LP38692MP-ADJ

LP38690-ADJ/LP38692-ADJ 1A Low Dropout CMOS Linear Regulators with Adjustable Output Stable with Ceramic Output Capacitors January 2005 LP38690-ADJ/LP38692-ADJ 1A Low Dropout CMOS Linear Regulators with Adjustable Output Stable with Ceramic Output Capacitors General Description The LP38690/2-ADJ low dropout CMOS linear regulators provide 2.5% precision reference voltage, extremely low dropout voltage (450mV @ 1A 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: 450 mV (typ) @ 1A (typ. 5V out). Ground Pin Current: 55 µA (typ) at full load. Adjust Pin Voltage: 2.5% (25˚C) accuracy. Features n n n n n n n n n n n Output voltage range of 1.25V - 9V 2.5% adjust pin voltage accuracy (25˚C) Low dropout voltage: 450mV @ 1A (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 (LP38692-ADJ) Applications n n n n Hard Disk Drives Notebook Computers Battery Powered Devices Portable Instrumentation Typical Application Circuits 20126701 20126702 VOUT = VADJ x (1 + R1/R2) Note: *Minimum value required for stability. © 2005 National Semiconductor Corporation DS201267 www.national.com LP38690-ADJ/LP38692-ADJ Connection Diagrams 20126703 SOT-223, Top View LP38692MP-ADJ 20126704 20126705 6-Lead LLP, Bottom View LP38690SD-ADJ 6-Lead LLP, Bottom View LP38692SD-ADJ Pin Description 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 (500mA 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 LP38690SD-ADJ LP38692SD-ADJ LP38692MP-ADJ LP38690SDX-ADJ LP38692SDX-ADJ LP38692MPX-ADJ Package Marking L112B L122B LJNB L112B L122B LJNB 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 LP38690-ADJ/LP38692-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) V(max) All pins (with respect to GND) −65˚C to +150˚C 260˚C 2 kV Internally Limited -0.3V to 12V IOUT Junction Temperature 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 Electrical Characteristics 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 Parameter VIN = 2.7V VADJ ∆VO/∆VIN ∆VO/∆IL ADJ Pin Voltage Output Voltage Line Regulation (Note 6) Output Voltage Load Regulation (Note 7) 3.2V ≤ VIN ≤ 10V 100 µA < IL < 1A VO + 0.5V ≤ VIN ≤ 10V IL = 25mA 1 mA < IL < 1A VIN = VO + 1V (VO = 1.8V) IL = 1A (VO = 2.5V) IL = 0.1A IL = 1A VIN - VO Dropout Voltage (Note 8) (VO = 3.3V) IL = 0.1A IL = 1A (VO = 5V) IL = 0.1A IL = 1A IQ IL(MIN) IFB PSRR TSD TSD (HYST) IADJ Quiescent Current 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 ≤ 10V, IL = 100 µA - 1A VEN ≤ 0.4V, (LP38692-ADJ Only) VIN - VO ≤ 4V VIN - VO > 5V VIN - VO < 4V VIN = VO + 2V(DC), with 1V(p-p) / 120Hz Ripple 450 1500 55 160 ˚C 10 0.01 100 nA Conditions Min 1.219 1.187 Typ (Note 4) 1.25 1.25 0.03 1.8 950 80 800 65 650 45 450 55 0.001 Max 1.281 1.313 0.1 5 1600 145 1300 110 1000 100 800 100 1 100 mA dB µA mV V Units %/V %/A 3 www.national.com LP38690-ADJ/LP38692-ADJ Electrical Characteristics 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. (Continued) Symbol en VO (LEAK) VEN Parameter Output Noise Output Leakage Current Enable Voltage (LP38692-ADJ Only) Conditions BW = 10Hz to 10kHz VO = 3.3V VO = VO(NOM) + 1V @ 10VIN Output = OFF Output = ON, VIN = 4V Output = ON, VIN = 6V Output = ON, VIN = 10V IEN Enable Pin Leakage (LP38692-ADJ Only) VEN = 0V or 10V, VIN = 10V 1.8 3.0 4.0 -1 0.001 1 µA Min Typ (Note 4) 0.7 0.5 2 0.4 V Max Units µV/ 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 LP38690-ADJ/LP38692-ADJ Block Diagrams 20126706 FIGURE 1. LP38690-ADJ Functional