RT9179
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DS9179-11 April 2011 www.richtek.com
Pin Configurations
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Adjustable, 300mA LDO Regulator with Enable
General Description
The RT9179 is a high performance linear voltage regulator
with enable high function and adjustable output with a
1.175V reference voltage. It operates from an input of 3V
to 5.5V and provides output current up to 300mA with two
external resistors to set the output voltage ranges from
1.175V to 4.5V.
The RT9179 has superior regulation over variations in line
and load. Also it provides fast respond to step changes in
load. Other features include over-current and over-
temperature protection. The device has enable pin to reduce
power consumption in shutdown mode.
The devices is available in the popular SOT-23-5 package. Applications
zBattery-Powered Equipment
zGraphic Card
zPeripheral Cards
zPCMCIA Card
Ordering Information
Features
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z300mV Dropout @ 300mA
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z150uA Low Ground Pin Current
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zExcellent Line and Load Regulation
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z<1uA Standby Current in Shutdown Mode
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zGuaranteed 300mA Output Current
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zStable with 1uF In put and Output Cera mic Ca pacitor
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zAdjustable Output Voltage Ra nge s from 1.175V to
4.5V
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zOver-T emperature/Over-Current Protection
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zRoHS Compliant and 100% Lead (Pb)-Free
(TOP VIEW)
SOT-23-5
Note :
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
VIN GND EN
VOUT ADJ
4
23
5
RT9179
Package Type
B : SOT-23-5
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
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Function Block Diagram
Functional Pin Description
Pin No. Pin Name Pin Function
1 VIN Power Input Voltage
2 GND Ground
3 EN Chip Enable (Active High)
4 ADJ
Adjust Output Voltage. The output voltage is set by the internal feedback resistors when
this pin grounded. If external feedback resistors are applied, the output voltage will be:
VOUT = 1.175 × (1 + ) Volts
5 VOUT Output Voltage
2
1
R
R
Current-Limit
and
Thermal Protection
MOS
Driver
VOUT
Shutdown
and
Logic Control
VIN
Error
Amplifier
1.175V
VREF
ADJ
EN
GND
Thermal
SHDN
+
_
Typical Application Circuit
2
1
R
R
1+
Adjustable Operation
Note: The external feedback resistors are in hundreds of OHM to hundreds of kOHM ranges.
VOUT = 1.175 x ( ) Volts
VIN VOUT
ADJ
EN
RT9179
C2
1uF
1uF
0.1uF R2
R1
VOUT
VIN
C1
C3
GND
Chip Enable
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zSupply Input Voltage ------------------------------------------------------------------------------------------------ 3V to 5.5V
zEnable Input Voltage ------------------------------------------------------------------------------------------------ 0V to 5.5V
zJunction Temperature Range -------------------------------------------------------------------------------------- −40°Cto 125°C
Electrical Characteristics
(VIN = VOUT + 0.7V, IOUT = 10uA, CIN = COUT = 1uF (Ceramic), TA = 25°C unless otherwise specified)
Recommended Operating Conditions (Note 4)
Absolute Maximum Ratings (Note 1)
zSupply Input Voltage ------------------------------------------------------------------------------------------------ 6V
zPower Dissipation, PD @ TA = 25°C
SOT-23-5 --------------------------------------------------------------------------------------------------------------- 0.4W
zPackage Thermal Resistance (Note 2)
SOT-23-5, θJA --------------------------------------------------------------------------------------------------------- 250°C/W
zLead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
zJunction Temperature ----------------------------------------------------------------------------------------------- 150°C
zStorage Temperature Range --------------------------------------------------------------------------------------- −65°C to 150°C
zESD Susceptibility (Note 3)
HBM (Human Body Mode) ----------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------ 200V
Parameter Symbol Test Conditions Min Typ Max Unit
Reference Voltage Tolerance VREF 1.163 1.175 1.187 V
Adjust Pin Current I
ADJ -- -- 10 nA
Output Voltage Range VOUT 1.175 -- 4.5 V
Quiescent Current (Note 5) IQ Enabled, IOUT = 0mA -- 150 -- μA
Standby Current (Note 6) ISTBY V
IN = 5.5V, Shutdown -- -- 1 μA
Current Limit ILIM 0.5 -- -- A
IOUT = 10mA -- 10 --
Dropout Voltage (Note 7) VDROP IOUT = 300mA -- 300 - mV
Line Regulation ΔVLINE V
OU T + 0.7V < VIN < 5.5V -- 0.001 -- %/V
Thermal Shutdown Temperature TSD -- 170 -- °C
Thermal Shutdown Hysteresis ΔTSD -- 40 -- °C
Logic-Low Voltage VIL V
IN = 3.3V, Shutdown -- -- 0.4
EN Threshold Logic-High Voltage VIH V
IN = 3.3V, Enable 2.0 -- -- V
EN Current IEN V
IN = 5.5V, Enable -- -- 10 nA
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DS9179-11 April 2011www.richtek.com
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Quiescent, or ground current, is the difference between input and output currents. It is defined by IQ = IIN - IOUT under
no load condition (IOUT = 0mA). The total current drawn from the supply is the sum of the load current plus the ground
pin current.
