a8500 Allegro MicroSystems, Inc., a8500 Datasheet
a8500
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a8500 Summary of contents
Page 1
... Each LED channel can sink 25 mA, and channels can be paralleled for higher currents. Flexible dimming allows output channels to either run at an adjustable DC value or with externally controlled PWM duty cycles. The A8500 is available pin × QFN/MLP package that is only 0.75 mm nominal in height. Applications include: ▪ Thin notebook displays ▪ ...
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... A8500 Selection Guide Part Number A8500EECTR × QFN/MLP *Contact Allegro for additional packing options Device package is lead (Pb) free, with 100% matte tin leadframe plating. Absolute Maximum Ratings Characteristic SW and OVP Pins LED1 through LED8 Pins VIN Pin Remaining Pins ...
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... A8500 ±10 VIN COMP C C Reference and Soft Start SKIP FSET 100 kΩ R FSET AGND EN 100 kΩ Serial Interface SEL1 PWM Generator SEL2 SEL3 PWM 100 kΩ ISET Amp R ISET APWM Flexible WLED/RGB Backlight Driver Functional Block Diagram ...
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... A8500 ELECTRICAL CHARACTERISTICS, valid at T Characteristics Input Voltage Range Undervoltage Lockout Threshold UVLO Hysteresis Window Supply Current APWM Frequency Range Error Amplifier Error Amplifier Open Loop Gain Error Amplifier Unity Gain Bandwidth Error Amplifier Transconductance Error Amplifier Output Sink Current Error Amplifier Output Source Current ...
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... A8500 ELECTRICAL CHARACTERISTICS (continued), valid at T otherwise noted Characteristics LED Current Sinks LEDx Regulation Voltage Current Gain SET LEDx Voltage on ISET Pin I Allowable Current Range SET LEDx Accuracy LEDx Matching LEDx Switch Leakage Current LEDx Switch Leakage Current Serial Pulse Timing (see figure 4 for further explanation) ...
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... A8500 Efficiency with EN dimming is similar to that with APWM dimming. APWM light load efficiency can be improved by reducing boost switching frequency with SKIP set high. PWM Efficiency ch. with 7 LEDs per ch per ch (V) BAT 80 5 8.5 17 Duty Cycle (%) ...
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... A8500 EN Pin Turn ch., 8 LEDs per ch. IN BAT Symbol Parameter Units/Division OUT C3 V OUT time PWM Turn On at 50% Duty Cycle ch., 8 LEDs per ch. IN BAT Symbol Parameter Units/Division ...
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... For higher LED power or more LEDs, an inductor can be connected to a separate power supply, V the A8500 IC powered from source. The LED sinks can sink current. The boost converter is a constant frequency current-mode con- verter. The integrated boost DMOS switch is rated for ...
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... Note: Only one dimming technique can be used at a time. Serial Dimming Through the EN Pin. high with PWM, and the APWM pin is low, the A8500 starts up in serial programming mode. In this mode, series of pulses applied to the EN pin are used to adjust the output current level, ...
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... On/off Control (PWM) with an External PWM Signal on the When the PWM pin is pulled high with the EN and PWM Pin. APWM pins low, the A8500 turns on and all enabled LEDx pins sink 100% current. When the PWM pin is pulled low, the IC EN ...
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... Analog Dimming with an External PWM Signal on the APWM When the APWM pin is pulled high, with the EN and PWM Pin. pins low, the A8500 turns on in this mode. The first pulse after shutdown should be greater than t HI(init) signal applied to the APWM pin multiplies I to set the reference current level for the LED pins ...
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... The A8500 has protection against open Open LED Protection. LEDs. If any enabled LED string opens, voltage on the corre- sponding LEDx pin goes to zero. The boost loop operates in open loop till the OVP level is reached. The A8500 identifies the open I OUT V OUT ...
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... Figure 14. Typical accuracy, normalized to the 100% current level, LEDX versus dimming level, with ±10% ROVP VIN SW SW OVP EN PWM AGND APWM PGND SKIP A8500 COMP SEL3 FSET SEL2 SEL1 ISET LED2 LED1 LED3 LED5 LED7 LGND LED8 LED6 LED4 for Medium Size LCDs ISET RISETP RISET Q1 1 ...
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... Medium Size LCDs COUT AGND PGND V SEL3 IN SEL2 SEL1 LED1 Part Number Vendor C3216X7R1H105K TDK C3216X7R1H105K TDK IR 10MQ060NTRPBF International Rectifier A8500 Allegro MicroSystems SLF6028T-100M1R3-PF TDK Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 14 ...
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... A8500 Terminal List Table Number Name 1 PGND Power ground pin. Reduces boost switching frequency in case of light load to improve frequency. Normally, this pin should be low; when 2 SKIP high divided COMP Compensation pin; connect external compensation network for boost converter. ...
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... A8500 (Top View) D 27X 0.08 C 0.20 0.40 0. (Bottom View) Copyright ©2006, 2007, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec tions as may be required to per- mit improvements in the per for mance, reliability, or manufacturability of its products ...