Preliminary
RT9177/A
DS9177/A-04 December 2002
www.richtek.com
1
Ultra-Low-Noise 200mA/500mA LDO Regulator
General Description
The RT9177/A is a 200mA/500mA low dropout and
low noise micro-power regulator suitable for portable
RF applications. The output voltage accuracy is
within
2% and range from 2.4V to 3.2V in 100mV
increments could be selected. It is designed for
using very low ESR output capacitor. Its output
remains stable even when using a 1
F ceramic as its
output capacitor.
With an internal PMOS as the pass device, it does
not need extra GND current in heavy load and
dropout conditions. In shutdown mode, nearly zero
operation current makes the IC suitable for
battery-power devices. Other features including
current limiting and over temperature protection. The
noise performance can be improved by connecting a
capacitor to the bypass pin.
Ordering Information
RT9177/A-
Features
Ultra-Low-Noise (150nV/
Hz
) for RF Application
1
F Ceramic C
OUT
Stable
Low Dropout Voltage (220mV @ 200mA)
Low Operation Current - 80
A Typical
Shutdown Function
Low Temperature Coefficient
Current and Thermal Limiting
Customized Voltage Available
SOT-25 Package
Applications
Cellular Phones
Laptop, Notebook, and Palmtop Computers
Battery-powered Equipment
Hand-held Equipment
Pin Configurations
Part Number
Pin Configurations
RT9177/A-
CB
(Plastic SOT-25)
TOP VIEW
1. IN
2. GND
3. SHDN
4. BP
5. OUT
RT9177/A-
CBR
(Plastic SOT-25)
TOP VIEW
1. OUT
2. GND
3. IN
4. SHDN
5. BP
Typical Application Circuit
5
4
3
2
1
5
4
3
2
1
Operating Temperature Range
C : Commercial Standard
Package Type
B : SOT-25 Type I
BR : SOT-25 Type II
:
:
Output Voltage
24 : 2.4V
25 : 2.5V
31 : 3.1V
32 : 3.2V
2H : 2.85V
500mA Output Current
200mA Output Current
RT9177/A
ON
OFF
GND
IN
OUT
V
OUT
C
BP
10nF
C
OUT
1F
V
IN
C
IN
1F
SHDN BP
RT9177/A
Preliminary
www.richtek.com
DS9177/A-04 December 2002
2
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.
Pin Description
Pin Name
Pin Function
IN Input
GND Ground
SHDN
Active Low Shutdown Input
BP
Reference Noise Bypass
OUT Output
Function Block Diagram
MOS Driver
Current-Limit
and
Thermal
Protection
Shutdown
and
Logic Control
VREF
GND
OUT
IN
SHDN
BP
Error Amp
+
_
Preliminary
RT9177/A
DS9177/A-04 December 2002
www.richtek.com
3
Absolute Maximum Ratings
Input Voltage
7V
Power Dissipation, P
D
@ T
A
= 25
C
SOT-25
0.25W
Operating Junction Temperature Range
-40C to 125C
Storage Temperature Range
-65C to 150C
Package Thermal Resistance
SOT-25,
JA
250
C/W
Lead Temperature (Soldering, 5 sec.)
