LED7706 STMicroelectronics, LED7706 Datasheet - Page 29

• Manufacturer Part Number: LED7706
• Description: IC LED DRIVR WHT BCKLT 24-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Backlight, White LEDr

Specifications of LED7706

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 250kHz ~ 1MHz
• Voltage - Supply: 4.5 V ~ 36 V
• Voltage - Output: 36V
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• Current - Output / Channel: 30mA
• Internal Switch(s): Yes
• Operating Supply Voltage: 4.5 V to 36 V
• Maximum Supply Current: 1 mA
• Maximum Power Dissipation: 2300 mW
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• For Use With: 497-10043 - BOARD EVAL LCD BACKLIGHT LED7706497-8360 - BOARD EVAL FOR LED7707497-6445 - EVALUATION BOARD FOR LED7706
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Operating Temperature: -
• Efficiency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

LED7706
6.3.2
6.3.3
best trade off between the different loss contributions varies from manufacturer to
manufacturer.
A 6.8 µH inductor has been experimentally found as the most suitable for applications
running at a 660 kHz switching frequency.
Table 7.
Capacitors selection
The input and output capacitors should have very low ESR (ceramic capacitors) in order to
minimize the ripple voltage. The boost converter of the LED7706 has been designed to
support ceramic capacitors. The required capacitance depends on the programmed LED
current and the minimum dimming frequency (the boost converter is off when the DIM pin is
low and the output capacitor is slowly discharged). Considering the worst case (i.e. 200 Hz
dimming frequency and 30 mA/channel), two 2.2 µF MLCCs are suitable for almost all
applications. Particular care must be taken when selecting the rated voltage and the
dielectric type of the output capacitors: 50 V rated MLCC may show a significant
capacitance drop when biased, especially in case of Y5V dielectric.
As in most of boost converters, the input capacitor is less critical, although it is necessary to
reduce the switching noise on the supply rail. The input capacitor is also important for the
internal LDO of the LED7706 and must be kept as close as possible to the chip. The rated
voltage of the input capacitor can be chosen according to the supply voltage range; a 10 µF
X5R MLCC is recommended.
Table 8.
Flywheel diode selection
The flywheel diode must be a Schottky type to minimize the losses. This component is
subject to an average current equal to the output one and must sustain a reverse voltage
equal to the maximum output rail voltage. Considering all the channels sinking 30mA each
(i.e. 180 mA output current) and the maximum output voltage (36 V), the STP1L40M
(I
involving lower output voltage and/or lower output current.
f,ave
Manufacturer
Taiyo Yuden
Manufacturer
Murata
Murata
= 1 A, V
Coilcraft
Wurth
Recommended inductors
Recommended capacitors
r
= 40 V) diode is a good choice. Smaller diodes can be used in applications
GRM31CR71H225KA88B
GRM31CR71H475KA88B
UMK325BJ106KM-T
Part number
LPS6235-682MLC
Part number
7440650068
Ceramic, 35V, X5R, 20 %
Ceramic, 50V, X7R, 20 %
Ceramic, 50V, X7R, 20 %
6.8 μH, 75 mΩ, 2.7 A
6.8 μH, 33 mΩ, 3.6 A
Description
Description
Application information
SMD 1210
SMD 1206
SMD 1206
Package
10x10 mm
6x6 mm
Size
Notes
C
C
C
OUT
OUT
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IN