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RT2515A
2A, Low Input Voltage, Ultra-Low Dropout Linear Regulator
with Enable
General Description
Features
The RT2515A is a high performance positive voltage
regulator designed for use in applications requiring ultralow input voltage and ultra-low dropout voltage at up to 2
amperes. It operates with an input voltage as low as 1.4V,
with output voltage programmable as low as 0.5V. The
RT2515A features ultra low dropout, ideal for applications
where output voltage is very close to input voltage.
Additionally, the RT2515A has an enable pin to further
reduce power dissipation while shutdown. The RT2515A
provides excellent regulation over variations in line, load
and temperature. The RT2515A is available in the SOP-8
(Exposed Pad) package. The output voltage can be set
by an external divider or fixed at 1.2V depending on how
the FB pin is configured.
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Applications
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Ordering Information
RT2515A
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Package Type
SP : SOP-8 (Exposed Pad-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Input Voltage as Low as 1.4V
Ultra-Low Dropout Voltage 400mV @ 2A
Adjustable Output Voltage from 0.5V to 3.8V
Over Current Protection
Over Temperature Protection
1μ
μA Input Current in Shutdown Mode
Enable Control
RoHS Compliant and Halogen Free
Telecom/Networking Cards
Motherboards/Peripheral Cards
Industrial Applications
Wireless Infrastructure
Set Top Box
Medical Equipment
Notebook Computers
Battery Powered Systems
Pin Configurations
(TOP VIEW)
Note :
NC
Richtek products are :
EN
2
VIN
NC
3

RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

Suitable for use in SnPb or Pb-free soldering processes.
8
GND
ADJ
6
VOUT
5
NC
9
4
GND
7
SOP-8 (Exposed Pad)
Marking Information
RT2515AGSP : Product Number
RT2515A
GSPYMDNN
YMDNN : Date Code
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS2515A-02 November 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT2515A
Typical Application Circuit
RT2515A
RT2515A
3
VIN
VIN
VOUT
6
Chip Enable
VOUT =
0.5(R1+R2)
R2
R1
2
VIN
VOUT
C1
10µF
ADJ 7
3
VOUT
6
C1
10µF
C2
10µF
Chip Enable
2
R2
EN
VIN
ADJ 7
C2
10µF
VOUT
1.2V
EN
GND
8,
9 (Exposed Pad)
GND
8,
9 (Exposed Pad)
(V)
Figure 1. Adjustable Voltage Regulator
Figure 2. Fixed Voltage Regulator
Functional Pin Description
Pin No.
Pin Name
1, 4, 5
NC
2
EN
Pin Function
No Internal Connection.
Chip Enable (Active-High). Pulling this pin below 0.4V turns the regulator off,
reducing the quiescent current to a fraction of its operating value. The device will
be enabled if this pin is left open. Connect to VIN if not being used.
3
VIN
Input voltage. For regulation at full load, the input to this pin must be between
(VOUT + 0.5V) and 5.5V. Minimum input voltage is 1.4V. A large bulk capacitance
should be placed closely to this pin to ensure that the input supply does not sag
below 1.4V. Also a minimum of 10F ceramic capacitor should be placed directly at
this pin.
6
VOUT
Output Voltage. A minimum of 10F capacitor should be placed directly at this pin.
7
ADJ
8,
GND
9 (Exposed pad)
When this pin is grounded, an internal resistor divider sets the output voltage to
1.2V. If connected to the VOUT pin, the output voltage will be set at 0.5V. If
external feedback resistors are used, the output voltage will be determined by the
resistor ratio.
Ground. The exposed pad must be soldered to a large PCB and connected to GND
for maximum power dissipation.
Function Block Diagram
RSENSE
VOUT
VIN
VPUMP
-
-
+
+
Mode
Select
+
VIN
ADJ
-
0.5µA
0.5V
EN
VIN
Thermal
Shutdown
VOUT
+
VIN
-
0.1V
GND
Reverse Voltage
Shutdown
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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2
Reference
Generator
is a registered trademark of Richtek Technology Corporation.
