AAT1146 Analogic Corporation, AAT1146 Datasheet - Page 16

• Manufacturer Part Number: AAT1146
• Manufacturer: Analogic Corporation

Step-Down Converter Design Example
Specifications
V
V
F
T
1.8V Output Inductor
For Sumida inductor CDRH3D16, 4.7µH, DCR = 105mΩ.
1.8V Output Capacitor
V
16
L1 = 3
∆I
P
C
I
P
I
RMS
PKL1
S
AMB
O
IN
DROOP
esr
L1
OUT
L1
= I
= esr · I
=
=
= I
=
O
µsec
2
L1 ⋅ F
V
O
2
= 1.8V @ 400mA (adjustable using 0.6V version), Pulsed Load ∆I
= 2.7V to 4.2V (3.6V nominal)
= 1.4MHz
= 85°C
= 0.1V
3 · ∆I
·
A
DROOP
1
⋅ DCR = 0.4A
V
+
O
3
∆I
RMS
2
·
⋅ V
LOAD
L1
⋅ 1 -
(V
· F
2
⎛
⎝
= 0.4A + 0.068A = 0.468A
O2
= 5mΩ · (45mA)
O
L1 · F · V
S
) · (V
= 3
=
V
V
IN
0.1V · 1.4MHz
O
µsec
IN(MAX)
2
⎞
⎠
A
⋅ 105mΩ = 17mW
3 · 0.3A
=
IN(MAX)
4.7µH ⋅ 1.4MHz
- V
⋅ 1.8V = 5.4µH
O
)
2
1.8 V
= 10µW
=
2
= 6.4µF; use 10µF
·
1
3
·
4.7µH · 1.4MHz · 4.2V
1.8V · (4.2V - 1.8V)
Fast Transient 400mA Step-Down Converter
⋅ 1 -
⎛
⎝
(use 4.7µH; see Table 1)
1.8V
4.2V
⎞
⎠
= 156mA
= 45mArms
LOAD
= 300mA
AAT1146
1146.2006.01.1.2