Ap7168, 2a low dropout regulator with pok, New prod uc t typical performance characteristics – Diodes AP7168 User Manual
Page 7: R1 v v, 1 v v r r
AP7168
1.2A LOW DROPOUT REGULATOR WITH POK
AP7168
Document number: DS32019 Rev. 2 - 2
7 of 11
September 2010
© Diodes Incorporated
NEW PROD
UC
T
Typical Performance Characteristics
(Continued)
Current Limit vs. Temperature
1.4
1.5
1.6
1.7
1.8
-50
-25
0
25
50
75
100
Temperature (
o
C)
C
u
rre
nt
Lim
it
(
A
)
VIN =2.8V,Vout=1.8V
VIN =3.3V,Vout=1.8V
Application Note
Input Capacitor
A 1
μF ceramic capacitor is recommended to connect
between IN and GND pins to decouple input power supply
glitch and noise. The amount of the capacitance may be
increased without limit. A lower ESR (Equivalent Series
Resistance) capacitor allows the use of less capacitance,
while higher ESR type requires more capacitance. This
input capacitor should be located as close as possible to
the device to assure input stability and less noise. For
PCB layout, a wide copper trace is required for both IN
and GND.
Output Capacitor
The output capacitor is required to stabilize and help the
transient response of the LDO. The AP7168 is designed to
have excellent transient response for most applications
with a small amount of output capacitance. The AP7168 is
stable for all available types and values of output
capacitors
≥ 4.7μF. The device is also stable with multiple
capacitors in parallel, which can be of any type of value.
Additional capacitance helps to reduce undershoot and
overshoot during transient. This capacitor should be
placed as close as possible to OUT and GND pins for
optimum performance.
Adjustable Operation
The AP7168 provides output voltage from 0.8V to 5.0V
through external resistor divider as shown below.
IN
GND
EN
OUT
Enable
FB
V
IN
V
OUT
POK
100kOhm
R
1
R
2
AP7168
C
IN
C
OUT
The output voltage is calculated by:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
+
=
2
1
REF
OUT
R
R
1
V
V
Where V
REF
=0.8V (the internal reference voltage)
Rearranging the equation will give the following equation
to find the approximate resistor divider values:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
−
=
1
V
V
R
R
REF
OUT
2
1
To maintain the stability of the internal reference voltage,
R
2
needs to be kept smaller than 250k
Ω.