LP38693-ADJ

LP38691-ADJ/LP38693-ADJ 500mA Low Dropout CMOS Linear Regulators with Adjustable OutputStable with Ceramic Output Capacitors LP38691-ADJ LP38693-ADJ September 24, 2010 500mA Low Dropout CMOS Linear Regulators with Adjustable Output Stable with Ceramic Output Capacitors General Description The LP38691/3-ADJ low dropout CMOS linear regulators provide 2.0% precision reference voltage, extremely low dropout voltage (250mV @ 500mA load current, VOUT = 5V) and excellent AC performance utilizing ultra low ESR ceramic output capacitors. The low thermal resistance of the LLP and SOT-223 packages allow the full operating current to be used even in high ambient temperature environments. The use of a PMOS power transistor means that no DC base drive current is required to bias it allowing ground pin current to remain below 100 µA regardless of load current, input voltage, or operating temperature. Dropout Voltage: 250 mV (typ) @ 500mA (typ. 5V out). Ground Pin Current: 55 µA (typ) at full load. Adjust Pin Voltage: 2.0% (25°C) accuracy. Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Output voltage range of 1.25V - 9V 2.0% adjust pin voltage accuracy (25°C) Low dropout voltage: 250mV @ 500mA (typ, 5V out) Wide input voltage range (2.7V to 10V) Precision (trimmed) bandgap reference Guaranteed specs for -40°C to +125°C 1µA off-state quiescent current Thermal overload protection Foldback current limiting SOT-223 and 6-Lead LLP packages Enable pin (LP38693-ADJ) Applications ■ ■ ■ ■ Hard Disk Drives Notebook Computers Battery Powered Devices Portable Instrumentation Typical Application Circuits 20126801 20126802 VOUT = VADJ x (1 + R1/R2) Note: *Minimum value required for stability. © 2010 National Semiconductor Corporation 201268 www.national.com LP38691-ADJ/LP38693-ADJ Connection Diagrams 20126803 SOT-223, Top View LP38693MP-ADJ 20126804 20126805 6-Lead LLP, Bottom View LP38691SD-ADJ 6-Lead LLP, Bottom View LP38693SD-ADJ Pin Descriptions Pin VIN GND VOUT VEN ADJ Description This is the input supply voltage to the regulator. For LLP package devices, both VIN pins must be tied together for full current operation (250mA maximum per pin). Circuit ground for the regulator. This is connected to the die through the lead frame, and also functions as the heat sink when the large ground pad is soldered down to a copper plane. Regulated output voltage. The enable pin allows the part to be turned ON and OFF by pulling this pin high or low. The adjust pin is used to set the regulated output voltage by connecting it to the external resistors R1 and R2 (see Typical Application Circuit). Ordering Information Order Number LP38691SD-ADJ LP38693SD-ADJ LP38693MP-ADJ LP38691SDX-ADJ LP38693SDX-ADJ LP38693MPX-ADJ Package Marking L117B L127B LJUB L117B L127B LJUB Package Type 6-Lead LLP 6-Lead LLP SOT-223 6-Lead LLP 6-Lead LLP SOT-223 Package Drawing SDE06A SDE06A MP05A SDE06A SDE06A MP05A Supplied As 1000 Units Tape and Reel 1000 Units Tape and Reel 1000 Units Tape and Reel 4500 Units Tape and Reel 4500 Units Tape and Reel 2000 Units Tape and Reel www.national.com 2 LP38691-ADJ/LP38693-ADJ Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Storage Temperature Range Lead Temp. (Soldering, 5 seconds) ESD Rating (Note 3) Power Dissipation (Note 2) −65°C to +150°C 260°C 2 kV Internally Limited V(max) All pins (with respect to GND) IOUT Junction Temperature -0.3V to 12V Internally Limited −40°C to +150°C Operating Ratings VIN Supply Voltage Operating Junction Temperature Range 2.7V to 10V −40°C to +125°C Limits in standard typeface are for TJ = 25°C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = VOUT + 1V, CIN = COUT = 10 µF, ILOAD = 10mA. Min/Max limits are guaranteed through testing, statistical correlation, or design. Symbol VADJ ΔVO/ΔVIN ΔVO/ΔIL Parameter VIN = 2.7V ADJ Pin Voltage Output Voltage Line Regulation (Note 6) Output Voltage Load Regulation (Note 7) 3.2V ≤ VIN ≤ 10V 100 µA < IL < 0.5A VO + 0.5V ≤ VIN ≤ 10V IL = 25mA 1 mA < IL < 0.5A VIN = VO + 1V (VO = 2.5V) IL = 0.1A IL = 0.5A VIN - VO Dropout Voltage (Note 8) (VO = 3.3V) IL = 0.1A IL = 0.5A (VO = 5V) IL = 0.1A IL = 0.5A IQ Quiescent Current VIN ≤ 10V, IL = 100 µA - 0.5A VEN ≤ 0.4V, (LP38693-ADJ Only) IL(MIN) IFB PSRR TSD TSD (HYST) IADJ Minimum Load Current Foldback Current Limit Ripple Rejection Thermal Shutdown Activation (Junction Temp) Thermal Shutdown Hysteresis (Junction Temp) ADJ Input Leakage Current VADJ = 0 - 1.5V VIN = 10V -100 VIN - VO ≤ 