RT9178-32GB资料

RT9178

200mA, Ultra-Low Noise, Ultra-Fast CMOS LDO Regulator

General Description

The RT9178 is designed for portable RF and wirelessapplications with demanding performance and spacerequirements.

The RT9178’s performance is optimized for battery-powered systems to deliver ultra low noise and lowquiescent current. A noise bypass pin is also available forfurther reduction of output noise. Regulator ground currentincreases only slightly in dropout, further prolonging thebattery life. The RT9178 also works with low-ESR ceramiccapacitors, reducing the amount of board space necessaryfor power applications, critical in hand-held wirelessdevices.

The RT9178 consumes less than 0.01μA in shutdown modeand has fast turn-on time less than 100μs. The otherfeatures include ultra low dropout voltage, high outputaccuracy, current limiting protection, and high ripplerejection ratio. Available in the SOT-23-5 package.

Features

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Ultra-Low-Noise for RF Application

Ultra-Fast Response in Line/Load TransientQuick Start-Up (Typically 100μs)

< 0.01μA Quiescent Current When ShutdownLow Dropout : 200mV at 200mA

Wide Operating Voltage Ranges : 2.5V to 6.0VTTL-Logic-Controlled Shutdown InputLow Temperature CoefficientCurrent Limiting ProtectionThermal Shutdown Protection

Only 1μF Output Capacitor Required for StabilityHigh Power Supply Rejection RatioCustom Voltage Available

RoHS Compliant and 100% Lead (Pb)-Free

Applications

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Ordering Information

RT9178- Package TypeB : SOT-23-5 BR : SOT-23-5 (R-Type) Operating Temperature RangeP : Pb Free with Commercial StandardG : Green (Halogen Free with Commer- cial Standard)Output Voltage24 : 2.4V25 : 2.5V :

31 : 3.1V32 : 3.2V2H : 2.85V

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CDMA/GSM Cellular HandsetsBattery-Powered Equipment

Laptop, Palmtops, Notebook ComputersHand-Held InstrumentsPCMCIA Cards

Portable Information Appliances

Marking Information

For marking information, contact our sales representativedirectly or through a RichTek distributor located in yourarea, otherwise visit our website for detail.

Pin Configurations

(TOP VIEW)

Note :

RichTek Pb-free and Green products are :

`RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020.

`Suitable for use in SnPb or Pb-free soldering processes.`100% matte tin (Sn) plating.

VINGNDEN

1235VOUTVOUTGND

1235BP

4BPVIN4EN

SOT-23-5

R-Type

SOT-23-5

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RT9178

Typical Application Circuit

RT9178VIN

CIN1uFVINGNDENBPVOUTCOUT2.2uFVOUT

++Chip EnableCBP10nFFunctional Pin Description

Pin No. RT9178-󰂅󰂅CB RT9178-󰂅󰂅CBR Pin Name Pin Function 1 3 VIN Power Input Voltage 5 1 VOUT Output Voltage 2 2 GND Ground Enable Input Logic, Active Low. If the Shutdown Feature is 3 4 EN not Required, Connect EN to VIN. 4 5 BP Reference Noise Bypass

Function Block Diagram

EN

QuickStartBP

VREF+-ErrorAmplifierShutdownandLogic ControlVINMOS DriverVOUTCurrent-LimitandThermalProtectionGNDwww.richtek.com2

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RT9178

Absolute Maximum Ratings (Note 1)

Supply Input Voltage-------------------------------------------------------------------------------------------------7V󰁺 Enable Input Voltage-------------------------------------------------------------------------------------------------7V󰁺 Power Dissipation, PD @ TA = 25°C

SOT-23-5--------------------------------------------------------------------------------------------------------------- 0.4W󰁺 Package Thermal Resistance (Note 8)

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 2)

HBM (Human Body Mode)-----------------------------------------------------------------------------------------2kV MM (Machine Mode)-------------------------------------------------------------------------------------------------200V

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Recommended Operating Conditions (Note 3)

