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| AAT1156 Datasheet, PDF (12/14 Pages) Advanced Analogic Technologies – 1MHz 700mA Step-Down DC-DC Converter | |||
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AAT1156
1MHz 700mA Step-Down DC-DC Converter
Output Capacitor Ripple Current:
IRMS =
1
2·
·
3
VOUT · (VIN - VOUT)
L · F · VIN
= 1 · 2.5V · (4.2V - 2.5V)
2· 3 4.7µH · 1MHz · 4.2V
= 62mArms
Pesr = esr · IRMS2 = 5m⦠· (62 mA)2 = 19µW
AAT1156 Dissipation:
PTOTAL
=
IO2
·
(RDSON(HS)
·
VO +
VIN
RDSON(LS)
·
(VIN
-VO))
+ (tsw · F · IO + IQ) · VIN
(0.7A)2 · (0.17⦠· 2.5V + 0.16⦠· (4.2V - 1.5V))
=
+ (20nsec · 1MHz · 0.7A + 300µA) · 4.2V = 0.141W
4.2V
TJ(MAX) = TAMB + ÎJA · PLOSS = 85°C + 50°C/W · 0.141W = 92°C
INPUT
R1
100
C1
10µF
C2
0.1 µF
U1
AAT1156
12 VP
FB 4
11 VP
LX 15
10 VP
LX 14
7 EN
LX 13
9 VCC
N/C 16
6 LL
PGND 3
8 N/C
PGND 2
5 SGND
PGND 1
L1
2.2µH
R4
59k
0.8V
R3
19.6k
C3, C4
2 x 22µF
C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3
C3, C4 MuRata 22µF 6.3V GRM21BR60J226ME39L X5R 0805
L1 Sumida CDRH3D16-2R2NC
AAT1156 Efficiency
(VOUT = 0.8V; L = 2.2µH; CDRH3D16)
100
90
80 VIN = 2.7V
70
VIN = 4.2V
60
VIN = 3.6V
50
40
30
20
1
10
100
Output Current (mA)
Figure 5: 0.8V Solution.
1000
12
1156.2005.11.1.2
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