INFINEON TLE 4241 GM User Manual
LED Driver with Adjustable Current
TLE 4241 GM
Features
• Adjustable constant output current
• Wide input voltage range
• Low drop voltage
• Open load detection
• Overtemperature protection
• Short circuit proof
• Reverse polarity proof
T
• Wide temperature range: -40 °C <
< 150 °C
j
• Very small SMD-Package
Functional Description
The TLE 4241 GM is an integrated adjustable constant current source. It provides an
output current adjustable via different means (SET, PWM, reference resistor) which is
kept nearly independent from load and supply voltage changes. The IC is designed to
supply LEDs under the severe conditions of automotive applications resulting in constant
brightness and extended LED lifetime. It is provided in the very small P-DSO-8-9
(Micro 8) package. Protection circuits prevent damage to the device in case of overload,
short circuit, reverse polarity and overtemperature. The connected LEDs are pr otected
against reverse polarity as well as excess voltages up to 45 V. A status output allows
handling of open load and short circuit at the main output.
A PWM input offers the possibility to adjust the LED brightness by pulse width
modulation.
With an implemented high/low current switch the output current level can be reduced e.g.
for brake/tail light application.
The implemented features such as adjustable output current, the high/low current switch
and the provided PWM input make the device well suited for a broad ran ge of LED an d
other applications.
P-DSO-8-3, -6, -7, -8, -9
Type Ordering Code Package
TLE 4241 GM Q67006-A9644 P-DSO-8-9
Data Sheet 1 Rev. 1.2, 2004-04-13
Circuit Description
TLE 4241 GM
Q
REF
AEB03003
ST
PWM
SET
I
Regulation
High
Status
Regulation
Low
Control
Reference
Voltage
GND
V/I Converter
Figure 1 Block Diagram
An internal reference voltage of typ. 1.20 V supplies the REF pin which is connected to
GND via an external resistor. In the SET = H mode the reference current flowing on the
REF pin is mirrored with an amplification to form the desired output current. The typ.
output current in the SET = H mode calculates:
1.20
I
/mA
Qtyp,
----------------------
R
REF
/kΩ
487 0.1+×=
(1)
The output current is shown as a function of the reference resistance on Page 10 for the
high as well as for the low current mode.
With the PWM input the LED brightness can be regulated via duty cycle. Also PWM = L
sets the TLE 4241 in sleep mode resulting in a very low current consumption of << 1 µA
I
typ. Due to the high impedance of the PWM input (see timing diagram
PWM
versus V
PWM
on Page 12) the PWM pin can thus also be used as an Enable input.
Data Sheet 2 Rev. 1.2, 2004-04-13
TLE 4241 GM
81GND
I
ST 2 7
PWM 3 6
SET 4 5
Figure 2 Pin Configuration (top view)
Table 1 Pin Definitions and Functions
Pin No. Symbol Function
1GNDGround; internally connected to pin 5
2STStatus Output; open collector output, connect to external
pull-up resistor (10 kΩ or higher)
3PWMPulse Width Modulation Input; if not needed connect to
4 SET High/Low Current Input; choice of current level
5GNDGround; internally connected to pin 1
6REFReference Input; connect to GND via an external resistor to
adjust the output current
7QOutput
8IInput; block to GND directly at the IC with a 100 nF ceramic
capacitor
Q
REF
GND
AEP03002
V
I
Data Sheet 3 Rev. 1.2, 2004-04-13
Application Information
µC
V
Q
WD R
10 k
TLE 4241 GM
W
RO
TLE 4271
22 µF
Ω
ST
PWM
SET
TLE 4241G
I
Q
R
REF
100 nF
V
Batt
LA E67B
OSRAM
AED03098
Figure 3 Application Circuit
Figure 3 shows a typical application with the TLE 4241 GM LED driver. The 3 LEDs are
driven with an adequate supply current adjusted by the resistor R
. Thus brightness
REF
variations due to forward voltage spread of the LEDs are prevented. The lumi nosity
spread arising from the LED production process can be compensated via software by an
appropriate duty cycle applied to the PWM pin. Hence selection of the LEDs to forward
voltage as well as to luminosity classes can be spared. The slightly negative temperature
coefficient of the TLE 4241 GM output current protects the LEDs against overtemperature stress if the IC is placed nearby the LEDs.
V
The voltage drop (
- VQ) across the TLE 4241 GM is monitored in order to detect an
I
open load condition indicated at the status ou tput pin ST. In case of open load, the
voltage drop will decrease below the lower status switching threshold V
. Hence, the
dr,L
status output ST will be driven low. In normal operation , the voltage drop is above the
V
upper status threshold
, thus the open collector output ST is in high-ohmic state (see
dr,H
also section Status Output at the Electrical Characteristics).
The function of ST, SET and PWM as well as their timings are shown in Figure 4.
Data Sheet 4 Rev. 1.2, 2004-04-13
TLE 4241 GM
V
I
V
V
PWM, H
V
V
V
PWM
PWM, L
V
SET
SET, H
SET, L
I
mA
V
ST
V
STL
t
t
t
SET, L
t
Q
SET, H
t
PWM, ON
t
PWM, OFF
47
10
t
t
Open Load
t
AET03339.VSD
Figure 4 Function and Timing Diagram
Data Sheet 5 Rev. 1.2, 2004-04-13
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