RT9178 200mA, Ultra-Low Noise, Ultra-Fast CMOS LDO Regulator General Description The RT9178 is designed for portable RF and wireless applications with demanding performance and space requirements. The RT9178’ s performance is optimized for batterypowered systems to deliver ultra low noise and low quiescent current. A noise bypass pin is also available for further reduction of output noise. Regulator ground current increases only slightly in dropout, further prolonging the battery life. The RT9178 also works with low-ESR ceramic capacitors, reducing the amount of board space necessary for power applications, critical in hand-held wireless devices. The RT9178 consumes less than 0.01μA in shutdown mode and has fast turn-on time less than 100μs. The other features include ultra low dropout voltage, high output accuracy, current limiting protection, and high ripple rejection ratio. Available in the SOT-23-5 package. Ordering Information RT9178Package Type B : SOT-23-5 BR : SOT-23-5 (R-Type) Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) Output Voltage 24 : 2.4V 25 : 2.5V : 31 : 3.1V 32 : 3.2V 2H : 2.85V Note : RichTek Pb-free and Green products are : Features Ultra-Low-Noise for RF Application Ultra-Fast Response in Line/Load Transient Quick Start-Up (Typically 100μ μs) < 0.01μ μA Quiescent Current When Shutdown Low Dropout : 200mV at 200mA Wide Operating Voltage Ranges : 2.5V to 6.0V TTL-Logic-Controlled Shutdown Input Low Temperature Coefficient Current Limiting Protection Thermal Shutdown Protection Only 1μ μF Output Capacitor Required for Stability High Power Supply Rejection Ratio Custom Voltage Available RoHS Compliant and 100% Lead (Pb)-Free Applications CDMA/GSM Cellular Handsets Battery-Powered Equipment Laptop, Palmtops, Notebook Computers Hand-Held Instruments PCMCIA Cards Portable Information Appliances 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 Configurations (TOP VIEW) VIN 1 GND 2 EN 3 5 VOUT VOUT 1 GND 2 VIN 3 5 BP 4 EN `RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. 4 `Suitable for use in SnPb or Pb-free soldering processes. `100% matte tin (Sn) plating. DS9178-15 March 2007 SOT-23-5 BP R-Type SOT-23-5 www.richtek.com 1 RT9178 Typical Application Circuit RT9178 Chip Enable VIN VOUT GND EN BP + CIN 1uF + VIN COUT 2.2uF VOUT CBP 10nF Functional Pin Description Pin No. RT9178- Pin Name CB RT9178- Pin Function CBR 1 3 VIN Power Input Voltage 5 1 VOUT Output Voltage 2 2 GND Ground 3 4 EN 4 5 BP Enable Input Logic, Active Low. If the Shutdown Feature is not Required, Connect EN to VIN. Reference Noise Bypass Function Block Diagram EN Shutdown and Logic Control Quick Start BP VIN VREF + - Error Amplifier MOS Driver VOUT Current-Limit and Thermal Protection GND www.richtek.com 2 DS9178-15 March 2007 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 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 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 ΔVOUT IOUT = 1mA −2 -- +2 % Current Limit ILIM RLOAD = 1Ω -- 400 -- mA IQ VEN > 1.0V, IOUT = 0mA -- 90 150 μA VDROP IOUT = 200mA -- 200 300 mV -- -- 6 mV/V Quiescent Current Dropout Voltage (Note 6) (Note 4) ΔVLINE Line Regulation VIN = (VOUT + 0.3V) to 6.0V, IOUT = 1mA Load Regulation (Note 5) ΔVLOAD 1mA < IOUT < 200mA -- 7 20 mV Standby Current (Note 7) ISTBY VEN = GND, Shutdown -- 0.01 1 μA IIBSD VEN = GND or VIN -- 0 100 nA VIL VIN = 3V to 5.5V, Shutdown -- -- 0.4 1.0 -- -- -- 50 -- -- −70 -- -- −40 -- -- 150 -- EN Input Bias Current EN Threshold Logic-Low Voltage Logic-High Voltage VIH Output Noise Voltage Power Supply Rejection Rate eNO f = 100Hz f = 10kHz Thermal Shutdown Temperature DS9178-15 March 2007 PSRR TSD VIN = 3V to 5.5V, Start-Up 10Hz to 100kHz, IOUT = 200mA COUT = 10μF COUT = 10μF, IOUT = 200mA V μVRMS dB °C www.richtek.com 3 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 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. 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 ground pin 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 T A = 25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. www.richtek.com 4 DS9178-15 March 2007 RT9178 Typical Operating Characteristics Output Voltage vs. Temperature Quiescent Current vs. Temperature 100 95 3.3 3.1 2.9 VIN = 4V CBP = 10nF CIN = 1uF COUT = 1uF 2.7 Quiescent Current (uA) Output Voltage (V) 3.5 90 85 80 VIN = 4V CBP = 10nF CIN = 1uF COUT = 1uF 75 70 2.5 -35 -15 5 25 45 65 85 105 -35 125 -15 5 25 PSRR -10 -10 -20 -20 -30 100mA -40 -50 1mA -60 VIN = 4V CBP = 10nF CIN = 1uF COUT = 1uF TA = 25°C -70 -80 -90 0.01 0.1 1 10 105 125 100 -50 VIN = 4V CBP = 10nF CIN = 1uF COUT = 1uF TA = -35°C -60 -70 -80 -90 0.01 1000 1mA 100mA -40 0.1 1 10 100 1000 Frequency (kHz) Dropout Voltage vs. Load Current Line Transient Response Input Voltage Deviation(V) 0.3 TJ = 125°C 0.2 TJ = 25°C VIN = 3.2 to 3.8V CBP = 10nF CIN = 1uF COUT = 10uF 3.8 3.2 0.15 0.1 TJ = -35°C 0.05 VIN = 4V CBP = 10nF CIN = 1uF COUT = 1uF 0 0 25 50 75 100 125 150 175 200 Output Voltage Deviation(mV) Dropout Voltage (V) 85 -30 Frequency (kHz) 0.25 65 PSRR 0 PSRR (dB) PSRR(dB) 0 45 Temperature (° C) Temperature (° C) 20 0 -20 Time (500us/Div) Load Current (mA) DS9178-15 