LM3533 Datasheet, PDF (14/53 Pages) Texas Instruments – Complete Lighting Power Solution for Smartphone Handsets

LM3533
Operational Description
The LM3533 provides the power for two high-voltage LED strings (up to 40V at 30mA each) and 5 low-voltage LEDs (up to 6V at
30mA each). The two high-voltage LED strings are powered from an integrated boost converter. The five low-voltage LEDs are
powered from an integrated 2X charge pump.
The device is programmable over an I²C-compatible interface. Additional features include a Pulse Width Modulation (PWM) input
for content adjustable brightness control, an ambient light sensor input (ALS) for ambient light current control, and 4 programmable
pattern generators for RGB and indicator blinking functions on the low-voltage LEDs.
CONTROL BANK MAPPING
Control of the LM3533’s current sinks is not done directly, but through the programming of Control Banks. The current sinks are
then assigned to the programmed Control Bank. This allows for a wide variety of current control possibilities where LEDs can be
grouped and controlled via specific Control Banks (see Figure 3).
High-Voltage Control Banks (A/B)
There are 2 high-voltage control banks (A and B). Both high-voltage current sinks can be assigned to either Control Bank A or
Control Bank B. Assigning both current sinks to the same control bank allows for better LED current matching. Assigning each
current sink to different control banks allows for each current sink to be programmed with a different current. The high-voltage
control bank mapping is done via bits [1:0] of the Current Sink Output Configuration Register #1 (address 0x10).
Low-Voltage Control Banks (C, D, E, and F)
There are 4 low-voltage control banks (C, D, E, and F). Any low-voltage current sink (LVLED1-LVLED5) can be assigned to any
of the low-voltage control banks. Assigning every low-voltage current sink to the same control bank allows for the best matching
between LEDs. Assigning each low-voltage current sink to different control banks allows for each current sink to be programmed
with different current levels.
PATTERN GENERATOR
The LM3533 contains 4 independently programmable pattern generators for each Control Bank. Each pattern generator can have
its own separate pattern: different rise and fall times, delays from turn-on, high and low-current settings, and pattern high and low
times.
AMBIENT LIGHT SENSOR INTERFACE
The LM3533 contains an ambient light sensor interface (ALS). The ALS input is designed to connect to the output of either an
analog output or PWM output ambient light sensor. The sensor output (or ambient light information) is digitized and processed by
the LM3533. The light information is then compared against the LM3533’s five user-configurable brightness zones. Each brightness
zone points to a brightness zone target current. Each group of target currents forms an ALS mapper. The LM3533 has three groups
of ALS Mappers where each mapper can be assigned to any of the high or low-voltage control banks (see Figure 7 ).
PWM INPUT
The PWM input which can be assigned to any of the high- or low-voltage control banks. When assigned to a control bank, the
programmed current in the control bank also becomes a function of the duty cycle at the PWM input.
HWEN INPUT
HWEN is the global hardware enable to the LM3533. HWEN must be pulled high to enable the device. HWEN is a high-impedance
input so it cannot be left floating. When HWEN is pulled low the LM3533 is placed in shutdown, and all the registers are reset to
their default state.
THERMAL SHUTDOWN
The LM3533 contains a thermal shutdown protection. In the event the die temperature reaches +140°C, the boost, charge pump
and current sinks will shutdown until the die temperature drops to typically +125°C.
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