ADP3025 datasheet(13/24 Pages) AD

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ADP3025

Rev. A | Page 13 of 24

OUTPUT VOLTAGE ADJUSTMENT

Fixed output voltages (5 V/3.3 V) are selected when ADJ/FX5 =

ADJ/FX3 = 0 V. The output voltage of each controller can also

be set by an external feedback resistor network when

ADJ/FX5 = ADJ/FX3 = 5 V, as shown in Figure 16. There should

be two external feedback resistor dividers for each controller,

one for the voltage feedback loop and one for the output voltage

monitor. Both resistor dividers must be identical. The mini-

mum output voltage is 800 mV, and the maximum output

voltage is 6.0 V.

ADP3025

DRVH

DRVL

ADJ/FX

VIN

EAN

VOUT

Figure 16. Adjustable Output Mode

The output voltage can be calculated using the following

formula:

⎟

⎠

⎞

⎜

⎝

⎛ +

V T

800

(3)

where R1/R2 = R3/R4.

If the loop is carefully compensated, R3 and R4 can be removed

and FB and EAN can be tied together.

APPLICATION INFORMATION

A typical application circuit using the ADP3025 is shown in

Figure 17. Although the component values given in Figure 17

are based on a 5 V @ 4 A/3.3 V @ 4 A/2.5 V @ 1.5 A design, the

ADP3025 output drivers are capable of handling output

currents anywhere from <1 A to over 10 A. Throughout this

section, design examples and component values are given for

three different power levels. For simplicity, these levels are

referred to as low power and basic power. Table 5 shows the

input/output specifications for these three levels.

Table 5. Typical Power Level Examples

Low Power

Basic

Input Voltage Range

5.5 V to 25 V

Switching Output 1

3.3 V/2 A

3.3 V/4 A

Switching Output 2

5 V/2 A

5 V/4 A

Linear Output

2.5 V/1 A

2.5 V/1.5 A

INPUT VOLTAGE RANGE

The input voltage range of the ADP3025 is 5.5 V to 25 V. The

converter design is optimized to deliver the best performance

within a 7.5 V to 18 V range, which is the nominal voltage for

three to four cell Li-Ion battery stacks. Voltages above 18 V may

occur under light loads and when the system is powered from

an ac adapter with no battery installed.

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