260
C
Electrical Characteristics
(V
IN
= 5.0V, C
IN
= 1
F, C
OUT
= 1
F, T
A
= 25
C, unless otherwise specified)
Parameter Symbol Test
Conditions Min
Typ
Max
Units
Input Voltage Range
V
IN
2.5
--
6 V
Output Voltage Accuracy
V
OUT
I
L
= 1mA
-2
--
+2
%
RT9177
200
--
--
Maximum Output
Current
RT9177A
I
MAX
500
--
--
mA
RT9177 --
300
--
Current Limit
RT9177A
I
LIMIT
R
LOAD
= 1
-- 700 --
mA
RT9177/A No
Load
--
80
150
RT9177 I
OUT
= 200mA
--
90
150
GND Pin Current
RT9177A
I
G
I
OUT
= 500mA
--
90
150
A
RT9177/A I
OUT
= 1mA
--
1.1
5
RT9177/A I
OUT
= 50mA
--
55
100
RT9177/A I
OUT
= 200mA
--
220 300
Dropout Voltage
(Note)
(V
OUT
(Nominal)
3.0V
Version)
RT9177A
V
DROP
I
OUT
= 500mA
--
550 700
mV
Line Regulation
V
LINE
V
IN
= (V
OUT
+0.15) to 6V, I
OUT
= 1mA
--
--
6
mV
RT9177 I
OUT
= 0mA to 200mA
--
--
20
Load Regulation
RT9177A
V
LOAD
I
OUT
= 0mA to 500mA
--
--
30
mV
SHDN Input High Threshold
V
IH
1.0
--
-- V
SHDN Input Low Threshold
V
IL
V
IN
= 3V to 5.5V
--
--
0.4
V
SHDN Bias Current
I
SD
--
--
100
nA
Shutdown Supply Current
I
GSD
V
OUT
= 0V
--
0.01
1
A
Thermal Shutdown Temperature
T
SD
--
150
--
C
Output Noise
e
NO
C
BP
= 10nF, C
OUT
= 10
F
-- 150 -- nV/
Hz
Ripple Rejection
PSRR
F = 100Hz, C
BP
= 10nF, C
OUT
= 10
F
-- 68 -- dB
Notes: Dropout voltage definition: V
IN
- V
OUT
when V
OUT
is 50 mV below the value of V
OUT
at V
IN
= V
OUT
+ 0.5V
RT9177/A
Preliminary
www.richtek.com
DS9177/A-04 December 2002
4
Typical Operating Characteristics
GND Current vs. Load
65
66
67
68
69
70
71
72
73
74
75
0
50
100
150
200
250
I
OUT
(mA)
I
G
(u
A
)
T
A
= 25
C
V
OUT
vs. V
IN
2.50
2.60
2.70
2.80
2.90
3.00
3.10
2.5
3.0
3.5
4.0
4.5
5.0
V
IN
(V)
V
OUT
(V
)
200mA
100mA
50mA
20mA
V
OUT
= 3V
T
A
= 25
C
Dropout Voltage vs. Output Current
0
50
100
150
200
250
20
50
80
110
140
170
200
Output Current (mA)
Drop
o
u
t
V
o
l
t
ag
e (m
V
)
25 C
80 C
V
OUT
= 3V
Output Voltage Variation vs. Temperature
-1.00
-0.75
-0.50
-0.25
0.00
0.25
0.50
0.75
1.00
-40
-10
20
50
80
110
140
Temperature ( C)
V
OUT
(%
)
No Load
Output Voltage Variation vs. Load
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0
50
100
150
200
250
I
OUT
(mA)
V
OUT
(%
)
T
A
= 25
C
GND Current vs. Temperature
63
64
65
66
67
68
69
70
71
-40
-10
20
50
80
110
140
Temperature ( C)
I
G
(u
A
)
Preliminary
RT9177/A
DS9177/A-04 December 2002
www.richtek.com
5
PSRR
100
-90
-80
-70
-60
-50
-40
-30
-20
Frequency (Hz)
10 100 1K 10K 100K 1M
10mA
100mA
C
BP
= 10nF
V
OUT
= 3V
T
A
= 25
C
C
BP
= 10nF
PSRR
-100
-90
-80
-70
-60
-50
-40
-30
-20
Frequency (Hz)
PS
R
R
(
d
B)
10 100 1K 10K 100K 1M
100mA
10mA
V
OUT
= 3V
T
A
= 25
C
C
BP
= 470pF
Noise Signal & Spectrum Distribution
0
20
40
60
80
100
0
25
50
75
100
125
Frequency (KHz)
No
i
s
e
L
e
v
e
l
(
u
V
)
-1
-7
-5
-2
0
25
0
2
4
6
8
10
Time (mS)
C
IN
= 1uF TAN
C
OUT
= 4.7uF TAN
C
BP
= 470pF
Load = 10mA
Sampling Rate = 250KHz
250
0
-250
N
o
i
s
e
S
i
gna
l
(
u
V
)
Noise Signal & Spectrum Distribution
0
20
40
60
80
100
0
25
50
75
100
125
Frequency (KHz)
Noi
s
e L
e
v
e
l
(u
V
)
-10
-75
-50
-25
0
25
0
2
4
6
8
10
Time (mS)
C
IN
= 1uF TAN
C
OUT
= 4.7uF TAN
C
BP
= 470pF
Load = 100mA
Sampling Rate = 250KHz
250
0
-250
N
o
i
s
e
S
i
gna
l
(
u
V
)
Noise Signal & Spectrum Distribution
0
10
20
30
40
50
0
25
50
75
100
125
Frequency (KHz)
Noi
s
e L
e
v
e
l
(u
V
)
-35
-25
-15
-50
50
150
0
2
4
6
8
10
Time (mS)
C
IN
= 1uF TAN
C
OUT
= 4.7uF TAN
C
BP
= 10nF
Load = 100mA
Sampling Rate = 250KHz
150
50
-50
N
o
i
s
e
S
i
gna
l
(
u
V
)
Noise Signal & Spectrum Distribution
0
10
20
30
40
50
0
25
50
75
100
125
Frequency (KHz)
Noi
s
e L
e
v
e
l