Note 6. Standby current is the input current drawn by a regulator when the output voltage is disabled by a shutdown signal
(VEN 0.4V). It is measured with VIN = 5.5V.
Note 7. The dropout voltage is defined as VIN -VOUT, which is measured when VOUT is VOUT(NORMAL) − 100mV.
≤
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Typical Operating Characteristics
Quiescent Current vs. Input Voltage
120
130
140
150
33.5 44.5 55.5
Input Voltage (V)
Quiescent Current (uA)1
PSRR
-100
-90
-80
-70
-60
-50
-40
-30
-20
10 100 1000 10000 100000
Frequency (Hz)
PSRR (dB)
1K 10K 100K
IL = 10mA
COUT = 1uF (X7R)
VIN = 4V
Output Voltage v s. Temperature
3.24
3.25
3.26
3.27
3.28
3.29
-50 -25 0 25 50 75 100 125
Temperature
Output Voltage (V)
(°C)
VIN = 5V
R1 = 1.8KΩ
R2 = 1kΩ
ADJ Pin Voltage vs. Temperature
1.14
1.15
1.16
1.17
1.18
1.19
1.2
-50 -25 0 25 50 75 100 125
Temperature
ADJ Pin Voltage (V)
(°C)
VIN = 5V
Quiescent Current v s. Temperature
120
130
140
150
160
-50 -25 0 25 50 75 100 125
Temperature
Quiescent Current (uA)
(°C)
VIN = 5V
Dropout Voltage vs. Io
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300
Io (mA)
Dropout Voltage (mV)
TJ = 25°C
TJ = -40°C
TJ = 125°C
VOUT = 3.3V
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Current Limit vs. Temperature
0.7
0.75
0.8
0.85
0.9
0.95
1
-50 -25 0 25 50 75 100 125
Temperature
Current Limit (A)
(°C)
VIN = 5V
Enable Threshold Voltage
vs. Temperature
0.5
0.6
0.7
0.8
0.9
1
-50 -25 0 25 50 75 100 125
Temperature
Enable Threshold Voltage (V)1
VOUT TURN ON
VOUT TURN OFF
(°C)
Enable Response
Time (100us/Div)
Enable
Voltage(V)
2
6
0
4
Output Voltage
Deviation(V)
1
3
2
0
VIN =5V
R1 =1.8kΩ
R2 =1kΩ
CIN =1uF
CO =1uF
ILOAD : 150mA
Line Transient Regulation
Time (100us/Div)
Input Voltage
Deviation(V)
Output Voltage
Deviation(mV)
5
6
7
10
-10
0
- 20
20
4
VIN = 4V to 5V
ILOAD : 150mA
R1=1.8KΩ, R2=1KΩ
CIN=1uF(Electrolytic)
CO=1uF(Electrolytic)
Load Transient Regulation
Time (100us/Div)
0
0.1
0.2
-20
0
20
40
60
-0.1
VIN = 5V, R1 = 1.8KΩ
R2 = 1KΩ
CIN = 1uF(Ceramic)
CO = 2.2uF(Ceramic)
Output Voltage
Deviation(mV)Load Current(A)
Time (1ms/Div)
Output Short-Circuit Protection
Source Current (A)
0
0.2
0.4
0.6
0.8
1
2
4
VIN = 5V
R1 = 1.8kΩ
R2 = 1kΩ
CIN = 1uF
CO = 1uF
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DS9179-11 April 2011 www.richtek.com
Like any low-dropout regulator, the RT9179 requires input
and output decoupling capacitors. These capacitors must
be correctly selected for good performance (see Capacitor
Characteristics Section). Please note that linear regulators
with a low dropout voltage have high internal loop gains
which require care in guarding against oscillation caused
by insufficient decoupling capacitance.