4V VIN - VO > 5V VIN - VO < 4V VIN = VO + 2V(DC), with 1V(p-p) / 120Hz Ripple 350 850 55 160 °C 10 0.01 100 nA Conditions Min 1.225 1.200 Typ (Note 4) 1.25 1.25 0.03 1.8 80 430 65 330 45 250 55 0.001 Max 1.275 1.300 0.1 5 145 725 110 550 100 450 100 1 100 mA dB µA V Units Electrical Characteristics %/V %/A mV 3 www.national.com LP38691-ADJ/LP38693-ADJ Symbol en VO (LEAK) VEN Parameter Output Noise Output Leakage Current Enable Voltage (LP38693-ADJ Only) Conditions BW = 10Hz to 10kHz VO = 3.3V VO = VO(NOM) + 1V @ VIN = 10V Output = OFF Output = ON, VIN = 4V Output = ON, VIN = 6V Output = ON, VIN = 10V Min Typ (Note 4) 0.7 0.5 Max Units µV/ 2 0.4 µA 1.8 3.0 4.0 -1 0.001 1 V IEN Enable Pin Leakage (LP38693ADJ Only) VEN = 0V or 10V, VIN = 10V µA Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Operating ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications, see Electrical Characteristics. Specifications do not apply when operating the device outside of its rated operating conditions. Note 2: At elevated temperatures, device power dissipation must be derated based on package thermal resistance and heatsink values (if a heatsink is used). The junction-to-ambient thermal resistance (θJ-A) for the SOT-223 is approximately 125 °C/W for a PC board mounting with the device soldered down to minimum copper area (less than 0.1 square inch). If one square inch of copper is used as a heat dissipator for the SOT-223, the θJ-A drops to approximately 70 °C/W. The θJ-A values for the LLP package are also dependent on trace area, copper thickness, and the number of thermal vias used (refer to application note AN-1187). If power disspation causes the junction temperature to exceed specified limits, the device will go into thermal shutdown. Note 3: ESD is tested using the human body model which is a 100pF capacitor discharged through a 1.5k resistor into each pin. Note 4: Typical numbers represent the most likely parametric norm for 25°C operation. Note 5: If used in a dual-supply system where the regulator load is returned to a negative supply, the output pin must be diode clamped to ground. Note 6: Output voltage line regulation is defined as the change in output voltage from nominal value resulting from a change in input voltage. Note 7: Output voltage load regulation is defined as the change in output voltage from nominal value as the load current increases from 1mA to full load. Note 8: Dropout voltage is defined as the minimum input to output differential required to maintain the output within 100mV of nominal value. www.national.com 4 LP38691-ADJ/LP38693-ADJ Block Diagrams 20126806 FIGURE 1. LP38691-ADJ Functional Diagram (LLP) 20126807 FIGURE 2. LP38693-ADJ Functional Diagram (SOT-223, LLP) 5 www.national.com LP38691-ADJ/LP38693-ADJ Typical Performance Characteristics Unless otherwise specified: TJ = 25°C, CIN = COUT = 10 µF, enable pin is tied to VIN (LP38693-ADJ only), VO = 1.25V, VIN = 2.7V, IL = 10mA. Noise vs Frequency Noise vs Frequency 20126835 20126836 Noise vs Frequency Ripple Rejection 20126817 20126837 Ripple Rejection Ripple Rejection 20126819 20126821 www.national.com 6 LP38691-ADJ/LP38693-ADJ VREF vs Temperature Line Transient Response 20126823 20126830 Line Transient Response Line Transient Response 20126824 20126825 Line Transient Response Line Transient Response 20126826 20126827 7 www.national.com LP38691-ADJ/LP38693-ADJ Line Transient Response Load Transient Response 20126828 20126842 Load Transient Response Enable Voltage vs Temperature 20126844 20126853 Load Regulation vs Temperature Line Regulation vs Temperature 20126854 20126855 www.national.com 8 LP38691-ADJ/LP38693-ADJ VOUT vs VIN , VOUT = 1.25V VOUT vs VIN , VOUT = 1.80V 20126858 20126859 VOUT vs VIN, Power-Up VOUT vs VEN, ON (LP38693 Only) 20126860 20126861 VOUT vs VEN, OFF (LP38693 Only) MIN VIN vs IOUT 20126862 20126856 9 www.national.com LP38691-ADJ/LP38693-ADJ Dropout Voltage vs IOUT (VOUT = 1.8V) 20126857 www.national.com 10 LP38691-ADJ/LP38693-ADJ Application Hints EXTERNAL CAPACITORS Like any low-dropout regulator, external capacitors are required to assure stability. These capacitors must be correctly selected for proper performance. INPUT CAPACITOR: An input capacitor of at least 1µF is required (ceramic recommended). The capacitor must be located not more than one centimeter from the input pin and returned to a clean analog ground. OUTPUT CAPACITOR: An output capacitor is required for loop stability. It must be