Datasheet

ADP1882/ADP1883
Rev. 0 | Page 30 of 40
Loss Calculations
P
SW(LOSS)
= f
SW
× R
GATE
× C
TOTAL
× I
LOAD
× V
IN
× 2
= 300 × 103 × 1.5 Ω × 3.3 × 10 − 9 × 15 A × 12 × 2
= 534.6 mW
Duty cycle = 1.8/12 V = 0.15.
[
R
ON (N2)
= 5.4 m.
t
BODY(LOSS)
= 20 ns (body conduction time).
V
F
= 0.84 V (MOSFET forward voltage).
C
IN
= 3.3 nF (MOSFET gate input capacitance).
Q
N1,N2
= 17 nC (total MOSFET gate charge).
R
GATE
= 1.5  (MOSFET gate input resistance).
()
[
]
2
LOAD
I×1
N2(ON)N1(ON)N1,N2(CL)
RDRDP ×−+×=
= (0.15 × 0.0054 + 0.85 × 0.0054) × (15 A)
2
= 1.215 W
2
)(
)(
×××=
F
LOAD
SW
LOSSBODY
LOSSBODY
VI
t
t
P
= 20 ns × 300 × 10
3
× 15 A × 0.84 × 2
= 151.2 mW
(
)
]
BIAS
DR
upperFET
SW
DR
LOSSDR
IVCfVP
=
×
+
)(
+
[
(
)
]
I
f
V
BIAS
DD
upperFET
SW
DD
VC +×
2
LOAD
I
= (5.12 × (300 × 10
3
× 3.3 × 10
−9
× 5.12 + 0.002))
+ (5.5 × (300 × 10
3
× 3.3 × 10
−9
× 5.5 + 0.002))
= 77.13 mW
P
COUT
= (I
RMS
)
2
× ESR = (1.5 A)
2
× 1.4 m = 3.15 mW
P
DCR(LOSS)
= DCR × = 0.003 × (15 A)
2
= 675 mW
P
CIN
= (I
RMS
)
2
× ESR = (7.5 A)
2
× 1 m = 56.25 mW
P
LOSS
= P
N1,N2
+ P
BODY(LOSS)
+ P
SW
+ P
DCR
+ P
DR
+ P
COUT
+ P
CIN
= 1.215 W + 151.2 mW + 534.6 mW + 77.13 mW +
3.15 mW + 675 mW + 56.25 mW
= 2.62 W