Page 1
Preliminary
RT9179
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.
Ordering Information
RT9179
Package Type
B : SOT-23-5
Operating Temperature Range
C : Commercial Standard
P : Pb Free with Commercial Standard
Features
zz
300mV Dropout @ 300mA
z
zz
μμ
zz
z 150
μA Low Ground Pin Current
zz
μμ
zz
z Excellent Line and Load Regulation
zz
μμ
zz
z <1
μA Standby Current in Shutdown Mode
zz
μμ
zz
z Guaranteed 300mA Output Current
zz
zz
z Stable with 1
zz
zz
z Adjustable Output Voltage Ranges from 1.175V to
zz
μμ
μF Input a nd Output Ceramic Capacitor
μμ
4.5V
zz
z Over-Temperature/Over-Current Protection
zz
zz
z RoHS Compliant and 100% Lead (Pb)-Free
zz
Applications
z Battery-Powered Equipment
z Graphic Card
z Peripheral Cards
z PCMCIA Card
Marking Information
For marking information, contact our sales representative
directly or through a RichTek distributor located in your
area, otherwise visit our website for detail.
Note :
RichTek Pb-free products are :
Pin Configurations
−RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
(TOP VIEW)
−Suitable for use in SnPb or Pb-free soldering processes.
−100% matte tin (Sn) plating.
VIN
GND
1
2
354
VOUT
ADJEN
SOT-23-5
DS9179-05 March 2005 www.richtek.com
1
Page 2
RT9179
Typical Application Circuit
Preliminary
V
IN
Chip Enable
C
V
1uF
OUT
1
C
3
0.1uF
Note: The external feedback resistors are in hundreds of OHM to hundreds of KOHM ranges.
RT9179CB
GND
1+
VOUT
ADJ
1
R
2
R
VIN
EN
= 1.175 x ( ) Volts
Adjustable Operation
Functional Pin Description
Pin No. Pin Name Pin Function
1 VIN Power Input Voltage
2 GND Ground
3 EN Chip Enable (Active High)
Adjust Output Voltage. The output voltage is set by the internal feedback resistors when
4 ADJ
this pin grounded. If external feedback resistors are applied, the output voltage will be:
1
V
= 1.175 × (1 + ) Volts
OUT
R
2
R
V
OUT
R
1
C
2
R
1uF
2
5 VOUT Output Voltage
Function Block Diagram
EN
Shutdown
Logic Control
1.175V
V
REF
and
+
_
Error
Amplifier
Current-Limit
and
Thermal Protection
MOS
Driver
VIN
Thermal
SHDN
VOUT
ADJ
GND
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Page 3
Preliminary
RT9179
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage -------------------------------------------------------------------------------------------------- 6V
z Power Dissipation, P
@ TA = 25°C
D
SOT-23-5 ---------------------------------------------------------------------------------------------------------------- 0.4W
z Package Thermal Resistance (Note 7)
SOT-23-5, θJA----------------------------------------------------------------------------------------------------------- 250°C/W
z Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260°C
z Junction Temperature ------------------------------------------------------------------------------------------------- 150°C
z Storage Temperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 2)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 3)
z Supply Input Voltage -------------------------------------------------------------------------------------------------- 3V to 5.5V
z Shutdown Input Voltage ---------------------------------------------------------------------------------------------- 0V to 5.5V
z Junction Temperature Range ---------------------------------------------------------------------------------------- −40°Cto 125°C
Electrical Characteristics
(V
= V
IN
+ 0.7V, I
OUT
Parameter Symbol Test Conditions Min Typ Max Units
Reference Voltage Tolerance V
Adjust Pin Current I
Output Voltage Range V
Quiescent Current (Note 5) IQ Enabled, I
Standby Current (Note 6) I
Current Limit I
Dropout Voltage (Note 4) V
Line Regulation ΔV
Thermal Shutdown Temperature TSD -- 170 -- °C
Thermal Shutdown Hysteresis ΔTSD -- 40 -- °C
EN Threshold
EN Current IEN V
= 10μA, C
OUT
Logic-Low Voltage VIL V
Logic-High Voltage V
= C
IN
= 1μF (Ceramic), T
OUT
1.163 1.175 1.187 V
REF
-- -- 10 nA
ADJ
1.175 -- 4.5 V
OUT
VIN = 5.5V, Shutdown -- -- 1 μA
STBY
0.5 -- -- A
LIM
DROP
V
LINE
V
IH
= 25°C unless otherwise specified)
A
I
= 10mA -- 10 --
OUT
I
= 300mA -- 300 -
OUT
+ 0.7V < VIN < 5.5V -- 0.001 -- %/V
OUT
= 3.3V, Shutdown -- -- 0.4
IN
= 3.3V, Enable 2.0 -- --
IN
= 5.5V, Enable -- -- 10 nA
IN
= 0mA -- 150 -- μA
OUT
mV
V
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Page 4
RT9179
Preliminary
Note 1. Stresses listed as the abovez "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. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
-V
Note 4. The dropout voltage is defined as V
IN
, which is measured when V
OUT
Note 5. Quiescent, or ground current, is the difference between input and output currents. It is defined by I
no load condition (I
= 0mA). The total current drawn from the supply is the sum of the load current plus the ground
OUT
OUT
is V
OUT(NORMAL)
− 100mV.
= IIN - I
Q
OUT
under
pin current.
Note 6. Standby current is the input current drawn by a regulator when the output voltage is disabled by a shutdown signal
(V
Note 7. θ
0.4V). It is measured with V
≤
EN
is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of
JA
= 5.5V.
