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Advanced Monolithic Systems
FEATURES
* Stable with low ESR Output Ceramic Capacitors * Up to 95% Efficiency * 2A Continuous Output Current * Wide 4.75V to 20V Operating Input Range * Fixed 480kHz Frequency * Thermal Shutdown * Cycle-by-cycle + hiccup Over Current Protection * Under Voltage Lockout * Frequency Synchronization Input * Operating Temperature: -40C to 125C * Available in an 8-Pin SO Package
AMS4155
2A OUTPUT PWM BUCK CONVERTER
RoHS compliant
APPLICATIONS
* Battery Chargers * Portable (Notebook) Computers * Industrial power supply * Point of regulation for high performance electronics * Consumer Electronics * Audio Power Amplifiers * Distributed Power Systems * Pre-Regulator for Linear Regulators * LCD TVs and LCD monitors
GENERAL DESCRIPTION
The AMS4155 is a monolithic step down switch mode converter with a built in internal power Switch Transistor. It achieves 2A continuous output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes cycleby-cycle current limiting and thermal shutdown. In shutdown mode the regulator draws 17A of supply current.
ORDERING INFORMATION
OUTPUT VOLTAGE Adjustable PACKAGE TYPE 8 Lead SOIC AMS4155S -25C to 125C TEMP. RANGE
TYPICAL APPLICATION
PIN CONNECTIONS
8L SOIC
INPUT 470F/ 10F CER ON OFF EN 8 VIN 3 BST 2
1F 10 H 4 LX B230A 6 F/B 5 GND COMP 10nF 7 30k 40F ceramic 10k
SO Package (S)
OUTPUT 5V/3A
AMS4155
SYNC 1
SYNC BST
1 2
8 7 6 5
EN COMP FB GND
VIN 3 LX 4
5k
Top View
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS4155
PIN DESCRIPTION
Pin Number 1 2 NAME SYNC BST DESCRIPTION Synchronization Input. This pin is used to synchronize the internal oscillator frequency to an external source. Leave SYNC unconnected or connect to GND if unused. Bootstrap. This capacitor is needed to drive the power switch above the supply voltage. It is connected between LX and BST pins to form a floating supply across the power switch driver. The voltage across Cbst is about 5V and is supplied by the internal Vcc supply when LX pin voltage is low. Supply Voltage. The AMS4155 operates from a+4.75V to +23V unregulated input. Cin is needed to prevent large voltage spikes from appearing at the input power supply. This connects the inductor to the internal Switch Ground Pin connected to PCB ground plane. This pin is also the ground for internal voltage reference. Feedback. A resistor network of two resistors is used to set-up the output voltage connected between Output to GND. The node between the two resistors is connected to Feedback pin. Compensation. This node is the output of the transconductance error amplifier and the input to the current comparator. Frequency compensation is done at this node by connecting a series R-C to ground. Enable. A voltage greater than 2.495V at this pin enables device operation.
3 4 5 6 7
VIN LX GND FB COMP
8
ENABLE
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS4155
ABSOLUTE MAXIMUM RATINGS
VIN F/B EN BST 28V -0.3V to +6V -0.3V to +6V VLX + 6V LX COMP SYNC -1V to +28V -0.3V to +6V -0.3v to +6V
Junction Temperature Storage Temperature Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds
+150C -65C to +150C 260C
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at TA= 25 C and VIN=12V (unless otherwise noted). PARAMETER TEST CONDITIONS Min. AMS4155 Typ. Max. Units
Feedback Voltage Switch On Resistance Switch Leakage Current Limit
(1)
4.75V VIN 20V, VCOMP < 2V VEN = 0V; VLX = 0V
1.215
1.255 0.18 0
1.285 10 6
V A A A/V V/V A/V KHz MHz % % V mV A V mV A mA C
3.4
4 1.9
Current Amplifier Gain Error Amplifier Voltage Gain Error Amplifier Transconductance Oscillator Frequency Sync Frequency Maximum Duty Cycle Minimum Duty Cycle Enable Threshold Enable Hysteresis Enable Pull-up Current Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis Supply Current (Shutdown) Supply Current (Quiescent) Thermal Shutdown IC = 10A Sync Drive 0.5V to 2.7V VFB = 1.0V VFB = 1.5V 420 0.460
400 730 460 85
500 1.1 3.2 2.55
2.2
2.475 220 0.7 2.5 200 17 0.95 153
2.4 VEN 0.4V VEN 2.8V; VFB = 1.5V
2.6 25 1.1
Note: 1) Equivalent output current = 1.5A 50% Duty Cycle 2.0A 50% Duty Cycle Assumes ripple current = 30% of load current.
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS4155
TYPICAL PERFORMANCE CHARACTERISTICS
Light load start up
Full load start up
PWM rising edge
PWM Falling edge
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS4155
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
0.5-3A transient on 5V output Full load Sat (reference = supply at IC)
Typical waveform set at 3.3V output, 2A load and 12V input.
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723
AMS4155
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
8 LEAD SOIC PLASTIC PACKAGE (S)
0.189-0.197* (4.801-5.004) 8 7 6 5 8
0.123 (3.12) 0.137 (3.48) 7 6
5
0.228-0.244 (5.791-6.197)
0. 150-0.157** (3.810-3.988)
0.090 (2.28) 0.102 (2.59)
1
2
3
4
1
2
3
4
0.053-0.069 (1.346-1.752)
0.010-0.020 x 45 (0.254-0.508) 0.004-0.010 (0.101-0.254) 0.008-0. 010 (0.203-0.254) 0-8 TYP
0.014-0.019 (0.355-0.483)
0.050 (1.270) TYP
0.016-0.050 (0.406-1.270)
S (SO- 8 ) AMS DRW# 042293
0.024(0.61) 0.063(1.60)
0.050(1.27)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.105(2.67)
0.213(5.41)
0.138 (3.50) RECOMMENDED LAYOUT PATTERN
Advanced Monolithic Systems, Inc. www.advanced-monolithic.com
Phone (925) 443-0722
Fax (925) 443-0723

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