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AX3021
200KHz, 1.5A PWM Buck DC/DC Converter
GENERAL DESCRIPTION The AX3021 series are monolithic IC designed for a step-down DC/DC converter, and own the ability of driving a 1.5A load without additional transistor. It saves board space. The external shutdown function can be controlled by logic level and then come into standby mode. The internal compensation makes feedback control having good line and load regulation without external design. Regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is against over current operating of the output switch. If current limit function occurs and VFB is down below 0.5V, the switching frequency will be reduced. The AX3021 series operates at a switching frequency of 200KHz thus allow smaller sized filter components than what would be needed with lower frequency switching regulators. Other features include a guaranteed +3% tolerance on output voltage under specified input voltage and output load conditions. The chips are available in a standard 8-lead SOP Expose-Pad package.
•yÑb€ R ` w FEATURES VÛm om c . ch version. e t Output voltage: adjustable output o of voltage range: 0.75V to 22V+3%. g . Adjustable version output ww w 200KHz fixed switching frequency.
Voltage mode non-synchronous PWM control. Thermal-shutdown and current-limit protection. ON/OFF shutdown control input. Short Circuit Protect (SCP). Operating voltage can be up to 24V. Output load current: 1.5A. Expose-Pad (EP) SOP-8L Pb-Free packages. Low power standby mode. Built-in switching transistor on chip.
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Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.1.2 Aug.09, 2010
AX3021
BLOCK DIAGRAM
EN
200mV
V CC
220mV CURRENT SOURCE BIAS 0.75V REFERENCE 2.5V REGULATOR START UP
COMP.
+ _
Current limit
COMP.
FB
+ AMP _ COMP.
+
COMP.
CONTROL + DRIVER
Thermal Shutdown
PIN ASSIGNMENT The package of AX3021 is SOP-8L-EP; the pin assignment is given by:
( Top View ) NC VCC SW VSS 1 2 3 4 SOP-8L-EP
VÛm
Ñb€ • y w`R
ww
o f8 o g w.
7 6 5
t NC
EN
om c . ech
NC FB
Name VCC SW FB EN VSS
Operating voltage input Switching output Output voltage feedback control ON/OFF Shutdown GND pin
ORDER/MARKING INFORMATION Order Information
AX3021 XX X
Package Type Packing ES: SOP-8L-EP Blank : Tube A : Taping
Logo
3 0 21 AX Y Y WW X
Axelite Confidential Materials, do not copy or distribute without written consent.
_
200KHz OSC.
+
_
SW Vss
Description
AX3021
Top Marking
Part number ID code:internal WW: 01~52 Year: 10=2010 11=2011
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Rev.1.2 Aug.09, 2010
AX3021
ABSOLUTE MAXIMUM RATINGS Characteristics Maximum Supply Voltage ON/OFF Pin Input Voltage Feedback Pin Voltage Output Voltage to Ground Power Dissipation Internally limited Storage Temperature Range Operating Junction Temperature Range Operating Supply Voltage Thermal Resistance from Junction to case Thermal Resistance from Junction to ambient
Symbol VCC VEN VFB VOUT PD TST TJ VOP θJC θJA
Rating +26 -0.3 to VCC -0.3 to 12 -0.8 ( TJ-TA ) / θJA -65 to +150 -20 to +125 +4.0 to +24 20 50
Unit V V V V W °C °C V °C/W °C/W
Note: θJA is measured with the PCB copper area(need connect to Expose-Pad) of approximately 1.5 in2 (Multi-layer).
ELECTRICAL CHARACTERISTICS (Unless otherwise specified, TA=25°C, VCC=12V, VOUT=3.3V, IOUT = 0.2A) Characteristics Symbol Conditions Min Typ Max Units Feedback Voltage VFB IOUT=0.2A 0.728 0.750 0.773 V Quiescent Current IQ VFB=1.2V force driver off 4 8 mA Feedback bias current IFB IOUT=0.1A -10 -50 nA Shutdown supply Current ISD VEN =0V 2 10 uA Oscillator frequency FOSC 140 200 260 KHz Oscillator frequency of short F (Adjustable) When 80 KHz SCP VÛmw`R•yÑb€ circuit protect VFB<0.5V Max. Duty Cycle (ON) VFB=1.2V force driver off 0 DC % Min. Duty Cycle (OFF) VFB=0V force driver on 100 Pear current, No outside w.goftech.com Current limit ICL circuit 1.8 A VFB=0V force driver on IOUT=1.5A, No outside Saturation voltage VSA T circuit 1.2 1.5 V VFB=0V force driver on SW pin leakage current No outside circuit -200 uA SW pin=0V V =1.0V force driver off ISW L FB SW pin leakage current VCC=24V force driver off -5 mA SW pin=-0.8V VIH High (regulator ON) 2.0 EN pin logic input threshold 1.2 V voltage VIL Low (regulator OFF) 0.5 EN pin logic input current IH VEN=2.5V (ON) 20 uA EN pin input current IL VEN=0.3V (OFF) -5 Thermal shutdown Temp TSD 135 °C
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Axelite Confidential Materials, do not copy or distribute without written consent.
Rev.1.2 Aug.09, 2010
AX3021
APPLICATION CIRCUIT (1) Adjustable Output Voltage Version
VIN=12V U1 AX3021 8 NC NC 7 2 Vcc EN 3 SW 6 NC 5 4 Vss FB 1 C2 220uF C3 0.1uF L1 33uH Vout=5V/1.5A R1 6.8K C5 330uF C8 0.1uF R2 1.2K
D1 B240A
(2) EN PIN with Delayed Startup
VIN=12V U1 AX3021 8 NC NC 7 2 Vcc EN 3 SW 6 NC 5 4 Vss FB 1 C2 220uF C3 0.1uF R3 100k L1 33uH Vout=5V/1.5A R1 6.8K C5 330uF C8 0.1uF R2 1.2K
D1 B240A
C4 0.1uF
VOUT = VFB (1Ñb +€
V 1 Resistor select Table .cofor .