Preliminary RT9184
DS9184-00 March 2002 www.richtek-ic.com.tw
1
500mA Dual LDO Regulator
General Description
The RT9184 is a dual-channel, low noise, and low
dropout regulator supplying up to 500mA current at
each channel. The output voltage ranges from 1.5V
to 3.3V in 100mV increment and 2% accuracy by
operating from a +2.7V to +6.5V input.
The RT9184 uses two internal PMOS as the pass
device, which consumes 185µA supply current (both
LDOs on) independent of load current and dropout
conditions. Other features include a current limiting
and over temperature protection.
Applications
z Desktop Computers
z CD-RW
z LCD Monitor
z Information Appliance
Ordering Information
RT9184
Features
z Up to 500mA Output Current (Each LDO)
z Current Limiting and Thermal Protection
z Short Circuit Protection
z 650mV Dropout at 500mA Load
z Two LDOs in Power SOP-8 Package
Pin Configurations
Part Number Pin Configurations
RT9184CH
(Plastic PSOP-8)
TOP VIEW
Typical Application Circuit
Operating temperature range
C : Commercial standard
Package type
H:PSOP
-
8
Output voltage
A : 3.3V (Output1), 1.8V (Output2)
B : 3.3V (Output1), 2.5V (Output2)
Other voltage versions please
contact RichTek for detail.
GND
GND
GND
VOUT2
1
2
3
4
8
7
6
5
VIN
VIN
VOUT1
NC
VOUT1
VOUT2
RT9184
VIN
GND
10µF
VOU T2 VOU T1
10µF
10µF
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Pin Description
Pin Name Pin Function
VIN Power Input
GND Ground
VOUT1 Output1 Voltage
VOUT2 Output2 Voltage
NC No Connected
Function Block Diagram
VOUT2
+
_
+
_
Vref
Bias
Thermal ProtectionCurrent Limit Current Limit
GND
VIN
VOUT1
Preliminary RT9184
DS9184-00 March 2002 www.richtek-ic.com.tw
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Absolute Maximum Ratings
z Input Voltage 7V
z Package Thermal Resistance
PSOP-8, θJC 28°C/W
z Junction Temperature Range -40°C ~ 125°C
z Storage Temperature Range -65°C ~ 150°C
z Operating Temperature Range -40°C ~ 85°C
z Lead Temperature (Soldering, 10 sec.) 260°C
Electrical Characteristics
(VIN = 5V, CIN = COUT = 10µF, typical values at TA = 25°C, for each LDO unless otherwise specified.)
Parameter Symbol Test Conditions Min Typ Max Units
Input Voltage Range VIN 2.7 -- 6.5 V
Output Voltage Accuracy ∆VOUT IOUT = 1mA -2 -- +2 %
Maximum Output Current IMAX Continuous 500 -- -- mA
Current Limit ILIMIT RLOAD = 1Ω510 -- 1000 mA
GND Pin Current (Whole Chip) IGNo Load -- 185 260 µA
Dropout Voltage Note VDROP IOUT = 500mA -- 650 -- mV
Line Regulation ∆VLINE
VIN = (VOUT +0.4V or 2.7V) to 6.5V
IOUT = 1mA -0.2 -- +0.2 %/V
Load Regulation ∆VLOAD IOUT = 1mA to 500mA -35 -20 +5 mV
Thermal Shutdown Temperature 125 180 -- °C
Thermal Shutdown Hysteresis TSD -- 20 -- °C
Output Voltage AC PSRR 100Hz, COUT = 10µF
ILOAD = 100mA -- 62 -- dB
Note : Dropout voltage definition: VIN – VOUT when VOUT is 50mV below the value of VOUT (normal)
RT9184 Preliminary
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Typical Operating Characteristics
ILOAD = 100mA, VIN = 5V, COUT = 10µF, and CIN = 10µF, unless otherwise noted.
Output Voltage Accuracy vs. Temp.
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
-40 -15 10 35 60 85
Temperature ( C)
Output Voltage (%)
°
Quiescent Current vs. Temp.
