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RT9179A
Adjustable, 500mA LDO Regulator with Enable
General Description
The RT9179A 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 500mA with two external resistors to set the output voltage ranges from 1.175V to 4.5V. The RT9179A has superior regulation over variations in line and load. Also it provides fast response 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 device is available in SOP-8 package.
Features
400mV Dropout @ 500mA 150A Low Quiescent Current Excellent Line and Load Regulation <1A Standby Current in Shutdown Mode Guaranteed 500mA Output Current Adjustable Output Voltage Ranges from 1.175V to 4.5V Over-Temperature/Over-Current Protection RoHS Compliant and 100% Lead (Pb)-Free
Applications
Battery-Powered Equipments Graphic Card Peripheral Cards PCMCIA Card
Ordering Information
RT9179A Package Type S : SOP-8 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard)
Pin Configurations
(TOP VIEW)
EN VIN VOUT ADJ 2 3 4 8 7 6 5 GND GND GND GND
Note : RichTek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100%matte tin (Sn) plating.
SOP-8
Typical Application Circuit
RT9179A VIN Chip Enable C3 0.1uF C1 1uF EN GND ADJ R2 VIN VOUT R1 C2 3.3uF VOUT
VOUT = 1.175 x ( 1+ Note: R2 around 200k is recommended. Refer to the "Application Information" for COUT selection.
R1 ) Volts R2
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RT9179A
Functional Pin Description
Pin No. 2 5, 6, 7, 8 1 4 3 Pin Name VIN GND EN ADJ VOUT Power Input Voltage Ground Chip Enable (Active High) Adjust Output Voltage. The output voltage is set by the external feedback resistors connecting to ADJ pin and is calculated as : Output Voltage VOUT = 1.175 x (1 +
R1 ) Volts R2
Pin Function
Function Block Diagram
Shutdown and Logic Control Current-Limit and Thermal Protection Thermal SHDN
1.175V VREF
EN
VIN
+ _
Error Amplifier
MOS Driver VOUT ADJ
GND
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Absolute Maximum Ratings
(Note 1) Supply Input Voltage ------------------------------------------------------------------------------------------------- 6V Power Dissipation, PD @ TA = 25C, TJ = 125C SOP-8 -------------------------------------------------------------------------------------------------------------------- 1.67W Package Thermal Resistance (Note 7) SOP-8, JA -------------------------------------------------------------------------------------------------------------- 60C/W Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------- 260C Junction Temperature ------------------------------------------------------------------------------------------------ 150C Storage Temperature Range ---------------------------------------------------------------------------------------- -65C to 150C ESD Susceptibility (Note 2) HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 3)
Supply Input Voltage ------------------------------------------------------------------------------------------------- 3V to 5.5V Enable Input Voltage ------------------------------------------------------------------------------------------------- 0V to 5.5V Junction Temperature Range --------------------------------------------------------------------------------------- -40C to 125C
Electrical Characteristics
(VIN = VOUT + 0.7V, IOUT = 10A, CIN = 1F, COUT = 3.3F (Ceramic), TA = 25C unless otherwise specified)
Parameter Reference Voltage Tolerance Adjust Pin Current Output Voltage Range Quiescent Current Standby Current Current Limit Dropout Voltage Line Regulation Thermal Shutdown Temperature Thermal Shutdown Hysteresis EN Threshold EN Current Logic-Low Voltage Logic-High Voltage (Note 4) (Note 5) (Note 6)
Symbol VREF IADJ VOUT IQ ISTBY ILIM VDROP VLINE TSD TSD VIL VIH IEN
Test Conditions
Min 1.163 -1.175
Typ 1.175 --150 --10 400 0.001 170 40 ----
Max 1.187 10 4.5 -1 ------0.4 -10
Units V nA V A A mA mV %/V C C V nA
Enabled, IOUT = 0mA VIN = 5.5V, Shutdown
--700
IOUT = 10mA IOUT = 500mA VOUT + 0.7V < VIN < 5.5V & 3.3V < VIN < 5.5V
------
VIN = 3.3V, Shutdown VIN = 3.3V, Enable VIN = VCE = 5.5V
-2.0 --
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RT9179A
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 VIN -VOUT, which is measured when VOUT is VOUT(NORMAL) - 100mV. 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. JA is measured in the natural convection at TA = 25C on the demo board, which has connected footprints as wide heat sink. Please see the thermal considerations on application information.
