LM2991QML Negative Low Dropout Adjustable Regulator General Description Features The LM2991 is a low dropout adjustable negative regulator with a output voltage range between −2V to −25V. The LM2991 provides up to 1A of load current and features a On /Off pin for remote shutdown capability. n n n n n n n n The LM2991 uses new circuit design techniques to provide a low dropout voltage, low quiescent current and low temperature coefficient precision reference. The dropout voltage at 1A load current is typically 0.6V and a guaranteed worstcase maximum of 1V over the entire operating temperature range. The quiescent current is typically 1 mA with a 1A load current and an input-output voltage differential greater than 3V. A unique circuit design of the internal bias supply limits the quiescent current to only 9 mA (typical) when the regulator is in the dropout mode (VO − VI ≤ 3V). The LM2991 is short-circuit proof, and thermal shutdown includes hysteresis to enhance the reliability of the device when inadvertently overloaded for extended periods. Output voltage adjustable from −2V to −25V Output current in excess of 1A Dropout voltage typically 0.6V at 1A load Low quiescent current Internal short circuit current limit Internal thermal shutdown with hysteresis TTL, CMOS compatible ON/OFF switch Functional complement to the LM2941 series Applications n Post switcher regulator n Local, on-card, regulation n Battery operated equipment Ordering Information NS Part Number SMD Part Number NS Package Number LM2991J-QML 5962-9650501QEA J16A LM2991J-QMLV 5962-9650501VEA J16A LM2991WG-QML 5962-9650501QXA WG16A Connection Diagrams Package Description 16LD Ceramic Dip 16LD Ceramic Dip 16LD Ceramic SOIC 16-Lead Ceramic Surface-Mount Package 16-Lead Ceramic Dual-in-Line Package 20158730 20158729 Top View See NS Package Number J16A © 2006 National Semiconductor Corporation DS201587 Top View See NS Package Number WG16A www.national.com LM2991QML Negative Low Dropout Adjustable Regulator March 2006 www.national.com 2 Equivalent Schematic 20158708 LM2991QML LM2991QML Absolute Maximum Ratings (Note 1) Input Voltage −26V to +0.3V Power Dissipation (Note 2) Internally limited Junction Temperature (TJmax) 150˚C Storage Temperature Range −65˚C ≤ TA ≤ +150˚C Thermal Resistance θJA Ceramic DIP (Still Air @ 0.5˚C/W) 75˚C/W Ceramic DIP (500LF/Min Air flow @ 0.5˚C/W) 35˚C/W Ceramic SOIC (Still Air @ 0.5˚C/W) 119˚C/W Ceramic SOIC (500LF/Min Air flow @ 0.5˚C/W) 73˚C/W θJC (Note 3) Ceramic DIP 5˚C/W Ceramic SOIC 3˚C/W Package Weight (Typical) TBD Lead Temperature (Soldering, 10 sec.) 260˚C ESD Susceptibility (Note 4) 1,500V Recommended Operating Conditions (Note 1) −55˚C ≤ TA ≤ +125˚C Operating Temperature Range (TA) Maximum Input Voltage (Operational) −26V Quality Conformance Inspection Mil-Std-883, Method 5005 - Group A Subgroup Description 1 Static tests at Temp ˚C 25 2 Static tests at 125 3 Static tests at -55 4 Dynamic tests at 25 5 Dynamic tests at 125 6 Dynamic tests at -55 7 Functional tests at 25 8A Functional tests at 125 8B Functional tests at -55 9 Switching tests at 25 10 Switching tests at 125 11 Switching tests at -55 12 Settling time at 25 13 Settling time at 125 14 Settling time at -55 3 www.national.com LM2991QML LM2991 Electrical Characteristics DC Parameters The following conditions apply, unless otherwise specified. DC: VI = −10V, VO = −3V, IO = 1A, CO = 47µF, RL = 2.7KΩ Symbol VRef Parameter Reference Voltage Conditions Notes 5mA ≤ IO ≤ 1A 5mA ≤ IO ≤ 1A, VO - 1V ≥ VI ≥ -26V VO Min Max Units Subgroups -1.234 -1.186 V 1 -1.27 -1.15 V 2, 3 -3.0 V 1 V 1 Output Voltage Range VI = -26V -24 V 2, 3 VRLine Line Regulation IO = 5mA, VO - 1V ≥ VI ≥ -26V -26 -25 +26 mV 1, 2, 3 VRLoad Load Regulation 50mA ≤ IO ≤ 1A -12 +12 mV 1 -15 +15 mV 2, 3 VDO Dropout Voltage IO = 0.1A, ∆VO ≤ 100mV 0.2 V 1 0.3 V 2, 3 IO = 1A, ∆VO ≤ 100mV 0.8 V 1 1.0 V 2, 3 Quiescent Current IO ≤ 1A 5.0 mA 1, 2, 3 Dropout Quiescent Current VI = VO, IO ≤ 1A 50 mA 1, 2, 3 Output Noise 10Hz - 100KHz, IO = 5mA IQ VON ON/OFF Input Voltage VO : ON VO : OFF ON/OFF Input Current Output Leakage Current ILimit Current Limit µV 1 µV 2, 3 0.8 V 1, 2, 3 V 1, 2, 3 2.4 VON/OFF = 0.8V (VO : ON) VON/OFF = 2.4V (VO : OFF) IL 450 500 VI = -26V, VON/OFF = 2.4V, VO = 0V VO = 0V 10 µA 1 25 µA 2, 3 100 µA 1 150 µA 2, 3 250 µA 1 300 µA 2, 3 1.5 2.5 A 1 1.0 4.0 A 2, 3 Min Max Units Subgroups dB 1 AC Parameters The following conditions apply, unless otherwise specified. AC: VI = −10V, VO = −3V, IO = 1A, CO = 47µF, RL = 2.7KΩ Symbol RR Parameter Ripple Rejection www.national.com Conditions VRipple = 1VRMS, FRipple = 1KHz, IO = 5mA 4 Notes 50 LM2991QML LM2991 Electrical Characteristics (Continued) DC Drift Parameters The following conditions apply, unless otherwise specified. DC: VI = −10V, VO = −3V, IO = 1A, CO = 47µF, RL = 2.7KΩ Deltas not required on B−Level product. Deltas required for S−Level product ONLY. Symbol VRef Parameter Reference Voltage Conditions 5mA ≤ IO ≤ 1A Notes Min Max Units Subgroups ± 20 mV 1 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test conditions. Note 2: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature), θJA (package junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PDmax = (TJmax - TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. Note 3: The package material for these devices allows much improved heat transfer over our standard ceramic packages. In order to take full advantage of this improved heat transfer, heat sinking must be provided between the package base (directly beneath the die), and either metal traces on, or thermal vias through, the printed circuit board. Without this additional heat sinking, device power dissipation must be calculated using θJA, rather than θJC, thermal resistance. It must not be assumed that the device leads will provide substantial heat transfer out the package, since the thermal resistance of the leadframe material is very poor, relative to the material of the package base. The stated θJC thermal resistance is for the package material only, and does not account for the additional thermal resistance between the package base and the printed circuit board. The user must determine the value of the additional thermal resistance and must combine this with the stated value for the package, to calculate the total allowed power dissipation for the device. The user must determine the value of the additional thermal resistance and must combine this with the stated value for the package, to calculate the total allowed power dissipation for the device. Note 4: Human body model, 1.5 kΩ in series with 100 pF. 5 www.national.com LM2991QML Typical Performance Characteristics Dropout Voltage Normalized Output Voltage 20158713 20158714 Output Voltage Output Noise Voltage 20158715 20158716 Quiescent Current Maximum Output Current 20158717 www.national.com 20158718 6 LM2991QML Typical Performance Characteristics (Continued) Line Transient Response Load Transient Response 20158719 20158720 Maximum Output Current Ripple Rejection 20158722 20158721 Output Impedance ON /OFF Control Voltage 20158723 20158724 7 www.national.com LM2991QML Typical Performance Characteristics (Continued) Adjust Pin Current Low Voltage Behavior 20158726 20158725 CERAMIC BYPASS CAPACITORS Many designers place distributed ceramic capacitors whose value is in the range of 1000 pF to 0.1 µF at the power input pins of the IC’s across a circuit board. These can cause reduced phase margin or oscillations in LDO regulators. The advent of multi-layer boards with dedicated power and ground planes has removed the trace inductance that (previously) provided the necessary "decoupling" to shield the output of the LDO from the effects of bypass capacitors. These capacitors should be avoided if possible, and kept as far away from the LDO output as is practical. Application Hints EXTERNAL CAPACITORS Like any low-dropout regulator, external capacitors are reqired to stabilize the control loop. These capacitors must be correctly selected for proper performance. INPUT CAPACITOR An input capacitor is required if the regulator is located more than 6" from the input power supply filter capacitor (or if no other input capacitor is present). A solid Tantalum or ceramic capacitor whose value is at least 1 µF is recommended, but an aluminum electrolytic (≥ 10 µF) may be used. However, aluminum electrolytics should not be used in applications where the ambient temperature can drop below 0˚C because