(u
V
)
-
-
-
-
5
1
0
2
4
6
8
10
Time (mS)
C
IN
= 1uF TAN
C
OUT
= 4.7uF TAN
C
BP
= 10nF
Load = 10mA
Sampling Rate = 250KHz
150
50
-50
N
o
i
s
e
S
i
gna
l
(
u
V
)
RT9177/A
Preliminary
www.richtek.com
DS9177/A-04 December 2002
6
Load Transient Response
from 1mA to 100mA
-50
-30
-10
10
30
50
70
90
-10
10
30
50
70
90
Time (uS)
O
u
tp
u
t
Vo
l
t
a
g
e
Va
r
i
a
t
i
o
n
(
m
V)
100
1
Lo
ad
(m
A
)
C
IN
= 1
F
C
OUT
= 1
F
V
IN
= 5V
T
A
= 25
C
Time20uS/Div
Load Transient Response
Load Transient Response
from 100mA to 1mA
-20
0
20
40
60
80
100
120
-10
10
30
50
70
90
Time (uS)
O
u
t
p
u
t
Vo
l
t
a
g
e
Va
r
i
a
t
i
o
n
(
m
V)
100
1
Lo
ad
(m
A
)
C
IN
= 1
F
C
OUT
= 1
F
V
IN
= 5V
T
A
= 25
C
Time20uS/Div
Load Transient Response
Preliminary
RT9177/A
DS9177/A-04 December 2002
www.richtek.com
7
Application Guides
Capacitor Selection and Regulator Stability
Like any low-dropout regulator, the external capacitors
used with the RT9177/A must be carefully selected for
regulator stability and performance.
Using a capacitor whose value is
1F on the
RT9177/A input and the amount of capacitance can be
increased without limit. The input capacitor must be
located at a distance of no more than 0.5" from the
input pin of the IC and returned to 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 must meet both requirements for
minimum amount of capacitance and ESR in all LDO
applications. The RT9177/A is designed specifically for
working with low ESR ceramic output capacitor in
space-saving and performance considerations. Using a
ceramic capacitor whose value is at least 1
F with
ESR is > 5m
on the RT9177/A output ensures
stability. The RT9177/A works well even with a output
capacitor of other types due to the wide stable ESR
range. Fig.1 shows the curves of allowable ESR range
as a function of load current for various output voltages
and capacitor values. An 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 V
OUT
pin of the RT9177/A and return to a
clean analog ground.
Note that some ceramic dielectrics exhibit large
capacitance and ESR variation with temperature. It
may be necessary to use 2.2
F or more to ensure
stability at temperatures below -10C in this case. Also,
tantalum capacitors, 2.2
F 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
currents 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.
Use a 10nF bypass capacitor at BP for low output
voltage noise. The capacitor, in conjunction with an
internal 200K
resistor, which connects bypass pin
and the band-gap reference, creates an 80Hz
low-pass filter for noise reduction. Increasing the
capacitance will slightly decrease the output noise,
but increase the start-up time. The capacitor
connected to the bypass pin for noise reduction must
have very low leakage. This capacitor leakage
current causes the output voltage to decline by a
proportional amount to the current due to the voltage
drop on the internal 200K
resistor. Fig. 2 shows the
power on response.
Fig. 1
C
OUT
= 4.7
F
C
OUT
= 1
F
Region of Stable C
OUT
ESR vs. Load
Load Current (mA)
C
OUT
ESR
0 40 80 120
100
10
1
0.1
0.01
0.001
(
)
Unstable Region
Unstable Region
Stable Region
RT9177/A
Preliminary
www.richtek.com
DS9177/A-04 December 2002
8
Fig. 2
Fig.2
Load-Transient Considerations
The RT9177/A load-transient response graphs (see
Typical Operating Characteristics) 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 1mA to 100mA is
tens mV, depending on the ESR of the output
capacitor. Increasing the output capacitor's value and
decreasing the ESR attenuates the overshoot.
