bd9575fv-e2 ROHM Co. Ltd., bd9575fv-e2 Datasheet - Page 12

• Manufacturer Part Number: bd9575fv-e2
• Description: Switching Regulators Ddr-sdram Cores
• Manufacturer: ROHM Co. Ltd.

© 2009 ROHM Co., Ltd. All rights reserved.
BD9575FV
www.rohm.com
5. Setting Detection Resistance
4. MOSFET Selection
Current limit
Current limit
V
V
IN
IN
I
L
L
V
L
r
IN
main switch
L
I
synchronous switch
L
R
C
L
R
Co
Co
V
Co
OUT
V
V
OUT
OUT
=
=
(Ron: On-resistance of FET; Ciss: FET gate capacity;
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
(V
When the over current protection is detected by DCR of coil L, this
parameter (setting value) is determined as in formula (14) below.
I
(V
Loss on the main MOSFET
Pmain=P
(RL=
DRIVE
V
LMIT
LMIT
V
(Application circuit:P20)
V
IN
ILIM
ILIM
OUT
IN
V
-V
=
=V
IN
: Gate peak current)
: ILIM voltage; R: Detection resistance)
:ILIM voltage RL: the DCR value of coil)
OUT
r×C
ILIM
RON
L
×R
V
12/20
RON
ILIM
×0.1×
×R
+P
ON
R
)
+P
×0.1
×I
GATE
ON
GATE
OUT
×I
r×C
[A]・・・(13)
OUT
+P
2
L
+Ciss×f×V
TRAN
2
+Ciss×f×V
[A]・・・(14)
DD
+
DD
V
IN
・・・(12)
2
×Crss×I
I
DRIVE
OUT
Technical Note
2009.04 - Rev.B
×f
・・・(11)