescent current will increase. Higher value resistors should be avoided because the ADJ

leakage current will influence the voltage set by the resistor divider making the above

formula no more valid.

7.2

Power dissipation

In order to ensure proper operation, the STLQ50 junction temperature should never exceed

125 °C, this limits the maximum power dissipation the regulator can sustain in any

application. The maximum power dissipation can be calculated as:

data).

The power dissipation can be calculated simply as: