RT2516
Application Information
The RT2516 is a low voltage, low dropout linear regulator
with an external bias supply input capable of supporting
an input voltage range from 1.4V to 6V with a fixed output
voltage from 1V to 2V in 0.1V increments.
Output Voltage Setting
The RT2516 output voltage is adjustable from 1.4V to 6V
via the external resistive voltage divider. The voltage divider
resistors can have values of up to 800kΩ because of the
very high impedance and low bias current of the sense
comparator. The output voltage is set according to the
following equation :
V
OUT
= V
ADJ
× ⎛
1+ R1
⎞
⎜
⎟
⎝
R2
⎠
The RT2516 is designed specifically to work with low ESR
ceramic output capacitor for space saving and performance
consideration. Using a ceramic capacitor with capacitance
of at least 10μF and ESR larger than 1mΩ on the RT2516
output ensures stability. Nevertheless, the RT2516 can
still work well with other types of output capacitors due to
its wide range of stable ESR. Figure 3 shows the allowable
ESR range as a function of load current for various output
capacitance. Output capacitors with larger capacitance can
reduce noise and improve load transient response,
stability, and PSRR. The output capacitor should be located
at a distance of not more than 0.5 inch from the output pin
of the RT2516.
Region of Stable C
OUT
ESR vs. Load Current
100
where V
ADJ
is the reference voltage with a typical value of
0.5V.
Unstable Range
10
The RT2516 goes into sleep mode when the EN pin is in
a logic low condition. In this condition, the pass transistor,
error amplifier, and band gap are all turned off, reducing
the supply current to only 10μA (max.). The EN pin can
be directly tied to VIN to keep the part on.
Current Limit
The RT2516 contains an independent current limit circuitry,
which monitors and controls the pass transistor's gate
voltage, limiting the output current to 3A (typ.).
C
IN
and C
OUT
Selection
Like any low dropout regulator, the external capacitors of
the RT2516 must be carefully selected for regulator stability
and performance. Using a capacitor of at least 10μF is
suitable. The input capacitor must be located at a distance
of not more than 0.5 inch from the input pin of the IC. Any
good quality ceramic capacitor can be used. However, a
capacitor with larger value and lower ESR (Equivalent
Series Resistance) is recommended since it will provide
better PSRR and line transient response.
C
OUT
ESR (
Ω
)
Chip Enable Operation
1
Stable Range
0.1
0.01
V
IN
= 3.3V, V
OUT
= 2.5V, C
OUT
= 10μF / X7R
0.001
0.0
0.3
0.5
0.8
1.0
Load Current (A)
Figure 3
Thermal Considerations
Thermal protection limits power dissipation in RT2516.
When the operation junction temperature exceeds 160°C,
the OTP circuit starts the thermal shutdown function and
turns the pass element off. The pass element turns on
again after the junction temperature cools by 30°C.
RT2516 output voltage will be closed to zero when output
short circuit occurs as shown in Figure 4. It can reduce
the IC temperature and provides maximum safety to end
users when output short circuit occurs.
Copyright
©
2012 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2516-01 July 2012
www.richtek.com
7
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
