AP22800 datasheet(10/14 Pages) DIODES

10 / 14 page

AP22800

Document number: DS36046 Rev. 3 - 2

10 of 14

www.diodes.com

January 2015

AP22800

Application Information (Cont.)

For heavier loads, it is recommended that the VIN and VOUT trace lengths be kept to

a minimum. In addition, a bulk capacitor (≥ 10μF) may also

be placed close to the VOUT pin. If using a bulk capacitor on VOUT, it is important to control the inrush current by choosing an appropriate soft-

start time in order to minimize the droop on the input supply.

Adjustable Slew Rate/Soft-Start

The SS pin allows the output ramp time of the switch to be controlled using an external capacitor (CSS). The capacitor voltage rises to

approximately twice the value of VIN. Table 1 shows typical rise times (in µs) associated with various timing capacitors at different VIN values.

Output Voltage Rise Time (

in μs)

Measured at +25°C Using 0805 X7R 10% 25V Ceramic Capacitors

VIN

1.8V

2.5V

3.3V

5.0V

VSS

CSS

3.5V

4.8V

6.4V

9.7V

470pF

6.9

7.0

7.1

7.3

1nF

12.0

12.1

12.3

14.3

10nF

120

127

135

145

47nF

626

636

652

692

100nF

1305

1320

1340

1420

470nF

6320

6400

6660

7020

1000nF

13400

13040

13120

13800

Table 1. Timing Capacitors and Rise Times

Extra capacitance will allow further increase in rise time if desired. The timing capacitor should have a breakdown voltage of at least 25V to allow

for a high voltage on this pin.

Adjustable Discharge

When EN goes low, VOUT is discharged to ground through the discharge resistor (RDIS). The discharge/fall time on VOUT is largely controlled by

RDIS and by the output capacitor. The data in Table 2 shows typical fall times associated with various discharge resistors with CL = 1μF, for

different values of VIN.

1206 250mW 1%

Discharge Resistor (

Ω)

Fall Time (in ms)

Measured at +25°C, with CL = 1μF, RL = Open

1.8V

2.5V

3.3V

100

0.25

0.26

0.27

470

1.07

1.09

1.12

1.18

1000

2.28

2.32

2.40

2.54

4700

10.42

10.65

10.90

11.50

10000

23.33

24.30

24.50

25.05

Table 2. Discharge Resistors and Output Voltage Fall Times

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