LM3431MH National Semiconductor, LM3431MH Datasheet
LM3431MH
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LM3431MH Summary of contents
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... IC and LED array. The enhanced LM3431A features reduced offset voltge for higher accuracy LED current. Typical Application Circuit © 2008 National Semiconductor Corporation Features ■ 3-channel programmable LED current ■ ...
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... Connection Diagram Ordering Information Order Number Operating Temp Range LM3431MHX -40°C to 125°C LM3431MH -40°C to 125°C LM3431AMHX -40°C to 125°C LM3431AMH -40°C to 125°C www.national.com Top View 28 Lead Plastic Exposed Pad TSSOP Package Type Package Drawing TSSOP-28 MXA28A TSSOP-28 MXA28A ...
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Pin Descriptions Pin # Pin Name 1 VIN Power supply input. 2 PGND Power ground pin. Connect to ground. 3 VCC Internal reference voltage output. Bypass to PGND with a minimum 4.7 µF capacitor Boost controller gate drive ...
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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. Voltages from the indicated pins to SGND: VIN EN DIM MODE/F REFIN THM DLY SNSx NDRVx CFB SC AFB Electrical Characteristics apply over the junction temperature (TJ) range of -40°C to +125°C. Unless otherwise stated, V limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm 25° ...
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Symbol Parameter bw SNSx amp bandwidth V LEDOFF voltage LEDOFF V DIM threshold DIM hysteresis T Minimum internal DIM pulse width DIM (Note 8) DIM DIM to NDRV delay time DLY_R DIM DIM to NDRV delay time DLY_F TH MODE/F ...
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Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics. ...
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Typical Performance Characteristics 12V 25° vs. Temperature REF SNS Temperature (LM3431 or LM3431A) OS IQ_SB vs Temperature Unless otherwise specified the following conditions apply Voltage vs. Temperature FB 30041104 ...
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Normalized Switching Frequency vs. Temperature (700 kHz) Line Transient Response LED Ripple Current www.national.com Efficiency vs. Input Voltage LED Current = 140 LED Vf = 25V 30041110 Dimming Transient Response 30041112 30041114 8 30041111 30041113 NDRV Waveforms ...
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Block Diagram 9 30041116 www.national.com ...
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Operation Description The LM3431 combines a boost controller and 3 constant cur- rent regulator controllers in one device. To simplify the de- scription, these two blocks will be described separately as Boost Controller and LED Current Regulator. All descriptions and ...
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SOFT-START The SS/SH pin is a dual function softstart and sample/hold pin. The SH function is described in sections below. When the EN pin is pulled above the programmable UVLO threshold and VCC rises above the internal UVLO threshold, the ...
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FIGURE 3. Switching Frequency vs R For a given application, the maximum switching frequency is limited by the minimum on time. When the LM3431 reaches its minimum on-time, pulse skipping will occur and output rip- ple will increase. To avoid ...
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L will typically give the best performance. CURRENT SENSING Switch current is sensed via the sense resistor, R3, while the switch is on and the inductor is charging. The sensed ...
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INPUT CAPACITOR SELECTION Because the inductor is at the input of a boost converter, the input current waveform is continuous and triangular. The in- ductor ensures that the input capacitor sees relatively low ripple currents. The rms current in the ...
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Rc and Cc is recommended for the compensation network, shown as R9 and C4 in the typical application circuit. The series combination of Rc and Cc introduces a pole-zero pair according to the following equations: where R is ...
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NDRV The NDRV pins drive the base of the external NPN or N- channel MOSFET current regulators. Each pin is capable of driving base current typically. Therefore, NPN devices with sufficient gain must be selected. ...
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To ensure good linearity, select NPN regulators with short and similar rise and fall times. SETTING FF To minimize voltage transients during LED dimming, the out- put voltage is regulated via the AFB pin during LED off times. However, ...
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DLY pin remains high. In this condition, the DLY pin will charge to a maximum of 3.6V (typical). In case of a Type 2 fault, when the DLY voltage reaches 2.8V (typical), the LM3431 will shut down ...
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Shorted LED If an LED fails short circuit, the SC voltage will increase. When SC reaches 3.1V, the same Type 1 fault as an open LED will be triggered. Current in the affected string will continue to be regulated, with ...
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During startup (and re-start), the THM monitor is active. Therefore, the thermistor temperature must be below the restart threshold for the LM3431 to startup. TSD If the LM3431 internal junction temperature increases above 160°C TSD is activated. This is a ...
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Following the important guidelines below will help min- imize switching noise and its effect on current sensing. As shown in Figure 15, ground the output capacitor as close ...
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Physical Dimensions www.national.com inches (millimeters) unless otherwise noted eTSSOP-28 Package 28 Lead Exposed Pad TSOP Package NS Package Number MXA28A 22 ...
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Notes 23 www.national.com ...
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