Input Capa citor
An input capacitance of ≅1μF is required between the device
input pin and ground directly (the amount of the capacitance
may be increased without limit). The input capacitor MUST
be located less than 1 cm from the device to assure input
stability (see PCB Layout Section). A lower ESR capacitor
allows the use of less capacitance, while higher ESR type
(like aluminum electrolytic) require more capacitance.
Capacitor types (aluminum, ceramic and tantalum) can be
mixed in parallel, but the total equivalent input capacitance/
ESR must be defined as above to stable operation.
There are no requirements for the ESR on the input
capacitor, but tolerance and temperature coefficient must
be considered when selecting the capacitor to ensure the
capacitance will be ≅1μF over the entire operating
temperature range.
Output Ca pacitor
The RT9179 is designed specifically to work with very small
ceramic output capacitors. The recommended minimum
capacitance (temperature characteristics X7R or X5R) is
1μF to 4.7μF range with 10mΩ to 50mΩ range ceramic
capacitor between LDO output and GND for transient
stability, but it may be increased without limit. Higher
capacitance values help to improve transient. The output
capacitor's ESR is critical because it forms a zero to provide
phase lead which is required for loop stability. (When using
the Y5V dielectric, the minimum value of the input/output
capacitance that can be used for stable over full operating
temperature range is 3.3μF.)
Application Information
Short-Circuit Protection
The device is short circuit protected and in the event of a
peak over-current condition, the short-circuit control loop
will rapidly drive the output PMOS pass element off. Once
the power pass element shuts down, the control loop will
rapidly cycle the output on and off until the average power
dissipation causes the thermal shutdown circuit to respond
to servo the on/off cycling to a lower frequency. Please
refer to the section on thermal information for power
dissipation calculations.
Input-Output (Dropout) V olatge
A regulator's minimum input-to-output voltage differential
(dropout voltage) determines the lowest usable supply
voltage. In battery-powered systems, this determines the
useful end-of-life battery voltage. Because the device uses
a PMOS, its dropout voltage is a function of drain-to-source
on-resistance, RDS(ON), multiplied by the load current :
VDROPOUT = VIN - VOUT = RDS(ON) × IOUT
Current Limit
The RT9179 monitors and controls the PMOS’ gate
voltage, minimum limiting the output current to 0.5A. The
output can be shorted to ground for an indefinite period of
time without damaging the part.
No Load Stability
The device will remain stable and in regulation with no
external load. This is specially important in CMOS RAM
keep-alive applications
Region of Stable COUT ESR vs. Load Current
0.001
0.01
0.1
1
10
100
0 50 100 150 200 250 300
Load Current (mA)
Region of Stable C OUT ESR (Ω)
Region of Instable
Region of Instable
Region of Stable
COUT
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Ceramic :
For values of capacitance in the 10μF to 100μF range,
ceramics are usually larger and more costly than tantalums
but give superior AC performance for by-passing high
frequency noise because of very low ESR (typically less
than 10mΩ). However, some dielectric types do not have
good capacitance characteristics as a function of voltage
and temperature.
Z5U and Y5V dielectric ceramics have capacitance that
drops severely with applied voltage. A typical Z5U or Y5V
capacitor can lose 60% of its rated capacitance with half of
the rated voltage applied to it. The Z5U and Y5V also exhibit
a severe temperature effect, losing more than 50% of
nominal capacitance at high and low limits of the
temperature range.
X7R and X5R dielectric ceramic capacitors are strongly
recommended if ceramics are used, as they typically
maintain a capacitance range within ±20% of nominal over
full operating ratings of temperature and voltage. Of course,
they are typically larger and more costly than Z5U/Y5U
types for a given voltage and capacitance.
Tantalum :
Solid tantalum capacitors are recommended for use on
the output because their typical ESR is very close to the
ideal value required for loop compensation. They also work
well as input capacitors if selected to meet the ESR
requirements previously listed.
Tantalums also have good temperature stability: a good
quality tantalum will typically show a capacitance value
that varies less than 10 to 15% across the full temperature
range of 125° C to -40°C. ESR will vary only about 2X
going from the high to low temperature limits.
The increasing ESR at lower temperatures can cause
oscillations when marginal quality capacitors are used (if
the ESR of the capacitor is near the upper limit of the
stability range at room temperature).