located less than 1 centimeter from the device and connected directly to the output and ground pins using traces which have no other currents flowing through them. The minimum amount of output capacitance that can be used for stable operation is 1µF. Ceramic capacitors are recommended (the LP38691/3-ADJ was designed for use with ultra low ESR capacitors). The LP38691/3-ADJ is stable with any output capacitor ESR between zero and 100 Ohms. SETTING THE OUTPUT VOLTAGE: The output voltage is set using the external resistors R1 and R2 (see Typical Application Circuit). The output voltage will be given by the equation: VOUT = VADJ x (1 + ( R1 / R2 ) ) Because the part has a minimum load current requirement of 100 µA, it is recommended that R2 always be 12k Ohms or less to provide adequate loading. Even if a minimum load is always provided by other means, it is not recommended that very high value resistors be used for R1 and R2 because it can make the ADJ node susceptible to noise pickup. A maximum Ohmic value of 100k is recommended for R2 to prevent this from occurring. ENABLE PIN (LP38693-ADJ only): The LP38693–ADJ has an Enable pin (EN) which allows an external control signal to turn the regulator output On and Off. The Enable On/Off threshold has no hysteresis. The voltage signal must rise and fall cleanly, and promptly, through the ON and OFF voltage thresholds. The Enable pin has no internal pull-up or pulldown to establish a default condition and, as a result, this pin must be terminated either actively or passively. If the Enable pin is driven from a source that actively pulls high and low, the drive voltage should not be allowed to go below ground potential or higher than VIN. If the application does not require the Enable function, the pin should be connected directly to the VIN pin. FOLDBACK CURRENT LIMITING: Foldback current limiting is built into the LP38691/3-ADJ which reduces the amount of output current the part can deliver as the output voltage is reduced. The amount of load current is dependent on the differential voltage between VIN and VOUT. Typically, when this differential voltage exceeds 5V, the load current will limit at about 350 mA. When the VIN -VOUT differential is reduced below 4V, load current is limited to about 850 mA. SELECTING A CAPACITOR 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. Capacitor Characteristics CERAMIC For values of capacitance in the 10 to 100 µF range, ceramics are usually larger and more costly than tantalums but give superior AC performance for bypassing high frequency noise because of very low ESR (typically less than 10 mΩ). 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 have good temperature stability: a high quality Tantalum will typically show a capacitance value that varies less than 10-15% across the full temperature range of -40°C to 125°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). REVERSE VOLTAGE A reverse voltage condition will exist when the voltage at the output pin is higher than the voltage at the input pin. Typically this will happen when VIN is abruptly taken low and COUT continues to hold a sufficient charge such that the input to output voltage becomes reversed. A less common condition is when an alternate voltage source is connected to the output. There are two possible paths for current to flow from the output pin back to the input during a reverse voltage condition. 1) While VIN is high enough to keep the control circuity alive, and the Enable pin (LP38693-ADJ only) is above the VEN(ON) threshold, the control circuitry will attempt to regulate the output voltage. If the input voltage is less than the programmed output voltage, the control circuit will drive the gate of the pass element to the full ON condition. In this condition, reverse current will flow from the output pin to the input pin, limited only by the RDS(ON) of the pass element and the output to input voltage differential. Discharging an output capacitor up to 1000 μF in this manner will not damage the device as the current will rapidly decay. However, continuous reverse current should be avoided. When the Enable pin is low this condition will be prevented. 