TLD1125EL_15 Datasheet, PDF (30/36 Pages) Marl International Limited – Basic LED Driver

TLD1125EL
Power Stage
11
Power Stage
The output stage is realized as high side current source with a current of 360 mA. During off state the leakage
current at the output stage is minimized in order to prevent a slightly glowing LED.
The maximum current of the channel is limited by the power dissipation and used PCB cooling areas (which results
in the applications R_thJA).
For an operating current control loop the supply and output voltages according to the following parameters have
to be considered:
• Required supply voltage for current control V_S(CC), Pos. 6.3.10
• Voltage drop over output stage during current control V_PS(CC), Pos. 11.2.6
• Required output voltage for current control V_OUT(CC), Pos. 11.2.7
11.1
Protection
The device provides embedded protective functions, which are designed to prevent IC destruction under fault
conditions described in this data sheet. Fault conditions are considered as “outside” normal operating range.
Protective functions are neither designed for continuous nor for repetitive operation.
11.1.1 Over Load Behavior
An over load detection circuit is integrated in the Basic LED Driver IC. It is realized by a temperature monitoring
of the output stage (OUT).
As soon as the junction temperature exceeds the current reduction temperature threshold T_j(CRT) the output current
will be reduced by the device by reducing the IN_SET reference voltage V_{IN_SET(ref)}. This feature avoids LED’s
flickering during static output overload conditions. Furthermore, it protects LEDs against over temperature, which
are mounted thermally close to the device. If the device temperature still increases, the output current decreases
close to 0 A. As soon as the device cools down the output current rises again.
IOU T
VIN_ SET
T_{j (CR T)}
T_j
Figure 25 Output current reduction at high temperature
Note: This high temperature output current reduction is realized by reducing the IN_SET reference voltage voltage
(Pos. 10.3.1). In case of very high power loss applied to the device and very high junction temperature the
output current may drop down to I_OUT = 0 mA, after a slight cooling down the current increases again.
11.1.2 Reverse Battery Protection
The TLD1125EL has an integrated reverse battery protection feature. This feature protects the driver IC itself, but
also connected LEDs. The output reverse current is limited to I_OUTx(rev) by the reverse battery protection.
Data Sheet
30
Rev. 1.0, 2013-08-08