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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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LP55231 Datenblatt(PDF) 37 Page - Texas Instruments |
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LP55231 Datenblatt(HTML) 37 Page - Texas Instruments |
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37 / 53 page  LP55231 www.ti.com SNOSCR5 – MARCH 2013 • See description above for ENG1 MAPPING register. 74H ENG3 MAPPING MSB • Valid engine 3-to-LED -mapping information can be read from ENG3 MAPPING register. • 74H — Bit [0] D9 • See description above for ENG1 MAPPING register. 75H ENG3 MAPPING LSB • 75H — Bit [7] D8 to Bit [0] D1 • See description above for ENG1 MAPPING register. 76H GAIN_CHANGE_CTRL • With hysteresis and timer bits the user can optimize the charge pump performance to better meet the requirements of the application at hand. Some applications need to be optimized for efficiency and others need to be optimized for minimum EMI, for example. • 76H - Bits[7:6] THRESHOLD • Threshold voltage (typ.) pre-setting. Bits set the threshold voltage at which the charge-pump gain changes from 1.5x to 1x. The threshold voltage is defined as the voltage difference between highest voltage output (D1 to D6) and input voltage VDD: VTHRESHOLD = VDD - MAX(voltage on D1 to D6). • If VTHRESHOLD is larger than the set value (100 mV to 400 mV), the charge pump is in 1x mode. • 00 = 400 mV • 01 = 300 mV • 10 = 200 mV • 11 = 100 mV • Values above are typical and should not be used as product-specification. • Writing to threshold [7:6] bits by the user overrides factory settings. Factory settings aren't user-accessible. • 76H - Bit [5] ADAPTIVE_TRESH_EN • 1 = Adaptive threshold enabled. • 0 = Adaptive threshold disabled. • Gain-change hysteresis prevents the mode from toggling back and forth (1x -> 1.5x -> 1x...) , which would cause ripple on VIN and LED flicker. When the adaptive threshold is enabled, the width of the hysteresis region depends on the choice of threshold bits (see above), saturation of the current sources, charge pump load current, PWM overlap and temperature. • 76H - Bits [4:3] TIMER • A forced mode change from 1.5x to 1x is attempted at the interval specified with these bits. Mode change is allowed if there is enough voltage over the LED drivers to ensure proper operation. Set FORCE_1x to "1" (see below) to activate this feature. • 00 = 5ms • 01 = 10 ms • 10 = 50 ms • 11 = infinite. The charge pump switches gain from 1x mode to 1.5x mode only. The gain reset back to 1x is enabled under certain conditions, for example in the powersave mode. • 76H - Bit [2] FORCE_1x • Activates forced mode change. In forced mode, charge pump mode change from 1.5x to 1x is attempted at the constant interval specified with the TIMER bits. • 1 = forced mode changes enabled. • 0 = forced mode changes disabled. Copyright © 2013, Texas Instruments Incorporated Submit Documentation Feedback 37 Product Folder Links: LP55231 |
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