100
120
140
160
180
200
-40 -15 10 35 60 85
Temperature ( C)
Quiescent Current ( A)
°
µ
PSRR vs. Frequency
0
10
20
30
40
50
60
70
Frequency (Hz)
PSRR
(dB)
ILOAD = 1mA
10 100 1K 10K 100K 1M
Channel-to-Channel Isolation
vs. Frequency
0
20
40
60
80
100
120
Frequency (Hz)
Channel Isolation (dB)
RL
O
AD = 100Ω
100 1K 10K 100K 1M
T
T
T
1
>
1
>
1
>
1
>
2
↓
2
↓
2
↓
2
↓
≈
≈
4.5
3.5
20mV/Div
Line Transient Response
50µS/Div
Time
Input Voltage (V) Output Voltage Deviation
(
AC-Cou
p
led
)
Load Transient Response
(ILOAD
= 10 to 500mA)
Time
T
T
T
T
1
>
1
>
1
>
1
>
3
>
3
>
3
>
3
>
1) Ch 1: 1 Volt 250 us
3
)
Ref B: 50 mVolt 250 us
ILOAD
VOUT
COUT = 100µF
500mA
Preliminary RT9184
DS9184-00 March 2002 www.richtek-ic.com.tw
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Functional Description
The RT9184 integrate two low noise, low dropout,
and low quiescent current linear regulators. Output
voltages are optional ranging from 1.5V to 3.3V, and
each channel can supply current up to 500mA.
Internal P-Channel Pass Transistor
The RT9184 features double typical 1.3Ω P-channel
MOSFET pass transistors. It provides several
advantages over similar designs using PNP pass
transistors. The P-channel MOSFET requires no
base drive, which reduces quiescent current
significantly than PNP-based regulator, which wastes
considerable current in dropout when the pass
transistor saturates. They also use high base-drive
currents under large loads. The RT9184 does not
suffer from these problems and consume only 185µA
of quiescent current whether in dropout, light-load, or
heavy-load applications.
Current Limit and Thermal Protection
The RT9184 includes two independent current limit
structure which monitor and control each pass
transistor’s gate voltage limiting the guaranteed
maximum output current to 510mA minimum.
Thermal-overload protection limits total power
dissipation in the RT9184. When the junction
temperature exceeds TJ = +180°C, the thermal
sensor signals the shutdown logic turning off the pass
transistor and allowing the IC to cool down. The
thermal sensor will turn the pass transistor on again
after the IC’s junction temperature cools by 20°C,
resulting in a pulsed output during continuous
thermal-overload conditions. Thermal-overloaded
protection is designed to protect the RT9184 in the
event of fault conditions. Do not exceed the absolute
maximum junction-temperature rating of TJ = +125°C
for continuous operation. The output can be shorted
to ground for an indefinite amount of time without
damaging the part by cooperation of current limit and
thermal protection.
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Applications Information
Capacitor Selection and Regulator Stability
Like any low-dropout regulator, the external
capacitors used with the RT9184 must be carefully
selected for regulator stability and performance.
Using a capacitor whose value is greater than 1µF on
the RT9184 input and the amount of capacitance can
be increased without limit. The input capacitor must
be located a distance of not more than 0.5" from the
input pin of the IC and returned with a clean analog
ground. Any good quality ceramic or tantalum can be
used for this capacitor. The capacitor with larger
value and lower ESR (equivalent series resistance)
provides better PSRR and line-transient response.
The RT9184 is designed specifically to work with low
ESR ceramic output capacitor in space-saving and
performance consideration. Using a ceramic
capacitor whose value is at least 1µF on the RT9184
output ensures the stability. The RT9184 still works
well with output capacitor of other types due to the
wide stable ESR range. Output capacitor of larger
capacitance can reduce noise and improve load-
transient response, stability, and PSRR. The output
capacitor should be located not more than 0.5"
from the VOUT pin of the RT9184 and returned with a
clean analog ground.
Note that some ceramic dielectrics exhibit large
capacitance and ESR variation with temperature. It
may be necessary to use 2.2µF or more to ensure
stability at temperatures below -10°C in this case.
Also, tantalum capacitors, 2.2µF or more may be
needed to maintain capacitance and ESR in the
stable region for strict application environment.
Tantalum capacitors maybe suffer failure due to
surge current when it is connected to a low-
impedance source of power (like a battery or very
large capacitor). If a tantalum capacitor is used at the
input, it must be guaranteed to have a surge current
rating sufficient for the application by the
manufacture.
