AAT1149 Analogic Corporation, AAT1149 Datasheet - Page 17

• Manufacturer Part Number: AAT1149
• Manufacturer: Analogic Corporation

Input Capacitor
Input Ripple V
AAT1149 Losses
1149.2006.11.1.0
C
I
P = esr · I
P
T
RMS
J(MAX)
TOTAL
IN
=
=
⎛
⎝
=
+ (t
+ (5ns · 3MHz · 0.4A + 70μA) · 4.2V = 140mW
= T
=
I
2
O
V
I
I
0.4
PP
O
O
= 0.2Arms
RMS
sw
AMB
2
· (R
2
· F
- ESR · 4 · F
2
· (0.725 Ω · 1.8V + 0.7Ω · [4.2V - 1.8V])
+ Θ
PP
= 5mΩ · (0.2A)
S
DS(ON)H
· I
= 25mV
1
JA
⎞
⎠
O
· P
+ I
· V
LOSS
Q
) · V
O
S
+ R
= 85°C + (160°C/W) · 140mW = 107°C
V
=
IN
IN
2
4.2V
DS(ON)L
⎛
⎝
= 0.2mW
25mV
0.4A
· [V
- 5mΩ · 4 · 3.0MHz
IN
-V
O
1
] )
⎞
⎠
= 1.45μF; use 2.2μF
400mA Step-Down Converter
3MHz Fast Transient
17