LM3532 datasheet(11/52 Pages) TI2

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ILED1

Outputs

(Slaves)

Controls

ALS

Processor

Environmental

Stimulus

PWM

Filters

CABC2

Bank_C

ILED2

ILED3

Bank_B

Bank_A

ALSP_1

PWM_0

PWM_1

CABC1

ALS2

ALS1

(Masters: Output configuration)

(Ramp rates, brightness management)

(ALS processor select, enable)

LM3532

www.ti.com

SNVS653E – JULY 2011 – REVISED AUGUST 2015

Feature Description (continued)

Figure 11. LM3532 Functional Control Diagram

7.3.5 PWM Inputs

The LM3532 provides two PWM inputs (PWM1 and PWM2) which can be mapped to any of the three Control

Banks. PWM input mapping is done through the Control A PWM Configuration register, the Control B PWM

Configuration register, and the Control C PWM Configuration register.

Both PWM inputs (PWM1 and PWM2) feed into internal level shifters and lowpass filters. This allows the PWM

inputs to accept logic level signals and convert them to analog control signals which can control the assigned

Control Banks LED current. The internal lowpass filter at each PWM input has a typical corner frequency of 540

Hz with a Q of 0.5. This gives a low end useful PWM frequency of around 2 kHz. Frequencies lower than this

cause the LED current to show larger ripple and result in non-linear behavior vs. duty cycle due to the response

time of the boost circuit. The upper boundary of the PWM frequency is greater than 100 kHz. Frequencies above

200 kHz begin to show non linear behavior due to propagation delays through the PWM input circuitry.

7.3.6 Full-Scale LED Current

There are 32 programmable full-scale current settings for each of the three control banks (Control A, Control B,

and Control C). Each control bank has its own independent full-scale current setting (ILED_FULL_SCALE). Full-scale

current for the respective Control Bank is set via the Control A Full-Scale Current Register, the Control B Full-

Scale Current Register, and the Control C Full-Scale Current Register (see Table 12).

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