APS1056 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'APS1056' PDF : 20 Pages View PDF
APS1056
Fast Transient 600mA Step-Down Converter
The adjustable version of the APS1056, combined
with an external feedforward capacitor (C4 in
Figure 1), delivers enhanced transient response for
extreme pulsed load applications. The addition of
the feedforward capacitor typically requires a larg-
er output capacitor C1 for stability.
VOUT (V)
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.8
1.85
2.0
2.5
3.3
R2 = 59kΩ
R1 (kΩ)
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
267
R2 = 221kΩ
R1
75K
113K
150K
187K
221K
261K
301K
332K
442K
464K
523K
715K
1.00M
Table 2: Adjustable Resistor Values For Use
With 0.6V Step-Down Converter.
Thermal Calculations
There are three types of losses associated with
the APS1056 step-down converter: switching loss-
es, conduction losses, and quiescent current loss-
es. Conduction losses are associated with the
RDS(ON) characteristics of the power output switch-
ing devices. Switching losses are dominated by
the gate charge of the power output switching
devices. At full load, assuming continuous con-
duction mode (CCM), a simplified form of the LDO
losses is given by:
PTOTAL
=
IO2
·
(RDSON(HS)
·
VO
+ RDSON(LS)
VIN
·
[VIN
-
VO])
+ (tsw · F · IO + IQ) · VIN
IQ is the step-down converter quiescent current.
The term tsw is used to estimate the full load step-
down converter switching losses.
VIN
VOUT
C1
10µF
GND
1
2
3
Enable
R1
118k
L1
4.7µH
R2
59k
U1
APS1056
EN
OUT
VIN
GND
LX
C2
4.7µF
GND2
LX
U1 APS1056 SOT23-5
L1 CDRH3D16-4R7
C1 10µF 10V 0805 X5R
C2 4.7µF 10V 0805 X5R
Figure 5: APS1056 Adjustable Evaluation Board Schematic.
14
(PRELIMINARY INFORMATION) APS1056.2007.04.0.9
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