RT9008GE

RT9008 Low Dropout Linear Regulator Controller with Soft-Start General Description Features The RT9008 is a wide input range, low dropout voltage regulator controller with soft-start function. The part drives an external N-MOSFET and can operate with VCC power range from 4.5V to 13.5V. With this flexible topology and wide input voltage range, the RT9008 is suitable for various applications. The soft-start function can reduce the input inrush current by adjusting the external capacitor. The RT9008 uses the small footprint package of the SOT-23-6. z Programmable Output Voltage z High Current Driver for High Current FET Adjustable Soft Start Time High Accuracy ±2% Reference Voltage Quick Line and Load Transient Response Enable Control Small Footprint Package SOT-23-6 RoHS Compliant and 100% Lead (Pb)-Free Ordering Information Applications RT9008 z z z z z z z Package Type E : SOT-23-6 Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) z Desktop/Notebook PC DSC z Processor Power Sequencing Pin Configurations (TOP VIEW) Note : VCC DRI SS Richtek products are : ` RoHS compliant and compatible with the current require- 6 ments of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. 5 4 2 3 EN GND FB SOT-23-6 Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area. Typical Application Circuit VIN VCC RT9008 SS 4 6 VCC CCC Chip Enable DRI 5 CIN Q1 VOUT 1 EN 2 GND CSS R1 FB 3 COUT R2 VOUT = VREF x ( DS9008-01 April 2011 R1 + R2 ) R2 www.richtek.com 1 RT9008 Test Circuit V IN V CC RT9008 SS 4 6 VCC C CC 1µF/X7R Chip Enable DRI 5 1 EN 2 GND C SS 100pF/ Ceramic C IN 100µF/EC Q1 PHD3055 V OUT R1 1k FB 3 R2 2k C OUT 100µF/EC Figure 1. Typical Test Circuit V CC 12V C CC 1µF Chip Enable 5V RT9008 6 VCC SS 4 DRI 5 1 EN A V DRI FB 3 V FB 2 GND C FB Figure 2. DRI Source/Sink Current Test Circuit Functional Pin Description Pin No. Pin Name Pin Function 1 EN Enable Input Pin. (Active High) 2 GND Ground. 3 FB Output Voltage Feedback Reference Input. 4 SS Soft Start Control. 5 DRI Driver Output. 6 VCC Power Supply Input. Function Block Diagram EN Shutdown Logic VCC 0.8V Reference + DRI - SS FB GND www.richtek.com 2 DS9008-01 April 2011 RT9008 Absolute Maximum Ratings z z z z z z z z (Note 1) Supply Input Voltage, VCC ----------------------------------------------------------------------------------------------Enable Voltage ------------------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C SOT-23-6 -------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2) SOT-23-6, θJA --------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature Range -------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------ Recommended Operating Conditions z z z z 15V 7V 0.4W 250°C/W 260°C 150°C −65°C to 150°C 2kV 200V (Note 4) Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------Enable Voltage -----------------------------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------------Ambient Temperature Range ------------------------------------------------------------------------------------------- 4.5V to 13.5V 0V to 5.5V −40°C to 125°C −40°C to 85°C Electrical Characteristics (VCC = 12V, TA = 25°C, unless otherwise specified). Parameter Symbol Test Condition Typ Max Unit 4.0 4.2 4.5 V -- 0.2 -- V POR Threshold Voltage VCC_POR POR Hysteresis VCC_PORHY VCC Quiescent Current IQ V CC = 12V -- 0.3 0.8 mA Driver Source Current IDRI_SR V CC = 12V, V DRI = 6V 5 -- -- mA Driver Sink Current IDRI_SK V CC = 12V, V DRI = 6V 5 -- -- mA Feedback Reference Voltage VREF V CC = 12V, V DRI = 5V 0.784 0.8 0.816 V Reference Line Regulation VREF_Line V CC = 4.5V to 15V -- 3 6 mV V CC = 12V, No Load -- 70 dB V CC = 12V, No Load 50 -- dB Amplifier Voltage Gain PSRR at 100Hz, No Load PSRR V CC Rising Min Chip Enable EN Threshold Logic-High Voltage VIH 1.4 -- 5.5 Logic-Low Voltage VIL 0 -- 0.4 