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Preliminary
RT9184A
Dual, Ultra-Fast Transient Response, 500mA LDO Regulator
General Description
The RT9184A series are an efficient, precise dual-cha nnel
CMOS LDO regulator optimized for ultra-low-quiescent
a pplications. Both regulator outputs are capa ble of sourcing
500mA of output current.
The RT9184A's performa nce is optimized for CD/D VD-ROM,
CD/RW or wireless communication supply applications.
The RT9184A regulators are sta ble with output cap acitors
as low a s 1µF. The other features include ultra low dropout
voltage, high output accura cy , current limiting protection,
and high ripple re jection ratio.
The RT9184A regulators are available in fused SOP-8
package. Key features include current limit, thermal
shutdown, fast transient response, low dropout voltage,
high output accura cy , current limiting protection, and high
ripple rejection ratio.
Applications
z CD/DV D-ROM, CD/R W
z Wireless LAN Card/Keyboard/Mouse
z Battery-Powered Equipment
z XDSL Router
Features
zz
Low Quiescent Current (Typically 440
z
zz
zz
z Guaranteed 500mA Output Current
zz
zz
z Low Dropout Voltage: 600mV at 500mA
zz
zz
z Wide Operating Voltage Ranges: 2.8V to 5.5V
zz
zz
z Ultra-Fast T ran sient Response
zz
zz
z Tight Load and Line Regulation
zz
zz
z Current Limiting Protection
zz
zz
z Thermal Shutdown Protection
zz
zz
z Only low-ESR Ceramic Capacitors Required for
zz
Stability
zz
z Custom Voltage Available
zz
zz
z RoHS Compliant and 100% Lead (Pb)-Free
zz
µµ
µA)
µµ
Ordering Information
RT9184A-
Package Type
S : SOP-8
Operating Temperature Range
C : Commercial Standard
P : Pb Free with Commercial Standard
Output 2
Output 1
Note:
z The output 2 is designated to larger than or equal to
Pin Configurations
(TOP VIEW)
VOUT1
VIN1
VOUT2
VIN2
2
3
4
output 1 in voltage code order below, i.e. V
For example, the part number of RT9184A-FNCS is
assigned for 2.5V
8
GND
7
GND
6
GND
5
GND
number of RT9184A-NFCS is opposite to the rule and
doesn't exist in the system.
V oltage Code f or Both Outputs:
OUT1
/3.3V
, contrary to the part
OUT2
OUT2
≥≥
≥
V
≥≥
OUT1
2: 1.2V A: 2.0V K: 3.0V U: 4.0V
SOP-8
3: 1.3V B: 2.1V L: 3.1V V: 4.1V
4: 1.4V C: 2.2V M: 3.2V W: 4.2V
: : : :
9: 1.9V J: 2.9V T: 3.9V Z: 4.5V
z RichTek Pb-free 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.
−100%matte tin (Sn) plating.
DS9184A-04 March 2005 www.richtek.com
.
