TLE4242G Datasheet, PDF (2/13 Pages) Infineon Technologies AG – Adjustable LED Driver

TLE 4242 G
Circuit Description
I¹
PWM ²
Bias Supply
Bandgap
Reference
Comparator
Status
Delay
7Q
5 _REF
3 _ST
4
6
GND
D
AEB03500.VSD
Figure 1 Block Diagram
An external shunt resistor in the ground path of the connected LEDs is used to sense the
LED current. A regulation loop helds the voltage drop at the shunt resistor on a constant
level of typ. 177 mV. Selecting the shunt resistance permits to adjust the appropriate
constant current level. The typ. output current calculates
I_{Q, typ}
=
V_{-----R---E---F-}
R_REF
(1)
where V_REF is the reference voltage with a typical level of 177 mV (see Page 10). The
equation applies in a range of 0.39 Ω ≤ R_REF ≤ 1.8 Ω.
The output current is shown as a function of the reference resistance on Page 10. With
the PWM input the LED brightness can be regulated via duty cycle. Also PWM = L sets
the TLE 4242 in sleep mode resulting in a very low current consumption of << 1 µA typ.
Due to the high impedance of the PWM input (see “PWM Pin Input Current versus
PWM Voltage” on Page 11) the PWM pin can thus also be used as an enable input.
Data Sheet
2
Rev. 1.0, 2004-01-01