AAT1157 AAT, AAT1157 Datasheet - Page 11

• Manufacturer Part Number: AAT1157
• Description: DC/DC Converter
• Manufacturer: AAT

Design Example
Specifications
I
I
V
V
F
T
Maximum Input Capacitor Ripple:
Inductor Selection:
Select Sumida inductor CDRH5D28 3.0µH.
Output Capacitor Ripple Current:
1157.2005.11.1.4
P = esr · I
L =
P = I
I
Pesr = esr · I
OUT
RIPPLE
I
∆I =
I
RMS
RMS
PK
S
AMB
OUT
IN
= I
=
=
∆I
O
L ⋅ F
V
2
I
OUT
2
PP
O
V
·
OUT
⋅ DCR = (1.2A)
1
1.2A
330mA
2.5V
3.0V to 4.2V
1MHz
= 85°C
O
·
⋅ F
+
3
RMS
V
V
⋅ 1 -
·
∆I
O
IN
2
⋅ 1 -
⎛
⎝
(V
RMS
2
·
⎛
⎝
= 1.2A + 0.17A = 1.37A
= 5mΩ · 0.59
⎛
⎝
OUT
1
2
V
-
V
= 5mΩ · (97.4mA)
) · (V
L F V
IN
V
O
V
V
V
· ·
OUT
IN
O
⎞
⎠
IN
⎞
⎠
=
⎞
⎠
2
IN
=
⋅ 31mΩ = 45mW
IN
=
3.0µH ⋅ 1MHz
- V
0.59Arms
OUT
2
0.33A ⋅ 1MHz
A = 1.7mW
2.5 V
)
2.5 V
=
2
2
·
1
= 47.4µW
3
⋅ 1-
·
⎛
⎝
3.0µH · 1MHz · 4.2V
2.5V · (4.2V - 2.5V)
⋅ 1 -
2.5V
4.2V
⎛
⎝
⎞
⎠
2.5V
4.2V
= 340mA
⎞
⎠
= 3.07µH
1MHz 1.2A Buck DC/DC Converter
= 97.4mArms
AAT1157
11