AAT1171 Datasheet, PDF (20/22 Pages) Advanced Analogic Technologies – 600mA Voltage-Scaling Step-Down Converter for RF Power Amplifiers with Bypass Switch

AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Input Capacitor
Specify a maximum input voltage ripple of V_PP = 25mV.
1
1
C_IN(MIN) = _{⎛ VPP}
⎝ I_O
- ESR^⎞⎠ · 4 · F_S
=
⎛ 25mV
⎝ 0.6A
= 3.4µF
- 5mΩ⎞⎠ · 4 · 2.0MHz
I_RMS =
I_O
2
= 0.3Arms
P = ESR · I_RMS2 = 5mΩ · (0.3A)² = 0.45mW
AAT1171 Losses
P_TOTAL = I_O2 · R_DS(ON) + (t_sw · F_S · I_O + I_Q) · V_IN
= 0.6² · 0.29Ω + (5ns · 2.0MHz · 0.6A + 60µA) · 4.2V = 104mW
T_J(MAX) = P_TOTAL · Θ_JA + T_AMB = 104mW · 50°C/W = 5.2°C + 70°C = 75.2°C
AAT1171 Dropout Losses
P_TOTAL = I_O2 · R_DS(ON)(HS) + I_Q · V_IN
= 0.6² · 310mΩ + 100µA · 3.5V = 112mW
T_J(MAX) = P_TOTAL · Θ_JA + T_AMB = 112mW · 50°C/W = 5.6°C + 70°C = 75.6°C
20
1171.2006.06.1.0