LM9022

LM9022 NSC | Alldatasheet

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Technical content

Features

n No transformers required n SO or DIP packaging

Applications

Typical Application TA = 25˚C, VDD = 5V, unless otherwise specified. Connection Diagram MSOP, Small Outline, and DIP Package 20021502 Top View Order Number LM9022M or LM9022N See NS Package Number M08A or N08E 20021501 FIGURE 1. Typical Application Circuit

Absolute Maximum Ratings(Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage -0.3V to +6.0V Supply Temperature −65˚C to +150˚C Input Voltage −0.3V to V DD +0.3V Power Dissipation (Note 3) Internally Limited ESD Susceptibility (Note 4) 5000V ESD Susceptibility (Note 5) 250V Junction Temperature 150˚C Soldering Information Small Outline Package Vapor Phase (60 sec.) 215˚C Infrared (15 sec.) 220˚C See AN-450 ’Surface Mounting and their Effects on Product Reliability’ for other methods of soldering surface mount devices. θ JC (typ) — M08A 35˚C/W θJA (typ) — M08A 140˚C/W θJC (typ) — N08E 37˚C/W θJA (typ) — N08E 107˚C/W Operating Ratings Temperature Range Supply Voltage 2.0V ≤ VDD ≤ 5.5V Electrical Characteristics(Notes 1, 2) The following specifications apply for V DD = 5V, VPIN3 =V PIN2,V SHUTDOWN = 0V, and R L =1 0Ω unless otherwise specified. Limits apply for T A = 25˚C. Symbol Parameter Conditions LM9022 Min (Note 7) Typical (Note 6) Max (Note 7) Units IDD Quiescent Power Supply Current VIN = 0V, Io = 0A, VSHUTDOWN = 0V 6.5 10.0 mA Power Supply Current during shutdown VSHUTDOWN =V DD (Note 8) 0.6 2 µA VBP Bypass Pin Voltage V IN = 0V 2.4 2.5 2.6 V VOUT Output Voltage Across R L RL =1 0Ω 3.6 4.3 V RL =2 0Ω 4.2 4.6 V Note 1: Absolute Maximum Ratingsindicate limits beyond which damage to the device may occur. Operating Ratingsindicate conditions for which the device is functional, but do not guarantee specific performance limits.Electrical Characteristicsstate DC and AC electrical specifications under particular test conditions which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit is given, however, the typical value is a good indication of device performance. Note 2: All voltages are measured with respect to the ground pin, unless otherwise specified. Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature TA. The maximum allowable power dissipation is P DMAX =( TJMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM9022, T JMAX = 150˚C. For the θJA’s for different packages, please see the Application Informationsection or the Absolute Maximum Ratingssection. Note 4: Human body model, 100pF discharged through a 1.5k Ω resistor. Note 5: Machine Model, 220pF–240pF discharged through all pins. Note 6: Typicals are specified at 25˚C and represent the parametric norm. Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level) by design, test, or statistical analysis. Note 8: Both outputs are high impedance when in shutdown mode. LM9022 www.national.com 2

Typical Performance Characteristics TA = 25˚C, VDD = 5V, unless otherwise specified. Power Derating Curve Output Saturation Voltage vs Load 20021514 20021515 Open Loop Frequency Response Supply Current vs Supply Voltage 20021519 20021520 Differential Output Voltage vs Load 20021540 LM9022 www.national.com3