Supply Input Voltage-------------------------------------------------------------------------------------------------2.5V to 6V󰁺 Enable Input Voltage-------------------------------------------------------------------------------------------------0V to 6V󰁺 Junction Temperature Range---------------------------------------------------------------------------------------−40°C to 125°C

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Electrical Characteristics

(VIN = VOUT + 1V, CIN =COUT = 1μF, CBP = 1nF, TA = 25°C unless otherwise specified)Parameter Symbol Test Conditions Min Typ Max Units Output Voltage Accuracy Current Limit Quiescent Current (Note 6) Dropout Voltage (Note 4) Line Regulation Load Regulation (Note 5) Standby Current (Note 7) EN Input Bias Current EN Threshold ΔVOUT IOUT = 1mA ILIM IQ VDROP ΔVLINE RLOAD = 1Ω VEN > 1.0V, IOUT = 0mA IOUT = 200mA VIN = (VOUT + 0.3V) to 6.0V, IOUT = 1mA −2 -- +2 % -- 400 -- mA -- 90 150 μA -- -- -- -- -- -- 1.0 200 300 mV -- 6 mV/V 7 0.01 0 -- -- 20 mV 1 100 0.4 -- μA nA V < IOUT < 200mA ΔVLOAD 1mA ISTBY IIBSD VEN = GND, Shutdown VEN = GND or VIN VIN = 3V to 5.5V, Shutdown VIN = 3V to 5.5V, Start-Up 10Hz to 100kHz, IOUT = 200mA COUT = 10μF Logic-Low Voltage VIL Logic-High Voltage VIH eNO f = 100Hz f = 10kHz Output Noise Voltage Power Supply Rejection Rate -- 50 -- μVRMS -- -- −70 -- dB PSRR COUT = 10μF, IOUT = 200mA TSD −40 -- Thermal Shutdown Temperature -- 150 -- °C DS9178-15 March 2007

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RT9178

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 theoperational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extendedperiods 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. Regulation is measured at constant junction temperature by using a 20ms current pulse. Devices are tested for load

regulation in the load range from 1mA to 200mA.

Note 6. 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 groundpin current.

Note 7. Standby current is the input current drawn by a regulator when the output voltage is disabled by a shutdown signal

(VEN = GND). It is measured with VIN = 6V.

Note 8. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of

JEDEC 51-3 thermal measurement standard.

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Typical Operating Characteristics

Output Voltage vs. Temperature

3.5

10095

Quiescent Current vs. Temperature

Quiescent Current (uA)Output Voltage (V)3.3

9085807570

3.1

2.9

2.7

VIN = 4VCBP = 10nFCIN = 1uFCOUT = 1uF-35

-15

5

25

45

65

85

105

125

2.5

VIN = 4VCBP = 10nFCIN = 1uFCOUT = 1uF-35

-15

5

25

45

65

85

105

125

Temperature(°C)Temperature(°C)

PSRR

0-10-20

0-10-20

PSRR

PSRR(dB)PSRR (dB)-30-40-50-60-70-80-900.01

0.1

1

100mA-30-40-50-60-70-80-900.01

0.1

1

10

100mA1mA1mAVIN = 4VCBP = 10nFCIN = 1uFCOUT = 1uFTA = 25°C10

100

1000

VIN = 4VCBP = 10nFCIN = 1uFCOUT = 1uFTA = -35°C100

1000

Frequency (kHz)Frequency (kHz)

Dropout Voltage vs. Load Current

0.30.25

Line Transient Response

Input VoltageDeviation(V)VIN = 3.2 to 3.8VCBP = 10nF3.83.2

CIN = 1uFCOUT = 10uF

TJ = 125°CDropout Voltage (V)0.2

TJ = 25°C0.15

Output VoltageDeviation(mV)0.10.0500

25

50

75

100

125

TJ = -35°CVIN = 4VCBP = 10nFCIN = 1uFCOUT = 1uF150

175

200

200-20

Time (500us/Div)

Load Current (mA)

