STEVAL-ILL021V1 STMicroelectronics, STEVAL-ILL021V1 Datasheet - Page 33

• 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

LED7707
6.4.4
Output capacitor choice
The choice of the output capacitor is mainly affected by the desired output voltage ripple.
Since the voltage across the LEDs can be considered almost constant, this ripple is
transferred across the current generators, affecting their dynamic response.
The output ripple can be estimated as (neglecting the contribution of ESR of C
in case of MLCC):
Equation 31
where I
Equation 32
whereas D, working in DCM, is:
Equation 33
defining M as:
Equation 34
Figure 21. Inductor current in DCM operation
I
L, peak
I
L, peak
L
T
ON
is the inductor peak current (see
D
T
=
SW
I
T
, L
OFF
= 1/F
peak
2
⋅
M
F
sw
SW
=
=
⋅
F
V
V
Δ
L
R
sw
IN
V
OUT
V
⋅
0
IN
M
OUT
⋅
⋅
D
L
(
M
⎧
⎨
⎩
=
. 2
. 2
=
−
⎧
⎨
⎩
015
463
) 1
. 1
(
. 1
I
, L
762
915
=
peak
⎧
⎨
⎩
@
. 0
@
2
A
A
. 0
−
Figure 21
⋅
414
I
C
55
OUT
@
V
@
OUT
V
IN
IN
,
)
,
@
max
min
@
⋅
V
V
T
IN
IN
OFF
) calculated as:
=
,
=
,
max
min
V
V
10
13
IN
IN
`
,
min
,
=
8 .
max
=
2 .
10
13
V
V
=
=
8 .
2 .
10
Application information
13
V
V
8 .
2 .
V
V
OUT
, very low
t
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