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RT2517A
1A, 6V, Ultra Low Dropout Linear Regulator
General Description
Features
The RT2517A is a high performance positive voltage
regulator designed for applications requiring low input
voltage and ultra low dropout voltage at up to 1A. The
feature of ultra low dropout voltage is ideal for applications
where output voltage is very close to input voltage. The
input voltage can be as low as 2.2V and the output voltage
is adjustable by an external resistive divider. The RT2517A
provides an excellent output voltage regulation over
variations in line, load and temperature. Current limit and
thermal shutdown functions are provided. Additionally, an
enable pin is designed to further reduce power
consumption while shutdown and the shutdown current is
as low as 0.1μA.

The RT2517A is available in the VDFN-8AL 3x3 package.

Ordering Information
Marking Information






Input Voltage Range : 2.2V to 6V
VOUT Range from 1.2V to VIN − VDROP
Reference Voltage : 1.2V ±2.5% over −40°°C to 85°°C
Ultra Low Dropout Voltage : 150mV at 1A over
−40°°C to 85°°C
Low Quiescent 0.1μ
μA in Shutdown Mode
Soft-Discharge Function
Thermal Shutdown and Current Limit
Applications



Automotive Audio, Navigation, & Info systems
Industrial Grade General Purpose Point of Load
Digital Set top Boxes
Vehicle Electronics
RT2517A
27= : Product Code
Package Type
QV : VDFN-8AL 3x3 (V-Type)
YMDNN : Date Code
27=YM
DNN
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Pin Configurations
Richtek products are :

(TOP VIEW)
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.

Suitable for use in SnPb or Pb-free soldering processes.
VOUT
1
NC
2
8
VIN
7
IC
6
NC
5
EN
GND
ADJ
3
GND
4
9
VDFN-8AL 3x3
Simplified Application Circuit
VIN
VIN
RT2517A
VOUT
C1
Enable
EN
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
C2
ADJ
GND
DS2517A-00 March 2014
VOUT
R1
R2
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RT2517A
Functional Pin Description
Pin No.
1
Pin Name
Pin Function
VOUT
Output Voltage. A minimum 10F capacitor should be placed directly at this pin.
2, 6
NC
No Internal Connection.
3
ADJ
Feedback Voltage Input. Connect an external resistor divider to this pin for output
voltage setting. If this pin is connected to the VOUT pin, the output voltage will be
set at 1.2V.
4,
GND
9 (Exposed pad)
Ground. The exposed pad must be soldered to a large PCB and connected to GND
for maximum the power dissipation.
5
EN
Enable Control Input (Active High). This pin will be pulled up by internal circuit if this
pin is open.
7
IC
Internal Connection. Leave floating and do not make connection to this pin.
8
VIN
Supply Voltage Input. Connect a minimum 10F ceramic capacitor at this pin.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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DS2517A-00 March 2014
RT2517A
Function Block Diagram
RSENSE
VOUT
VIN
VPUMP
-
-
+
+
ADJ
VIN
EN
VIN
Thermal
Shutdown
VOUT
+
VIN
-
Reference
Generator
GND
Reverse Voltage
Shutdown
Operation
The RT2517A is a low input voltage low dropout LDO that
can support the input voltage range from 1.4V to 6V and
the output current can be up to 1A. The RT2517A uses
internal charge pump to achieve low input voltage operation
and the internal compensation network is well designed
to achieve fast transient response with good stability.
In steady-state operation, the feedback voltage is
regulated to the reference voltage by the internal regulator.
When the feedback voltage signal is less than the
reference, the on resistance of the power MOSFET is
decreased to increase the output current through the power
MOSFET, and the feedback voltage will be charge back to
reference. If the feedback voltage is less than the
reference, the power MOSFET current is decreased to
make the output voltage discharge back to reference by
the loading current.
Reverse Current Protection
The reverse current protection is guarantee by the NMOSFET with bulk capacitors connected to GND and the
internal circuit. The reverse voltage detection circuit shuts
the total loop down if the output voltage is higher than
input voltage.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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Output Under-Voltage Protection (UVP) and OverCurrent Fold-Back
When the feedback voltage is lower than 0.15V after
internal soft-start end, the UVP is triggered. If the overcurrent condition is trigged during UVP state, the OC limit
current will be decreased to limit the output power and
change into re-soft start state at the same time.
Soft-Start
An internal current source charges an internal capacitor
to build the soft-start ramp voltage. The typical soft-start
time is 150μs. During the soft-start state, the output
current will be limited to prevent the inrush current.
Over-Temperature Protection (OTP)
The RT2517A has an over-temperature protection. When
the device triggers the OTP, the device shuts down until
the temperature back to normal and move to re-soft start
state.
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RT2517A
Absolute Maximum Ratings