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RT9178

Load Transient Response

LoadCurrent (mA)LoadCurrent (mA)VIN = 4VCBP = 10nF

IOUT = 1 to 100mA1000

CIN = 1uF, CeramicCOUT = 1uF, Ceramic

Load Transient Response

VIN = 4VCBP = 10nF

IOUT = 100 to 200mA200100

CIN = 1uF, CeramicCOUT = 1uF, Ceramic

Output VoltageDeviation (mV)Output VoltageDeviation (mV)200-20

200-20

Time (1ms/Div)Time (1ms/Div)

OutputEN PinVoltage(V) Input Voltage (V)4203210

VIN = 4VCBP = 10nF

CIN = 1uF, CeramicCOUT = 1uF, Ceramic

EN Pin Input Voltage (V)6

Start Up

203

Start Up

OutputVoltage(V)210

VIN = 4VCBP = 10nF

CIN = 1uF, CeramicCOUT = 10uF, Ceramic

Time (5us/Div)Time (10us/Div)

6

Start Up

VIN = 4VCBP = 10nF150

Noise

CIN = 1uF, Ceramic

COUT = 1uF, Ceramic

OutputEN PinVoltage(V) Input Voltage (V)4

03210

VIN = 4VCBP = 100nF

CIN = 1uF, CeramicCOUT = 1uF, Ceramic

Noise (uV)2100500-50

-100

f = 10Hz to 100kHz

Time (25us/Div)Time (10ms/Div)

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RT9178

Application Information

The RT9178 is ideal for mobile phone and similar battery-powered wireless applications. It provides up to 200mA,from a 2.5V to 6V input. Like any low-dropout regulator,the device requires input and output decoupling capacitors.These capacitors must be correctly selected for goodperformance (see Capacitor Characteristics Section).Please note that linear regulators with a low dropoutvoltage have high internal loop gains which require care inguarding against oscillation caused by insufficientdecoupling capacitance.Input Capacitor

An input capacitance of ≅1μF is required between thedevice input pin and ground directly (the amount of thecapacitance may be increased without limit). The inputcapacitor MUST be located less than 1 cm from the deviceto assure input stability (see PCB Layout Section). A lowerESR capacitor allows the use of less capacitance, whilehigher ESR type (like aluminum electrolytic) require morecapacitance.

Capacitor types (aluminum, ceramic and tantalum) canbe mixed in parallel, but the total equivalent inputcapacitance/ESR must be defined as above to stableoperation.

There are no requirements for the ESR on the inputcapacitor, but tolerance and temperature coefficient mustbe considered when selecting the capacitor to ensure thecapacitance will be ≅1μF over the entire operatingtemperature range.Output Capacitor

The RT9178 is designed specifically to work with verysmall ceramic output capacitors. The recommendedminimum capacitance (temperature characteristicsX7R, X5R, Z5U or Y5V) is 1μF to 10μF range with 5mΩ to50mΩ range ceramic capacitor between LDO output andGND for transient stability, but it may be increased withoutlimit. Higher capacitance values help to improve transient.The output capacitor's ESR is critical because it forms azero to provide phase lead which is required for loopstability.

Region of Stable COUT ESR vs. Load Current

100.00100

Unstable1010.00

COUT ESR (Ω)1.00

Stable0.10

0.01

Unstable0.00

0

40

80

120

160

200

Load Current (mA)

Reference Bypass Capacitor (BP)

Connecting a 10nF between the BP (reference bypass)pin and GND significantly reduces noise on the regulatoroutput. It should be noted that the capacitor is connecteddirectly to a high impedance circuit in the band gapreference. Because this circuit has only a few micro-amperes flowing into it, any significantly loading on thisnode will cause a change on the regulated output voltage.For this reason, DC leakage current through the noisebypass capacitor must never exceed 100nA, and shouldbe kept as low as possible for best output voltageaccuracy. The type of capacitors best suited for the noisebypass capacitor with either NP0 or C0G dielectrictypically have very low leakage. 10nF polypropylene andpolycarbonate film capacitors are available in smallsurface mount packages and typically have extremely lowleakage current.No Load Stability

The device will remain stable and in regulation with noexternal load. This is specially important in CMOS RAMkeep-alive applicationsShutdown Input Operation

The RT9178 is shutdown by pulling the EN pin low, andturned on by driving the input high. If the shutdown featureis not required, the EN pin should be tied to VIN to keepthe regulator on at all times (the EN pin MUST NOT beleft floating).

