AAT1270_08 Datasheet, PDF (13/18 Pages) Advanced Analogic Technologies – 1A Step-Up Current Regulator for Flash LEDs

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PRODUCT DATASHEET
AAT1270
1A Step-Up Current Regulator for Flash LEDs
Manufacturer
Murata
Murata
CoilCraft
Cooper Bussmann
Cooper Bussmann
Sumida
Part Number
LQM2HPN1R0MG0
LQH3NPN1R0G0
LPS3010
SD3110
SD3812
CDH38D11/S
Inductance (μH)
1.0
1.0
1.0
1.0
1.0
1.0
Max DC I_SAT
Current (A)
1.6
1.58
1.6
1.47
2.69
2.8
DCR
(mΩ)
55
110
85
68.3
48
39
Size (mm)
(LxWxH)
2.5x2.0x0.9
3.0X3.0x1.0
3.0x3.0x1.0
3.1x3.1x1.0
4.0x4.0x1.2
4.0x4.0x1.2
Table 2: Typical Suggested Surface Mount Inductors.
Type
Multilayer
Wirewound
Wirewound
Wirewound
Wirewound
Wirewound
For a given inductor type, smaller inductor size leads to
an increase in DCR winding resistance and, in most
cases, increased thermal impedance. Winding resistance
degrades boost converter efficiency and increases the
inductor’s operating temperature:
P_{LOSS(INDUCTOR)} = I_RMS2 · DCR
Selecting the Boost Capacitors
In general, it is good design practice to place a decou-
pling capacitor (input capacitor) between the IN and
GND pins. An input capacitor in the range of 2.2μF to
10μF is recommended. A larger input capacitor in this
application may be required for stability, transient
response, and/or ripple performance.
The high output ripple inherent in the boost converter
necessitates the use of low impedance output filtering.
Multi-layer ceramic (MLC) capacitors provide small size
and adequate capacitance, low parasitic equivalent
series resistance (ESR) and equivalent series inductance
(ESL), and are well suited for use with the AAT1270
boost regulator. MLC capacitors of type X7R or X5R are
recommended to ensure good capacitance stability over
the full operating temperature range.
The output capacitor is selected to maintain the output
load without significant voltage droop (∆V_OUT) during the
power switch ON interval. A ceramic output capacitor
2.2μF is recommended (see Table 3).
Typically, 6.3V or 10V rated capacitors are required for
this flash LED boost output. Ceramic capacitors selected
as small as 0603 are available which meet these require-
ments. MLC capacitors exhibit significant capacitance
reduction with applied voltage. Output ripple measure-
ments should confirm that output voltage droop and
operating stability are within acceptable limits. Voltage
derating can minimize this factor, but results may vary
with package size and among specific manufacturers.
To maintain stable operation at full load, the output
capacitor should be selected to maintain ∆V_OUT between
100mV and 200mV. The boost converter input current
flows during both ON and OFF switching intervals. The
input ripple current is less than the output ripple and, as
a result, less input capacitance is required.
Manufacturer
Murata
Murata
Murata
Murata
Murata
Murata
Part Number
GRM185R60J225KE26
GRM188R71A225KE15
GRM21BR70J225KA01
GRM21BR71A225KA01
GRM219R61A475KE19
GRM21BR71A106KE51
Capacitance
(μF)
2.2
2.2
2.2
2.2
4.7
10
Voltage
Rating (V)
6.3
10
6.3
10
10
10
Temp Co.
X5R
X7R
X7R
X7R
X5R
X7R
Table 3: Typical Suggested Surface Mount Capacitors.
Case Size
0603
0603
0805
0805
0805
0805
1270.2008.07.1.5
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