RT9179 - Farnell

RT9179
Adjustable, 300mA LDO Regulator with Enable
General Description
Features
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.
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300mV Dropout @ 300mA
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150uA Low Ground Pin Current
Excellent Line and Load Regulation
<1uA Standby Current in Shutdown Mode
Guaranteed 300mA Output Current
Stable with 1uF Input and Output Ceramic Capacitor
Adjustable Output Voltage Ranges from 1.175V to
4.5V
Over-Temperature/Over-Current Protection
RoHS Compliant and 100% Lead (Pb)-Free
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 overtemperature protection. The device has enable pin to reduce
power consumption in shutdown mode.
The devices is available in the popular SOT-23-5 package.
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Applications
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Ordering Information
RT9179
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Package Type
B : SOT-23-5
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
Battery-Powered Equipment
Graphic Card
Peripheral Cards
PCMCIA Card
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Richtek products are :
`
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
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Suitable for use in SnPb or Pb-free soldering processes.
Pin Configurations
(TOP VIEW)
VOUT
ADJ
5
4
2
3
VIN GND EN
SOT-23-5
DS9179-11 April 2011
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RT9179
Typical Application Circuit
RT9179
VIN
VOUT
VOUT
VIN
Chip Enable
R1
EN
C1
1uF
C3
0.1uF
GND
ADJ
R2
VOUT = 1.175 x ( 1 +
C2
1uF
R1
) Volts
R2
Adjustable Operation
Note: The external feedback resistors are in hundreds of OHM to hundreds of kOHM ranges.
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
5
ADJ
this pin grounded. If external feedback resistors are applied, the output voltage will be:
VOUT
Output Voltage
VOUT = 1.175 × (1 +
R1
) Volts
R2
Function Block Diagram
EN
Shutdown
and
Logic Control
1.175V
VREF
Current-Limit
and
Thermal Protection
VIN
Thermal
SHDN
+_
Error
Amplifier
MOS
Driver
VOUT
ADJ
GND
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DS9179-11 April 2011
RT9179
Absolute Maximum Ratings
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(Note 1)
Supply Input Voltage ------------------------------------------------------------------------------------------------ 6V
Power Dissipation, PD @ TA = 25°C
SOT-23-5 --------------------------------------------------------------------------------------------------------------- 0.4W
Package Thermal Resistance (Note 2)
SOT-23-5, θJA --------------------------------------------------------------------------------------------------------- 250°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
Junction Temperature ----------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range --------------------------------------------------------------------------------------- −65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ----------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions
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(Note 4)
Supply Input Voltage ------------------------------------------------------------------------------------------------ 3V to 5.5V
Enable Input Voltage ------------------------------------------------------------------------------------------------ 0V to 5.5V
Junction Temperature Range -------------------------------------------------------------------------------------- −40°Cto 125°C
Electrical Characteristics
(VIN = VOUT + 0.7V, IOUT = 10uA, CIN = COUT = 1uF (Ceramic), TA = 25° C unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Reference Voltage Tolerance
VREF
1.163
1.175
1.187
V
Adjust Pin Current
IADJ
--
--
10
nA
Output Voltage Range
VOUT
1.175
--
4.5
V
Quiescent Current
IQ
Enabled, IOUT = 0mA
--
150
--
μA
ISTBY
V IN = 5.5V, Shutdown
--
--
1
μA
0.5
--
--
A
IOUT = 10mA
--
10
--
IOUT = 300mA
--
300
-
V OUT + 0.7V < VIN < 5.5V
--
0.001
--
%/V
Standby Current
(Note 5)
(Note 6)
Current Limit
Dropout Voltage
ILIM
(Note 7)
VDROP
mV
Line Regulation
ΔVLINE
Thermal Shutdown Temperature
TSD
--
170
--
°C
Thermal Shutdown Hysteresis
ΔTSD
--
40
--
°C
--
--
0.4
EN Threshold
Logic-Low Voltage
VIL
V IN = 3.3V, Shutdown
Logic-High Voltage
VIH
V IN = 3.3V, Enable
2.0
--
--
IEN
V IN = 5.5V, Enable
--
--
10
EN Current
DS9179-11 April 2011
V
nA
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RT9179
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. θJA is measured in the natural convection at T A = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Quiescent, or ground current, is the difference between input and output currents. It is defined by IQ = IIN - IOUT under
no load condition (IOUT = 0mA). The total current drawn from the supply is the sum of the load current plus the ground
pin current.
Note 6. Standby current is the input current drawn by a regulator when the output voltage is disabled by a shutdown signal
(VEN ≤ 0.4V). It is measured with VIN = 5.5V.
Note 7. The dropout voltage is defined as VIN -VOUT, which is measured when VOUT is VOUT(NORMAL) − 100mV.