their internal impedance increases significantly at cold temperatures. Output Capacitor ESR Range OUTPUT CAPACITOR The output capacitor must meet the ESR limits shown in the graph, which means it must have an ESR between about 25 mΩ and 10Ω. A solid Tantalum (value ≥ 1 µF) is the best choice for the output capacitor. An aluminum electrolytic (≥ 10 µF) may be used if the ESR is in the stable range. It should be noted that the ESR of a typical aluminum electrolytic will increase by as much as 50X as the temperature is reduced from 25˚C down to −40˚C, while a Tantalum will exhibit an ESR increase of about 2X over the same range. For this and other reasons, aluminum electrolytics should not be used in applications where low operating temperatures occur. The lower stable ESR limit of 25 mΩ means that ceramic capacitors can not be used directly on the output of an LDO. A ceramic (≥ 2.2 µF) can be used on the output if some external resistance is placed in series with it (1Ω recommended). Dielectric types X7R or X5R must be used if the temperature range of the application varies more than ± 25˚C from ambient to assure the amount of capacitance is sufficient. www.national.com 20158705 MINIMUM LOAD A minimum load current of 500 µA is required for proper operation. The external resistor divider can provide the minimum load, with the resistor from the adjust pin to ground set to 2.4 kΩ. SETTING THE OUTPUT VOLTAGE The output voltage of the LM2991 is set externally by a resistor divider using the following equation: VOUT = VREF x (1 + R2/R1) − (IADJ x R2) where VREF = −1.21V. The output voltage can be programmed within the range of −3V to −24V, typically an even greater range of −2V to −25V. The adjust pin current is about 60 nA, causing a slight error in the output voltage. However, 8 FORCING THE OUTPUT POSITIVE (Continued) Due to an internal clamp circuit, the LM2991 can withstand positive voltages on its output. If the voltage source pulling the output positive is DC, the current must be limited to 1.5A. A current over 1.5A fed back into the LM2991 could damage the device. The LM2991 output can also withstand fast positive voltage transients up to 26V, without any current limiting of the source. However, if the transients have a duration of over 1 mS, the output should be clamped with a Schottky diode to ground. using resistors lower than 100 kΩ makes the adjust pin current negligible. For example, neglecting the adjust pin current, and setting R2 to 100 kΩ and VOUT to −5V, results in an output voltage error of only 0.16%. ON/OFF PIN The LM2991 regulator can be turned off by applying a TTL or CMOS level high signal to the ON/OFF pin (see Adjustable Current Sink Application). Typical Applications 20158701 VO = VRef (1 + R2/R1) *Required if the regulator is located further than 6 inches from the power supply filter capacitors. A 1 µF solid tantalum or a 10 µF aluminum electrolytic capacitor is recommended. **Required for stability. Must be at least a 10 µF aluminum electrolytic or a 1 µF solid tantalum to maintain stability. May be increased without bound to maintain regulation during transients. Locate the capacitor as close as possible to the regulator. The equivalent series resistance (ESR) is critical, and should be less than 10Ω over the same operating temperature range as the regulator. Fully Isolated Post-Switcher Regulator 20158706 9 www.national.com LM2991QML Application Hints LM2991QML Typical Applications (Continued) Adjustable Current Sink 20158710 www.national.com 10 Released 03/10/06 Revision A Section Originator New Release, Corporate format L. Lytle 11 Changes 1 MDS data sheet converted into one Corp. data sheet format. MNLM2991-X Rev 1A1 will be archived. www.national.com LM2991QML Revision History LM2991QML Physical Dimensions inches (millimeters) unless otherwise noted 16-Lead Ceramic Dual-in-Line Package NS Package Number J16A 16-Lead Ceramic Surface-Mount Package NS Package Number WG16A www.national.com 12 LM2991QML Negative Low Dropout Adjustable Regulator 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. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. Leadfree products are RoHS compliant. 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