Datasheet

ADP160/ADP161/ADP162/ADP163 Data Sheet
Rev. H | Page 12 of 24
THEORY OF OPERATION
The ADP16x are ultralow quiescent current, low dropout linear
regulators that operate from 2.2 V to 5.5 V and can provide up to
150 mA of output current. Drawing only 560 nA (typical) at no
load and a low 42 µA of quiescent current (typical) at full load
makes the ADP16x ideal for battery-operated portable equip-
ment. Shutdown current consumption is typically 50 nA.
Using new innovative design techniques, the ADP16x provide
ultralow quiescent current and superior transient performance
for digital and RF applications. The ADP16x are also optimized
for use with small 1 µF ceramic capacitors.
REFERENCE
SHORT CIRCUIT,
UVLO, AND
THERMAL
PROTECT
SHUTDOWN
R1
R2
VOUT
VIN
GND
EN
R3
08628-028
ADP160
Figure 30. Internal Block Diagram, Fixed Output with Output Discharge Function
REFERENCE
SHORT CIRCUIT,
UVLO, AND
THERMAL
PROTECT
SHUTDOWN
VOUT
ADJ
VIN
GND
EN
R1
08628-030
ADP161
Figure 31. Internal Block Diagram, Adjustable Output with Output Discharge
Function
08628-053
REFERENCE
SHORT CIRCUIT,
UVLO, AND
THERMAL
PROTECT
SHUTDOWN
VOUTVIN
GND
EN
R1
R2
ADP162
Figure 32. Internal Block Diagram, Fixed Output without Output Discharge
Function
08628-054
REFERENCE
SHORT CIRCUIT,
UVLO, AND
THERMAL
PROTECT
SHUTDOWN
VOUT
ADJ
VIN
GND
EN
ADP163
Figure 33. Internal Block Diagram, Adjustable Output without Output
Discharge Function
Internally, the ADP16x consists of a reference, an error amplifier, a
feedback voltage divider, and a PMOS pass transistor. 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 pass 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 pass
and decreasing the output voltage.
The adjustable ADP161/ADP163 have an output voltage range
of 1.0 V to 4.2 V. The output voltage is set by the ratio of two
external resistors, as shown in Figure 2. The device servos the
output to maintain the voltage at the ADJ pin at 1.0 V refe-
renced to ground. The current in R1 is then equal to 1.0 V/R2,
and the current in R1 is the current in R2 plus the ADJ pin bias
current. The ADJ pin bias current, 10 nA at 25°C, flows through
R1 into the ADJ pin.
The output voltage can be calculated using the equation:
V
OUT
= 1.0 V(1 + R1/R2) + (ADJ
I-BIAS
)(R1)
The value of R1 should be less than 200 kΩ to minimize errors in
the output voltage caused by the ADJ pin bias current. For example,
when R1 and R2 each equal 200 kΩ, the output voltage is 2.0 V.
The output voltage error introduced by the ADJ pin bias current
is 2 mV or 0.05%, assuming a typical ADJ pin bias current of
10 nA at 25°C.