CS3972 CS3972 1.25A High Efficiency Switching Regulator Features 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. ■ 75VMAX, 2APEAK Internal Switch ■ 3V to 60V Input Voltage Range ■ 6mA Input Supply Current ■ 1.24V Precision Reference ■ 40kHz Switching Frequency ■ Variable Current Limit with External Voltage Clamp ■ Under-Voltage Protection ■ Over-Temperature Protection ■ External Synchronization Package Options Block Diagram 16L SO Wide NC VSW VIN Output Protection 2.3V Reg 40kHz OSC Logic + 1.25A, 75V Switch Driver Gnd 1 VC NC VFB E2 NC VSW NC NC NC E1 NC NC NC VIN 8L PDIP COMP 5L TO-220 Tab (Gnd) - VC Gnd 1 Error Amp VFB + VC + Current Amp - 0.22Ω 0.22Ω 1.24V Ref E2 VSW VFB E1 NC VIN 1 VC E2* 2 VFB E1* 3 Gnd Gnd 4 VSW 5 VIN *Always connect E1 to Ground Pin on DIP package. Both emitters are tied to ground on TO-220 Package. 1 ON Semiconductor 2000 South County Trail, East Greenwich, RI 02818 Tel: (401)885–3600 Fax: (401)885–5786 N. American Technical Support: 800-282-9855 Web Site: www.cherry–semi.com June, 1999 - Rev. 8 1 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 1.214 1.244 MAX UNIT ■ 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 ■ Error Amplifier Transconductance Source/Sink Current High Voltage Clamp Low Voltage Clamp Gain ■ Output Switch Breakdown Voltage On Resistance Control Voltage to Switch Current Transconductance Current Limit VC=0.8V; VFB=VREF VC=0.8V; VFB=VREF, 3V≤VIN≤60V VC=0.8V; VFB=VREF 1.274 V 0.03 %/V 350 1100 nA VC=VFB=VREF VC=0.6V; 3V≤VIN≤60V 2.6 6.0 3.0 9.0 V mA 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% 25 40 92 0.90 33 0.60 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 VC=0.5V; 3V≤VIN≤60V, IOUT=5mA VC=open, VFB=0.8V, IOUT=1.25A 1.2V≤VC≤1.8V 75 90 0.6 2 Duty Cycle≤50%, TJ≥25°C Duty Cycle≤50%, TJ<25°C Duty Cycle=80% Duty Cycle=80% (Note 1) 1.25 1.25 1.00 0.50 Note 1: 16 lead SO wide package only. 2 47 1.25 7000 400 mA/A kHz % V µmho µA V V V/V 1.0 V Ω A/V 3.00 3.50 2.50 2.50 A A A A CS3972 Package Pin Description PACKAGE PIN # PIN SYMBOL FUNCTION 16L SO Wide 5L TO-220 8L PDIP 16 3 1 Gnd Logic and power ground on TO-220. Logic ground only on 8L PDIP. 2 1 2 VC Control voltage can be used for frequency compensation, current limit threshold, frequency synchronization, and soft start. 3 2 3 VFB Feedback voltage is the negative input to the error amplifier. 4 NC No connection. 5 VIN Supply input voltage with a range of 3V to 60V. 6 E1 Emitter One is a power ground which should always be connected to logic ground since it is used as the negative input to the current sense amp. 7 VSW 8 E2 1,4,5,6,7,8, 10,12,15 9 5 11 13 4 14 Collector of internal 75V NPN power switch. Emitter Two is a power ground which can be left disconnected to reduce the switch rating to 625mA. Typical Performance Characteristics Switching Frequency vs. Temperature 1.274 47 1.264 45 Driver Current vs. Switch Current 100 90 80 1.254 1.244 1.234 1.224 43 Driver Current (mA) Frequency (kHz) Reference Voltage (V) Reference Voltage vs. Temperature 41 39 37 35 70 60 50 40 30 20 10 1.214 -50 -25 -0 25 50 75 100 125 33 -50 150 -25 -0 Temperature (°C) 25 50 75 100 125 150 Temperature (°C) 1.6 97 Switch Saturation Voltage (V) Tj=25°C Duty Cycle (%) 96 95 93 92 91 90 -50 -25 -0 25 50 75 100 Junction Temperature (°C) 125 150 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 0.25 0.50 0.75 1.00 1.25 1.50 Switch Current (A) 3 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Switch Current (A) Switch Saturation Voltage Maximum Duty Cycle 0 1.75 2.0 1.6 1.8 2.0 CS3972 Circuit Description The CS3972 has an on board, high current NPN transistor in its output stage. The output transistor is switched on every 25µs by the on board 40 kHz oscillator. The output is switched