EVALED7706 STMicroelectronics, EVALED7706 Datasheet - Page 35

• Manufacturer Part Number: EVALED7706
• Description: EVALUATION BOARD FOR LED7706
• Manufacturer: STMicroelectronics

Specifications of EVALED7706

• Current - Output / Channel: 30mA
• Outputs And Type: 6, Non-Isolated
• Voltage - Output: 36 V
• Features: Dimmable, Extra 5V Output
• Voltage - Input: 4.5 ~ 36 V
• Utilized Ic / Part: LED7706
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6445

LED7706
6.4.9
Power dissipation estimate
As explained in
Neglecting the power dissipated by the LDO (surely less significant compared with the other
contributions), equation (19), (21), (22) and (23) help to estimate the overall power
dissipation.
Before starting the power dissipation estimate it is important to highlight that the following
calculations are considering the worst case (the actual value of the dissipated power would
require measurements). Therefore the power dissipation is estimated according to the
following assumptions:
1.
2.
3.
4.
The conduction and switching losses on the internal power switch can be calculated as:
Equation 42
Equation 43
where t
The power dissipation related to the current generators is given by:
Equation 44
Equation 45
Equation 46
The junction temperature can be estimated by equation (18) considering T
Equation 47
Minimum input voltage (9.6 V), which leads to maximum input current (and also D will
have the higher value, see
Maximum R
LEDs in the row of the leading generator will have the maximum forward voltage,
whereas all other LEDs in the other rows will have the minimum forward voltage.
100 % dimming signal duty cycle is considered.
r
= t
f
= 15 ns
P
GEN
Section 6.2
DS(on)
=
P
I
ROW
, D
of the internal power MOSFET;
P
tot
, D
sw
⋅
≅
, there are several contributions to the total power dissipation.
P
(
P
n
P
GEN
, D
=
ROWs
T
, D
cond
J
cond
V
Section 6.4.4
,
=
OUT
Master
T
=
−
+
Amb
1
⋅
R
P
I
)
IN
, D
DSon
⋅
=
(
sw
+
V
⋅
I
ROW
f
IFB
R
sw
+
th
⋅
P
I
⋅
,
IN
2
+
JA
GEN
);
t (
⋅
Δ
V
⋅
r
⋅
D
IFB
V
P
+
2
,
Master
, f
⋅
, D
LEDs
) t
D
f
⋅
tot
D
DIM
⋅
DIM
D
=
+
⋅
DIM
n
46
=
P
LEDs
=
GEN
34
5 .
8
=
mW
°
mW
111
)
C
=
⋅
D
513
DIM
mW
Application information
mW
=
360
mW
A
= 25 °C:
35/46