AAT2113A Datasheet, PDF (16/19 Pages) Advanced Analogic Technologies – 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package

PRODUCT DATASHEET
AAT2113A
SwitchReg^TM 3MHz, Fast Transient 1.5A Step-Down Converter in 2mm x 2mm Package
AAT2113A Design Example
Specifications
V_OUT = 1.2V @ 1.5A, Pulsed Load ΔI_LOAD = 1.5A
V_IN = 3.3V
F_S = 3MHz
T_AMB = 85°C in 8-pin 2x2mm DFN low profile package
Output Inductor
For Murata, 0.47μH LQM2HPNNR47MG0 shielded chip inductor has a 40mΩ DCR.
ΔI
=
V_O
L1 · F_S
·
1-
V_O
V_IN
=
1.2V
0.47μH ·
3MHz
·
1-
1.2V
3.3V
= 542mA
I_PK
=
I_OUT
+
ΔI
2
=
1.5A
+
0.271A
=
1.8A
P_L1 = I_OUT2 · DCR = 1.5A² · 40mΩ = 90mW
Output Capacitor
For V_DROOP = 0.12V (10% Output Voltage)
C_OUT
=
3 · ΔI_LOAD
V_DROOP · F_S
=
3 · 1.5A _{= 12.5μF; use 10μF}
0.12V · 3MHz
For V_DROOP = 0.06V (5% Output Voltage)
C_OUT
=
3 · ΔI_LOAD
V_DROOP · F_S
=
3 · 1.5A ₌
0.06V · 3MHz
25μF; use 22μF
I = _RMS(MAX)
1 _· V_OUT · (V_IN(MAX) - V_OUT) ₌ 1 _·
2· 3
L · F_S · V_IN(MAX)
2· 3
1.2V · (5V - 1.2V)
1.5μH · 3MHz · 5V
= 58.5mA_rms
P_RMS = ESR · I_RMS2 = 5mΩ · (58.5mA)² = 17μW
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2113A.2009.06.1.1