Data Sheet

ADP222/ADP223/ADP224/ADP225

Rev. B | Page 17 of 24

THEORY OF OPERATION

The ADP222/ADP223/ADP224/ADP225 are low quiescent

current, fixed and adjustable dual output, low dropout linear

regulators that operate from 2.5 V to 5.5 V and provide up to

300 mA of current from each output. Drawing a low 300 μA

quiescent current (typical) at full load make the ADP222/

ADP223/ADP224/ADP225 ideal for battery-operated portable

equipment. Shutdown current consumption is typically 200 nA.

Optimized for use with small 1 μF ceramic capacitors, the

ADP222/ADP223/ADP224/ADP225 provide excellent

transient performance.

THERMAL

SHUTDOWN

EN1

EN2

GND

CURRENT

LIMIT

CURRENT

LIMIT

REFERENCE

ADP225 ONLY

CONTROL

LOGIC

AND

ENABLE

VIN

VOUT1

140Ω

VOUT2

ADP223/ADP225

ADJ1

ADJ2

140Ω

Figure 62. Internal Block Diagram, ADP223/ADP225

THERMAL

SHUTDOWN

EN1

EN2

GND

CURRENT

LIMIT

CURRENT

LIMIT

REFERENCE

ADP224

ONLY

CONTROL

LOGIC

AND

ENABLE

VIN

VOUT1

140Ω

VOUT2

ADP222/ADP224

SENSE1

SENSE2

140Ω

Figure 63. Internal Block Diagram, ADP222/ADP224

Internally, the ADP222/ADP223/ADP224/ADP225 consist of a

reference, two error amplifiers, and two PMOS pass transistors.

Output current is delivered via the PMOS pass device, which is

controlled by the error amplifier. The error amplifier compares

the reference voltage with the feedback voltage from the output

and amplifies the difference. If the feedback voltage is lower

than the reference voltage, the gate of the PMOS device is

pulled lower, allowing more current to flow and increasing the

output voltage. If the feedback voltage is higher than the

reference voltage, the gate of the PMOS device is pulled higher,

allowing less current to flow and decreasing the output voltage.

EN1

VOUT1

VIN

EN2

GND

6

4

3

2

ADJ2

VOUT2

1

8

5

7

ADJ1

ADP223/

ADP225

R1

R4

R2

ON

OFF

ON

OFF

+ C1

1µF

+ C3

1µF

+ C2

1µF

VOUT1 = 2.8V

VOUT2 = 2.0V

R3

Figure 64. Typical Application Circuit for Setting Output Voltages,

ADP223/ADP225

The ADP223/ADP225 are exactly the same as the ADP222/

ADP224 except that the output voltage dividers are internally

disconnected and the feedback input of the error amplifiers is

brought out for each output. The output voltages can be set

according to the following equations:

The value of R1 and R3 should be less than 200 kΩ to minimize

errors in the output voltage caused by the ADJx pin input current.

For example, when R1 and R2 each equal 200 kΩ, the output

voltage is 1.0 V. The output voltage error introduced by the ADJx

pin input current is 2 mV or 0.20%, assuming a typical ADJx pin

input current of 10 nA at 25°C.

The output voltage of the ADP223/ADP225 may be set from

0.5 V to 5.0 V.

The ADP222/ADP224 are available in multiple output voltage

options ranging from 0.8 V to 3.3 V.

The ADP224/ADP225 are identical to the ADP222/ADP223

with the addition of a quick output discharge (QOD) feature.

This allows the output voltage to start up from a known state.

The ADP222/ADP223/ADP224/ADP225 use the EN1/EN2 pins

to enable and disable the VOUT1/VOUT2 pins under normal

operating conditions. When EN1/EN2 are high, VOUT1/VOUT2

turn on; when EN1/EN2 are low, VOUT1/VOUT2 turn off. For

automatic startup, EN1/EN2 can be tied to VIN.