2) The internal PFET pass element has an inherent parasitic diode. During normal operation, the input voltage is higher than the output voltage and the parasitic diode is reverse biased. However, when VIN is below the value where the control circuity is alive, or the Enable pin is low (LP38693-ADJ only), and the output voltage is more than 500 mV (typical) above the input voltage the parasitic diode becomes forward biased and current flows from the output pin to the input pin through the diode. The current in the parasitic diode should be limited to less than 1A continuous and 5A peak. 11 www.national.com LP38691-ADJ/LP38693-ADJ If used in a dual-supply system where the regulator output load is returned to a negative supply, the output pin must be diode clamped to ground to limit the negative voltage transition. A Schottky diode is recommended for this protective clamp. PCB LAYOUT Good PC 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 regulator using traces which do not have other currents flowing in them (Kelvin connect). The best way to do this is to lay out 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 IC 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. RFI/EMI SUSCEPTIBILITY RFI (radio frequency interference) and EMI (electromagnetic interference) can degrade any integrated circuit’s performance because of the small dimensions of the geometries inside the device. In applications where circuit sources are present which generate signals with significant high frequency energy content (> 1 MHz), care must be taken to ensure that this does not affect the IC regulator. If RFI/EMI noise is present on the input side of the regulator (such as applications where the input source comes from the output of a switching regulator), good ceramic bypass capacitors must be used at the input pin of the IC. If a load is connected to the IC output which switches at high speed (such as a clock), the high-frequency current pulses required by the load must be supplied by the capacitors on the IC output. Since the bandwidth of the regulator loop is less than 100 kHz, the control circuitry cannot respond to load changes above that frequency. This means the effective output impedance of the IC at frequencies above 100 kHz is determined only by the output capacitor(s). In applications where the load is switching at high speed, the output of the IC may need RF isolation from the load. It is recommended that some inductance be placed between the output capacitor and the load, and good RF bypass capacitors be placed directly across the load. PCB layout is also critical in high noise environments, since RFI/EMI is easily radiated directly into PC traces. Noisy circuitry should be isolated from "clean" circuits where possible, and grounded through a separate path. At MHz frequencies, ground planes begin to look inductive and RFI/ EMI can cause ground bounce across the ground plane. In multi-layer PCB applications, care should be taken in layout so that noisy power and ground planes do not radiate directly into adjacent layers which carry analog power and ground. OUTPUT NOISE Noise is specified in two ways- Spot Noise or Output Noise density is the RMS sum of all noise sources, measured at the regulator output, at a specific frequency (measured with a 1Hz bandwidth). This type of noise is usually plotted on a curve as a function of frequency. Total Output Noise or Broad-Band Noise is the RMS sum of spot noise over a specified bandwidth, usually several decades of frequencies. Attention should be paid to the units of measurement. Spot noise is measured in units µV/root-Hz or nV/root-Hz and total output noise is measured in µV(rms) The primary source of noise in low-dropout regulators is the internal reference. Noise can be reduced in two ways: by increasing the transistor area or by increasing the current drawn by the internal reference. Increasing the area will decrease the chance of fitting the die into a smaller package. Increasing the current drawn by the internal reference increases the total supply current (ground pin current). www.national.com 12 LP38691-ADJ/LP38693-ADJ Physical Dimensions inches (millimeters) unless otherwise noted 6-lead, LLP Package NS Package Number SDE06A SOT-223 Package NS Package Number MP05A 13 www.national.com LP38691-ADJ/LP38693-ADJ 500mA Low Dropout CMOS Linear Regulators with Adjustable OutputStable with Ceramic Output Capacitors Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage References PowerWise® Solutions Temperature Sensors PLL/VCO www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Applications & Markets Mil/Aero PowerWise® Design University Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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