Aluminum :
This capacitor type offers the most capacitance for the
money. The disadvantages are that they are larger in
physical size, not widely available in surface mount, and
have poor AC performance (especially at higher
frequencies) due to higher ESR and ESL.
Compared by size, the ESR of an aluminum electrolytic is
higher than either Tantalum or ceramic, and it also varies
greatly with temperature. A typical aluminum electrolytic
can exhibit an ESR increase of as much as 50X when going
from 25°C down to -40°C.
It should also be noted that many aluminum electrolytics
only specify impedance at a frequency of 120Hz, which
indicates they have poor high frequency performance. Only
aluminum electrolytics that have an impedance specified
at a higher frequency (between 20kHz and 100kHz) should
be used for the device. Derating must be applied to the
manufacturer's ESR specification, since it is typically only
valid at room temperature.
Any applications using aluminum electrolytics should be
thoroughly tested at the lowest ambient operating
temperature where ESR is maximum.
Ca pacitor Characteristics
It is important to note that capacitance tolerance and
variation with temperature must be taken into consideration
when selecting a capacitor so that the minimum required
amount of capacitance is provided over the full operating
temperature range. In general, a good tantalum capacitor
will show very little capacitance variation with temperature,
but a ceramic may not be as good (depending on dielectric
type).
Aluminum electrolytics also typically have large
temperature variation of capacitance value.
Equally important to consider is a capacitor's ESR change
with temperature: this is not an issue with ceramics, as
their ESR is extremely low. However, it is very important in
Tantalum and aluminum electrolytic capacitors. Both show
increasing ESR at colder temperatures, but the increase
in aluminum electrolytic capacitors is so severe they may
not be feasible for some applications.
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Thermal Considerations
The RT9179 can deliver a current of up to 300mA over the
full operating junction temperature range. However, the
maximum output current must be derated at higher ambient
temperature to ensure the junction temperature does not
exceed 125°C. With all possible conditions, the junction
temperature must be within the range specified under
operating conditions. Power dissipation can be calculated
based on the output current and the voltage drop across
regulator.
PD = (VIN - VOUT) IOUT + VIN IGND
The final operating junction temperature for any set of
conditions can be estimated by the following thermal
equation :
PD (MAX) = ( TJ (MAX) - TA ) / θθ
θθ
θJA
Where TJ (MAX) is the maximum junction temperature of
the die (125°C) and TA is the maximum ambient
temperature. The junction to ambient thermal resistance
(θJA) for SOT-23-5 package at recommended minimum
footprint is 250°C/W (θJA is layout dependent). Visit our
website in which “Recommended Footprints for Soldering
Surface Mount Packages” for detail.
PCB Layout
Good board layout practices must be used or instability
can be induced because of ground loops and voltage drops.
The input and output capacitors MUST be directly
connected to the input, output, and ground pins of the
device using traces which have no other currents flowing
through them.
The best way to do this is to layout CIN and COUT near the
device with short traces to the VIN, VOUT, and ground pins.
The regulator ground pin should be connected to the
external circuit ground so that the regulator and its
capacitors have a “single point ground”.
It should be noted that stability problems have been seen
in applications where “vias” to an internal ground plane
were used at the ground points of the device and the input
and output capacitors. This was caused by varying ground
potentials at these nodes resulting from current flowing
through the ground plane.
Using a single point ground technique for the regulator
and it's capacitors fixed the problem. Since high current
flows through the traces going into VIN and coming from
VOUT, Kelvin connect the capacitor leads to these pins so
there is no voltage drop in series with the input and output
capacitors.
Optimum performance can only be achieved when the
device is mounted on a PC board according to the diagram
below:
SOT-23-5 Board Layout
GND
ADJ
GND
GND
VIN
VOUT
EN
+
+
+
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DS9179-11 April 2011www.richtek.com
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design,
specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed
by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
Richtek Technology Corporation
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 95, Minchiuan Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
Outline Dimension
Dimensions In Millimeters Dimensions In Inches Symbol
Min Max Min Max
A 0.889 1.295 0.035 0.051
A1 0.000 0.152 0.000 0.006
B 1.397 1.803 0.055 0.071
b 0.356 0.559 0.014 0.022
C 2.591 2.997 0.102 0.118
D 2.692 3.099 0.106 0.122
e 0.838 1.041 0.033 0.041
H 0.102 0.254 0.004 0.010
L 0.356 0.610 0.014 0.024
SOT-23-5 Surface Mount Package
H
A
e
A1
C
D
B
b
L
