LM3532 datasheet(14/52 Pages) TI2

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BRIGHTNESS CODE (D)

16 32

64 80 96 112 128 144 160 176 192 208 224 240 256

LM3532

SNVS653E – JULY 2011 – REVISED AUGUST 2015

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Device Functional Modes (continued)

Figure 13. Linear Mapping Response

7.4.7 LED Current Control

Once the full-scale current is set, control of the LM3532 device’s LED current can be done via 2 methods:

1. I2C Current Control

2. Ambient Light Sensor Current Control

I2C current control allows for the direct control of the LED current by writing directly to the specific brightness

interface.

7.4.7.1 I2C Current Control

I2C current control is accomplished by using one of the Zone Target Registers (for the respective Control Bank)

as the brightness register. This is done via bits[4:2] of the Control (A, B, or C) Brightness Registers (see Table 9,

Table 10, and Table 11). For example, programming bits[4:2] of the Control A Brightness Register with (000)

makes the brightness register for Bank A (in I2C Current Control) the Control A Zone Target 0 Register.

7.4.7.2 I2C Current Control With PWM

I2C current control can also incorporate the PWM duty cycle at one of the PWM inputs (PWM1 or PWM2). In this

situation the LED current is then a function of both the code in the programmed brightness register and the duty

cycle input into the assigned PWM inputs (PWM1 or PWM2).

7.4.8 Assigning and Enabling a PWM Input

To make the backlight current a function of the PWM input duty cycle, one of the PWM inputs must first be

assigned to a particular Control Bank. This is done via bit [0] of the Control A, B, or C PWM Registers (see

Table 6, Table 7, or Table 8). After assigning a PWM input to a Control Bank, the PWM input is then enabled via

bits [6:2] of the Control A/B/C PWM Enable Registers. Each enable bit is associated with a specific Zone Target

7.4.9 Enabling a Current Sink

Once the brightness register and PWM inputs are configured in I2C Current Control, the current sinks assigned to

the specific control bank are enabled via the Control Enable Register (see Table 14). Table 1 below shows the

possible configurations for Control Bank A in I2C Current Control. Table 1 would also apply to Control Bank B

and Control Bank C.

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