LED7707TR STMicroelectronics, LED7707TR Datasheet - Page 33

• Manufacturer Part Number: LED7707TR
• Description: IC LED DRIVR WHT BCKLT 24-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Backlight, White LEDr

Specifications of LED7707TR

• 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
• Operating Temperature: 0°C ~ 85°C
• Current - Output / Channel: 85mA
• Internal Switch(s): Yes
• 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
• Minimum Operating Temperature: - 40 C
• For Use With: 497-10044 - BOARD EVAL LCD BACKLIGHT LED7707
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Efficiency: -
• Lead Free Status / Rohs Status: Details
• Other names: 497-8492-2

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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