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DS9179-11 April 2011
RT9179
Typical Operating Characteristics
ADJ Pin Voltage vs. Temperature
Output Voltage vs. Temperature
3.29
VIN = 5V
R1 = 1.8KΩ
R2 = 1kΩ
VIN = 5V
1.19
ADJ Pin Voltage (V)
3.28
Output Voltage (V)
1.2
3.27
3.26
3.25
1.18
1.17
1.16
1.15
1.14
3.24
-50
-25
0
25
50
75
100
125
-50
-25
0
Temperature (° C)
25
50
75
100
125
Temperature (° C)
Quiescent Current vs. Input Voltage
Quiescent Current vs. Temperature
150
160
Quiescent Current (uA)1
Quiescent Current (uA)
VIN = 5V
150
140
130
140
130
120
120
-50
-25
0
25
50
75
100
3
125
3.5
4
Temperature (° C)
-40
300
Dropout Voltage (mV)
PSRR (dB)
350
-50
-60
-70
VIN = 4V
IL = 10mA
-90
5.5
400
-30
-80
5
Dropout Voltage vs. Io
PSRR
-20
4.5
Input Voltage (V)
COUT = 1uF (X7R)
-100
VOUT = 3.3V
TJ = 125°C
TJ = 25°C
250
200
TJ = -40°C
150
100
50
0
10
100
1K
1000
10K
10000
Frequency (Hz)
DS9179-11 April 2011
100K
100000
0
50
100
150
200
250
300
Io (mA)
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RT9179
Current Limit vs. Temperature
1
4
VIN = 5V
2
Source Current (A)
0.95
Current Limit (A)
Output Short-Circuit Protection
0.9
0.85
0.8
0.75
1
0.8
0.6
0.4
VIN = 5V
R1 = 1.8kΩ
R2 = 1kΩ
CIN = 1uF
CO = 1uF
0.2
0
0.7
-50
-25
0
25
50
75
100
125
Time (1ms/Div)
Temperature (° C)
Load Transient Regulation
6
60
R1=1.8KΩ, R2=1KΩ
CIN=1uF(Electrolytic)
CO=1uF(Electrolytic)
VIN = 4V to 5V
ILOAD : 150mA
Output Voltage
Deviation(mV)
Input Voltage
Deviation(V)
Line Transient Regulation
7
5
4
Load Current(A)
Output Voltage
Deviation(mV)
20
10
0
-10
- 20
40
0
-20
0.2
0.1
0
-0.1
Enable Threshold Voltage
vs. Temperature
Enable
Voltage(V)
0.9
6
4
2
0
VOUT TURN ON
Output Voltage
Deviation(V)
Enable Threshold Voltage (V)1
Time (100us/Div)
Enable Response
1
0.7
CIN = 1uF(Ceramic)
CO = 2.2uF(Ceramic)
20
Time (100us/Div)
0.8
VIN = 5V, R1 = 1.8KΩ
R2 = 1KΩ
VOUT TURN OFF
0.6
VIN =5V
R1 =1.8kΩ
R2 =1kΩ
CIN =1uF
CO =1uF
3
2
1
0
ILOAD : 150mA
0.5
-50
-25
0
25
50
75
Temperature (° C)
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100
125
Time (100us/Div)
DS9179-11 April 2011
RT9179
Application Information
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 Capacitor
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.)
DS9179-11 April 2011
Region of Stable COUT ESR vs. Load Current
Region of Stable CC OUT
OUT ESR (Ω)
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.
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Region of Instable
1
Region of Stable
0.1
0.01
Region of Instable
0.001
0
50
100
150
200
250
300
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) Volatge
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, RDS(ON), multiplied by the load current :
VDROPOUT = VIN - VOUT = RDS(ON) × IOUT
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.
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RT9179
Capacitor Characteristics
Tantalum :
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).
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.
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.
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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.
DS9179-11 April 2011
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.
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
VOUT, Kelvin connect the capacitor 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 diagram
below:
ADJ
PD = (VIN - VOUT) IOUT + VIN IGND
GND
EN
+
PCB Layout
+
PD (MAX) = ( TJ (MAX) - TA ) / θJA
Where TJ (MAX) is the maximum junction temperature of
the die (125° C) and T A 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 (θJA is layout dependent). Visit our
website in which “Recommended Footprints for Soldering
Surface Mount Packages” for detail.
GND
VOUT
VIN
+
The final operating junction temperature for any set of
conditions can be estimated by the following thermal
equation :
GND
SOT-23-5 Board 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 COUT near the
device with short traces to the VIN, VOUT, and ground pins.
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.
DS9179-11 April 2011
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RT9179
Outline Dimension
H
D
L
B
C
b
A
A1
e
Symbol
Dimensions In Millimeters
Dimensions In Inches
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-23-5 Surface Mount Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design,
specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed
by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
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DS9179-11 April 2011