1
RT9184A
Typical Application Circuit
Preliminary
V
OUT2
V
IN2
VOUT2
VIN2 VIN1
VOUT1
RT9184A
GND
Function Block Diagram
VIN1
V
OUT1
1uF1uF
Note: To prevent oscillation, a 1
dielectric is strongly recommended if ceramics are used
µµ
µF minimum X7R or X5R
µµ
as in put/output cap acitors. When using the Y5V dielectric,
V
IN1
1uF1uF
the minimum value of the input/output capacitance that
can be used for stable over full operating temperature
µµ
3.3
range is
µF. (see Application Information Section for
µµ
further details)
VOUT1
Current
Limiting
Sensor
Thermal
Shutdown
Error
Amplifier
1.2V
Reference
+
-
VIN2
Functional Pin Description
Pin No. Pin Name Pin Function
1 VOUT1 Channel 1 Output Voltage
2 VIN1 Channel 1 Supply Input
5,6,7,8 GND Common Ground
3 VOUT2 Channel 2 Output Voltage
4 VIN2 Channel 2 Supply Input
Current
Limiting
Sensor
Thermal
Shutdown
Error
Amplifier
1.2V
Reference
VOUT2
+
-
GND
DS9184A-04 March 2005www.richtek.com
2
Preliminary
RT9184A
Absolute Maximum Ratings (Note 1)
z Supply Input V oltage-------------------------------------------------------------------------------------------------- 6.5V
z Power Dissipation, P
@ T
D
= 25°C
A
SOP-8-------------------------------------------------------------------------------------------------------------------- 0.625W
z Package Thermal Resistance (Note 7)
SOP-8, θJA-------------------------------------------------------------------------------------------------------------- 160°C/W
z Lead Temperature (Soldering, 10 sec.)--------------------------------------------------------------------------- 260°C
z Junction T emperature------------------------------------------------------------------------------------------------- 150°C
z Storage T emperature Range ---------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 2)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV
MM (Ma chine Mode)-------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 3)
z Supply Input V oltage-------------------------------------------------------------------------------------------------- 2.8V to 5.5V
z Junction T emperature Range---------------------------------------------------------------------------------------- −40°Cto 125°C
Electrical Characteristics
(V
= V
IN
+ 1V, or V
OUT
Parameter Symbol Test Conditions Min Typ Max Units
Output Voltage Accurac y ∆V
Current Limit I
Quiescent Current (both LDOs)
(Note 6)
Dropout Voltage (Note 4) V
Line Regulation ∆V
Load Regulation (Note 5) ∆V
Power Supply Rejection Rate PSRR f = 1kHz, C
Thermal Shutdown Protection TSD -- 170 -- °C
Thermal Shutdown Hysteresis
= 2.8V whichever is greater, CIN = 1µF, C
IN
I
OUT
R
LIM
I
I
Q
I
DROP
LINE
1mA < I
LOAD
∆T
SD
= 1mA −1 -- +3 %
OUT
LOAD
= 0mA -- 440 600 µA
OUT
= 500mA -- 600 -- mV
OUT
= (V
V
IN
I
= 1mA
OUT
-- 40 --
= 1µF, TA = 25°C, for each LDO unless otherwise specified)
OUT
= 1Ω 500 -- -- mA
+ 0.3V) to 5.5V,
OUT
< 500mA -- 30 -- mV
OUT
= 1µF -- −55 -- dB
OUT
-- 0.2 -- %/V
°C
DS9184A-04 March 2005 www.richtek.com
3
RT9184A
Preliminary
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. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. The dropout voltage is defined as V
IN
, which is measured when V
OUT
OUT
is V
OUT(NORMAL)
− 100mV.
-V
Note 5. Regulation is measured at constant junction temperature by using a 20ms current pulse. Devices are tested for load
regulation in the load range from 1mA to 500mA.
Note 6. Quiescent, or ground current, is the difference between input and output currents. It is defined by I
load condition (I
= 0mA). The total current drawn from the supply is the sum of the load current plus the ground pin
OUT
= IIN - I
Q
under no
OUT
current.
Note 7. θ
is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of
JA
JEDEC 51-3 thermal measurement standard.
