SMD7325 PWM Cntroller IC for Flyback Power Supply

Transcription

1 FEATUES Excellent Gate Driving Capability for High Efficiency Performance 1uA Low Startup Current 0.8mA Low Operating Current Low Power Consumption at Burst Mode Multiple Protection Functions (OTP, OVP, OLP) Internal 200nS Leading Edge Blanking Minimum Frequency of 21KHz to Avoid Audible Noise Accurate Current Hysteresis for External OTP for Auto-estart Version Internal 6mS Soft-Start Time Cycle-by-Cycle Current Limit Frequency Jittering for EMI eduction DESCIPTION The SMD7325 is a highly integrated current mode controller targeting at 60W Flyback power supply designs. Under light load conditions, the controller enters frequency optimization followed by burst mode to minimize the input standby power and maintain high efficiency performance. This feature allows the power supplies to meet the stringent worldwide energy requirements. A Protection pin is added in the SMD7325 for programming multiple protection functions. This pin allows designers to implement latched or auto-recovery behavior; which greatly enhances the reliability and robustness of the power supply. The SMD7325 also features frequency dithering centered at 65KHz, 100KHz to spread the EMI spectrums and save cost on EMI components. The SMD7325 is available in SOT-26 package. TYPICAL APPLICATIONS General Purpose SMPS AC Adaptors for Notebook PC, Netbook Off-Line Battery Charger LCD Monitor, Set-Top Boxes, DVD, Power Tools Open-Frame SMPS Standby Power for TV, PC, Home Appliances 1 / 7

2 BLOCK DIAGAM VCC LATCH OVP Sensor 8 cks Debounce Vcc OVP PG Bias OK Bias & Bandgap UVLO 14V/8V OTP Sensor 8 cks Debounce ESET S ESET 2V Vcc OVP 25V Open Loop Prorection 4.5V Frequency Jitter 100mS Debounce OSC Vcc UV S COMP Internal Bias=5V 3 No Green Mode control (VFB<1.2V) Burst Mode control (VFB<0.6V) Internal OTP Slope compensation 0V Soft start time=6ms S PG Driver Stage GATE CS LEB VCS limit (0.8V) OPP Compensate PCAKAGE INFOMATION VCC COMP CS OUT TOP VIEW LATCH GND SOT-26 2 / 7

3 PIN FUNCTIONS Pin No. Pin Name Function 1 VCC Power supply for the IC 2 CS Current sense input 3 OUT Gate drive of the main MOSFET Switch 4 GND Ground 5 LATCH Protection pin. This pin combines OVP, and OTP functions 6 COMP Voltage feedback pin. Connect a photo-coupler to close the control loop for output voltage regulation ODEING INFOMATION Product Number PKG. OHS Shipping SMD7325 SOT-26 GEEN 3000 / Tape & eel 3 / 7

4 POWE DISSIPATION TABLE SOT-26 PACKAGE Total Power Dissipation PD 250 mw Operational junction temperature T J -40 to OTP ºC Storage temperature T STG -65 to +150 ºC Junction-to-Air Thermal esistance θja 250 ºC/W ABSOLUT MAXIMUM ATINGS (Note 1) Item Symbol atings Units VCC pin voltage V CC -0.3 to OVP V OUT pin voltage V OUT -0.3 to Clamping V OUT pin driver curent I OUT 300 ma FB, CS, POT pin voltage V FB -0.3 to 7 V ESD Human Body Model HBM 3 KV ESD Machine Model MM 250 V Note 1: Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. 4 / 7

5 ELECTICAL CHAACTEISTICS (Ta=25, VCC =15V,unless otherwise noted) Symbol Parameter Test conditions Min. Typ. Max. Unit Supply Voltage(VCC) V CC (ovp) Internal OVP Trigger Point V T VCC(ovp) De bounce when internal OVP 8 CK VCC (on) Turn on Threshold Level, Vcc Going up UVLO_ON? V VCC (min) Minimum Operating Voltage after Turn on UVLO_OFF? V VCC (reset) Internal Latch eset Level (latch only) 1 V V CC_ clamp Input V CC clamp Point 30 V I start start up current IC Operating Current at V CC =10V 1 2 ua I cc1 IC Operating Current with OUT Load = 1nF IC Operating Current at Vcc=15V, V COMP =2V ma I cc2 IC Operating Current with No Load. IC Operating Current at Vcc=15V, V COMP =2V ma Icc_burst IC Operating Current in Burst Mode Vcc=15V, VCOMP=0V ua GATE Output Section (OUT) VOL Output Voltage Low Io = -20mA 0.8 V VOH Output Voltage High Io = 20mA 6 V Vgate_Clamp Gate Output Clamp Voltage VCC = 15V V Tr ising time CL = 1nF 100 ns Tf Falling time CL = 1nF 40 ns Current Sense Section (CS) VCS_Max1 V CS_Max2 T CS(delay) Max. Peak Current limit VCS voltage (Duty>75%) Max. Peak Current limit VCS voltage (Duty<25%) Propagation Delay from CS Detected to Gate Turned off 0.75 V V 100 ns TLEB Leading-Edge Blanking time 300 ns I SLOPE Max. slope current 20 ua 5 / 7

6 Internal Oscillator Section F OSC Oscillation Frequency VCC=15V, VCOMP=2V, VCS=0V KHz F OSCG Minimum Oscillation Frequency VCC=15V, VCOMP=1.3V, VCS=0V KHz Vburst_in Burst Mode Entering Setpoint 1.2 V Vburst_off Burst Mode Leaving Setpoint 1.3 V Fjitter Frequency Jittering in Percentage ±5 % Fswing Jittering Switching Frequency 4 ms Dmax Maximum Duty Cycle % Feedback (COMP) UP Internal Pull-up esistor 40 KΩ V ATION Voltage Divider atio from FB pin 3.5 to CS Pin VFB(max) Maximum V FB Voltage 5 V Tsoft Soft start time ms Protection (LATCH) I OTP Maximum OTP Shutdown Source Vcc=15V, Vcomp=0V, VOTP=0.55V ua Current Sink V OTP External OTP Trigger Point V T OTP OTP De-Bounced Time 8 CK VHOLD Latch Holding Voltage Vcc=15V, Vcomp=0V V V OVP External OVP Trigger Point V T OVP OVP De-Bounced Time 8 CK TFB(OLP) TSD TSD_HY OLP(open loop protection) De-Bounced Time Internal Temperature Shutdown, Maximum Value Internal Temperature Shutdown Hysteresis ms / 7

7 PACKAGE DIMENSION 7 / 7