IN
JEDEC 51-3 thermal measurement standard.
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Page 5
Preliminary
Typical Operating Characteristics
RT9179
Output Voltage vs. Temperature
3.29
3.28
3.27
3.26
Output Voltage (V)
3.25
3.24
-50 -25 0 25 50 75 100 125
Temp erature
(°C)
V
R1 = 1.8KΩ
R2 = 1kΩ
Quiescent Current vs. Temperature
160
150
IN
= 5V
V
IN
= 5V
ADJ Pin Voltage vs. Temperature
1.2
1.19
1.18
1.17
1.16
ADJ Pin Voltage (V)
1.15
1.14
-50 -25 0 25 50 75 100 125
Temperature
(°C)
Quiescent Current v s. Input Voltage
150
140
V
= 5V
IN
140
130
Quiescent Current (uA)
120
-50 -25 0 25 50 75 100 125
Temperature
(°C)
PSRR
-20
-30
-40
-50
-60
-70
PSRR (dB)
V
= 4V
-80
-90
-100
10 100 1000 10000 100000
1K 10K 100K
Frequency (Hz)
IN
IL = 10mA
C
= 1uF (X7R)
OUT
130
Quiescent Current (uA)1
120
33.544.555.5
Input Voltage (V)
Dropout Voltage vs. Io
400
V
= 3.3V
OUT
350
300
250
200
150
100
Dropout Voltage (mV)
50
0
0 50 100 150 200 250 300
TJ = 25° C
Io (mA)
TJ = 125° C
TJ = -40° C
DS9179-05 March 2005 www.richtek.com
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Page 6
RT9179
Preliminary
Current Limit vs. Temperature
1
0.95
0.9
0.85
0.8
Current Limit (A)
0.75
0.7
-50 -25 0 25 50 75 100 125
Temperature
(°C)
Line Transient Regulation
7
6
5
Deviation(V)
Input Voltage
4
20
V
= 4V to 5V
IN
I
LOAD
: 150mA
R1=1.8KΩ, R2=1KΩ
=1uF(Electrolytic)
C
IN
CO=1uF(Electrolytic)
Output Short-Circuit Protection
V
= 5V
IN
4
2
1
0.8
0.6
0.4
Source Current (A)
0.2
0
Time (1ms/Div)
V
= 5V
IN
R1 = 1.8kΩ
R2 = 1kΩ
C
= 1uF
IN
CO = 1uF
Load Transient Regulation
60
V
R2 = 1KΩ
40
20
0
Deviation(mV)Load Current(A)
Output Voltage
-20
= 5V, R1 = 1.8KΩ
IN
C
= 1uF(Ceramic)
IN
CO = 2.2uF(Ceramic)
10
0
-10
Deviation(mV)
Output Voltage
- 20
Time (100us/Div)
Enable Threshold Voltage
vs. Temperature
1
0.9
0.8
0.7
0.6
V
OUT
TURN OFF
Enable Threshold Voltage (V)1
0.5
-50 -25 0 25 50 75 100 125
Temp erature
V
OUT
(°C)
TURN ON
0.2
0.1
0
-0.1
6
4
2
Enable
Voltage(V)
0
3
2
1
Deviation(V)
Output Voltage
0
Time (100us/Div)
Enable Response
I
Time (100us/Div)
V
IN
R1 =1.8kΩ
R2 =1kΩ
C
=1uF
IN
CO =1uF
: 150mA
LOAD
=5V
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Page 7
Preliminary
Application Information
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.
ESR (Ω)
OUT
OUT
C
Region of Stable C
100
10
1
0.1
RT9179
ESR vs. Load
OUT
Current
Region of Instable
Region of Stable
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). 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 Capa citor
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.)
0.01
Region of Stable C
0.001
0 50 100 150 200 250 300
Region of Instable
Load Current (mA)
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 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, R
V
DROPOUT
, multiplied by the load current:
DS(ON)
= V
- V
OUT
= R
DS(ON)
IN
× I
OUT
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.
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.
DS9179-05 March 2005 www.richtek.com
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Page 8
RT9179
Preliminary
Cap acitor 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.
DS9179-05 March 2005www.richtek.com
8
Page 9
Preliminary
RT9179
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 - V
OUT
) I
OUT
+ VIN I
GND
The final operating junction temperature for any set of
conditions can be estimated by the following thermal
equation:
P
D (MAX)
Where T
= ( T
J (MAX)
- TA ) /
J (MAX)
is the maximum junction temperature of
θθ
θ
θθ
JA
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 (θ
is layout dependent). Visit our
JA
website in which “Recommended Footprints for Soldering
Surface Mount Packages” for detail.
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 V
V
, Kelvin connect the capacitor leads to these pins so
OUT
and coming from
IN
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
V
OUT
GND
V
IN
+
+
+
GND
GND
EN
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 C
device with short traces to the VIN, V
, and ground pins.
OUT
OUT
near the
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.
SOT-23-5 Board Layout
DS9179-05 March 2005 www.richtek.com
9
Page 10
RT9179
Outline Dimension
Preliminary
H
D
L
C
B
b
A
A1
e
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
RICHTEK TECHNOLOGY CORP .
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
10
SOT-23-5 Surface Mount Package
RICHTEK TECHNOLOGY CORP .
Taipei Office (Marketing)
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)89191466 Fax: (8862)89191465
Email: marketing@richtek.com
DS9179-05 March 2005www.richtek.com
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