ADP7182ACPZ-R7 datasheet(22/28 Pages) ANACHIP

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ADP7182

Data Sheet

Rev. A | Page 22 of 28

ENABLE PIN OPERATION

The ADP7182 provides a dual polarity enable pin (EN) that turns

on the LDO when |VEN| ≥ 2 V. The enable voltage can be positive or

negative with respect to ground.

–2.0

–1.5

–1.0

–0.5

–2.0

–1.5

–1.0

–0.5

0.5

1.0

1.5

ENABLE VOLTAGE (V)

VOUT WITH RISING VEN

VOUT WITH FALLING VEN

Figure 80. Typical EN Pin Operation

Figure 80 shows the typical hysteresis of the EN pin. This prevents

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

it passes through the threshold points.

Figure 81 shows typical EN thresholds when the input voltage

varies from −2.7 V to −28 V.

1.0

–2.0

–1.5

–1.0

–0.5

0.5

–30

–26

–22

–18

–14

–10

–6

–2

INPUT VOLTAGE (V)

ENABLE+

DISABLE+

ENABLE–

DISABLE–

Figure 81. Typical EN Pin Thresholds vs. Input Voltage

Figure 82 and Figure 83 show the start-up behavior for a −5 V

output with positive and negative going enable signals.

CH1 500mV BW

CH2 500mV BW

M40µs

A CH1

590mV

T 10.20%

VOUT

Figure 82. Typical Start-Up Behavior, Positive Going Enable

CH1 500mV BW

CH2 500mV BW

M40µs A CH1

–580mV

T 10.20%

VOUT

Figure 83. Typical Start-Up Behavior, Negative Going Enable

SOFT START

The ADP7182 uses an internal soft start to limit the inrush current

when the output is enabled. The start-up time for the −5 V option

is approximately 450 µs from the time the EN active threshold is

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

in Figure 84, the start-up time is dependent on the output voltage

setting.

–6

–5

–4

–3

–2

–1

1000

900

800

700

600

500

400

300

200

100

TIME (µs)

VEN

VOUT = –1.22V

VOUT = –3V

VOUT = –5V

Figure 84. Typical Start-Up Behavior, Different Output Voltages

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