BD9A301MUV-LB Datasheet, PDF (22/35 Pages) Rohm – This is the product guarantees long time support in Industrial market

BD9A301MUV-LB
Datasheet
Selection of Components Externally Connected
1. Output LC Filter Constant
The DC/DC converter requires an LC filter for smoothing the output voltage in order to supply a continuous current to the
load. BD9A301MUV-LB is returned to the IC and IL ripple current flowing through the inductor for SLLM^TM control. This
feedback current, Inductance value is the behavior of the best when the 1.5µH. Therefore, the inductor to use is
recommended 1.5µH.
IL
Inductor saturation current > I_OUTMAX +⊿I_L /2
IOUTMAX
⊿I_L
Average inductor current
t
Figure 49. Waveform of current through inductor
Figure 50. Output LC filter circuit
Computation with VIN = 5V, VOUT = 1.8V, L=1.5µH, and the switching frequency F_OSC = 1MHz, the method is as below.
Inductor ripple current ∆IL
ΔI _L V_OUT V_IN -V_OUT
V_IN
1
F_OSC
L
768 mA
The saturation current of the inductor must be larger than the sum of the maximum output current and 1/2 of the inductor
ripple current ∆IL.
The output capacitor C_OUT affects the output ripple voltage characteristics. The output capacitor COUT must satisfy the
required ripple voltage characteristics.
The output ripple voltage can be represented by the following equation.
ΔV _RPL
ΔI _L
R _ESR
8
1
C _OUT
F_OSC ^[V]
R_ESR is the Equivalent Series Resistance (ESR) of the output capacitor.
With COUT = 44µF, RESR = 10mΩ the output ripple voltage is calculated as
ΔV _RPL 0.768
10m
1
8 44μ 1MHz
9.8 mV 
*Be careful of total capacitance value, when additional capacitor CLOAD is connected in addition to output capacitor COUT.
Use maximum additional capacitor CLOAD(max.) condition which satisfies the following method.
Maximum starting inductor ripple current IL_START Over Current limit 3.8 A min
Maximum starting inductor ripple current ILSTART can be expressed in the following method.
IL_START Maximum starting output current I_OMAX Charge current to output capacitor I_CAP
ΔI _L
2
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20.Aug.2014 Rev.001