RT9014 RICHTEK [Richtek Technology Corporation], RT9014 Datasheet - Page 10

• Manufacturer Part Number: RT9014
• Description: Ultra Low Noise 300mA Dual LDO Regulator with POR, NMOS Driver and Requiring No Bypass Capacitor
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9014/A
Applications Information
Like any low-dropout regulator, the external capacitors used
with the RT9014/A must be carefully selected for regulator
stability and performance. Using a capacitor whose value
is > 1μF on the RT9014/A input and the amount of
capacitance can be increased without limit. The input
capacitor must be located a distance of not more than 0.5
inch from the input pin of the IC and returned to a clean
analog ground. Any good quality ceramic or tantalum can
be used for this capacitor. The capacitor with larger value
and lower ESR (equivalent series resistance) provides
better PSRR and line-transient response.
The output capacitor must meet both requirements for
minimum amount of capacitance and ESR in all LDOs
application. The RT9014/A is designed specifically to work
with low ESR ceramic output capacitor in space-saving
and performance consideration. Using a ceramic capacitor
whose value is at least 1μF with ESR is > 20mΩ on the
RT9014/A output ensures stability. The RT9014/A still
works well with output capacitor of other types due to the
wide stable ESR range. Figure 1. shows the curves of
allowable ESR range as a function of load current for various
output capacitor values. Output capacitor of larger
capacitance can reduce noise and improve load transient
response, stability, and PSRR. The output capacitor should
be located not more than 0.5 inch from the VOUT pin of
the RT9014/A and returned to a clean analog ground.
www.richtek.com
10
0.001
0.01
100
0.1
10
Region of Stable C
1
0
Figure 1. Stable Cout ESR Range
50
Unstable Range
Stable Range
Simulation Verify
100
Load Current (mA)
OUT
150
ESR vs. Load Current
RT9014-FM, V
C
C
IN
OUT2
200
= C
= 1uF/X7R
OUT1
250
=
IN
= 5V
Preliminary
300
Thermal Considerations
Thermal protection limits power dissipation in RT9014/A.
When the operation junction temperature exceeds 170°C,
the OTP circuit starts the thermal shutdown function and
turns the pass element off. The pass element turn on again
after the junction temperature cools by 40°C. RT9014/A
lowers its OTP trip level from 170°C to 110°C when output
short circuit occurs (V
limits IC case temperature under 100°C and provides
maximum safety to customer while output short circuit
occurring.
For continuous operation, do not exceed absolute
maximum operation junction temperature 125°C. The
power dissipation definition in device is :
P
The maximum power dissipation depends on the thermal
resistance of IC package, PCB layout, the rate of
surroundings airflow and temperature difference between
junction to ambient. The maximum power dissipation can
be calculated by following formula :
P
Where T
temperature 125°C, T
θ
IC Temperature
Figure 2. Short Circuit Thermal Folded Back Protection
OTP Trip Point
JA
D
D(MAX)
V
TSD
I
= (V
OUT
is the junction to ambient thermal resistance.
OUT
when Output Short Circuit Occurs (Patent)
IN
= ( T
170 C °
− V
J(MAX)
V
OUT
J(MAX)
OUT
Short to GND
110 C
) x I
is the maximum operation junction
− T
°
OUT
110 C °
80 C
A
A
OUT
is the ambient temperature and the
) /θ
°
+ V
< 0.4V) as shown in Figure 2. It
JA
IN
DS9014/A-08 August 2007
x I
Q
0.4V