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RT9178

To assure proper operation, the signal source used todrive the EN pin must be able to swing above and belowthe specified turn-on/off voltage thresholds listed in the“Electrical Characteristics” under VIH and VIL.The ON/OFF signal may comes from either CMOS output, or anopen-collector output with pull-up resistor to the deviceinput voltage or another logic supply. The high-level voltagemay exceed the device input voltage, but must remainwithin the absolute maximum ratings for the EN pin.Quick Start-Up Time

The start-up time is determined by the time constant ofthe bypass capacitor. The smaller the capacitor value, theshorter the power up time, but less noise gets reduced.As a result, start-up time and noise reduction need to betaken into design consideration when choosing the valueof the bypass capacitor.

Input-Output (Dropout) Voltage

A regulator's minimum input-to-output voltage differential(dropout voltage) determines the lowest usable supplyvoltage. In battery-powered systems, this determines theuseful end-of-life battery voltage. Because the device usesa PMOS, its dropout voltage is a function of drain-to-source on-resistance, RDS(ON), multiplied by the loadcurrent:

VDROPOUT = VIN - VOUT = RDS(ON) × IOUT

Current Limit

The RT9178 monitors and controls the PMOS’gatevoltage, limiting the output current to 400mA (typ). Theoutput can be shorted to ground for an indefinite period oftime without damaging the part.Short-Circuit Protection

The device is short circuit protected and in the event of apeak over-current condition, the short-circuit control loopwill rapidly drive the output PMOS pass element off. Oncethe power pass element shuts down, the control loop willrapidly cycle the output on and off until the average powerdissipation causes the thermal shutdown circuit torespond to servo the on/off cycling to a lower frequency.Please refer to the section on thermal information for powerdissipation calculations.

Capacitor Characteristics

It is important to note that capacitance tolerance andvariation with temperature must be taken intoconsideration when selecting a capacitor so that theminimum required amount of capacitance is provided overthe full operating temperature range. In general, a goodtantalum capacitor will show very little capacitancevariation with temperature, but a ceramic may not be asgood (depending on dielectric type).

Aluminum electrolytics also typically have large temperaturevariation of capacitance value.

Equally important to consider is a capacitor's ESR changewith temperature: this is not an issue with ceramics, astheir ESR is extremely low. However, it is very importantin Tantalum and aluminum electrolytic capacitors. Bothshow increasing ESR at colder temperatures, but theincrease in aluminum electrolytic capacitors is so severethey 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 tantalumsbut give superior AC performance for by-passing highfrequency noise because of very low ESR (typicallyless than 10mΩ). However, some dielectric types do nothave good capacitance characteristics as a function ofvoltage and temperature.

Z5U and Y5V dielectric ceramics have capacitance thatdrops severely with applied voltage. A typical Z5U or Y5Vcapacitor can lose 60% of its rated capacitance withhalf of the rated voltage applied to it. The Z5U and Y5Valso exhibit a severe temperature effect, losing more than50% of nominal capacitance at high and low limits of thetemperature range.

X7R and X5R dielectric ceramic capacitors are stronglyrecommended if ceramics are used, as they typicallymaintain a capacitance range within ±20% of nominalover full operating ratings of temperature and voltage. Ofcourse, they are typically larger and more costly than Z5U/Y5U types for a given voltage and capacitance.

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RT9178

Tantalum:

Solid tantalum capacitors are recommended for use onthe output because their typical ESR is very close to theideal value required for loop compensation. They also workwell as input capacitors if selected to meet the ESRrequirements previously listed.

Tantalums also have good temperature stability: a goodquality tantalum will typically show a capacitance valuethat varies less than 10 to 15% across the full temperaturerange of 125°C to −40°C. ESR will vary only about 2Xgoing from the high to low temperature limits.

