RT9179A
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Pin Configurations
Adjustable, 500mA LDO Regulator with Enable
General Description
The RT9179A 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 500mA
with two external resistors to set the output voltage ranges
from 1.175V to 4.5V.
The RT9179A has superior regulation over variations in line
and load. Also it provides fast response 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 device is available in SOP-8 package.
Applications
Battery-Powered Equipments
Graphic Card
Peripheral Cards
PCMCIA Card
Ordering Information
Features
400mV Dropout @ 500mA
150μμ
μμ
μA Low Quiescent Current
Excellent Line and Load Regulation
<1μμ
μμ
μA Standby Current in Shutdown Mode
Guaranteed 500mA Output Current
Adjustable Output Voltage Ranges from 1.175V to
4.5V
Over-T emperature/Over-Current Protection
RoHS Compliant and 100% Lead (Pb)-Free
(TOP VIEW)
SOP-8
VIN
GND
ADJ
EN
VOUT
2
3
45
8
7
6
GND
GND
GND
Typical Application Circuit
Note: R2 around 200kΩ is recommended.
Refer to the “Application Information” for COUT selection.
VIN VOUT
ADJ
EN
RT9179A
C2
3.3uF
1uF
0.1uF R2
R1
VOUT
VIN
C1
C3
GND
Chip Enable
VOUT = 1.175 x ( ) Volts
2
1
R
R
1+
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.
RT9179A
Package Type
S : SOP-8
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
2 VIN Power Input Voltage
5, 6, 7, 8 GND Ground
1 EN Chip Enable (Active High)
4 ADJ
Adjust Output Voltage. The output voltage is set by the external feedback resistors
connecting to ADJ pin and is calculated as : VOUT = 1.175 × (1 + ) Volts
3 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
+
_
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Electrical Characteristics
(VIN = VOUT + 0.7V, IOUT = 10μA, CIN = 1μF, COUT = 3.3μF (Ceramic), TA = 25°C unless otherwise specified)
Recommended Operating Conditions (Note 4)
Supply Input Voltage ----------------------------------------------------------------------------------------------- 3V to 5.5V
Enable Input Voltage ----------------------------------------------------------------------------------------------- 0V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------- −40°C to 125°C
Absolute Maximum Ratings (Note 1)
Supply Input Voltage ----------------------------------------------------------------------------------------------- 6V
Power Dissipation, PD @ TA = 25°C, TJ = 125°C
SOP-8 ------------------------------------------------------------------------------------------------------------------ 1.67W
Package Thermal Resistance (Note 2)
SOP-8, θJA ------------------------------------------------------------------------------------------------------------ 60°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
Junction Temperature ----------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range -------------------------------------------------------------------------------------- −65°C to 150°C
ESD 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 700 -- -- mA
IOUT = 10mA -- 10 --
Dropout Voltage (Note 7) VDROP
IOUT = 500mA -- 400 --
mV
Line Regulation ΔVLINE VOU T + 0.7V < VIN < 5.5V &
3.3V < 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 = VCE = 5.5V -- -- 10 nA
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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 the demo board, which has connected footprints as wide heat
sink. Please see the thermal considerations on application information.
Note 3. Devices are ESD sensitive. Handling precaution 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 v s . Input Voltage
120
130
140
150
33.5 44.5 55.5
Input Voltage (V)
Quiescent Current (uA)1
Output Voltage vs. 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 = 360KΩ
R2 = 200KΩ
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 vs. 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
100
200
300
400
500
600
0 100 200 300 400 500
Io (mA)
Dropout Voltage (mV)
TJ = 25°C
TJ = -40°C
TJ = 125°C
VOUT = 3.3V, R1 = 360KΩ, R2 = 200KΩ
CIN = 1uF (X7R)
COUT = 3.3uF (X7R)
PSRR
-80
-60
-40
-20
0
20
0.01 0.1 1 10 100 1000
Frequency (kHz)
PSRR(dB)
IL = 10mA
VIN = 3.3V, VEN = 3.3V
CIN = 1uF (X7R)
COUT = 3.3uF (X7R)
IL = 100mA
No Load
10 100 1K 10K 100K 1M
(Hz)
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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 =360kΩ
R2 =200kΩ
CIN =1uF
COUT =3.3uF
IO : 150mA
Time (250us/Div)
Input Voltage
Deviation(V)
Line Transient Response
Output Voltage
Deviation(mV)
5
4
VIN = 4V to 5V
IO : 150mA
R1 = 360KΩ, R2 = 200KΩ
CIN = 1uF(X7R)
COUT = 3.3uF(X7R)
10
0
-10
Load Transient Response
Time (500us/Div)
50
-50 VIN = 3.3V, R1 = 56KΩ
R2 = 200KΩ
CIN = 1uF (X7R)
COUT = 3.3uF (X7R)
Output Voltage
Deviation(mV) Load Current(mA)
0
500
0
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 = 360kΩ
R2 = 200kΩ
CIN = 1uF
COUT = 3.3uF
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Application Information
Like any low-dropout regulator, the RT9179A 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 Capacitor
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).
