BD9206EFV_14 Datasheet, PDF (12/21 Pages) Rohm – Simple Structure Constant Current Backlight Driver for LCD panels

BD9206EFV
Datasheet
6. Calculation of Electric Power Consumption for IC and the Deciding Method of External Resistance Value
Electric power consumption of IC is decided with formula below.
PN   I_CC V_CC  V_O - R_L  I_LED  - V_F  V_F  V_FT  M  N  I_LED
▪▪▪▪ ①
Vo
Where:
ICC is the IC current consumption
VCC is the Input voltage
VF is the LED VF voltage (normal temperature)
∆VF is the LED VF Variation
∆VFT is the LED VF Temperature variation
M is the stage number around LED 1 line
N is the LED line number
ILED is the LED Constant current value
VO is the Voltage of LED anode side
RL is the External resistance (external loss)
RRLL
VVFF
＊M
＊N
I_ILED_D
Figure 15
Please insert the heat-sink resistor RL in order to decrease the heat generation of the IC.
Increasing RL, decreases the heat generated, but if the terminal voltage VLED of the LED driver is less than 0.6V, then the
constant current operation becomes impossible, therefore RL has to be set to meet the condition below:
V_LED  V_O - V_F  V_F  V_FT  M - R_L  I _LED  0.6V
・・・・②
Please set the ILED and RL in such a way that the relational expressions ① & ② are met.
Moreover, the permissible loss of the package is shown in the graph below.
HTSSOP-B20 Pd
4 .0
3 .5
3.20
3 .0
2 .5
2.30
③
2 .0
②
1 .5
1.00
1 .0
①
0 .5
0 .0
0
25
50
75
100
125
150
Tempera_周tu_囲re A_温ro_度un_Td_aT₍a_℃(°₎C)
Figure 16
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00mmmm²) 2
②2layer base―plate
(Heat dissipation
②cop：p2e層r fo基il o板n I　ns　id　e　
(^a表^nd裏^ou層^tsid放^e 熱^lay銅^er:箔：
4⁴⁹9⁰0⁰0^mm^mm²⁾2)
③ _{(③H4e：}laa_4tyd層eirss_基biapsa_板eti―_{o　np　}la_　te_　
c(全opp層er放foi熱l on銅w箔ho：le
l₄a₉ye₀r₀: 4_m9_m00₂mm²)
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