Load-Transient Considerations
The RT9184 load-transient response graphs show
two components of the output response: a DC shift
from the output impedance due to the load current
change, and the transient response. The DC shift is
quite small due to the excellent load regulation of the
IC. Typical output voltage transient spike for a step
change in the load current from 0mA to 50mA is tens
mV, depending on the ESR of the output capacitor.
Increasing the output capacitor’s value and
decreasing the ESR attenuates the overshoot.
Input-Output (Dropout) Voltage
A regulator’s minimum input-output voltage
differential (or dropout voltage) determines the lowest
usable supply voltage. In battery-powered systems,
this will determine the useful end-of-life battery
voltage. Because the RT9184 uses a P-channel
MOSFET pass transistor, the dropout voltage is a
function of drain-to-source on-resistance [RDS(ON)]
multiplied by the load current.
Reverse Current Path
The power transistor used in the RT9184 has an
inherent diode connected between each regulator
input and output (see Fig.1). If the output is forced
above the input by more than a diode-drop, this diode
will become forward biased and current will flow from
the VOUT terminal to VIN. This diode will also be
turned on by abruptly stepping the input voltage to a
value below the output voltage. To prevent regulator
mis-operation, a Schottky diode could be used in the
applications where input/output voltage conditions
can cause the internal diode to be turned on (see
Fig.2). As shown, the Schottky diode is connected in
parallel with the internal parasitic diode and prevents
it from being turned on by limiting the voltage drop
across it to about 0.3V < 100mA to prevent damaging
the part.
Fig. 1 VOUT Structure of RT9184
VIN VOU T
Preliminary RT9184
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Fig. 2 External Schottky Diode to Prevent Internal
Diode Turning on
Power Dissipation and PCB Layout Note
The maximum power dissipation of RT9184 depends
on the thermal resistance from the case to circuit
board, the temperature difference between the die
junction and ambient air, and the rate of airflow. The
power dissipation across the device is
P = IOUT (VIN - VOUT).
The maximum power dissipation is:
PMAX = (TJ - TA) / θJA
where TJ - TA is the temperature difference between
the RT9184 die junction and the ambient
environment, θJA is the thermal resistance from the
junction to the ambient environment. The GND pin of
the RT9184 performs the dual function of providing
an electrical connection to ground and channeling
heat away. Connect the GND pin to ground using a
large pad or ground plane.
The RT9184 is assembled by power SOP-8 package
with direct slug solder to PCB (Fig.3). This structure
offers a low thermal resistance of junction to case
(θJC) and can dissipate the heat away by proper PCB
layout (a proper θCA, thermal resistance of case to
ambient). Because the bottom slug of RT9184 plays
the role as ground, the footprint in Fig.4 is a typical
configuration for heat dissipating copper clad.
Medium power dissipations of up to 2W are easily
obtainable in practice with this configuration. The
heat dissipating copper area on the PCB can be
configured in various shapes and sized depending
upon the particular application.
Fig. 3 Power SOP-8 Structure
Fig. 4 Typical Footprint of RT9184
VIN VOU T
1234
8765
Die
Gold Wire
Polymide Tape
LeadframeExposed Slug
RT9184 Preliminary
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Package Information
Dimensions In Millimeters Dimensions In Inches
Symbol Min Max Min Max
A 4.801 4.950 0.189 0.195
B 3.810 3.988 0.150 0.157
C 1.470 1.730 0.058 0.068
D 0.330 0.508 0.013 0.020
F 1.194 1.346 0.047 0.053
H 0.190 0.250 0.007 0.009
I 0.050 0.150 0.002 0.006
J 5.791 6.198 0.228 0.244
M 0.380 1.270 0.015 0.050
X 1.830 2.290 0.072 0.090
Y 1.830 2.290 0.072 0.090
Power 8–Lead SOP Plastic Package
D I
C
M
H
F
A
JBX
Y
Preliminary RT9184
DS9184-00 March 2002 www.richtek-ic.com.tw
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RT9184 Preliminary
www.richtek-ic.com.tw DS9184-00 March 2002
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RICHTEK TECHNOLOGY CORP.
Headquarter
6F, No. 35, Hsintai Road, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5510047 Fax: (8863)5537749
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-ic.com.tw