(Note 1)
Supply Voltage, VIN -----------------------------------------------------------------------------------------------------Other Pins ------------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
VDFN-8AL 3x3 ------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
VDFN-8AL 3x3, θJA -------------------------------------------------------------------------------------------------------VDFN-8AL 3x3, θJC ------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------CDM (Charged Device Model) -----------------------------------------------------------------------------------------MM (Machine Model) -----------------------------------------------------------------------------------------------------
Recommended Operating Conditions



−0.3V to 7V
−0.3V to 6V
1.667W
60°C/W
7°C/W
260°C
150°C
−65°C to 150°C
2kV
1kV
200V
(Note 4)
Supply Input Voltage, VIN ----------------------------------------------------------------------------------------------- 2.2V to 6V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 2.2V to 6V, IOUT = 10μA to 1A, VADJ = VOUT, −40°C ≤ TA ≤ 85°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
VIN = 3.3V, TA = 25C
Min
Typ
Max
1
--
1
2.5
--
2.5
Unit
Output Voltage
VOUT
Shutdown Current
ISHDN
VIN = 3.3V, VEN = 0V
--
0.1
--
A
Quiescent Current
IQ
VIN = 3.3V, IOUT = 0A
--
0.4
--
mA
Line Regulation
VLINE
IOUT = 10mA
--
0.01
--
%/V
Load Regulation
VLOAD
IOUT = 10mA to 1A, VIN = 3.3V
--
0.5
--
%A
Current Limit
ILIM
VIN = 3.3V
1.05
1.6
--
A
Short-Circuit Current
ISC
VOUT = 0V
--
700
--
mA
Current Foldback Threshold
VFold
VIN = 3.3V
--
0.4
--
V
Dropout Voltage
VDROP
IOUT = 1A
--
150
300
mV
ADJ Reference Voltage
VADJ
VIN = 3.3V, VADJ = VOUT , IOUT = 10mA
1.192
TA = 25C
1.2
1.216
V
ADJ Current
IADJ
VIN = 3.3V
--
20
--
nA
Power Supply Rejection Ratio
PSRR
f = 100Hz, IOUT = 1A
--
58
--
f = 10kHz, IOUT = 1A
--
37
--
Output Noise Voltage
eNO
COUT = 10F
--
27 x
VOUT
--
2.2V  VIN  6V, 10mA  IOUT  1A
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%
dB
VRMS
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RT2517A
Parameter
EN Input Voltage
Symbol
Test Conditions
Min
Typ
Max
Unit
Logic-High
VIH
1.7
--
--
Logic-Low
VIL
--
--
0.5
--
0.02
--
A
VIN = 6V, VEN = 0V
V
EN Input Current
IEN
Thermal Shutdown Threshold
TSD
--
160
--
C
Thermal Shutdown Hysteresis
TSD
--
30
--
C
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. The PCB copper area with exposed pad is 70mm2.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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RT2517A
Typical Application Circuit
RT2517A
8
VIN
VIN
VOUT
C1
10µF
Enable
R1
10k
5
ADJ 3
EN
VOUT
1.8V/1A
1
C2
10µF
R2
20k
GND
4,
9 (Exposed Pad)
Figure 1. 1.8V Output Voltage Operation Circuit
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RT2517A
Typical Operating Characteristics
Quiescent Current vs. Temperature
Reference Voltage vs. Temperature
1.15
Quiescent Current (mA)
Reference Voltage (V)
1.210
1.205
VIN = 5V
VIN = 3.3V
1.200
1.195
1.190
0.95
VIN = 5V
0.75
VIN = 3.3V
0.55
VOUT = 1.8V
VOUT = 1.8V
0.35
1.185
-50
-25
0
25
50
75
100
-50
125
-25
0
50
75
Shutdown Current vs. Temperature
125
UVLO vs. Temperature
1.8
1.7
1.4
1.6
UVLO (V)
Rising
1.0
VIN = 5V
VIN = 3.3V
0.6
1.5
1.4
Falling
VOUT = 1.8V
VEN = 5V
0.2
1.3
-50
-20
10
40
70
100
130
-50
-25
0
Temperature (°C)
25
50
75
100
125
Temperature (°C)
EN Threshold Voltage vs. Temperature
Dropout Voltage vs. IOUT
1.3
EN Threshold Voltage (V)
180
Dropout Voltage (mV)
100
Temperature (°C)
