AX3304SA

AX3304 PWM Control Controller  GENERAL DESCRIPTION The AX3304/A integrates Pulse-Width-Modulation (PWM) control circuit into a single chip, mainly designs for power-supply regulator. All the functions include an error amplifier, a soft-start, UVLO, OVP, SCP, TSD circuitry. This device features an internal 100KHz oscillator (300KHz for "A" version), the UVLO makes sure that the outputs are off until the internal circuit operates normally.  FEATURES - Input voltage：8V to 40V - Duty ratio：0% to 100% PWM control - Oscillation frequency：100K/300KHz - Thermal Shutdown function. Short Circuit Protect (SCP). External SW P-channel MOS. External OVP setting function. Current mode non-synchronous PWM converter - External current limit setting. - Under voltage Lockout. - SOP-8L Pb-Free package. 1/12 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.3 Jun.26, 2012 AX3304  BLOCK DIAGRAM EN/CT VCC CURRENT SOURCE BIAS 2.5 V REGULATOR 1.23V REFERENCE START-UP and Auto restart control 1.00V Current limit _ OSC. COMP. VSENSE + + AMP _ FB 115 mV + COMP. _ _ OVP VGATE AMP + 1.10V CONTROL + DRIVER OVP GATE + AMP _ 0.4V Thermal Shutdown SCP Line Compensation GND  PIN ASSIGNMENT The package of AX3304/A is SOP-8L; the pin assignment is given by: EN/CT 1 GND 2 VGATE 3 VCC 4 AX3304/A ( Top View ) 8 FB 7 OVP 6 VSENSE 5 GATE SOP-8L Name Description EN/CT Shutdown and auto restart control pin GND GND pin Driver gate clamping pin. The pin VGATE must connect a 0.1uF capacitor to VIN VCC Operating voltage input Switch pin. Connect external inductor GATE and diode here VSENSE Voltage Sense input OVP Over voltage detect pin FB Feedback pin  ORDER/MARKING INFORMATION Order Information AX3304 X X X Top Marking Logo AX 3 3 0 4 A Y YWWX Frequency Package Type Blank : 100KHz S: SOP-8L A: 300KHz Packing Blank : Tube A : Taping Blank: AX3304 A: AX3304A Part number ID code: internal WW: 01~52 Year: 11=2011 12=2012 2/12 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.3 Jun.26, 2012 AX3304  ABSOLUTE MAXIMUM RATINGS (at TA = 25°C) Characteristics VCC Pin Voltage Symbol Rating Unit VCC GND - 0.3 to GND + 45 V GND - 0.3 to VIN V GND - 0.3 to 6 V VGATE, VSENSE Pin Voltage Feedback, OVP, EN/CT Pin Voltage Switch Pin Voltage VSW GND - 0.3 to VIN + 0.3 V Power Dissipation PD (TJ – TA)/ θJA W Storage Temperature Range TST -40 to +165 °C Operating Temperature Range TOP -20 to +125 °C Operating Supply Voltage VOP +8 to +40 V Thermal Resistance from Junction to case θJC 15 °C/W Thermal Resistance from Junction to ambient θJA 40 °C/W Note : θJA is measured with the PCB copper are (need connect to Exposed pad) of approximately 1 in2(Multi-layer).  ELECTRICAL CHARACTERISTICS (VIN=12V, TA=25°C, unless otherwise specified) Characteristics Symbol Conditions Min. Typ. Max. Units Feedback Voltage VFB IOUT=10mA 0.98 1 1.02 V Under Voltage Lockout UVLO Rise 6 V UVLO Hysteresis OVP detect voltage Line Regulation Load Regulation VOVP - Quiescent Current ICCQ Oscillator frequency FOSC Max. Duty Cycle (ON) Min. Duty Cycle (OFF) Sense Voltage EN/CT pin logic input threshold voltage EN/CT pin current EN/CT pin current Thermal shutdown Temp Thermal Shutdown Hysteresis DC Internal define VIN=10 ~ 40V, IOUT=10mA IOUT=0~3A, RSENSE = 33mΩ AX3304/A VFB = 1.5V, force driver off. AX3304 IOUT = 0.5A AX3304A Force driver on VFB = 0.6V Force driver off VFB = 1.5V VCC-VSENSE VEN1 Shutdown mode VCT Auto restart, VFB1.23V, the OVP is happened that it can turn-off the driver. Under Voltage Lockout (UVLO) To avoid error-operation of the device at low input voltages an under voltage lockout is included that disables the device, if the input voltage falls below 6.0V. 4/12 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.3 Jun.26, 2012 AX3304 Thermal Considerations The SOP-8L package needs a heat sink under most conditions. The heat sink connect exposed pad of AX3304/A to obtain best effect. The size of the heat sink depends on the input voltage, output voltage, output current and ambient temperature.  APPLICATION INFORMATION Setting the Output Voltage Application circuit item shows the basic application circuit with adjustable output version. The external resistor sets the output voltage according to the following equation: VOUT = 1.0V × (1+ R3 ) R6 Table 1 Resistor select for output voltage setting VOUT R6 R3 5.0V 3K 12K 3.3V 3K6 8K2 Current Limit Protection The Current limit is set by external resistor (RSENSE), When the VSENSE pin voltage small than VCC 115mV, the current limit is happened that driver can be turned off. Refer to the following equation for set up current limit: Current Limit (A) = 115mV R SENSE The maximum output current table is shown as below; please refer the table to design. RSENSE (Ω) Current Limit (A) Maximum Output Current (A) 29m 3.96 3.7 38m 3.03 3.0 54m 2.13 1.9 5/12 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.3 Jun.26, 2012 AX3304 Inductor Selection For most designs, the different frequency can be reducing the inductor value; The AX3304/A is suggested 22µH to 100µH for 100K to 300KHz frequencies. Please refer the below table to design. L1 recommend value (VIN=10~30V ,VOUT=5V, IOUT=2A) Version AX3304 AX3304A L1 Value (H) 68~100u 22~47u Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high ripple currents. Choose inductor ripple current approximately 20% of the maximum load current 3A, ΔIL=0.6A. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (3A+0.3A). Input Capacitor Selection This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5 times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A 220~470µF low ESR capacitor for most applications is sufficient. Output Capacitor Selection The output capacitor is required to filter the output and provide regulator loop stability. The important capacitor parameters are; the 100 KHz Equivalent Series Resistance (ESR), the RMS ripples current rating, voltage rating, and capacitance value. For the output capacitor, the ESR value is the most important parameter. The ESR can be calculated from the following formula. V RIPPLE   I L  ESR = 0.6A x 80mΩ= 48mV 6/12 Axelite Confidential Materials, do not copy or distribute without written consent. Rev.1.3 Jun.26, 2012 AX3304 An aluminum electrolytic capacitor’s ESR value is related to the capacitance and its voltage rating. In most case, higher voltage electrolytic capacitors have lower ESR values. Most of the time, capacitors with much higher voltage ratings may be needed to provide the low ESR values required for low output ripple voltage. System stability is depending on output capacitor’s ESR, Correct to choose output capacitor’s ESR is very important. It is recommended to using a 220~470µF, the ESR values range is 40~130mΩ. EN/CT The pin is enable/shutdown and auto restart control functions. When system is normal operating, this pin is enable/shutdown function. Pulling this pin below a threshold voltage of under 0.3V shuts the regulator off, and pulling this pin from 0.5V to 1.5V turns the regulator on. However when VOUT is short (VFB