The increasing ESR at lower temperatures can causeoscillations when marginal quality capacitors are used (ifthe ESR of the capacitor is near the upper limit of thestability range at room temperature).Aluminum:

This capacitor type offers the most capacitance for themoney. The disadvantages are that they are larger inphysical size, not widely available in surface mount, andhave poor AC performance (especially at higher frequencies)due to higher ESR and ESL.

Compared by size, the ESR of an aluminum electrolyticis higher than either Tantalum or ceramic, and it also variesgreatly with temperature. A typical aluminum electrolyticcan exhibit an ESR increase of as much as 50X whengoing from 25°C down to −40°C.

It should also be noted that many aluminum electrolyticsonly specify impedance at a frequency of 120Hz, whichindicates they have poor high frequency performance.Only aluminum electrolytics that have an impedancespecified at a higher frequency (between 20kHz and100kHz) should be used for the device. Derating must beapplied to the manufacturer's ESR specification, since itis typically only valid at room temperature.

Any applications using aluminum electrolytics should bethoroughly tested at the lowest ambient operatingtemperature where ESR is maximum.

Thermal Considerations

The RT9178 series can deliver a current of up to 200mAover the full operating junction temperature range. However,the maximum output current must be derated at higherambient temperature to ensure the junction temperaturedoes not exceed 125°C.

With all possible conditions, the junction temperature mustbe within the range specified under operating conditions.Power dissipation can be calculated based on the outputcurrent and the voltage drop across regulator.

PD = (VIN − VOUT) IOUT + VIN IGND

The final operating junction temperature for any set ofconditions can be estimated by the following thermalequation:

PD (MAX) = ( TJ (MAX) − TA ) / θJA

Where TJ (MAX) is the maximum junction temperature ofthe die (125°C) and TA is the maximum ambienttemperature. The junction to ambient thermal resistance(θJA) for SOT-23-5 package at recommended minimumfootprint is 250°C/W (θJA is layout dependent). Visit ourwebsite in which “Recommended Footprints for SolderingSurface Mount Packages” for detail.PCB Layout

Good board layout practices must be used or instabilitycan be induced because of ground loops and voltage drops.The input and output capacitors MUST be directlyconnected to the input, output, and ground pins of thedevice using traces which have no other currents flowingthrough them.

The best way to do this is to layout CIN and COUT near thedevice with short traces to the VIN, VOUT, and ground pins.The regulator ground pin should be connected to theexternal circuit ground so that the regulator and itscapacitors have a “single point ground”.

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RT9178

It should be noted that stability problems have been seenin applications where “vias” to an internal ground planewere used at the ground points of the device and the inputand output capacitors. This was caused by varying groundpotentials at these nodes resulting from current flowingthrough the ground plane. Using a single point groundtechnique for the regulator and it’s capacitors fixed theproblem. Since high current flows through the traces goinginto VIN and coming from VOUT, Kelvin connect the capacitorleads to these pins so there is no voltage drop in serieswith the input and output capacitors.

Optimum performance can only be achieved when thedevice is mounted on a PC board according to the diagrambelow:

BP

VOUT

VIN

GNDEN

SOT-23-5 Board Layout

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RT9178

Outline Dimension

H

DL

CBbAA1

eSymbol A A1 B b C D e Dimensions In Millimeters Dimensions In Inches Min Max Min Max 0.8 0.000 1.397 0.356 2.591 2.692 0.838 1.295 0.152 1.803 0.559 2.997 3.099 1.041 0.035 0.000 0.055 0.014 0.102 0.106 0.033 0.051 0.006 0.071 0.022 0.118 0.122 0.041 H 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024

SOT-23-5 Surface Mount Package

Richtek Technology Corporation

Headquarter

5F, No. 20, Taiyuen Street, Chupei CityHsinchu, Taiwan, R.O.C.

Tel: (8863)55267 Fax: (8863)5526611

Richtek Technology Corporation

Taipei Office (Marketing)

8F, No. 137, Lane 235, Paochiao Road, Hsintien CityTaipei County, Taiwan, R.O.C.

Tel: (8862)191466 Fax: (8862)191465Email: marketing@richtek.com

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