lm2711 National Semiconductor Corporation, lm2711 Datasheet
lm2711
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lm2711 Summary of contents
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... LM2711 Step-up PWM DC/DC Converter Integrated with 4 Buffers General Description The LM2711 is a compact bias solution for TFT displays. It has a current mode PWM step-up DC/DC converter with a 1.4A, 0.17Ω internal switch. Capable of generating 8V at 300mA from a Lithium Ion battery, the LM2711 is ideal for generating bias voltages for large screen LCD panels. The LM2711 can be operated at switching frequencies of 600kHz or 1 ...
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Connection Diagram Pin Description Pin Name SHDN 4 FSLCT 5 Vs+ 6 GMA1-in 7 GMA2-in 8 GMA3-in 9 GMA4- GMA4-out 13 GMA3-out 14 GMA2-out 15 GMA1-out 16 SS ...
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... NC(Pin 10):No Connection. NC(Pin 11): No Connection. Ordering Information Order Number Package Type LM2711MT-ADJ LM2711MTX-ADJ GMA4-out(Pin 12): Gamma Buffer output pin. GMA3-out(Pin13): Gamma Buffer output pin. GMA2-out(Pin 14): Gamma Buffer output pin. GMA1-out(Pin 15): Gamma Buffer output pin. SS(Pin 16): Softstart pin. Connect capacitor to SS pin and AGND to slowly ramp inductor current on startup ...
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Block Diagrams www.national.com 20046803 20046851 4 ...
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Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications Voltage SW FB Voltage V Voltage C SHDN Voltage FSLCT Voltage Supply Voltage, Vs+ Buffer Input ...
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Electrical Characteristics Specifications in standard type face are for T ture Range ( T = −40˚C to +125˚C). Unless otherwise specified BUFFERS Symbol Parameter V Input offset voltage OS ∆V /∆T Offset Voltage Drift os I Input Bias ...
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Typical Performance Characteristics Efficiency vs. Load Current ( 600 kHz) OUT S Efficiency vs. Load Current (V = 10V 1.25 MHz) OUT S Switch Current Limit vs. V Efficiency vs. Load Current (V 20046826 ...
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Typical Performance Characteristics I vs (600 kHz, not switching (1.25 MHz, not switching (In shutdown) www.national.com (Continued) 20046821 (1.25 MHz, switching) 20046821 20046818 8 I vs. V ...
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Typical Performance Characteristics Frequency vs (1.25 MHz) C Pin Current vs Load Transient Response 600kHz OUT IN 1) Load, 80mA to 260mA to 80mA 500mA/div, ...
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Typical Performance Characteristics Internal Soft Start 27Ω none 600kHz OUT IN LOAD SS 1) SHDN, 1V/div 500mA/div 5V/div, DC ...
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Typical Performance Characteristics Output Voltage vs. Output Current (sinking) Supply Current vs. Common Mode Voltage Large Signal Step Response (no ext. compensation) (Continued) Output Voltage vs. Output Current 20046864 Large Signal Step Response (50Ω, 1nF ext. compensation) 20046866 Positive Slew ...
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Typical Performance Characteristics Negative Slew Rate vs. Capacitive Load Unity Gain Frequency vs. Capacitive Load PSRR vs. Frequency www.national.com (Continued) Phase Margin vs. Capacitive Load 20046870 CMRR vs. Frequency 20046872 20046874 12 20046871 20046873 ...
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... SOFT-START CAPACITOR The LM2711 has patented internal circuitry that is used to limit the inductor inrush current on start-up. This inrush current limiting circuitry serves as a soft-start. However, many applications may require much more soft-start than what is available with the internal circuitry ...
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... INTRODUCTION TO COMPENSATION = 330nF 4ms/div, 20046880 FIGURE 2. (a) Inductor current. (b) Diode current. The LM2711 is a current mode PWM boost converter. The signal flow of this control scheme has two feedback loops, one that senses switch current and one that senses output voltage. To keep a current programmed control converter stable above duty cycles of 50%, the inductor must meet certain criteria ...
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... A high phase margin (greater than 45˚) is desired for the best stability and transient response. For the purpose of stabilizing the LM2711, choosing a crossover point well be- low where the right half plane zero is located will ensure sufficient phase margin. A discussion of the right half plane zero and checking the crossover using the DC gain will follow ...
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... SON the Typical Performance Characteristics section. C BUFFER (Vcom and GMAx) COMPENSATION The architecture used for the buffers in the LM2711 requires external compensation on the output. Depending on the equivalent capacitive load of the TFT-LCD panel, external components at the buffer outputs may or may not be neces- sary ...
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... LAYOUT CONSIDERATIONS The LM2711 uses two separate ground connections, GND for the driver and NMOS power device of the boost regulator and AGND for the sensitive analog control circuitry of the boost regulator and the V and Gamma buffers ...
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Application Information www.national.com FIGURE 5. 600kHz, 8V Application FIGURE 6. 1.25MHz, 5V Application 18 20046859 20046884 ...
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Application Information (Continued) FIGURE 7. 1.25MHz, 10V Application FIGURE 8. 1.25MHz, 12V Application 19 20046885 20046886 www.national.com ...
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... 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 ...