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PDF AAT1150 Data sheet ( Hoja de datos )
| Número de pieza | AAT1150 | |
| Descripción | 1MHz 1A Step-Down DC/DC Converter | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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AAT1150
1MHz 1A Step-Down DC/DC Converter
General Description
The AAT1150 SwitchReg™ is a member of
AnalogicTech's Total Power Management IC™
(TPMIC™) product family. The step-down switch-
ing converter is ideal for applications where high
efficiency, small size, and low ripple are critical.
Able to deliver 1A with internal power MOSFETs,
the current-mode controlled IC provides high effi-
ciency using synchronous rectification. Fully inter-
nally compensated, the AAT1150 simplifies system
design and lowers external parts count.
The AAT1150 is available in an MSOP-8 package
and is rated over the -40°C to +85°C temperature
range.
Features
SwitchReg™
• VIN Range: 2.7V to 5.5V
• Up to 95% Efficiency
• 110mΩ RDS(ON) MOSFET Switch
• <1.0µA of Shutdown Current
• 1MHz Switching Frequency
• Fixed or Adjustable VOUT: 1.0V to 4.2V
• High Initial Accuracy: ±1%
• 1.0A Peak Current
• Integrated Power Switches
• Synchronous Rectification
• Internally Compensated Current Mode Control
• Constant PWM Mode for Low Output Ripple
• Internal Soft Start
• Current Limit Protection
• Over-Temperature Protection
• MSOP-8 package
• -40°C to +85°C Temperature Range
Typical Application
INPUT
10µF
100Ω
0.1µF
Applications
• Cable/DSL Modems
• Computer Peripherals
• High Efficiency Conversion From 5V or 3.3V
Supply
• Network Cards
• Set-Top Boxes
VP
AAT1150
FB
ENABLE
LX
VCC
SGND
PGND
4.1µH
2x 22µF
OUTPUT
1150.2005.03.1.2
1
1 page  
AAT1150
1MHz 1A Step-Down DC/DC Converter
Typical Characteristics
High Side RDS(ON) vs. Temperature
170
150 3.6V
2.7V
130
110
90 4.2V 5.5V
70
-20 0 20 40 60 80 100 120
Temperature (°C)
Low Side RDS(ON) vs. Temperature
170
150
130
110 2.7V
90
70
-20
0
3.6V
4.2V
5.5V
20 40 60 80
Temperature (°C)
100
120
130
120
110
100
90
80
2.5
RDS(ON) vs. Input Voltage
High Side
Low Side
3 3.5 4 4.5 5 5.5
Input Voltage (V)
Oscillator Frequency Variation vs.
Supply Voltage
3.5
2.5
1.5
0.5
-0.5
-1.5
2.5 3 3.5 4 4.5 5 5.5
Supply Voltage (V)
Enable Threshold vs. Input Voltage
1.2
1.1
VEN(H)
1
0.9
0.8 VEN(L)
0.7
2.5 3 3.5 4 4.5 5 5.5
Input Voltage (V)
Oscillator Frequency Variation vs. Temperature
(VIN = 3.6V)
10
6
2
-2
-6
-10
-20 0 20 40 60 80 100
Temperature (°C)
1150.2005.03.1.2
5
5 Page 
AAT1150
1MHz 1A Step-Down DC/DC Converter
3.5
3
2.5
2
1.5
1
0.5
0
0
VCC = VP = 5.0V
VO = 3.3V
Figure 2 Schematic
VCC = VP = 3.6V
VO = 1.5V
Figure 1 Schematic
0.5 1 1.5
IOUT (A)
2
2.5
Figure 3: Current Limit Characteristic.
Inductor
The output inductor is selected to limit the ripple
current to some predetermined value, typically
20% to 40% of the full load current at the maximum
input voltage. Manufacturer's specifications list
both the inductor DC current rating, which is a ther-
mal limitation, and the peak current rating, which is
determined by the saturation characteristics. The
inductor should not show any appreciable satura-
tion under normal load conditions. During overload
and short-circuit conditions, the average current in
the inductor can meet or exceed the ILIMIT point of
the AAT1150 without affecting converter perform-
ance. Some inductors may have sufficient peak
and average current ratings yet result in excessive
losses due to a high DCR. Always consider the
losses associated with the DCR and its effect on
the total converter efficiency when selecting an
inductor.
For a 1.0A load and the ripple set to 30% at the
maximum input voltage, the maximum peak-to-
peak ripple current is 300mA. The inductance
value required is 3.9µH.
L
=
VOUT
IO ⋅ k ⋅
F
⋅ ⎛⎝1
-
VOUT⎞
VIN ⎠
L
=
1.0A
⋅
1.5V
0.3 ⋅
830kHz
⋅
⎛⎝1
-
1.5V ⎞
4.2V⎠
L = 3.9µH
The factor "k" is the fraction of full load selected for
the ripple current at the maximum input voltage.
The corresponding inductor RMS current is:
IRMS =
⎝⎛Io2
+
∆I2⎞
12⎠
≈ Io = 1.0A
∆I is the peak-to-peak ripple current which is fixed by
the inductor selection above. For a peak-to-peak
current of 30% of the full load current, the peak cur-
rent at full load will be 115% of the full load. The
4.1µH inductor selected from the Sumida
CDRH5D18 series has a 57mΩ DCR and a 1.95A
DC current rating. At full load, the inductor DC loss
is 57mW which amounts to a 3.8% loss in efficiency.
Input Capacitor
The primary function of the input capacitor is to pro-
vide a low impedance loop for the edges of pulsed
current drawn by the AAT1150. A low ESR/ESL
ceramic capacitor is ideal for this function. To mini-
mize stray inductance, the capacitor should be
placed as closely as possible to the IC. This keeps
the high frequency content of the input current
localized, minimizing radiated and conducted EMI
while facilitating optimum performance of the
AAT1150. Ceramic X5R or X7R capacitors are
ideal for this function. The size required will vary
depending on the load, output voltage, and input
voltage source impedance characteristics. A typi-
cal value is around 10µF. The input capacitor RMS
1150.2005.03.1.2
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet AAT1150.PDF ] | |
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