AAT2148 Datasheet, PDF (10/18 Pages) Skyworks Solutions Inc. – Low-Noise, Fast Transient 1A Step-Down Converter

VIN
VIN
C1
4.7μF
VIN
JP1
1
2
3
DATA SHEET
AAT2148
Low-Noise, Fast Transient 1A Step-Down Converter
U1
AAT2148
12 _VP
LX ¹³
11 _VP
LX ¹⁴
10 _VP
LX ¹⁵
9 _VCC
EN 7 _EN
5 _N/C
6 _N/C
0 _EP
3 _PGND
FB ⁴
N/C ⁸
N/C ¹⁶
PGND ²
PGND ¹
L1 4.7μH
R1
118k
C3
100pF
VOUT
1.8V
C2
10μF
R2
59k
Figure 1: Enhanced Transient Response Schematic.
The output of the voltage error amplifier programs the
current mode loop for the necessary peak switch current
to force a constant output voltage for all load and line
conditions. Internal loop compensation terminates the
transconductance voltage error amplifier output. For
fixed voltage versions, the error amplifier reference volt-
age is internally set to program the converter output
voltage. For the adjustable output, the error amplifier
reference is fixed at 0.6V.
Soft Start / Enable
Soft start limits the current surge seen at the input and
eliminates output voltage overshoot. When pulled low,
the enable input forces the AAT2148 into a low-power,
non-switching state. The total input current during shut-
down is less than 1μA.
Current Limit and
Over-Temperature Protection
For overload conditions, the peak input current is limit-
ed. To minimize power dissipation and stresses under
current limit and short-circuit conditions, switching is
terminated after entering current limit for a series of
pulses. Switching is terminated for seven consecutive
clock cycles after a current limit has been sensed for a
series of four consecutive clock cycles.
Thermal protection completely disables switching when
internal dissipation becomes excessive. The junction
over-temperature threshold is 140°C with 15°C of hys-
teresis. Once an over-temperature or over-current fault
conditions is removed, the output voltage automatically
recovers.
Under-Voltage Lockout
Internal bias of all circuits is controlled via the V_IN input.
Under-voltage lockout (UVLO) guarantees sufficient V_IN
bias and proper operation of all internal circuitry prior to
activation.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
10
202009A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 28, 2012