AAT2522 Datasheet, PDF (16/19 Pages) Skyworks Solutions Inc. – Dual High-Current, Low-Noise, Step-Down Regulator

DATA SHEET
AAT2522
Dual High-Current, Low-Noise, Step-Down Regulator
AAT2522 Design Example
Specifications
V_OUT1 = 3.3V @ 1A, Pulsed Load IL_OAD = 1A
V_OUT2 = 1.2V @ 2A, Pulsed Load I_LOAD = 2A
V_IN1 = 3.6V
F_S = 1.4MHz
T_AMB = 85°C in TDFN34-16 Package
Step-Down Converter Output Inductor
The internal slope compensation for the AAT2522 is set to 75% of the inductor current down slope for a 1.8V output
and 1.8μH inductor:
m
=
0.75 ·
L
V_O
=
0.75 · 1.8V
1.8μH
=
0.75
A
μs
For 3.3V and 1.2V outputs, the inductor values are given in the following equations:
L=
0.75 ·
m
V_O
=
0.75 · 3.3V
A
= 3.3μH; use 3.3μH
0.75A _μs
L=
0.75 ·
m
V_O
=
0.75 · 1.2V
A
= 1.2μH; use 1.5μH
0.75A _μs
For Sumida inductor, CDRH6D38NP-3R3N, 3.3μH, I_SAT = 3.5A, DCR = 15mΩ.
For Sumida inductor, CDRH4D22HPNP-1R5NC, I_SAT = 3.9A, 1.5μH, DCR = 25mΩ.
ΔI₁ =
V_OUT1
L₁ · F_S
·
1-
V_OUT1
V_IN
=
3.3V
3.3μH · 1.4MHz
·
1-
3.3V
3.6V
= 0.06A
ΔI₂ =
V_OUT2
L₁ · F_S
·
1-
V_OUT2
V_IN
=
1.2V
1.2μH · 1.4MHz
·
1-
1.2V
3.6V
= 0.476A
I_PK1
=
I_OUT1
+
ΔI₁
2
= 1A + 0.03A = 1.03A
I_PK2
=
I_OUT2
+
ΔI₂
2
= 2A + 0.476A = 2.5A
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
16
202032A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012