BD8966FVM-TR Rohm Semiconductor, BD8966FVM-TR Datasheet - Page 10

• Manufacturer Part Number: BD8966FVM-TR
• Description: IC SWITCHING REG W/MOSFET MSOP8
• Manufacturer: Rohm Semiconductor
• Series: -r
• Type: Step-Down (Buck), PWM - Current Moder

Specifications of BD8966FVM-TR

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1 V ~ 2.5 V
• Current - Output: 800mA
• Frequency - Switching: 1MHz
• Voltage - Input: 4 V ~ 5.5 V
• Operating Temperature: -25°C ~ 85°C
• Mounting Type: *
• Package / Case: *
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

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BD8966FVM
www.rohm.com
2. Selection of output capacitor (C
3. Selection of input capacitor (Cin)
V
As the output rise time must be designed to fall within the soft-start time, the capacitance of output capacitor should be
determined with consideration on the requirements of equation (5):
In case of BD8966FVM, for instance, and if V
Inappropriate capacitance may cause problem in startup. A 10 μF to 100 μF ceramic capacitor is recommended.
A low ESR 10µF/10V ceramic capacitor is recommended to reduce ESR dissipation of input capacitor for better efficiency.
CC
Fig.26 Output capacitor
Fig.27 Input capacitor
Co≦
Co≦
V
CC
L
T
1m×(2-0.8)
SS
L
×(I
1.5
Cin
limit
V
OUT
-I
Co
OUT
ESR
Co
V
)
OUT
≒800[μF]
V
O
OUT
)
・・・(5)
Output capacitor should be selected with the consideration on the stability region
and the equivalent series resistance required to smooth ripple voltage.
Output ripple voltage is determined by the equation (4)：
ΔV
(ΔI
Input capacitor to select must be a low ESR capacitor of the capacitance
sufficient to cope with high ripple current to prevent high transient voltage.
The ripple current IRMS is given by the equation (5):
*Rating of the capacitor should be determined allowing sufficient margin
against output voltage. Less ESR allows reduction in output ripple voltage.
OUT
If V
L
I
< Worst case > I
When Vcc is twice the V
I
RMS
RMS
: Output ripple current, ESR: Equivalent series resistance of output capacitor)
=ΔI
CC
OUT
=I
=0.8×
=5.0V, V
L
OUT
×ESR [V]・・・(4)
=1.5V, I
×
Tss: Soft-start time
I
limit
10/14
√
√
OUT
OUT
V
5(5-1.5)
: Over current detection level, 2A(Typ)
RMS(max.)
OUT
=1.5V, and I
5
=0.8A, and T
(V
V
CC
CC
OUT
-V
, I
=0.67[A
OUT
RMS
OUTmax.=
)
SS
=
=1ms,
[A]・・・(5)
RMS
I
OUT
0.8A
2
]
Technical Note
2010.04 - Rev.B