STLED25JR STMicroelectronics, STLED25JR Datasheet - Page 17

• Manufacturer Part Number: STLED25JR
• Description: LED Lighting Drivers 5-Ch LED Step Up WH LED 2.3V to 5.5V
• Manufacturer: STMicroelectronics

Specifications of STLED25JR

• Product Category: LED Lighting Drivers
• Rohs: yes

STLED25
6
6.1
6.2
6.3
Detailed description
The STLED25 is a high efficiency white LED power supply which integrates a step-up
converter and 5 high-side current sources. The device is controlled by two enable inputs
called EN13 and EN45 according to the labels of the LED channels. EN13 enables LED
channels 1, 2, 3 and EN45 enables LED channels 4, 5. The device is protected against
shorted LED channels by short LED protection and against open LED channels by open
LED protection. The device is able to recognize which channel has failed, and switch off this
channel to maintain correct operation of the remaining channels. The STLED25 device is
125 mA total output current capable and works over a battery voltage range of 2.3 V to 5.5
V. The typical output voltage during operation corresponds to the voltage level equal to
V
high level of application efficiency (86%) with the typical battery voltage of 3.7 V. The device
is also able to work at high efficiency when not all the LED channels of the device are used.
Boost DC-DC converter operation
The step-up bridge with current mode control of the regulation regulates the output voltage
level according to the LED channel with the highest V
voltage headroom for the related current sources. The typical headroom of the current
sources is in the range of 135 mV. The STLED25 contains a current limiter, with a typical
value 600 mA, and soft-start control to limit the supply current from the battery. The method
of regulation during startup and normal operation is explained in
Current setting
Each LED channel regulates to the same current. The value of the LED current is set by
choosing the R
obtain the LED current. The multiplication factor is 390.
The LED current is calculated with the following formula:
Equation 1
where:
V
EN13 and EN45
EN13 and EN45 play the dual role of enable pin and PWM dimming. EN13 drives strings
D1, D2, D3 while EN45 drives D4 and D5. Both EN13 and EN45 are pulled down internally
by 100 k resistors.
The EN pins accept a signal between 100 Hz and 800 Hz, at duty cycles from 0.39% to
100%. The output average current maximum error is 10% at 0.39%, PWM duty cycle at 300
Hz.
FLED
SET
= 1.28 V typical
+ 125 mV. The STLED25 device has an optimized switching power bridge to reach a
SET
resistor. The current flowing through this resistor is mirrored in order to
Doc ID 022323 Rev 3
I
LED
=
R
V
SET
SET
×
390
FLED
, in order to maintain sufficient
Section 6.4
Detailed description
.
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