ADP150WACBZ-2.5-R7 datasheet(13/20 Pages) AD

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Data Sheet

ADP150

APPLICATIONS INFORMATION

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Rev. E | 13 of 20

CEFF = 0.94 µF × (1 − 0.15) × (1 − 0.1) = 0.719 µF

Therefore, the capacitor chosen in this example meets the mini-

mum capacitance requirement of the LDO over temperature and

tolerance at the chosen output voltage.

To guarantee the performance of the ADP150, it is imperative that

the effects of the dc bias, temperature, and tolerances on the

behavior of the capacitors be evaluated for each.

UNDERVOLTAGE LOCKOUT

The ADP150 has an internal undervoltage lockout circuit that disa-

bles all inputs and the output when the input voltage is less than

approximately 2.0 V. This ensures that the ADP150 inputs and

output behave in a predictable manner during power-up.

ENABLE FEATURE

The ADP150 uses the EN pin to enable and disable the VOUT pin

under normal operating conditions. As shown in Figure 30, when a

rising voltage on EN crosses the active threshold, VOUT turns on.

When a falling voltage on EN crosses the inactive threshold, VOUT

turns off.

Figure 30. Typical EN Pin Operation

As shown in Figure 30, the EN pin has hysteresis built in. This

prevents on/off oscillations that can occur due to noise on the EN

pin as it passes through the threshold points.

The EN pin active/inactive thresholds are derived from the VIN volt-

age; therefore, these thresholds vary with changing input voltage.

Figure 31 shows the typical EN active/inactive thresholds when the

input voltage varies from 2.2 V to 5.5 V.

Figure 31. Typical EN Pin Thresholds vs. Input Voltage (VIN)

The ADP150 uses an internal soft start to limit the inrush current

when the output is enabled. The start-up time for the 3.3 V option

is approximately 150 µs from the time the EN active threshold is

crossed to when the output reaches 90% of its final value. As

shown in Figure 32, the start-up time is dependent on the output

voltage setting.

Figure 32. Typical Start-Up Time

CURRENT LIMIT AND THERMAL OVERLOAD

PROTECTION

The ADP150 is protected against damage due to excessive power

dissipation by current and thermal overload protection circuits. The

ADP150 is designed to limit current when the output load reaches

260 mA (typical). When the output load exceeds 260 mA, the output

voltage is reduced to maintain a constant current limit.

Thermal overload protection is included, which limits the junction

temperature to a maximum of 150°C (typical). Under extreme

conditions (that is, high ambient temperature and power dissipation)

when the junction temperature starts to rise above 150°C, the

output is turned off, reducing the output current to zero. When the

junction temperature drops below 135°C, the output is turned on

again and the output current is restored to its nominal value.

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