STEVAL-ISA056V1 STMicroelectronics, STEVAL-ISA056V1 Datasheet - Page 48

• Manufacturer Part Number: STEVAL-ISA056V1
• Description: BOARD EVAL BASED ON PM6600
• Manufacturer: STMicroelectronics
• Type: PWM Controllersr

Specifications of STEVAL-ISA056V1

• Design Resources: STEVAL-ISA056V1 Gerber Files STEVAL-ISA056V1 Schematic STEVAL-ISA056V1 Bill of Material
• Current - Output / Channel: 30mA
• Outputs And Type: 6, Non-Isolated
• Voltage - Output: 36 V
• Features: Dimmable
• Voltage - Input: 4.5 ~ 28V
• Utilized Ic / Part: PM6600
• Input Voltage: 4.5 V to 28 V
• Output Voltage: 36 V
• Product: Power Management Modules
• Core Chip: PM6600
• Topology: Boost
• No. Of Outputs: 1
• Dimming Control Type: PWM
• Mcu Supported Families: PM6600
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PM6600
• Other names: 497-8414

Application note
Appendix B
B.1
B.2
B.3
48/60
Inductor selection
Being the PM6600 mostly dedicated to notebook backlighting, real-estate applications
dictate severe constrain in selecting the optimal inductor. The inductor choice must take into
account different parameters like conduction losses (DCR), core losses (ferrite or iron-
powder), saturation current and magnetic-flux shielding (core shape and technology).
The switching frequency of the PM6600 can be set in the 200 kHz-1 MHz range, allowing a
wide selecting room for the inductance value. Low switching frequencies takes to high
inductance value, resulting in significant DCR and size. On the other hand, high switching
frequencies result in significant core losses. The suggested range is 4.7-22 µH, even if the
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.
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 PM6600 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 30mA/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 PM6600 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.
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 30 mA each
(i.e. 180 mA output current) and the maximum output voltage (36 V), the STPS1L40M
(I
involving lower output voltage and/or lower output current.
f,ave
= 1 A, V
Application note
r
= 40 V) diode is a good choice. Smaller diodes can be used in applications
Doc ID 14248 Rev 7
PM6600