LED7707 STMicroelectronics, LED7707 Datasheet - Page 33

• Manufacturer Part Number: LED7707
• Description: LED Drivers 6-ROW 85mA LED DRIV BOOST REG LCD PANEL
• Manufacturer: STMicroelectronics

Specifications of LED7707

• High Level Output Current: 85 mA
• Operating Supply Voltage: 4.5 V to 36 V
• Maximum Supply Current: 1 mA
• Maximum Power Dissipation: 2.3 W
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Package / Case: VFQFPN-24
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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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