DS9184A-04 March 2005www.richtek.com
4
Preliminary
Typical Operating Characteristics
RT9184A
Output Voltage vs. Temperature
3.4
V
= 5V
IN1
= 1uF
C
IN1
= 1uF
C
3.35
3.25
Output Voltage (V)
OUT1
∞
R
=
L1
3.3
3.2
-50 -25 0 25 50 75 100 125
-40
Temperature
(°C)
Current Limit vs. Input Voltage
900
V
= 5V
IN1
C
= 1uF
IN1
C
= 1uF
OUT1
850
R
= 0.5Ω
L1
Quiescent Current vs. Temperature
500
V
= V
= C
= C
= RL2 =
IN2
IN2
= 5V
= 1uF
OUT2
∞
= 1uF
450
400
350
C
C
R
IN1
IN1
OUT1
L1
Quiescent Current (uA) A
300
-50 -25 0 25 50 75 100 125
-40
Temperature
(°C)
Current Limit vs. Temperature
900
V
= 5V
IN1
= 1uF
C
IN1
C
= 1uF
OUT1
850
R
= 0.5Ω
L1
800
Current Limit (mA)
750
700
33.544.555.5
Input Voltag e (V )
Load Transient Regulation
V
= V
I
OUT1
C
IN1
OUT1
= C
= 5V, C
IN2
OUT2
= C
IN1
IN2
= 1uF(X7R), I
= 1uF(X7R)
= 0A
OUT2
(100mA/Div)
≈ ≈
OUT1
V
(20mV/Div)
800
Current Limit (mA)
750
700
-50 -25 0 25 50 75 100 125
-40
Temperature
(°C)
Load Transient Regulation
V
= V
I
OUT2
C
IN1
OUT1
= C
= 5V, C
IN2
OUT2
= C
IN1
IN2
= 1uF(X7R), I
= 1uF(X7R)
= 0A
OUT1
(100mA/Div)
≈ ≈
OUT1
V
≈≈
(20mV/Div)
≈≈
OUT2
V
(20mV/Div)
Time (1ms/Div)
OUT2
V
(20mV/Div)
Time (1ms/Div)
DS9184A-04 March 2005 www.richtek.com
5
RT9184A
Preliminary
Dropout Voltage vs. Output Current
800
C
= 10uF
IN1
700
600
500
400
300
200
C
OUT1
= 10uF
T
J
= 25°C
T
= 125°C
J
T
Dropout Voltage (mA)
100
0
0 100 200 300 400 500
Output Current (mA)
Range of Stable ESR
100
)
Ω
10
Unstable Range
10uF
= -40°C
J
0
V
= 5V
IN1
C
= 10uF
IN1
-10
C
= 10uF
OUT1
-20
-30
PSRR (dB)
-40
1mA
-50
-60
10 100 1000 10000 100000 1000000
100mA
1k 10k 100k 1M
Frequency (Hz)
Line Transient Regulation
V
Power Supply Rejection Ratio
4
Deviation (V)
Input Voltage
3
IN1
V
IN2
= 3 to 4V
= 5V
C
C
IN1
OUT1
= 10uF
= 10uF
1
Stable Range
0.1
1uF
Output Capacitor ESR (
0.01
0 100 200 300 400 500
Output Current (mA)
Output Noise
V
= 5V
IN1
I
= 100mA
LOAD
4
3
2
0
Output Noise Signal (uV)
-2
F = 10Hz to 100kHz
C
C
IN1
OUT1
= 1uF
= 1uF
≈ ≈
2
0
Output Voltage
Deviation (mV)
-2
Time (1ms/Div)
Time (1ms/Div)
DS9184A-04 March 2005www.richtek.com
6
Application Information
Preliminary
RT9184A
Like any low-dropout regulator , the RT9184A requires in put
and output decoupling ca pacitors. The device is specifically
designed for portable a pplications requiring minimum board
space a nd smallest components. These ca p acitors must
be correctly selected for good performa nce (see Capa citor
Characteristics Section). Plea se 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 ca pa citance.
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
cap acitor MUST be located less than 1cm from the device
to assure in put 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
cap acitor , but tolerance a nd temperature coefficient must
be considered when selecting the ca pacitor to ensure the
capacitance will be ≅1µF over the entire operating
temperature range.
Output Capa citor
The RT9184A is designed specifically to work with very
small ceramic output capacitors. The recommended
minimum capacitance (temperature characteristics X7R
or X5R) are 1µF to 4.7µF range with 10mΩ to 50mΩ range
ceramic capacitors between each LDO output and GND
for tran sient stability , but it may be increa sed without limit.