DS2515A-02 November 2012
RT2515A
Absolute Maximum Ratings
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(Note 1)
Supply Voltage, VIN -----------------------------------------------------------------------------------------------------Other I/O Pin --------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------------SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------
Recommended Operating Conditions
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−0.3V to 7V
−0.3V to 6V
2.04W
49°C/W
15°C/W
260°C
150°C
−65°C to 150°C
2kV
(Note 4)
Supply Voltage, VIN ------------------------------------------------------------------------------------------------------ 1.4V to 6V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 1.4V to 6V, IOUT = 10μA to 2A, VADJ = VOUT, −40°C ≤ TA ≤ 85°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Quiescent Current
IQ
VIN = 3.3V, IOUT = 0A
--
0.7
1.5
mA
Shutdown Current
ISHDN
--
1.5
10
A
Output Voltage
(Fixed Output, VADJ = 0V)
VOUT
VIN = 5.5V, VEN = 0V
VIN = VOUT + 0.5V, IOUT = 10mA
TA = 25C
VIN = 1.8V, IOUT = 0.8A, TA = 25C
2
--
2
1.4V  VIN  5.5V, IOUT = 10mA
3
--
3
%
Line Regulation
VLINE
IOUT = 10mA
--
0.2
0.4
%/V
Load Regulation
VLOAD
IOUT = 10mA to 2A
--
0.5
1.5
%
IOUT = 1A, VIN  1.6V
--
120
200
IOUT = 1A, 1.4V < VIN < 1.6V
--
--
400
IOUT = 1.5A, VIN  1.6V
--
180
300
IOUT = 1.5A, 1.4V < VIN < 1.6V
--
--
500
IOUT = 2A, VIN  1.6V
--
240
400
IOUT = 2A, 1.4V < VIN < 1.6V
--
--
600
2.3
3
4.4
Dropout Voltage
Current Limit
VDROP
ILIM
VIN = 3.3V
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS2515A-02 November 2012
mV
A
is a registered trademark of Richtek Technology Corporation.
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RT2515A
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
VIN = 3.3V, VADJ = VOUT,
IOUT = 10mA, TA = 25C
0.495
--
0.505
VIN = 3.3V, VADJ = VOUT,
IOUT = 10mA
0.49
--
0.51
--
20
200
nA
0.05
0.1
0.15
V
--
1
10
A
Feedback
ADJ Reference Voltage
VADJ
V
ADJ Pin Current
IADJ
VADJ = 0.5V
ADJ Pin Threshold
VTH_ADJ
VIN = 3.3V
IEN
VEN = 0V, VIN = 5.5V
Logic-High
VIH
VIN = 3.3V
1.6
--
--
Logic-Low
VIL
VIN = 3.3V
--
--
0.4
OTP Trip Level
--
160
--
°C
Hysteresis
--
30
--
°C
Enable
EN Pin Current
EN Threshold
Voltage
V
Over Temperature Protection
Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS2515A-02 November 2012
RT2515A
Typical Operating Characteristics
Quiescent Current vs. Temperature
Reference Voltage vs. Temperature
1.15
0.520
Quiescent Current (mA)
Reference Voltage (V)
0.515
0.510
0.505
VIN = 5V
0.500
VIN = 3.3V
0.495
0.490
0.95
VIN = 5V
0.75
VIN = 3.3V
0.55
0.485
VOUT = 2.52V
0.35
0.480
-50
-25
0
25
50
75
100
-50
125
-25
0
Shutdown Current vs. Temperature
75
100
125
UVLO vs. Temperature
1.20
1.50
1.05
1.40
Logic-High
1.30
VIN = 5V
UVLO (V)
Shutdown Current (µA)1
50
Temperature (°C)
Temperature (°C)
0.90
25
0.75
VIN = 3.3V
1.20
1.10
Logic-Low
0.60
1.00
0.45
0.90
0.30
0.80
VEN = 5V
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature (°C)
Dropout Voltage vs. Load Current
50
75
100
125
EN Threshold Voltage vs. Temperature
1.3
350
EN Threshold Voltage (V)
300
Dropout Voltage (mV)
25
Temperature (°C)
125°C
250
25°C
200
150
−40°C
100
50
Logic-High
1.2
1.1
1.0
Logic-Low
0.9
0.8
VOUT = 2.5V
VIN = 5V
0.7
0
0
0.5
1
1.5
Load Current (A)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS2515A-02 November 2012
2
-50
-25
0
25
50
75
100
125
Temperature (°C)
is a registered trademark of Richtek Technology Corporation.
