CS3972YT5

CS3972 CS3972 1.25A High Efficiency Switching Regulator Description The CS3972 is a 1.25A, 60V, current mode, high efficiency, switching regulator circuit. It can be configured in buck, boost, forward, isolated and non-isolated topologies, using a single-ended switch. The IC contains a 1.25A high efficiency output switch, precision bandgap reference, voltage regulator, error amplifier, oscillator, control, and protection circuitry. Output transistor efficiency is achieved by keeping the switch in quasi-saturation when it is on. This minimizes the switch turn-off delay time and power dissipation, an important consideration for applications with wide ranging loads. The precision reference is internally trimmed to 1.24V, while the oscillator frequency is internally trimmed to 40kHz. The on board 2.3V regulator powers the internal circuitry. By keeping the voltage regulator at 2.3V, the IC is able to operate down to 3V and maintain a constant input supply current of 6mA(typ). Synchronization mode is achieved by applying a pulsating VC voltage of less than 0.2V with a duration of about 0.5µs to VC pin. The switching frequency can be adjusted from 50kHz to 70kHz. The IC's synchronization mode is set externally. Protection circuitry includes a variable current limit with external voltage clamp, under-voltage and over-temperature protection. Features s 75VMAX, 2APEAK Internal Switch s 3V to 60V Input Voltage Range s 6mA Input Supply Current s 1.24V Precision Reference s 40kHz Switching Frequency s Variable Current Limit with External Voltage Clamp s Under-Voltage Protection s Over-Temperature Protection s External Synchronization Package Options Block Diagram NC VC VFB VSW VIN 2.3V Reg Output Protection 1 16L SO Wide Gnd NC E2 VSW NC E1 NC VIN NC NC NC 40kHz OSC Logic Driver 1.25A, 75V Switch NC NC + VC COMP Gnd 1 8L PDIP E2 VSW E1 VIN 5L TO-220 Tab (Gnd) VFB Error Amp + 1.24V Ref VC + Current Amp 0.22Ω 0.22Ω E2 * E1 * Gnd VFB NC 1 VC 2 VFB 3 Gnd 4 VSW 5 VIN 1 *Always connect E1 to Ground Pin on DIP package. Both emitters are tied to ground on TO-220 Package. Cherry Semiconductor Corporation 2000 South County Trail, East Greenwich, RI 02818 Tel: (401)885-3600 Fax: (401)885-5786 Email: info@cherry-semi.com Web Site: www.cherry-semi.com Rev. 6/23/99 1 A ® Company CS3972 Absolute Maximum Ratings Input Voltage Range ........................................................................................................................................................3V to 60V Output Switching Voltage.........................................................................................................................................................75V Voltage Transient (tr=10µs, tf=400ms) ......................................................................................................................................60V ESD (Human Body Model; R=1.5kΩ, C=100pF) ...................................................................................................................2kV Junction Temperature Range...............................................................................................................................-40°C to +150°C Storage Temperature Range ................................................................................................................................-65°C to +150°C Lead Temperature Soldering Wave Solder (through hole styles only)......................................................................................10 sec. max, 260°C peak Reflow (SMD styles only) ......................................................................................60 sec. max above 183°C, 230°C peak Feedback Pin Voltage (1ms transient)...................................................................................................................................±15V Electrical Characteristics: For 3V≤VCC≤60V, -40°C≤TA≤125°C unless otherwise specified. PARAMETER TEST CONDITIONS MIN TYP MAX UNIT s Reference Voltage Line Regulation Feedback Input Current Minimum Input Voltage Supply Current Supply Current Increase during switch on time Switching Frequency Maximum Duty Cycle VC Threshold VC=0.8V; VFB=VREF VC=0.8V; VFB=VREF, 3V≤VIN≤60V VC=0.8V; VFB=VREF VC=VFB=VREF VC=0.6V; 3V≤VIN≤60V VC=open, 1.0V≤VFB≤1.5V VC=VFB=VREF; VSW=15V VC=2V; VFB=open, VSW=15V VFB=open; VSW =15V, duty cycle=0% 1.214 1.244 350 2.6 6.0 25 40 92 0.90 1.274 0.03 1100 3.0 9.0 V %/V nA V mA mA/A kHz % V 33 0.60 47 1.25 s Error Amplifier Transconductance Source/Sink Current High Voltage Clamp Low Voltage Clamp Gain s Output Switch Breakdown Voltage On Resistance Control Voltage to Switch Current Transconductance Current Limit VC=0.8V; VFB=VREF, ∆IC=±25µA VC=1.5V VFB=1.0V VFB=1.5V 0.9V≤VC≤1.4V, VFB=VREF 2400 120 4400 200 2.0 0.38 800 7000 400 µmho µA V V V/V VC=0.5V; 3V≤VIN≤60V, IOUT=5mA VC=open, VFB=0.8V, IOUT=1.25A 1.2V≤VC≤1.8V Duty Cycle≤50%, TJ≥25°C Duty Cycle≤50%, TJ