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Typical Operating Characteristics
Output Voltage vs. Temperature
3.29
ADJ Pin Voltage vs. Temperature
1.2
ADJ Pin Voltage (V)
3.28
VIN = 5V R1 = 360K R2 = 200K
VIN = 5V
1.19 1.18 1.17 1.16 1.15 1.14
Output Voltage (V)
3.27
3.26
3.25
3.24 -50 -25 0 25 50 75 100 125
-50
-25
0
25
50
75
100
125
Temperature (C)
Temperature (C)
Quiescent Current vs. Temperature
160
Quiescent Current vs. Input Voltage
150
VIN = 5V
150
Quiescent Current (uA)1
Quiescent Current (uA)
140
140
130
130
120 -50 -25 0 25 50 75 100 125
120 3 3.5 4 4.5 5 5.5
Temperature (C)
Input Voltage (V)
20
PSRR
VIN = 3.3V, VEN = 3.3V CIN = 1uF (X7R) COUT = 3.3uF (X7R)
600 500
Dropout Voltage vs. Io
VOUT = 3.3V, R1 = 360K, R2 = 200K CIN = 1uF (X7R) COUT = 3.3uF (X7R) TJ = 125C TJ = 25C
300 200 100 0
Dropout Voltage (mV)
0
PSRR(dB)
-20
No Load IL = 100mA
400
-40
IL = 10mA
-60
TJ = -40C
-80
10 0.01
100 0.1
1K 10K 100K 1 10 100 (Hz) Frequency (kHz)
1M 1000
0
100
200
300
400
500
Io (mA)
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Current Limit vs. Temperature
1
VIN = 5V
0.95
4 2
Output Short-Circuit Protection
Source Current (A)
Current Limit (A)
1 0.8 0.6 0.4 0.2 0 VIN = 5V R1 = 360k R2 = 200k CIN = 1uF COUT = 3.3uF
0.9 0.85 0.8 0.75 0.7 -50 -25 0 25 50 75 100 125
Temperature (C)
Time (1ms/Div)
Line Transient Response
5 4
Load Transient Response
Load Current(mA) Output Voltage Deviation(mV)
500 0
Input Voltage Deviation(V) Output Voltage Deviation(mV)
10 0 -10 VIN = 4V to 5V IO : 150mA R1 = 360K, R2 = 200K CIN = 1uF(X7R) COUT = 3.3uF(X7R)
50 0 -50 CIN = 1uF (X7R) COUT = 3.3uF (X7R) VIN = 3.3V, R1 = 56K R2 = 200K
Time (250us/Div)
Time (500us/Div)
Enable Threshold Voltage vs. Temperature
1
Enable Response
Enable Voltage(V)
6 4 2 0 VIN =5V R1 =360k R2 =200k CIN =1uF COUT =3.3uF
Enable Threshold Voltage (V)1
0.9
0.8
VOUT TURN ON
0.7
VOUT TURN OFF
Output Voltage Deviation(V)
3 2 1 0
0.6
IO : 150mA
0.5 -50 -25 0 25 50 75 100 125
Temperature (C)
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Time (100us/Div)
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Application Information
Like any low-dropout regulator, the RT9179A 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. Input Capacitor An input capacitance of 1F is required between the device input pin and ground directly (the amount of the capacitance may be increased without limit). 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 1F over the entire operating temperature range. Output Capacitor The RT9179A is designed specifically to work with very small ceramic output capacitors. The recommended minimum capacitance is 3.3F ceramic or tantalum capacitor between LDO output and GND for stability. But for output voltage lower than 1.35V, to use a minimum of 3.3F tantalum or electrolyte capacitor. 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. 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
10.000 10
Region of Stable COUT ESR vs. Load Current
Region of Stable COUT ESR ()
1 1.000
Region of Instable
0.100 0.1
Region of Stable
0.010
Region of Instable
0.001 0 100 200 300 400 500
Load Current (mA)
Input-Output (Dropout) Voltage 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) x IOUT Current Limit The RT9179A monitors and controls the PMOS' gate voltage, minimum limiting the output current to 700mA. 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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RT9179A
Capacitor Characteristics 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). 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 10F to 100F 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 10m). 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. 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 to 15% across the full temperature range of 125C to -40C. 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 25C down to -40C. 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.
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Thermal Considerations The RT9179A can deliver a current of up to 500mA 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 125C. 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. PD = (VIN - VOUT) IOUT + VIN IGND The final operating junction temperature for any set of conditions can be estimated by the following thermal equation : PD (MAX) = ( TJ (MAX) - TA ) / JA Where TJ (MAX) is the maximum junction temperature of the die (125C) and T A is the maximum ambient temperature. The junction to ambient thermal resistance (JA is layout dependent) for SOP-8 package is 60C/W at recommended minimum footprint. Visit our website in which "Recommended Footprints for Soldering Surface Mount Packages" for detail. More power can be dissipated if the maximum ambient temperature of the application is lower. Approaches for enhancing thermal performance is improving the power dissipation capability of the PCB design like cooper area increases. Thermal protection limits power dissipation in RT9179A. When the operation junction temperature exceeds 170C, starts the thermal shutdown function and turns the pass element off. The pass element turns on again after the junction temperature reduced about 40C. PCB 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. 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:
GND
+ EN ADJ
VIN + +
VOUT
GND
SOP-8 Board Layout
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RT9179A
The RT9179ACS regulator is packaged in SOP-8 package. This package is unable to efficiently dissipate the heat generated when the regulator is operating at high power levels. In order to control die-operating temperatures, the PCB layout should allow for maximum possible copper area at the GND pins of the RT9179ACS. The multiple GND pins on the SOP-8 package are internally connected, but lowest thermal resistance will result if these pins are tightly connected on the PCB. This will also aid heat dissipation at high power levels. If the large copper around the IC is unavailable, a buried layer may be used as a heat sink. Use vias to conduct the heat into the buried or backside of PCB layer.
Use vias to conduct the heat into the buried or backside of PCB layer.
RT9179ACS (SOP-8)
The PCB heat sink copper area should be solder-painted without masked. This approaches a "best case" pad heat sink.
To prevent this maximum junction temperature from being exceeded, the appropriate power plane heat sink MUST be used. Higher continuous currents or ambient temperature require additional heatsinking.
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RT9179A
Outline Dimension
A
H M
J
B
F
C I D
Dimensions In Millimeters Symbol Min A B C D F H I J M 4.801 3.810 1.346 0.330 1.194 0.170 0.050 5.791 0.400 Max 5.004 3.988 1.753 0.508 1.346 0.254 0.254 6.200 1.270
Dimensions In Inches Min 0.189 0.150 0.053 0.013 0.047 0.007 0.002 0.228 0.016 Max 0.197 0.157 0.069 0.020 0.053 0.010 0.010 0.244 0.050
8-Lead SOP Plastic Package
Richtek Technology Corporation
Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 8F, 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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