Shutdown Current V ISHDN V CC= 12V, VEN = 0V -- -- 5 μA ISS V SS = 0V V OUT = 1.2V, COUT = 1000μF, CSS = 4.7nF 2 5 10 μA -- 1 -- ms Soft-Start SS pin Source Current Output Turn-On Rise Time DS9008-01 April 2011 www.richtek.com 3 RT9008 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 TA = 25°C on a low effective thermal conductivity single layer 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. www.richtek.com 4 DS9008-01 April 2011 RT9008 Typical Operating Characteristics Quiescent Current vs. Temperature Feedback Voltage vs. Temperature 1.00 0.95 0.50 Feedback Voltage (V) Quiescent Current (mA) 0.60 0.40 0.30 0.20 0.10 0.90 0.85 0.80 0.75 0.70 0.65 VIN = 1.5V, VCC = 12V VIN = 1.5V, VCC = 12V 0.00 0.60 -50 -25 0 25 50 75 100 125 -50 -25 0 25 100 125 30 55 DRI Sink Current (mA) DRI Source Current (mA) 75 DRI Sink Current vs. Temperature DRI Source Current vs. Temperature 60 50 45 40 27 24 21 18 15 VFB = 1V, VCC = 12V, VDRI = 6V VFB = 0.6V, VCC = 12V, VDRI = 6V 35 12 -50 -25 0 25 50 75 100 125 -50 -25 Temperature (°C) 0 25 50 75 100 125 Temperature (°C) Sink Current vs. DRI Voltage Source Current vs. DRI Voltage 25 15 10 5 Source Current (mA) Refer to Test Circuit Figure 2 50 20 Sink Current (mA) 50 Temperature (°C) Temperature (°C) 40 30 20 10 VFB = 1V, VCC = 12V VFB = 0.6V, VCC = 12V 0 0 0 0.5 1 1.5 2 DRI Voltage (V) DS9008-01 April 2011 2.5 3 0 2 4 6 8 10 12 DRI Voltage (V) www.richtek.com 5 RT9008 Soft Start Time vs. CSS EN Threshold Voltage vs. Temperature 1.00 5000 EN Threshold Voltage (V) 0.95 Soft Start Time (us) 4000 3000 2000 1000 0.90 Rising 0.85 0.80 Falling 0.75 0.70 0.65 0.60 0 0 4 8 12 16 20 -50 24 -25 0 25 50 75 100 125 Temperature (°C) CSS (nF) Power On from EN Power Off from EN VIN = 5V, VOUT = 1.2V, ILOAD = 80mA VEN (5V/Div) VEN (5V/Div) VOUT (500mV/Div) VOUT (500mV/Div) VIN = 5V, VOUT = 1.2V, ILOAD = 80mA Time (500μs/Div) Time (1ms/Div) Load Transient Response Line Transient Response VIN = 2.5V, VOUT = 1.2V, CIN = COUT = 100μF VIN = 1.5V to 2.5V, ILOAD = 100mA CIN = 2.2μF, COUT = 100μF 20 10 VOUT (mV/Div) 0 VOUT (mV/Div) 0 -20 -10 5 2.5 I LOAD (A/Div) 0 VIN (V/Div) 1.5 Time (250μs/Div) www.richtek.com 6 Time (100μs/Div) DS9008-01 April 2011 RT9008 Application Information Output Voltage Setting MOSFET Selection and Thermal Consideration As shown in application circuit, the output voltage can be easy set by the external resistor divider of R1 and R2. The RT9008 is designed to drive an external N-MOSFET pass element. MOSFET selection criteria include threshold voltage VGS (VTH), maximum continuous drain VOUT = VREF (1 + R1 ) R2 Where VREF is the feedback reference voltage (0.8V typical). Chip Enable Operation Pull the EN pin low (< 0.4V) to shutdown the device. During shutdown mode, the standby current is lower than 5μA. The external capacitor and load current determine the output voltage decay rate. Drive the EN pin high (>1.4V) to turn on the device again. Soft-Start Soft-Start provides for the monotonic, glitch-free turn-on of the regulator. Soft-start limits the input inrush current which may cause a glitch, especially if the source impedance is high. The soft-start is achieved by the controller ramping up to the error amplifier reference input. The RT9008 soft-start time is 190us when the soft-start capacitor is 1nF, 920μs for 4.7nF and 1.9ms for 10nF. current ID, on-resistance RDS(ON), maximum drain-to-source voltage VDS and package thermal resistance θJA. The most critical specification is the MOSFET RDS(ON). The maximum allowed RDS(ON) can be calculated by the following formula : RDS(ON) = VIN − VOUT ILOAD For example, if the maximum load current is 2A, the input voltage is 1.5V and the output voltage is 1.2V, then RDS(ON) = (1.5V − 1.2V)/2A = 150mΩ. The MOSFET's RDS(ON) have to be selected to be lower than 150mΩ. A Philips PHD3055E MOSFET