TLD5098EL Datasheet, PDF (16/39 Pages) Infineon Technologies AG – DC/DC Boost, Buck-Boost, SEPIC controller

TLD5098EL
Enable and Dimming Function
7
Enable and Dimming Function
7.1
Description
The enable function powers ON or OFF the device. A valid logic LOW signal on enable pin EN/PWMI powers OFF
the device and current consumption is less than I_{q_OFF} (Parameter 7.2.14). A valid logic HIGH enable signal on
enable pin EN/PWMI powers on the device. The enable function features an integrated pull down resistor which
ensures that the IC is shut down and the power switch is OFF in case the enable pin EN is left open.
In addition to the enable function described above, the EN/PWMI pin detects a pulse width modulated (PWM) input
signal that is fed through to an internal gate driver. The internal gate driver outputs the same PWM signal on the
PWMO pin to an external N-channel enhancement mode MOSFET for PWM dimming an LED load. PWM dimming
an LED is a commonly practiced dimming method and can prevent color shift in an LED light source. Moreover
the PWM output function may also be used to drive other types of loads besides LED.
The enable and PWM input function share the same pin. Therefore a valid logic LOW signal at the EN/PWMI pin
needs to differentiate between an enable power OFF or an PWM dimming LOW signal. The device differentiates
between enable OFF and PWM dimming signal by requiring the enable OFF at the EN/PWMI pin to stay LOW for
the Enable Turn OFF Delay Time (t_EN,OFF,DEL Parameter 7.2.6).
IN
14
Enable
LDO
IVCC
1
Microcontroller
EN / PWMI
13
Enable / PWMI
Logic
Enable
Gate
Driver
SWO
2
PWMI
Gate
Driver
PWMO
5
Figure 6 Block Diagram and Simplified Application Circuit Enable and LED Dimming
Datasheet
16
Rev. 1.0, 2010-10-13