AAT1185 Datasheet, PDF (10/16 Pages) Skyworks Solutions Inc. – High Voltage Step-Down Controller

DATA SHEET
AAT1185
High Voltage Step-Down Controller
Network
Feedback
Feed-forward
Compensation
Components
R₆
R₇
C₁₂
R₅
C₁₀
C₁₁
R₄
V_OUT =3.3V
V_IN = 6V-24V
27.4k
6.04k
680pF
1k
33pF
680pF
20k
V_OUT = 5.0V
V_IN = 6V-24V
1.96k
14.3k
2.2nF
453Ω
2.2nF
150pF
3.92k
Table 1: AAT1185 Feedback and Compensation Components for V_OUT =3.3V and V_OUT = 5.0V.
Over-Current Protection
The controller provides true-load DC output current
sensing which protects the load and limits component
stresses. The output current is sensed through the DC
resistance in the output inductor (DCR). The controller
reduces the operating frequency when an over-current
condition is detected; limiting stresses and preventing
inductor saturation. This allows the smallest possible
inductor for a given output load. A small resistor divider
may be necessary to adjust the over-current threshold
and compensate for variation in inductor DCR. The pre-
set current limit threshold is triggered when the differen-
tial voltage from RS to OS exceeds 100mV (nominal).
V_OUT
5V/10A
LX
L1
3.9μH
R3
C9
1.74k
0.47μF
RS
R9
OS
R10
Figure 2: Resistor Network to Adjust the Current
Limit Less than the Pre-Set Over-Current
Threshold (Add R9, R10).
V _OUT
5.0V/10A
LX
L1
3.9μH
R3
1.74k
C9
0.47μF
RS
R8
R9
OS
Figure 3: Resistor Network to Adjust the Current
Limit Greater than the Pre-Set Over-Current
Threshold (Add R8, R9).
L1 R3 C9
(μH) (kΩ) (μF)
3.9 1.74 0.47
4.2
2
0.47
4.7 1.47 0.47
Part Number
B82559A0392A013, 3.9μH, Epcos,
I_SAT = 12A, DCR = 4.8mΩ
RLF12560T-4R2N100, 4.2μH, TDK,
I_SAT = 10.2A, DCR = 7.4mΩ
SER2013-472ML, 4.7μH, Coilcraft,
I_SAT = 18A, DCR = 1.7mΩ
Table 2: Current Limit Network vs. Inductor DCR.
Thermal Protection
The AAT1185 has an internal thermal protection circuit
which will turn on when the device die temperature
exceeds 135°C. The internal thermal protection circuit
will actively turn off the high side regulator output device
to prevent the possibility of over temperature damage.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
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202001A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 31, 2012