BD9528MUV ROHM [Rohm], BD9528MUV Datasheet - Page 21

• Manufacturer Part Number: BD9528MUV
• Description: Main Power Supply ICs for Note PC(Linear Regulator Integrated)
• Manufacturer: ROHM [Rohm]

below.
the formula will be the following: R
※To design the actual board, please consider enough margin for FET ON resistor dispersion, Coil inductor dispersion, IC over
current reference value dispersion, frequency dispersion.
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BD9528MUV
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6. Setting over current protection
(Example)
7. Relation between output voltage and T
as they affect the overall switching rise and fall time, so please confirm in reality by the instrument.
From T
If load current 5A want to be realized with VIN=6～19V, V
When VIN=6V, Iocp will be minimum(this is because the ripple current is also minimum) so that if each condition is input,
The BD9528MUV, both 1ch and 2ch, are high efficiency synchronous regulator controller with frequency variable.
T
T
However, real-life considerations (such as the external MOSFET gate capacitor and switching speed) must be factored in
3.5
2.5
1.5
0.5
ON
ON
3
2
1
0
0
time varies with Input voltage [VIN], output voltage [VOUT], and RFS of FS pin resistance.
time is calculated with the following formula:
RFS – ontime(VOUT=5V)
ON
20
time above, frequency on application condition is following:
VIN=7V
VIN=12V
VIN=21V
R
ILIM
40
I
ocp
RFS[kΩ]
=
60
Coil current
R
ILIM[kΩ]
80
I
I
LIM_ref
ocp
SW
PGND
V
IN
100
ILIM
10k
L
×R
Frequency =
＜109.1[kΩ].
T
120
ON
ON[mΩ]
=k
ON
Co
time
+
VOUT・RFS
2.5
1.5
0.5
2
1
0
RFS – ontime(VOUT=3.3V)
(△I
0
1
2
V
VIN
VOUT
OUT
×
L
VIN
However, the value, which set the over current protection actually, is
determined by the formula (13) below.
I
：Coil ripple current[A], VIN：Input voltage[V], Vo：Output voltage[V]
ocp
20
VIN - Vo
ｆ：Switching frequency[H
VIN=7V
VIN=12V
VIN=21V
=
=
I
I
40
L
21/33
LIM_ref
LIM_ref
(R
RON: Low side ON resistance value of FET[mΩ])
×
OUT
ILIM
RFS[kΩ]
Detecting the ON resistance (between SW and PGND
voltage) of MOSFET at low side, it set the over current
voltage protection.
Over current reference voltage (I
formula(12) below.
=5V, ｆ=400kH
60
×
: Resistance for setting of over current voltage protection value[kΩ]
I
+
+
Ton
LIM_
1
I
f
1
2
1
2
80
REF
×
×
△I
=
[nsec]・・・(14)
100
[kHz]・・・(15)
L
VIN
VIN - Vo
Vo
R
L
120
Z
ILIM
, L=2.5uH, R
＞ 5
Z
[
], L：Coil inductance[H])
K
×
Ω]×RON[mΩ]
10×10
I
f
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
×
1
0
0
ON
RFS – ontime(VOUT=1V)
VIN
3
Vo
=20mΩ, the formula would be
LIM_ref
20
VIN=7V
VIN=12V
VIN=21V
・・・(13)
) is determined as in
40
[A]・・・(12)
RFS[kΩ]
Technical Note
2010.03 - Rev.A
60
80
100
120