Temperature (°C)
Shutdown Current (µA)1
25
150
120
90
60
125°C
25°C
−40°C
30
1.2
Rising
1.1
1.0
Falling
0.9
0.8
VIN = 5V
IOUT = 1A
0.7
0
0
0.2
0.4
0.6
0.8
I OUT (A)
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DS2517A-00 March 2014
1
-50
-25
0
25
50
75
100
125
Temperature (°C)
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RT2517A
Line Transient Response
Load Transient Response
VOUT
(10mV/Div)
VIN
(1V/Div)
IOUT
(1A/Div)
VOUT
(10mV/Div)
VIN = 3.3V to 4.3V, VOUT = 1.8V, IOUT = 1A
VIN = 3.3V, VOUT = 1.8V, IOUT = 0 to 1A
Time (100μs/Div)
Time (500μs/Div)
Power On from EN
Power Off from EN
VEN
(2V/Div)
VEN
(2V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
I IN
(1A/Div)
VIN = 2.5V, VOUT = 1.5V, IOUT = 1A
I IN
(1A/Div)
VIN = 2.5V, VOUT = 1.5V, IOUT = 1A
Time (100μs/Div)
Time (100μs/Div)
PSRR vs. Frequency
0
-10
IOUT = 300mA
PSRR (dB)
-20
-30
IOUT = 100mA
-40
IOUT = 1mA
-50
-60
-70
VIN = 3.25V to 3.35V, VOUT = 1.8V
-80
100
1000
10000
100000
1000000
Frequency (Hz)
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is a registered trademark of Richtek Technology Corporation.
DS2517A-00 March 2014
RT2517A
Application Information
The RT2517A 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 RT2517A 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 RT2517A 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 RT2517A output ensures stability. Nevertheless, the
RT2517A can still work well with other types of output
capacitors due to its wide range of stable ESR. Figure 2
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 no more than
0.5 inch from the output pin of the RT2517A.
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 RT2517A 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 RT2517A contains an independent current limit
circuitry, which controls the pass transistor's gate voltage,
limiting the output current to 1.6A (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 2.
CIN and COUT Selection
Thermal Considerations
Like any low dropout regulator, the external capacitors of
the RT2517A 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 no 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.
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 :
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DS2517A-00 March 2014
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.
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RT2517A
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
VDFN-8AL 3x3 package, the thermal resistance, θJA, is
60°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) / (60°C/W) = 1.667W for
VDFN-8AL 3x3 package
Maximum Power Dissipation (W) 1
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 3 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
2.0
1.6
1.2
0.8
0.4
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 3. Derating Curve of Maximum Power Dissipation
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RT2517A
Outline Dimension
2
1
2
1
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min.
Max.
Min.
Max.
A
0.800
1.000
0.031
0.039
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.250
0.370
0.010
0.015
b1
0.230
0.009
D
2.900
3.100
0.114
0.122
D2
1.700
1.800
0.067
0.071
E
2.900
3.100
0.114
0.122
E2
1.450
1.550
0.057
0.061
e
0.650
0.026
e1
0.650
0.026
L
0.350
0.450
0.014
0.018
V-Type 8AL DFN 3x3 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st 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.
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