TLD2311EL_15 Datasheet, PDF (16/34 Pages) Marl International Limited – Basic LED Driver

TLD2311EL
6
IN_SETx Pin
The IN_SET pin is a multiple function pin for output current definition, input and diagnostics:
IN_SETx Pin
Logic
IN_SET
IIN_SET
high impedance
VIN_SET
VIN_SET(OL /SC)
GND
Figure 7 Block Diagram IN_SET pin
6.1
Output Current Adjustment via RSET
The output current of each channel can be adjusted independently. The current adjustment can be done by placing
a low power resistor (R_SET) at the IN_SETx pin to ground. The dimensioning of the resistor can be done using the
formula below:
R_SET
=
-----^k------
I_OUT
(2)
The gain factor k (R_SET * output current) is specified in Pos. 9.2.4 and Pos. 9.2.5. The current through the R_SET is
defined by the resistor itself and the reference voltage V_{IN_SET(ref)}, which is applied to the IN_SET during supplied
device.
6.2
Smart Input Pin
The IN_SETx pin can be connected via R_SET to the open-drain output of a µC or to an external NMOS transistor
as described in Figure 8. This signal can be used to turn off the output stages of the IC. A minimum IN_SET
current of I_{IN_SET(act)} is required to turn on the output stages. This feature is implemented to prevent glimming of
LEDs caused by leakage currents on the IN_SET pin, see Figure 11 for details. In addition, the IN_SET pin offers
the diagnostic feedback information, if the status pin is connected to GND. Another diagnostic possibility is shown
in Figure 9, where the diagnosis information is provided via the ST pin (refer to Chapter 7 and Chapter 8) to a
micro controller. In case of a fault event with the ST pin connected to GND the IN_SET voltage is increased to
V_{IN_SET(OL/SC)} Pos. 8.4.2. Therefore, the device has two voltage domains at the IN_SET-pin, which is shown in
Figure 12.
Note: If one output has a present fault (open load or short circuit) and one or both of the other channels are dimmed
via PWM at the IN_SET-pins a short spike to V_{IN_SET(OL/SC)} is possible. Please refer to Chapter 8.3.
Data Sheet
16
Rev. 1.1, 2015-03-24