Application Information

Typically a VFD filament requires a low voltage AC power source in order to create a constant brightness across its length. Such a power source is not readily available in a most systems. Existing implementations show different cir- cuits for supplying an AC power for a VFD filament but they require an AC power input, or do not have a standby control, or generate high EMI. The LM9022 can solve all these problems in one compact circuit. A DC power supply is employed to power two power opera- tional amplifiers: POA1 and POA2. The first power opera- tional amplifier (POA1) can utilize an external feedback cir- cuit that will cause it self-oscillate. In a second version, POA1 is driven from an external signal source. The shape of the output wave delivered by POA1 can be square, sinusoi- dal, triangular, trapezoidal, clipped sinusoidal or any other shape, depending on the feedback circuit or the signal source used. The output of this POA1 is connected exter- nally to one end of the VFD filament, and internally to the input of a second power operational amplifier: POA2. POA2 is internally configured as an inverting unity gain circuit. The output of the POA2 is connected to the second end of the VFD filament. This provides a differential and symmetrical AC signal to the fila An external standby control signal applied to the Shutdown pin can be used to turn of both power operational amplifiers. BRIDGE CONFIGURATION EXPLANATION As shown in Figure 1, the LM9022 has two operational amplifiers internally. Figure 1 shows that the output of am- plifier one serves as the input to amplifier two, which results in both amplifiers producing signals identical in magnitude, but 180˚ out of phase. By driving the load differentially through outputs Vo1 and Vo2, an amplifier configuration commonly referred to as “bridged mode” is established. Bridged mode operation is different from the classical single-ended amplifier configura- tion where one side of its load is connected to ground. A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output power is possible as compared to a single-ended amplifier under the same con- ditions. POWER DISSIPATION For the SO package, θ JA = 140˚C/W, for the DIP package, θJA = 107˚C/W, and for the MSOP package, θJA = 210˚C/W assuming free air operation. The θJA can be decreased by using some form of heat sinking. The resultantθJA will be the summation of the θJC, θCS, and θSA. θJC is the junction to case of the package, θCS is the case to heat sink thermal resistance and θSA is the heat sink to ambient thermal resistance. By adding additional copper area around the LM9022, the θ JA can be reduced from its free air value for the SO package. Depending on the ambient temperature, T A, and the θJA, Equation 2 can be used to find the maximum internal power dissipation supported by the IC packaging. If the result of Equation 1 is greater than that of Equation 2, then either the supply voltage must be decreased, the load impedance increased, the θ JA decreased, or the ambient temperature reduced. For the typical application of a 5V power supply, with an 10Ω load, and no additional heatsink- ing, the maximum ambient temperature possible without violating the maximum junction temperature is approximately 61˚C provided that device operation is around the maximum power dissipation point and assuming surface mount pack- aging. POWER SUPPLY PIN As with any power device, proper supply bypassing is critical for low noise performance. Typical applications will require both a 22µf electrolyte and a 0.1µF ceramic capacitor to bypass the supply pin to ground. These capacitors should be as close to the LM9022 as is physically possible, and are in addition to any capacitors that may be needed for regulator stability. BYPASS PIN The internal bias circuit (Fig 1) generates an internal refer- ence voltage that is typically equal to one half of V DD. This voltage is available at the bypass pin and is applied directly to the non-inverting input of the inverting driver. Typical applications will require a bypass capacitor in the range of 0.1µF to 1µF to bypass the supply pin to ground. This capacitor should be as close to the LM9022 as is physically possible. SHUTDOWN FUNCTION In order to reduce power consumption while not in use, the LM9022 contains a shutdown pin to externally turn off the amplifier’s bias circuitry. This shutdown feature turns the amplifier off when a logic high is placed on the shutdown pin. The trigger point between a logic low and logic high level is typically half- supply. It is best to switch between ground and supply to provide maximum device performance. By switch- ing the shutdown pin to V DD, the LM9022 supply current draw will be minimized in idle mode. While the device will be disabled with shutdown pin voltages less then V DD, the idle current may be greater than the typical value of 0.6µA. In either case, the shutdown pin should be tied to a definite voltage to avoid unwanted state changes. LM9022 www.national.com 4

Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM9022M Order Number LM9022N LM9022 www.national.com 6

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. National Semiconductor Corporation Americas Email: support@nsc.com National Semiconductor Europe Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: ap.support@nsc.com National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 www.national.com LM9022 Vacuum Fluorescent Display Filament Driver National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the righ t at any time without notice to change said circuitry and specifications.