BD8381EFV-E2 Rohm Semiconductor, BD8381EFV-E2 Datasheet - Page 13

• Manufacturer Part Number: BD8381EFV-E2
• Description: LED Drivers AUTOMOTIVE GRADE LED DRIVER
• Manufacturer: Rohm Semiconductor

Specifications of BD8381EFV-E2

• Operating Supply Voltage: 5 V to 30 V
• Maximum Supply Current: 7 mA
• Maximum Power Dissipation: 1.45 W
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: HTSSOP-28
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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BD8381EFV-M
www.rohm.com
The smaller
① Calculation of the maximum output voltage (Vout_max)
② Calculation of the output current Iout
③ Calculation of the input peak current I
・The worst case scenario for VIN is when it is at the minimum, and thus the minimum value should be applied in the equation.
・The L value of 10µF ∼ 47µF is recommended. The current-mode type of DC/DC conversion is adopted for BD8381EFV-M, which is
・n (efficiency) is approximately 80%
※
Choose Rcs with the use of the equation Vocp_min (=0.54V) / Rcs > I
When investigating the margin, it is worth noting that the L value may vary by approximately ±30%.
※
In order to achieve stable operation of the current-mode DC/DC converter, we recommend selecting the L value in the
range indicated below:
Computation of the Input Peak Current and IL_MAX
The setting of over-current protection
The selection of the L
optimized with the use of the recommended L value in the design stage. This recommendation is based upon the efficiency as well as
the stability. The L values outside this recommended range may cause irregular switching waveform and hence deteriorate stable
operation.
Selection of coil L, diode D1 and D2, MOSFET M1 and M2, and Rcs
To calculate the Vout_max, it is necessary to take into account of the VF variation and the number of LED connection in
Vout_max = (V
I
I
Δ I
series.
L_MAX
L_AVG
Allow some margin, such as the tolerance of the external components, when selecting.
In order to achieve fast switching, choose the MOSFETs with the smaller gate-capacitance.
Iout=
0.05 [V/µs] <
L
MOSFET M1
MOSFET M2
=
Diode D1
Diode D2
Coil L
= (V
= I
V
Vout×Rcs
Rcs
L
IN
L_AVG
IN
RISET
L
0.2V
×
+ Vout) × Iout / (n × V
F
Vout×Rcs
+ Δ V
+ 1/2Δ I
Fosc
1
allows stability improvement but slows down the response time.
L
F
) × N + 0.2+ RPWMON×Iout
Current rating
×
L
> I
> Iocp
> Iocp
> Iocp
> Iocp
< 0.3 [V/µs]
V
L_MAX
―
IN
Vout
+Vout
L_MAX
IN
)
I
L
Voltage rating
Fig.20 External Application Circuit
> VIN_MAX
> VIN_MAX
M1
Rcs
> Vout
> Vout
V
IN
―
―
13/20
D1
L
CS
Δ V
RPWMON: PWMOUT FET Ron
D: FB standard voltage variation
M: Output current resistance variation
n: efficiency Fosc: switching frequency
F
: VF Variation N: Number of LED connection in series
M2
L_MAX
D2
> Iocp
Heat loss
2
Co
× Rcs
Vout
2010.10 - Rev.0.11
Technical Note