AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Input Capacitor
Specify a maximum input voltage ripple of VPP = 25mV.
1
1
CIN(MIN)
=
=
= 3.4µF
⎛
⎝
VPP
IO
⎞
⎠
⎛
⎝
25mV
0.6A
⎞
· 4
- ESR
·
4
·
FS
- 5mΩ
· 2.0MHz
⎠
IO
2
IRMS
=
= 0.3Arms
IRMS2 = 5mΩ
P = ESR
·
·
(0.3A)2 = 0.45mW
AAT1171 Losses
PTOTAL = IO2 · RDS(ON) + (tsw · FS · IO + IQ) · VIN
= 0.62 · 0.29
+ (5ns · 2.0MHz · 0.6A + 60µA) · 4.2V = 104mW
PTOTAL TAMB = 104mW · 50°C/W = 5.2°C + 70°C = 75.2°C
ΘJA
Ω
TJ(MAX)
=
·
+
AAT1171 Dropout Losses
P
TOTAL = IO2 · RDS(ON)(HS) + IQ · VIN
= 0.62 · 310m
PTOTAL
ΘJA
Ω
+ 100µA · 3.5V = 112mW
TJ(MAX)
=
·
+
TAMB = 112mW · 50°C/W = 5.6°C + 70°C = 75.6°C
20
1171.2006.06.1.0