BD95242MUV ROHM Electronics, BD95242MUV Datasheet - Page 12

• Manufacturer Part Number: BD95242MUV
• Description: 2ch Switching Regurators for Desktop PC
• Manufacturer: ROHM Electronics

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www.rohm.com
OCP
OCP
4. MOSFET Selection
5. Setting Detection Resistance (Detect ILIMIT at the peak current)
(A) High accuracy current detective circuit (use the low resistance)
(B) Low loss current detective circuit (use the DCR value of inductor)
(C) Low loss current detective circuit (the DCR value of inductor : high)
Current limit
Current limit
VIN
VIN
VIN
Current limit
IL
L
VIN
L
r
R1
L
main switch
L
IL
synchronous switch
IL
(1-k)R
R
C
65mV
L
R
65mV
L
R2
65mV
C
Co
kR
L
Co
VOUT
Co
Co
VOUT
VOUT
VOUT
=
=
Loss on the main MOSFET
Pmain=P
(Ron: On-resistance of FET; Ciss: FET gate capacitance;
f: Switching frequency Crss: FET inverse transfer function;
I
Loss on the synchronous MOSFET
Psyn=P
The over current protection function detects the output ripple
current peak value. This parameter (setting value) is
determined as in formula (13) below.
I
(R: Detection resistance)
I
(R
I
(R
(
When the over current protection is detected by DCR of inductor L,
this parameter (setting value) is determined as in formula (13) below.
(Application circuit:P.18)
V
DRIVE
V
LMIT
LMIT
(R
LIMIT
V
k=
OUT
IN
L
L
IN
L
: the DCR value of inductor)
=
-V
: the DCR value of inductor)
V
=
=65mV(typ)×
=
R
IN
: Gate peak current)
OUT
r×C
R
1
×R
RON
L
+R
65mV(typ)
65mV(typ)
2
12/20
RON
2
k×R
+P
ON
×R
R
)
,
+P
×I
GATE
R
ON
L
GATE
L
L
OUT
×I
= kR
r×C
[A]・・・(12)
+P
2
[A]・・・(14)
OUT
L
+Ciss×f×V
TRAN
1
C )
2
+Ciss×f×V
[A]・・・(13)
DD
+
DD
VIN
・・・(11)
2
×Crss×I
I
DRIVE
OUT
Technical Note
2009.04 - Rev.B
×f
・・・(10)