off as soon as the output current reaches a dynamically controlled level. That level is determined by three factors: the current drawn by the load, the input voltage, and the output voltage. This control scheme has several benefits. The IC reacts quickly to overvoltage and short circuit conditions and it is less sensitive to input voltage fluctuation. Current drawn by the load influences when the output stage turns off. The voltage across the internal high precision resistor (0.11Ω) in the emitter of the output transistor generating the input to the current sensing amplifier. The output of the current sensing amplifier provides one of the inputs to the comparator. The other input to the comparator connected to the output of the error amplifier whose inverting input is connected to the output voltage through the feedback circuitry while its noninverting input is set to an internal reference voltage of 1.24V. When the current sensing amplifier output exceeds the error amplifier output, the comparator switches off, triggering the logic which turns off the output stage. All on board amplifier, logic and protection circuitry uses the internal 2.3V reference to minimize quiescent current drain (6mA) and permits IC operation down to 3V. The anti-saturation circuitry minimizes output switch turn off time and power dissipation, by keeping the power NPN at the edge of saturation. Application Diagrams L1 VIN D1 VOUT VIN L1 Q1 R2 VOUT R1 R3 VSW VSW VIN VIN VFB CS3972 VC (1.24V) Gnd C3 VC (1.24V) VFB CS3972 + + C3 Gnd + + C1 C1 R3 R1 R4 R2 D1 C2 C2 Figure 1: Boost Regulator Figure 2: Buck Regulator with the External Switch VOUT1 + TR1 VIN L1 D1 +VIN VOUT TR1 C5 + C4 C3 D2 VOUT2 R1 C1 + D3 C6 C5 1/2 OC1 R4 VSW VIN CS3972 VC + C2 VFB (1.24V) C2 + R5 VSW VIN VC R6 VFB CS3972 R1 C4 Gnd Gnd –VIN C3 Figure 3: Flyback Multiple Output Regulator U1 1/2 OC1 R2 R5 R2 C3 D1 R7 R3 Figure 4: Isolated Forward Regulator 4 R4 CS3972 Package Specification PACKAGE THERMAL DATA PACKAGE DIMENSIONS IN mm (INCHES) D Lead Count Metric Max Min 10.16 9.02 10.50 10.10 8 Lead PDIP 16 Lead SO Wide Thermal Data English Max Min .400 .355 .413 .398 RΘJC RΘJA typ typ 5L TO-220 1.7 50 8L PDIP 52 100 Plastic DIP (N); 300 mil wide 7.11 (.280) 6.10 (.240) 8.26 (.325) 7.62 (.300) 1.77 (.070) 1.14 (.045) 2.54 (.100) BSC 3.68 (.145) 2.92 (.115) .356 (.014) .203 (.008) 0.39 (.015) MIN. .558 (.022) .356 (.014) REF: JEDEC MS-001 Some 8 and 16 lead packages may have 1/2 lead at the end of the package. All specs are the same. D Surface Mount Wide Body (DW); 300 mil wide 7.60 (.299) 7.40 (.291) 10.65 (.419) 10.00 (.394) 0.51 (.020) 0.33 (.013) 1.27 (.050) BSC 2.49 (.098) 2.24 (.088) 1.27 (.050) 0.40 (.016) 2.65 (.104) 2.35 (.093) 0.32 (.013) 0.23 (.009) D REF: JEDEC MS-013 5 0.30 (.012) 0.10 (.004) 16L SO Wide 23 105 °C/W °C/W CS3972 Package Specification 5 Lead TO-220 (T) Straight 4.83 (.190) 4.06 (.160) 10.54 (.415) 9.78 (.385) 1.40 (.055) 1.14 (.045) 3.96 (.156) 3.71 (.146) 2.87 (.113) 6.55 (.258) 2.62 (.103) 5.94 (.234) 14.99 (.590) 14.22 (.560) 14.22 (.560) 13.72 (.540) 1.02 (.040) 0.76 (.030) 1.83(.072) 1.57(.062) 1.02(.040) 0.63(.025) 6.93(.273) 6.68(.263) 0.56 (.022) 0.36 (.014) 2.92 (.115) 2.29 (.090) Ordering Information Part Number CS3972YN8 CS3972YDW16 CS3972YDWR16 CS3972YT5 ON Semiconductor and the ON Logo are trademarks of Semiconductor Components Industries, LLC (SCILLC). ON Semiconductor reserves the right to make changes without further notice to any products herein. For additional information and the latest available information, please contact your local ON Semiconductor representative. Description 8L PDIP 16L SO Wide 16L SO Wide (tape & reel) TO-220 Straight 6 © Semiconductor Components Industries, LLC, 2000 Notes Notes 8