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 RT9179A is designed specifically to work with very
small ceramic output capacitors. The recommended
minimum capacitance is 3.3μF ceramic or tantalum
capacitor between LDO output and GND for stability. But
for output voltage lower than 1.35V, to use a minimum of
3.3μF tantalum or electrolyte capacitor. 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.
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
Input-Output (Dropout) V oltage
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 RT9179A monitors and controls the PMOS’ gate
voltage, minimum limiting the output current to 700mA. The
output can be shorted to ground for an indefinite period of
time without damaging the part.
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.
Region of Stable COUT ESR vs . Load Current
0.001
0.010
0.100
1.000
10.000
0 100 200 300 400 500
Load Current (mA)
Region of Stable COUT ESR (Ω)
Region of Instable
Region of Instable
Region of Stable
10
1
0.1
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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.
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.
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Thermal Considerations
The RT9179A can deliver a current of up to 500mA 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 is layout dependent) for SOP-8 package is 60°C/W at
recommended minimum footprint. Visit our website in which
“Recommended Footprints for Soldering Surface Mount
Packages” for detail. More power can be dissipated if the
maximum ambient temperature of the application is lower.
Approaches for enhancing thermal performance is
improving the power dissipation capability of the PCB
design like cooper area increases.
Thermal protection limits power dissipation in RT9179A.
When the operation junction temperature exceeds 170°C,
starts the thermal shutdown function and turns the pass
element off. The pass element turns on again after the
junction temperature reduced about 40°C.
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:
ADJ
GND
GND
VIN VOUT
EN
+
++
SOP-8 Board Layout
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Use vias to conduct the heat into the
buried or backside of PCB layer.
The PCB heat sink copper area should
be solder-painted without masked. This
approaches a “best case” pad heat sink.
RT917 9ACS (SOP-8)
The RT9179ACS regulator is packaged in SOP-8 package.
This package is unable to efficiently dissipate the heat
generated when the regulator is operating at high power
levels. In order to control die-operating temperatures, the
PCB layout should allow for maximum possible copper
area at the GND pins of the RT9179ACS. The multiple
GND pins on the SOP-8 package are internally connected,
but lowest thermal resistance will result if these pins are
tightly connected on the PCB. This will also aid heat
dissipation at high power levels. If the large copper around
the IC is unavailable, a buried layer may be used as a heat
sink. Use vias to conduct the heat into the buried or
backside of PCB layer.
To prevent this maximum junction temperature from being
exceeded, the appropriate power plane heat sink MUST
be used. Higher continuous currents or ambient
temperature require additional heatsinking.
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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
A
B
J
F
H
M
C
D
I
8-Lead SOP Plastic Package
Dim e nsions In Millimet e rs Dime nsio ns In I nc hes
Symbol Min Max Min Max
A 4.801 5.004 0.189 0.197
B 3.810 3.988 0.150 0.157
C 1.346 1.753 0.053 0.069
D 0.330 0.508 0.013 0.020
F 1.194 1.346 0.047 0.053
H 0.170 0.254 0.007 0.010
I 0.050 0.254 0.002 0.010
J 5.791 6.200 0.228 0.244
M 0.400 1.270 0.016 0.050
Outline Dimension