Higher cap acita nce values help to improve tran sient.
The output cap acitor'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 ca pacita nce that can be used for
stable over full operating temperature range is 3.3µF.)
No Load Stability
The device will remain stable and in regulation with no
external load. This is speci ally important in CMOS RAM
keep-alive application s.
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-tosource on-resistance, R
current:
V
DROPOUT
Current Limit
The RT9184A monitors and controls the PMOS' gate
voltage, limiting the output current to 500mA (min.). The
output can be shorted to ground for a n indefinite period of
time without da maging 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 pa ss element of f. Once
the power pass element shuts down, the control loop will
rapidly cycle the output on a nd off until the average power
dissipation causes the thermal shutdown circuit to
respond to servo the on/off cycling to a lower frequency .
Plea se refer to the section on thermal information for power
dissipation calculations.
Cap acitor Characteristics
It is important to note that capacitance tolerance and
variation with temperature must be taken into consideration
when selecting a cap acitor so that the minimum required
a mount of ca pacita nce is provided over the full operating
temperature range. In general, a good ta ntalum capa citor
will show very little cap acitance vari ation with temperature,
but a ceramic
may not be as good (depending on dielectric type).
Aluminum electrolytics also typically have large
temperature variation of ca pacita nce value.
= VIN − V
OUT
, multiplied by the load
DS(ON)
= R
DS(ON)
× I
OUT
DS9184A-04 March 2005 www.richtek.com
7
RT9184A
Preliminary
Equally important to consider is a ca pa citor'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
increa se in aluminum electrolytic ca pa citors is so severe
they may not be fea sible for some applications.
Ceramic:
For values of capacitance in the 10µF to 100µF range,
ceramics are usually larger a nd more costly than ta ntalums
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 cap acita nce characteristics a s a function of voltage
and temperature.
Z5U and Y5V dielectric ceramics have capacitance that
drops severely with applied voltage. A typical Z5U or Y5V
cap acitor 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 capa citance ra nge 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 ca pa citance.
The increasing ESR at lower temperatures can cause
oscillations when marginal quality ca pa citors 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, a nd
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 cera mic, 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 impeda nce specified
at a higher frequency (between 20kHz and 100kHz) should
be used for the device. Derating must be applied to the
manufa cturer's ESR specification, since it is typically only
valid at room temperature.
Any application s using aluminum electrolytics should be
thoroughly tested at the lowest ambient operating
temperature where ESR is maximum.
PCB Layout
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 10~15% a cross the full temperature
range of 125°C to -40°C. ESR will vary only about 2X going
from the high to low temperature limits.
8
Good board layout practices must be used or instability
can be induced because of ground loops a nd 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 C
device with short traces to the VIN, V
The regulator ground pin should be connected to the
external circuit ground so that the regulator and its
cap acitors have a “single point ground”.
and C
IN
, and ground pins.
OUT
DS9184A-04 March 2005www.richtek.com
near the
OUT
Preliminary
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 ca pa citors. 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 V
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 diagra m
below:
, Kelvin connect the cap acitor
OUT
GND
RT9184A
V
+
OUT1
GND GND
V
IN1
V
OUT2
SOP-8 Board Layout
+
V
IN2
++
DS9184A-04 March 2005 www.richtek.com
9
RT9184A
Outline Dimension
Preliminary
A
J
I
Dimensions In Millimeters Dimensions In Inches
Symbol
Min Max Min Max
A 4.801 5.004 0.189 0.197
B
F
C
D
H
M
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 0.178 0.254 0.007 0.010
I 0.102 0.254 0.004 0.010
J 5.791 6.198 0.228 0.244
M 0.406 1.270 0.016 0.050
RICHTEK TECHNOLOGY CORP .
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
8-Lead SOP Plastic 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
10
DS9184A-04 March 2005www.richtek.com
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