STEVAL-ILL021V1 STMicroelectronics, STEVAL-ILL021V1 Datasheet - Page 34
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STEVAL-ILL021V1
Manufacturer Part Number
STEVAL-ILL021V1
Description
BOARD EVAL LCD BACKLIGHT LED7707
Manufacturer
STMicroelectronics
Specifications of STEVAL-ILL021V1
Design Resources
STEVAL-ILL021V1 Bill of Material STEVAL-ILL021V1 Schematic
Current - Output / Channel
85mA
Outputs And Type
6, Non-Isolated
Voltage - Output
36 V
Features
Dimmable, Extra 5V Output
Voltage - Input
4.5 ~ 36 V
Utilized Ic / Part
LED7707
Description/function
LCD backlight demonstration board
Operating Voltage
4.5 V to 36 V
Product
Display Modules
Core Chip
LED7707
No. Of Outputs
1
Output Voltage
36V
Dimming Control Type
PWM
Mcu Supported Families
LED7707
Lead Free Status / RoHS Status
Lead free by exemption / RoHS compliant by exemption
For Use With/related Products
LED7707
Other names
497-10044
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
STEVAL-ILL021V1
Manufacturer:
STMicroelectronics
Quantity:
1
Application information
6.4.5
34/47
T
Equation 35
defining D
Equation 36
The worst case for the output voltage ripple is when input voltage is lower (V
A simple way to select the C
In order to affect as less as possible the current generators, it would be better to fix the
maximum ripple lower than the typical voltage across the generators.
For example considering ΔV
leading generator), the required capacitance is:
Equation 37
A margin from the calculated value should be taken into account because of the
capacitance drop due to the applied voltage when MLCCs are used.
One 10 µF MLCC (or two 4.7 µF MLCCs) can be a good choice for this application.
In case a dimming duty cycle different from 100% is used, a further contribution to the
capacitor discharge (during the off time of the dimming cycle) should be considered.
Input capacitor choice
The input capacitor of a boost converter is less critical than the output capacitor, due to the
fact that the inductor is in series with the input, and hence, the input current waveform is
continuous.
A low ESR capacitor is always recommended.
A capacitor of 10 µF is tentatively a good choice for most of the applications.
OFF
can be calculated as:
2
as:
D
T
2
OFF
=
=
C
2
OUT
OUT
R
T
OUT
⋅
SW
F
0
SW
⋅
lower than 70 mV (i.e. the 10 % of the voltage across the
value is fixing a maximum voltage ripple.
(
⋅
M
>
D
⋅
L
(
−
2
I
, L
⋅
1
=
peak
M
)
2
⎧
⎨
⎩
Δ ⋅
618
569
=
−
⎧
⎨
⎩
V
I
. 0
. 0
OUT
OUT
2 .
7 .
408
376
ns
ns
,
max
)
⋅
T
@
@
OFF
@
@
V
=
V
V
V
IN
IN
. 6
IN
IN
,
,
max
min
,
,
33
max
min
μ
=
=
=
F
=
10
13
10
13
8 .
2 .
8 .
2 .
V
V
V
V
IN,min
= 10.8 V).
LED7707