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5
RT2515A
Load Transient Response
Line Transient Response
VOUT
(20mV/Div)
VIN
(1V/Div)
VOUT
(10mV/Div)
IOUT
(1A/Div)
VIN = 3.3V, VOUT = 2.5V, IOUT = 1A to 2A
VIN = 3.3V to 4.3V, VOUT = 2.5V, IOUT = 2A
Time (50μs/Div)
Time (500μs/Div)
Power On from EN
Power Off from EN
VEN
(5V/Div)
VEN
(5V/Div)
VOUT
(2V/Div)
VOUT
(2V/Div)
I IN
(2A/Div)
I IN
(2A/Div)
VIN = 3.3V, VOUT = 2.5V, IOUT = 2A
Time (250μs/Div)
VIN = 3.3V, VOUT = 2.5V, IOUT = 2A
Time (250μs/Div)
PSRR
0
IOUT = 1mA
IOUT = 100mA
IOUT = 300mA
-10
PSRR (dB)
-20
-30
-40
-50
-60
-70
VIN = 3.25V to 3.35V, VOUT = 2.5V
-80
100
1000
10000
100000
1000000
Frequency (Hz)
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS2515A-02 November 2012
RT2515A
Application Information
The RT2515A 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 RT2515A 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 :
VOUT = VADJ   1+ R1 
 R2 
The RT2515A 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 RT2515A output ensures stability. Nevertheless, the
RT2515A 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 RT2515A.
Region of Stable COUT ESR vs. Load Current
100
where VADJ is the reference voltage with a typical value of
0.5V.
Unstable Range
The RT2515A 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 RT2515A contains an independent current limit
circuitry, which monitors and controls the pass transistor's
gate voltage, limiting the output current to 3A (typ.).
COUT ESR (Ω)
10
Chip Enable Operation
1
Stable Range
0.1
0.01
VIN = 3.3V, VOUT = 2.5V, COUT = 10μF / X7R
0.001
0.0
0.3
0.5
0.8
1.0
Load Current (A)
Figure 3
CIN and COUT Selection
Thermal Considerations
Like any low dropout regulator, the external capacitors of
the RT2515A 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.
Thermal protection limits power dissipation in RT2515A.
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.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
DS2515A-02 November 2012
RT2515A 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.
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RT2515A
VOUT Short to GND
ILIM
ILIM＇
IOUT
IC Temperature
Maximum Power Dissipation (W)
VOUT
3.2
Four-Layer PCB
2.8
2.4
2.0
1.6
1.2
0.8
0.4
0.0
Figure 4. Short Circuit Protection when Output Short
Circuit Occurs
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 5. Derating Curve of Maximum Power Dissipation
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
SOP-8 (Exposed Pad) package, the thermal resistance,
θJA, is 49°C/W on a standard JEDEC 51-7 four-layer
thermal test board. The maximum power dissipation at TA
= 25°C can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (49°C/W) = 2.04W for
SOP-8 (Exposed Pad) package
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 5 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Copyright © 2012 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS2515A-02 November 2012
RT2515A
Outline Dimension
H
A
M
EXPOSED THERMAL PAD
(Bottom of Package)
Y
J
X
B
F
C
I
D
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
4.801
5.004
0.189
0.197
B
3.810
4.000
0.150
0.157
C
1.346
1.753
0.053
0.069
D
0.330
0.510
0.013
0.020
F
1.194
1.346
0.047
0.053
H
0.170
0.254
0.007
0.010
I
0.000
0.152
0.000
0.006
J
5.791
6.200
0.228
0.244
M
0.406
1.270
0.016
0.050
X
2.000
2.300
0.079
0.091
Y
2.000
2.300
0.079
0.091
X
2.100
2.500
0.083
0.098
Y
3.000
3.500
0.118
0.138
Option 1
Option 2
8-Lead SOP (Exposed Pad) Plastic Package
Richtek Technology Corporation
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
DS2515A-02 November 2012
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