500mA Dual LDO Regulator (RT9184)
RT9184
Preliminary
500mA Dual LDO Regulator
General Description
Features
The RT9184 is a dual-channel, low noise, and low
z
Up to 500mA Output Current (Each LDO)
dropout regulator supplying up to 500mA current at
z
Current Limiting and Thermal Protection
each channel. The output voltage ranges from 1.5V
z
Short Circuit Protection
to 3.3V in 100mV increment and 2% accuracy by
z
650mV Dropout at 500mA Load
operating from a +2.7V to +6.5V input.
z
Two LDOs in Power SOP-8 Package
The RT9184 uses two internal PMOS as the pass
device, which consumes 185µA supply current (both
LDOs on) independent of load current and dropout
Pin Configurations
Part Number
conditions. Other features include a current limiting
RT9184…CH
and over temperature protection.
(Plastic PSOP-8)
Pin Configurations
TOP VIEW
Applications
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CD-RW
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LCD Monitor
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Information Appliance
GND 1
8 VIN
GND 2
7 VIN
GND 3
6 VOUT1
5 NC
VOUT2 4
Typical Application Circuit
Ordering Information
RT9184… … …
VOUT2
VOUT2 VOUT1
Package type
H : PSOP-8
Operating temperature range
10 µF
VOUT1
RT9184
GND
VIN
10 µF 10 µF
C : Commercial standard
Output voltage
A : 3.3V (Output1), 1.8V (Output2)
B : 3.3V (Output1), 2.5V (Output2)
Other voltage versions please
contact RichTek for detail.
DS9184-00 March 2002
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1
RT9184
Preliminary
Pin Description
Pin Name
Pin Function
VIN
Power Input
GND
Ground
VOUT1
Output1 Voltage
VOUT2
Output2 Voltage
NC
No Connected
Function Block Diagram
Current Limit
Thermal Protection
+
VOUT1
Vref
+
_
VOUT2
Bias
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2
Current Limit
_
VIN
GND
DS9184-00 March 2002
RT9184
Preliminary
Absolute Maximum Ratings
z
Input Voltage
z
Package Thermal Resistance
7V
PSOP-8, θJC
28°C/W
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Junction Temperature Range
-40°C ~ 125°C
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Storage Temperature Range
-65°C ~ 150°C
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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
2.7
--
6.5
V
Input Voltage Range
VIN
Output Voltage Accuracy
∆VOUT
IOUT = 1mA
-2
--
+2
%
Maximum Output Current
IMAX
Continuous
500
--
--
mA
Current Limit
ILIMIT
RLOAD = 1Ω
510
--
1000
mA
IG
No Load
--
185
260
µA
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
125
180
--
°C
--
20
--
°C
--
62
--
dB
GND Pin Current (Whole Chip)
Dropout Voltage
Note
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Output Voltage AC PSRR
TSD
100Hz, COUT = 10µF
ILOAD = 100mA
Note : Dropout voltage definition: VIN – VOUT when VOUT is 50mV below the value of VOUT (normal)
DS9184-00 March 2002
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RT9184
Preliminary
Typical Operating Characteristics
ILOAD = 100mA, VIN = 5V, COUT = 10µF, and CIN = 10µF, unless otherwise noted.
Quiescent Current vs. Temp.
Output Voltage Accuracy vs. Temp.
200
1.0
0.8
0.6
Output Voltage (%)
Quiescent Current (µ A)
180
160
140
120
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
100
-1.0
-40
-15
10
35
Temperature ( °C)
60
85
-40
85
ILOAD = 1mA
50
80
PSRR (dB)
Channel Isolation (dB)
60
40
40
30
20
10
RLOAD = 100Ω
100
1K
10K
Frequency (Hz)
100K
1M
0
10
100
1K
10K
100K
1M
Frequency (Hz)
Load Transient Response
(ILOAD = 10 to 500mA)
Line Transient Response
T
20mV/Div
Output Voltage Deviation
(AC-Coupled)
Input Voltage (V)
60
60
20
VOUT
3>
TT
1>
≈
4.5
≈
TT
3.5
TT
ILOAD
1>
2↓
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35
PSRR vs. Frequency
70
100
0
10
Temperature ( ° C)
Channel-to-Channel Isolation
vs. Frequency
120
-15
50µS/Div
Time
COUT = 100µF
1) Ch 1: 1
Volt 250 us
500mA
3) Ref B: 50 mVolt 250 us
Time
DS9184-00 March 2002
Preliminary
RT9184
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.
DS9184-00 March 2002
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5
RT9184
Preliminary
Applications Information
two components of the output response: a DC shift
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.
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
Using a capacitor whose value is greater than 1µF on
change in the load current from 0mA to 50mA is tens
the RT9184 input and the amount of capacitance can
mV, depending on the ESR of the output capacitor.
be increased without limit. The input capacitor must
Increasing
be located a distance of not more than 0.5" from the
decreasing the ESR attenuates the overshoot.
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
output
capacitor’s
value
and
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
The RT9184 is designed specifically to work with low
voltage. Because the RT9184 uses a P-channel
ESR ceramic output capacitor in space-saving and
MOSFET pass transistor, the dropout voltage is a
performance
function of drain-to-source on-resistance [RDS(ON)]
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 loadtransient 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.
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
Note that some ceramic dielectrics exhibit large
value below the output voltage. To prevent regulator
capacitance and ESR variation with temperature. It
mis-operation, a Schottky diode could be used in the
may be necessary to use 2.2µF or more to ensure
applications where input/output voltage conditions
stability at temperatures below -10°C in this case.
can cause the internal diode to be turned on (see
Also, tantalum capacitors, 2.2µF or more may be
Fig.2). As shown, the Schottky diode is connected in
needed to maintain capacitance and ESR in the
parallel with the internal parasitic diode and prevents
stable region for strict application environment.
it from being turned on by limiting the voltage drop
Tantalum capacitors maybe suffer failure due to
across it to about 0.3V < 100mA to prevent damaging
surge current when it is connected to a low-
the part.
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
VIN
VOUT
manufacture.
Load-Transient Considerations
The RT9184 load-transient response graphs show
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Fig. 1 VOUT Structure of RT9184
DS9184-00 March 2002
RT9184
Preliminary
Gold Wire
Die
Polymide Tape
VIN
VOUT
Fig. 2 External Schottky Diode to Prevent Internal
Exposed Slug
Leadframe
Diode Turning on
Fig. 3 Power SOP-8 Structure
Power Dissipation and PCB Layout Note
The maximum power dissipation of RT9184 depends
8
7
6
5
1
2
3
4
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:
Fig. 4 Typical Footprint of RT9184
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.
DS9184-00 March 2002
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7
RT9184
Preliminary
Package Information
H
A
M
J B
X
Y
F
C
D
Symbol
I
Dimensions In Millimeters
Dimensions In Inches
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
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DS9184-00 March 2002
Preliminary
DS9184-00 March 2002
RT9184
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9
RT9184
Preliminary
RICHTEK TECHNOLOGY CORP.
RICHTEK TECHNOLOGY CORP.
Headquarter
Taipei Office (Marketing)
6F, No. 35, Hsintai Road, Chupei City
8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5510047 Fax: (8863)5537749
Tel: (8862)89191466 Fax: (8862)89191465
Email: [email protected]
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10
DS9184-00 March 2002
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