with an RDS(ON) of 120mΩ (typ.) is a good choice. After that, consider the thermal resistance from junction to ambient θJA of the MOSFET's package. The power dissipation is calculated by : PD = (VIN − VOUT) x ILOAD Capacitors Selection The thermal resistance from junction to ambient θJA can be calculated by : Careful selection of the external capacitors is highly recommended for the best performance of the RT9008. θ (JA) = Regarding the supply voltage capacitor (CCC) connecting a ceramic capacitor 1μF between the VCC and GND is a must. (TJ − TA ) PD The capacitor CCC improves the supply voltage stability to provide chip normal operation. In this example, PD = (1.5V − 1.2V) x 2A = 0.6W. The PHD3055E's θJA is 75°C/W for its D-PAK package, which translates to a 45°C temperature rise above ambient. The package provides exposed backsides that directly transfer heat to the PCB board. As to the input capacitor ,CIN, connecting a 100μF between the VIN, and GND is recommended to increase stability. With large capacitor value could result in better performance for both PSRR and line transient response. The RT9008 maximum power dissipation depends on the thermal resitance of the IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction to ambient. When driving external pass element, a 100μF electrolytic capacitor on the output capacitor (COUT) is recommended for stability. With larger capacitor, the RT9008 can reduce noise the improve load transient response and PSRR. The maximum power dissipation can be calculated by following formula : DS9008-01 April 2011 PD(MAX) = (TJ(MAX) − TA) / θJA www.richtek.com 7 RT9008 Where T J(MAX) is the maximum operation junction temperature, TA is the ambient temperature and the θJA is the junction to ambient resistance. For recommended operating conditions specification of the RT9008, the maximum junction temperature is 125°C. The junction to ambient thermal resistance θJA for SOT23-6 package is 250°C/W on the standard JEDEC 51-3 single-layer thermal test board. The maximum allowed power dissipation at TA = 25°C can be calculated by following formula : For SOT-23-6 package, PD(MAX) = (125°C − 25°C)/(250°C/W) = 0.400 W The maximum power dissipation depends on operating ambient temperature for fixed T J(MAX) and thermal resistance θJA. For RT9008 package, the Figure 3 of derating curve allows the designer to see the effect of rising ambient temperature on the maximum power dissipation allowed. 0.50 Layout Considerations There are three critical layout considerations. One is the divider resistors should be located as close to the RT9008 FB pin as possible to minimize noise The second is the placement of capacitors. The CIN and COUT have to be placed near the N-MOSFET for improving performance. The third is the copper area for pass element, it should be as large as possible when the pass element operating under high power situation that could rise the junction temperature. Considering the package thermal resistance limitation, the copper area should be large enough to handle the power dissipation shown as Figure 4. VIN CIN Single Layer PCB DRI COUT Power Dissipation (W) 0.45 0.40 0.35 VCC SOT-23-6 0.30 VCC DRI SS 6 5 4 0.20 2 3 0.15 EN GND FB 0.25 CCC R1 0.10 R2 0.05 0.00 GND 0 25 50 75 100 Ambient Temperature (°C) VOUT GND 125 Figure 4. PCB Layout Guide Figure 3. Derating Curves for RT9008 Package www.richtek.com 8 DS9008-01 April 2011 RT9008 Outline Dimension H D L C B b A A1 e Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0.889 1.295 0.031 0.051 A1 0.000 0.152 0.000 0.006 B 1.397 1.803 0.055 0.071 b 0.250 0.560 0.010 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-23-6 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: marketing@richtek.com 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. DS9008-01 April 2011 www.richtek.com 9