Diagram (LLP) 20126707 FIGURE 2. LP38692-ADJ Functional Diagram (SOT-223, LLP) 5 www.national.com LP38690-ADJ/LP38692-ADJ Typical Performance Characteristics Unless otherwise specified: TJ = 25˚C, CIN = COUT = 10 µF, enable pin is tied to VIN (LP38692-ADJ only), VO = 1.25V, VIN = 2.7V, IL = 10mA. Noise vs Frequency Noise vs Frequency 20126735 20126736 Noise vs Frequency Ripple Rejection 20126717 20126737 Ripple Rejection Ripple Rejection 20126719 20126721 www.national.com 6 LP38690-ADJ/LP38692-ADJ Typical Performance Characteristics Unless otherwise specified: TJ = 25˚C, CIN = COUT = 10 µF, enable pin is tied to VIN (LP38692-ADJ only), VO = 1.25V, VIN = 2.7V, IL = 10mA. (Continued) VADJ vs Temperature Line Transient Response 20126723 20126730 Line Transient Response Line Transient Response 20126724 20126725 Line Transient Response Line Transient Response 20126726 20126727 7 www.national.com LP38690-ADJ/LP38692-ADJ Typical Performance Characteristics Unless otherwise specified: TJ = 25˚C, CIN = COUT = 10 µF, enable pin is tied to VIN (LP38692-ADJ only), VO = 1.25V, VIN = 2.7V, IL = 10mA. (Continued) Line Transient Response Load Transient Response 20126728 20126740 Load Transient Response Load Transient Response 20126741 20126742 Load Transient Response Load Transient Response 20126743 20126744 www.national.com 8 LP38690-ADJ/LP38692-ADJ Typical Performance Characteristics Unless otherwise specified: TJ = 25˚C, CIN = COUT = 10 µF, enable pin is tied to VIN (LP38692-ADJ only), VO = 1.25V, VIN = 2.7V, IL = 10mA. (Continued) Minimum VIN vs IOUT Dropout Voltage vs IOUT 20126750 20126751 Enable Voltage vs Temperature Load Regulation vs Temperature 20126753 20126754 Line Regulation vs Temperature 20126755 9 www.national.com LP38690-ADJ/LP38692-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 LP38690/2-ADJ was designed for use with ultra low ESR capacitors). The LP38690/2-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 value of 100k is recommended for R2 to prevent this from occurring. ENABLE PIN (LP38692-ADJ only): The LP38692-ADJ has an enable pin which turns the regulator output on and off. Pulling the enable pin down to a logic low will turn the part off. The voltage the pin has to be pulled up to in order to assure the part is on depends on input voltage (refer to Electrical Characteristics section). This pin should be tied to VIN if the enable function is not used. FOLDBACK CURRENT LIMITING: Foldback current limiting is built into the LP38690/2-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 450 mA. When the VIN -VOUT differential is reduced below 4V, load current is limited to about 1500 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. www.national.com 10 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). 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 LP38690-ADJ/LP38692-ADJ Application Hints (Continued) 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). 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. 11 www.national.com LP38690-ADJ/LP38692-ADJ Physical Dimensions inches (millimeters) unless otherwise noted 6-lead, LLP Package NS Package Number SDE06A SOT-223 Package NS Package Number MP05A www.national.com 12 LP38690-ADJ/LP38692-ADJ 1A Low Dropout CMOS Linear Regulators with Adjustable Output Stable with Ceramic Output Capacitors Notes National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. 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