LM3532TMX-40ANOPB National Semiconductor Corporation, LM3532TMX-40ANOPB Datasheet - Page 13

• Manufacturer Part Number: LM3532TMX-40ANOPB
• Description: High Efficiency White Led Driver With Programmable Ambient Light Sensing Capability And I2c-compatible Interface
• Manufacturer: National Semiconductor Corporation

LM3532 CURRENT SINK CONFIGURATION
Control of the LM3532’s three current sinks is done by con-
figuring the three internal control banks (Control A, Control B,
and Control C) (see
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 Configu-
ration 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 2kHz. Frequen-
cies lower then this will cause the LED current to show larger
ripple and result in non-linear behavior vs. duty cycle due to
Figure
2). Any of the current sinks (ILED1,
FIGURE 2. LM3532 Functional Control Diagram
13
ILED2, or ILED3) can be mapped to any of the three control
banks. Configuration of the control banks is done via the Out-
put Configuration register.
the response time of the boost circuit. The upper boundary of
the PWM frequency is greater than 100 kHz. Frequencies
above 200 kHz will begin to show non linear behavior due to
propagation delays through the PWM input circuitry.
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 (I
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
12).
LED_FULL_SCALE
). Full-scale current for
30115414
www.national.com
Table