LP5523 datasheet(36/56 Pages) TI1

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LP5523

SNVS550D – SEPTEMBER 2009 – REVISED MAY 2013

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74H — Bit [7] GPO

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See description above for ENG1 MAPPING register.

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74H — Bit [0] D9

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See description above for ENG1 MAPPING register.

75H ENG3 MAPPING LSB

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75H — Bit [7] D8 to Bit [0] D1

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See description above for ENG1 MAPPING register.

76H GAIN_CHANGE_CTRL

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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.

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76H - Bits[7:6] THRESHOLD

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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).

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If VTHRESHOLD is larger than the set value (100 mV to 400 mV), the charge pump is in 1x mode.

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00 = 400 mV

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01 = 300 mV

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10 = 200 mV

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11 = 100 mV

NOTE

Values above are typical and should not be used as product-specification.

NOTE

Writing to threshold [7:6] bits by the user overrides factory settings. Factory settings

aren't user-accessible.

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76H - Bit [5] ADAPTIVE_TRESH_EN

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1 = Adaptive threshold enabled.

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0 = Adaptive threshold disabled.

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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.

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76H - Bits [4:3] TIMER

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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.

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00 = 5ms

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01 = 10 ms

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10 = 50 ms

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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.

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76H - Bit [2] FORCE_1x

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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.

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1 = forced mode changes enabled.

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0 = forced mode changes disabled.

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