March 2007 www.richtek.com 5 RT9178 CIN = 1uF, Ceramic COUT = 1uF, Ceramic 100 VIN = 4V CBP = 10nF IOUT = 100 to 200mA 20 0 -20 100 20 0 -20 Time (1ms/Div) Time (1ms/Div) EN Pin Input Voltage (V) Start Up 4 2 0 3 2 VIN = 4V CBP = 10nF CIN = 1uF, Ceramic COUT = 1uF, Ceramic 1 0 4 2 0 2 Time (5us/Div) Time (10us/Div) Start Up Noise VIN = 4V 150 CBP = 10nF 2 100 0 3 VIN = 4V CBP = 100nF CIN = 1uF, Ceramic COUT = 1uF, Ceramic Time (25us/Div) www.richtek.com 6 CIN = 1uF, Ceramic COUT = 1uF, Ceramic 50 0 -50 2 0 VIN = 4V CBP = 10nF CIN = 1uF, Ceramic COUT = 10uF, Ceramic 1 4 1 Start Up 0 Noise (uV) Output Voltage(V) EN Pin Input Voltage (V) 6 6 3 Output Voltage(V) Output Voltage(V) EN Pin Input Voltage (V) 6 CIN = 1uF, Ceramic COUT = 1uF, Ceramic 200 Output Voltage Deviation (mV) 0 Load Transient Response Load Current (mA) VIN = 4V CBP = 10nF IOUT = 1 to 100mA Output Voltage Deviation (mV) Load Current (mA) Load Transient Response -100 f = 10Hz to 100kHz Time (10ms/Div) DS9178-15 March 2007 RT9178 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 RT9178 is designed specifically to work with very small ceramic output capacitors. The recommended minimum capacitance (temperature characteristics X7R, X5R, Z5U or Y5V) is 1μF to 10μF range with 5mΩ 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. DS9178-15 March 2007 Region of Stable COUT ESR vs. Load Current 100.00 100 Unstable 10 10.00 COUT ESR (Ω) The RT9178 is ideal for mobile phone and similar batterypowered 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 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. 1.00 Stable 0.10 0.01 Unstable 0.00 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 regulator output. It should be noted that the capacitor is connected directly to a high impedance circuit in the band gap reference. Because this circuit has only a few microamperes flowing into it, any significantly loading on this node will cause a change on the regulated output voltage. For this reason, DC leakage current through the noise bypass capacitor must never exceed 100nA, and should be kept as low as possible for best output voltage accuracy. The type of capacitors best suited for the noise bypass capacitor with either NP0 or C0G dielectric typically have very low leakage. 10nF polypropylene and polycarbonate film capacitors are available in small surface mount packages and typically have extremely low leakage current. 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 Shutdown Input Operation The RT9178 is shutdown by pulling the EN pin low, and turned on by driving the input high. If the shutdown feature is not required, the EN pin should be tied to VIN to keep the regulator on at all times (the EN pin MUST NOT be left floating). www.richtek.com 7 RT9178 To assure proper operation, the signal source used to drive the EN pin must be able to swing above and below the 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 an open-collector output with pull-up resistor to the device input voltage or another logic supply. The high-level voltage may exceed the device input voltage, but must remain within the absolute maximum ratings for the EN pin. Quick Start-Up Time The start-up time is determined by the time constant of the bypass capacitor. The smaller the capacitor value, the shorter the power up time, but less noise gets reduced. As a result, start-up time and noise reduction need to be taken into design consideration when choosing the value of the bypass capacitor. 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-tosource on-resistance, RDS(ON), multiplied by the load current: VDROPOUT = VIN - VOUT = RDS(ON) × IOUT Current Limit The RT9178 monitors and controls the PMOS’ gate voltage, limiting the output current to 400mA (typ). 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. www.richtek.com 8 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 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. DS9178-15 March 2007 RT9178 Tantalum: Thermal Considerations 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. The RT9178 series can deliver a current of up to 200mA 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. 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. 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. 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). The final operating junction temperature for any set of conditions can be estimated by the following thermal equation: Aluminum: 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. 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. DS9178-15 March 2007 PD = (VIN − VOUT) IOUT + VIN IGND PD (MAX) = ( TJ (MAX) − TA ) / θJA 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” . www.richtek.com 9 RT9178 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: BP VOUT VIN GND EN SOT-23-5 Board Layout www.richtek.com 10 DS9178-15 March 2007 RT9178 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 0.080 0.254 0.003 0.010 L 0.300 0.610 0.012 0.024 SOT-23-5 Surface Mount Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)89191466 Fax: (8862)89191465 Email: [email protected] DS9178-15 March 2007 www.richtek.com 11