LP55231 datasheet(37/59 Pages) TI2

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LP55231

www.ti.com

SNOSCR5D – MARCH 2013 – REVISED DECEMBER 2016

Product Folder Links: LP55231

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Valid engine 3-to-LED -mapping information can be read from ENG3 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 (typical) pre-setting. Bits set the threshold voltage at which the charge-pump gain changes

from 1.5× to 1×. 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

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

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Writing to threshold [7:6] bits by the user overrides factory settings. Factory settings are not 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 (1×

≥ 1.5× ≥ 1×...) , 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 1.5× to 1× 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 1×mode to 1.5× 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_1×

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Activates forced mode change. In forced mode, charge pump mode change from 1.5× to 1× 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.

7.6.3 Instruction Set

The LP55231 has three independent programmable execution engines. All the program execution engines have

their own program memory block allocated by the user. Note that in order to access program memory the

operation mode needs to be load program, at least for one of the three program execution engines. Program

execution is clocked with a 32.7-kHz clock. This clock can be generated internally or an external 32-kHz clock

can be connected to CLK pin. Using an external clock enables synchronization of LED timing to the external

clock signal.

Supported instruction set is listed in Table 4, Table 5, Table 6, and Table 7 below:

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