Document
1MHz 3A Buck DC/DC Converter General Description
The AAT1154 SwitchReg™ is a member of AnalogicTech™'s Total Power Management™ IC product family. The Step-down switching converter is ideal for applications where high efficiency, small size, and low ripple are critical. Able to deliver 3A with an internal power MOSFET, the current-mode controlled IC provides high efficiency. Fully internally compensated, the AAT1154 simplifies system design and lowers external part count. The AAT1154 is available in an SOP-8 package, rated over -40 to 85°C.
AAT1154
Features
• • • • • • • • • • • • • •
SwitchReg™
VIN Range: 2.7-5.5Volts Fixed or adjustable VOUT: 1.0V - 4.2V 3A output current Up to 95% efficiency Integrated low on resistance power switch Internally compensated current mode control 1MHz switching frequency Constant PWM mode Low output ripple with light load Internal softstart Current limit protection Over-Temperature protection SOP-8 package -40 to 85°C Temperature Range
Preliminary Information
Applications
• • • • • Computer Peripherals Set Top Boxes Network Cards Cable/DSL Modems High efficiency conversion from 5V or 3.3V supply
Typical Application
INPUT VP FB
10µF 100Ω
AAT1154
VCC LX
1.5µH
ENABLE 0.1µF GND OUTPUT 120µF
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1MHz 3A Buck DC/DC Converter Pin Descriptions
Pin #
1
AAT1154
Symbol
FB
Function
Feedback input pin. This pin must be connected to the converter’s output. It is used to set the output of the converter to regulate to the desired value. Ground connection. Enable input pin. When connected high, AAT1154 is in normal operation. When connected low, it is powered down. This pin should not be left floating. Power supply. It supplies power for the internal circuitry. Input Supply Voltage for converter power stage. Inductor connection pins. These pins should be connected to the output inductor. Internally, pins 6 & 7 are connected to the drain of the P-channel switch.
2 3
GND EN
4 5, 8 6, 7
VCC VP LX
Pin Configuration
SO-8
FB GND EN VCC
1 2
8 7
3 4
6 5
VP LX LX VP
1 2
2
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1MHz 3A Buck DC/DC Converter Absolute Maximum Ratings
Symbol
VCC, VP VLX VFB VEN TJ VESD
AAT1154
(TA=25°C unless otherwise noted) Value
6 -0.3 to VP+0.3 -0.3 to VCC+0.3 -0.3 to VCC+0.3 -40 to 150 3000
Description
VCC, VP to GND LX to GND FB to GND EN to GND Operating Junction Temperature Range ESD Rating 1 - HBM
Units
V V V V °C V
Note: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum rating should be applied at any one time. Note 1: Human body model is a 100pF capacitor discharged through a 1.5K resistor into each pin.
Thermal Characteristics
Symbol
ΘJA PD
Description
Thermal Resistance 2 Maximum Power Dissipation (TA = 25°C)
2, 3
Value
110 909
Units
°C/W mW
Note 2: Mounted on a demo board (FR4, in still air). Note 3: Derate 9.1mW/°C above 25°C.
Recommended Operating Conditions
Symbol
T
Description
Ambient Temperature Range
Rating
-40 to +85
Units
°C
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1MHz 3A Buck DC/DC Converter Electrical Characteristics
values are at TA = 25°C) Symbol
VIN VOUT VUVLO VUVLO(HYS) IQ ISHDN ILIM RDS(ON)L η ∆VOUT (VOUT*∆VIN) ∆VOUT/VOUT FOSC VEN(L) VEN(H) TSD THYS
AAT1154
(VIN = VCC = VP = 5V, TA= -40 to 85°C unless otherwise noted. Typical
Description
Input Voltage Range Output Voltage Tolerance Under Voltage Lockout Under Voltage Lockout Hysteresis Quiescent Supply Current Shutdown Current Current Limit High Side Switch On Resistance Efficiency Load Regulation Line Regulation Oscillator Frequency Enable Threshold Low Enable Threshold High Over Temp Shutdown Threshold Over Temp Shutdown Hysteresis
Conditions
VIN = VOUT + 0.2 to 5.5V, IOUT = 0 to 3A VIN Rising VIN Falling No Load, VFB= 0 V VEN = 0 V, VIN= 5.5V TA = 25°C TA = 25°C IOUT = 1.0 A ILOAD = 0 - 3A VIN= 2.7 to 5.5V TA = 25°C
Min Typ Max Units
2.7 -5.0 5.5 5.0 2.5 1.2 250 630 4.4 60 92 ±2.6 0.75 1 0.6 1.4 140 15 1000 1.0 V % V V mV µA µA A mΩ % %/V MHz V V °C °C
4
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1MHz 3A Buck DC/DC Converter Typical Characteristics
RDS(ON) vs. Temperature
90
0.5
AAT1154
Oscillator Frequency Variation vs. Supply Voltage
VIN = 2.7V
80
VIN = 4.2V Variation (%)
120
0.25
RDS(ON) (mΩ)
VIN = 3.6V
70 60
0
VIN = 5.5V
50 40 -20 0 20 40 60 80 100
VIN = 5V
-0.25
-0.5 3.5 4 4.5 5 5.5
Temperature (°C)
Input Voltage (V)
RDS(ON) vs. VIN, IDS = 1A
70 65
Oscillator Frequency Variation vs. Temperature VIN = 5V
1 0
RDS(ON) (mΩ)
Variation (%)
2.5 3 3.5 4 4.5 5 5.5
60 55 50 45 40
-1 -2 -3 -4 -20 0 20 40 60 80 100
Input Voltage (V)
Temperature (°C)
Enable Threshold vs. Input Voltage
1.2 0.4 0.2
Output Voltage vs. Temperature IOUT=2A
Enable Threshold (V)
1.1 1 0.9 0.8 0.7 0.6 2.5 3 3.5 4 4.5 5 5.5
Variation (%)
EN(H)
0 -0.2 -0.4 -0.6 -0.8
-20 0 20 40 60 80 100
EN(L)
Input Voltage (V)
Temperature (°C)
1154.200.