Shutdown Input Operation
The RT9177/A is shutdown by pulling the SHDN input
low, and turned on by driving the input high. If this
feature is not to be used, the SHDN input should be
tied to VIN to keep the regulator on at all times (the
SHDN input must not be left floating).
To ensure proper operation, the signal source used to
drive the SHDN input must be able to swing above and
below the specified turn-on/turn-off voltage thresholds
which guarantee an ON or OFF state (see Electrical
Characteristics). The ON/OFF signal may come from
either CMOS output, or an open-collector output with
pull-up resistor to the RT9177/A input voltage or
another logic supply. The high-level voltage may
exceed the RT9177/A input voltage, but must remain
within the absolute maximum ratings for the SHDN pin.
Internal P-Channel Pass Transistor
The RT9177/A features a typical 1.1
P-channel
MOSFET pass transistor. It provides several
advantages over similar designs using PNP pass
transistors, including longer battery life. The P-channel
MOSFET requires no base drive, which reduces
quiescent current considerably. PNP-based regulators
waste considerable current in dropout when the pass
transistor saturates. They also use high base-drive
currents under large loads. The RT9177/A does not
suffer from these problems and consume only 80A of
quiescent current whether in dropout, light-load, or
heavy-load applications.
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 RT9177/A uses a P-channel
MOSFET pass transistor, the dropout voltage is a
function of drain-to-source on-resistance [R
DS(ON)
]
multiplied by the load current.
Reverse Current Path
The power transistor used in the RT9177/A has an
inherent diode connected between the regulator input
and output (see Fig.3). 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
V
OUT
terminal to V
IN
. 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 should be used in
any applications where input/output voltage
conditions can cause the internal diode to be turned
on (see Fig.4). 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 and < 100 mA to
prevent mis-operation to damage the part.
T
T
T
1 >
2 >
C
B
= 470pF
10nF
2.2nF
V
IN
= 3.6V, C
IN
= 1
F, C
OUT
= 4.7
F
500
S/Div
CH1: 2V/div; CH2 = V
OUT
, 500mV/div
CH1
CH2
10nF
Preliminary
RT9177/A
DS9177/A-04 December 2002
www.richtek.com
9
Fig.3
Fig.4
Operating Region and Power Dissipation
The maximum power dissipation of RT9177/A depends
on the thermal resistance of the case and 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 = I
OUT
(V
IN
- V
OUT
).
The maximum power dissipation is:
P
MAX
= (T
J
- T
A
) /
JA
where T
J
- T
A
is the temperature difference between the
RT9177/A die junction and the surrounding environment,
JA
is the thermal resistance from the junction to the
surrounding environment. The GND pin of the
RT9177/A 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.
Current Limit and Thermal Protection
The RT9177/A is included a current limit circuit used to
monitor and control the pass transistor's gate voltage to
limit the output current to 300mA in typical and
thermal-overload protection circuit used to limit total
power dissipation. When the junction temperature
exceeds T
J
= 150C, the thermal sensor signals the
shutdown logic to turn off the pass transistor and allow
the IC to cool down. The thermal sensor will turn on the
pass transistor again after the IC's junction temperature
cool down to 120C. This will cause a pulsing output
during continuous thermal-overload conditions.
Thermal-overloaded protection is designed to protect
the RT9177/A in the event of fault conditions. Do not
exceed the absolute maximum junction-temperature
rating of T
J
= 125C 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.
V
IN
V
OUT
V
IN
V
OUT
RT9177/A
Preliminary
www.richtek.com
DS9177/A-04 December 2002
10
Package Information
Dimensions In Millimeters
Dimensions In Inches
Symbols
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
SOT- 25 Surface Mount Package
b
B
C
D
L
H
A1
e
A
Preliminary
RT9177/A
DS9177/A-04 December 2002
www.richtek.com
11
RT9177/A
Preliminary
www.richtek.com
DS9177/A-04 December 2002
12
RICHTEK TECHNOLOGY CORP.
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
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
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