GM38C45

Description GM38C4x is fixed frequency, high performance, and current- mode PWM controllers. Gamma's BiCMOS devices are pin compatible with standard 384x bipolar devices but with several improvements. Undervoltage lockout circuitry allows the '42 and '44 versions to start up at 14.5V and operate down to 9V, and the '43 and '45 versions start at 8.4V with operation down to 7.6V. All versions operate up to 16V. When compared to bipolar 384x devices operating from a 15V supply, start-up current has been reduced to 50µA typical and operating current has been reduced to 4.0 mA typical. Decreased output rise/fall times drive larger MOSFETs, and rail-to-rail output capability increases efficiency, especially at lower supply voltages. GM38C4x also features a trimmed oscillator discharge current and bandgap reference. GM38C4x denotes 8-pin plastic DIP and SOP packages. Features 40ns output rise and 30ns output fall times -40° to +85°C temp. range same as standard UC284x Low-power BiCMOS Process Very low start-up current (50µA typical) Low operating current (4mA typical) CMOS outputs with rail-to-rail swing 500kHz current-mode operation Pin-for-pin compatible with UC3842/ 3843 / 3844/ 3845(A) Trimmed oscillator discharge current UVLO with hysteresis Low cross-conduction currents Application Current-mode, off-line, switched-mode power supplies Current-mode, dc-to-dc converters. Step-down "buck" regulators Step-up "boost" regulators Flyback, isolated regulators Forward converters Synchronous FET converters GM38C42, GM38C43, GM38C44, GM38C45 1 w ww.gammamicro.com GM 431 V0.1 MARKING INFORMATION & PIN CONFIGURATIONS (TOP VIEW) SOP - 8 VDD VREF 8765 OUT GND DIP - 8 VDD VREF 8765 GM38CXX AYWW OUT GND GM38CXX AYWW 1234 COMP FB RT / C T ISNS COMP FB 1234 RT / C T ISNS A = Assembly Location Y = Year W W = Weekly GM38C42, GM38C43, GM38C44, GM38C45 ORDERING INFORMATION Ordering Number GM38C42S8T GM38C42S8R GM38C42D8T GM38C43S8T GM38C43S8R GM38C43D8T GM38C44S8T GM38C44S8R GM38C44D8T GM38C45S8T GM38C45S8R GM38C45D8T Package SOP - 8 SOP - 8 DIP-8 SOP - 8 SOP - 8 DIP-8 SOP - 8 SOP - 8 DIP-8 SOP - 8 SOP - 8 DIP-8 Shipping 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube * For detail Ordering Number identification, please see last page. 2 ABSOLUTE MAXIMUM RATINGS PARAMETER Zener Current Operation at 16V may require special precautions(Note6) Supply Voltage(Note 6) Switch Supply Voltage Current Sense Voltage Feedback Voltage Output Current Storage Temperature SYMBOL IDD VDD VD VISNS VFB IOUT TA VALUE 30 18 18 - 0.3 to + 5.5 - 0.3 to + 5.5 0.5 - 50 to + 150 UNIT mA V V V V A °C OPERATING RATINGS PARAMETER Junction Temperature SYMBOL TJ VALUE 150 UNIT °C PACKAGE PIN DESCRIPTION Compensation: Connect external Compensation network to modify the error amplifier output. Feedback (Input): Error amplifier input .Feedback is 2.5Vat desired output voltage. Current Sense (Input): Current sense comparator input. Connect to current sensing resistor or current transformer. Timing Resistor / Timing Capacitor: Connect external RC network to select switching frequency. Ground: Combined analog and power ground. Power Output: Totem - pole output. Analog Supply (Input): Controller circuitry supply input. Return to analog ground (AGND). 5V Reference (Output): Connect external RC network. 1 2 3 4 5 6 7 8 COMP FB ISNS RT / C T GND OUT VDD VREF BLOCK DIAGRAM VD D 7 35V 5V Reference UVLO * VREF 8 RT / C T 4 Oscillator T Q OUTPUT 6 FB 2 - 2R R 2.5V + - + + S RQ * COMP 1 GND* 5 ISNS 3 * 8 - lead versions only GM38C42, GM38C43, GM38C44, GM38C45 3 PIN LEAD FUNCTION FUNCTION P ower Management ELECTRICAL CHARACTERISTICS (TA = -40°C to 85°C, Note 4, VDD = 15V, CT=3.3 nF, RT=10kW, unless otherwise noted ) CHARACTERISTICS Reference Section Output Voltage Line Regulation Load Regulation Temp. Stability Total Output Variation Output Noise Voltage Long Term Stability Output Short Circuit TEST CONDITIONS MIN TYP MAX UNIT TA = 25°C, IO = 1mA 12V VDD 1 16V, IO = 5µA, (Note 6) IO 20mA 4.9 5.0 2 1 0.2 5.1 20 25 V mV mV mV / °C (Note 1) Line, Load, Temp.,Note 1 10Hz f 10kHz, TA = 25°C, (Note 1) 4.82 5.18 50 5 25 -180 V µV mV mA TA = 125°C, 1000hrs., (Note 1) -30 -80 Oscillator Section Initial Accuracy Voltage Stability Temp. Stability Clock Ramp Reset Current Amplitude TA = 25°C, (Note 5) 12 TMIN VDD TA 16V, (Note 6) TMAX, (Note 1) 49 52 0.2 0.04 55 1.0 KHz % % / °C TA = 25°C, VRT/CT = 2V, TMIN TA TMAX VRT/CT (Peak to Peak) 7.7 7.2 8.4 8.4 1.9 9.0 9.5 mA Vp-p GM38C42, GM38C43, GM38C44, GM38C45 Error Amplifier Section Input Current Input Voltage Open Loop Voltage Gain Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage Unity Gain Bandwidth VFB = 5V VCOMP = 2.5V 2V 12V VO VDD 4V 16V 2.42 65 60 2 -0.5 5.0 -0.1 2.5 90 -2 2.58 µA V dB dB VFB = 2.7V, VCOMP = 1.1V VFB = 2.3V, VCOMP = 5V VFB = 2.3V, RL = 15k to GND VFB = 2.7V, RL = 15k to VREF (Note 1) 14 -1 6.6 0.1 1.1 mA mA V V MHz 0.7 1.0 Current Sense Section Gain Maximum Threshold PSRR Input Bias Current Delay to Output Note 2 and 3 VCOMP = 5V, (Note 2) 12V VDD 16V, (Note 2) 2.85 0.9 3.0 1.0 70 -1.0 120 3.15 1.1 V/V V dB -2 250 µA ns 4 ELECTRICAL CHARACTERISTICS (TA = -40°C to 85°C, Note 4, VDD = 15V, CT=3.3 nF, RT=11kW, unless otherwise noted ) CHARACTERISTICS Output Section RDS(ON) High RDS(ON) Low Rise Time Fall Time Undervoltage Lockout Section GM38C42, GM38C44 Start Threshold GM38C43, GM38C45 GM38C42, GM38C44 Minimum Operating Voltage GM38C43, GM38C45 PWM Section Maximum Duty Cycle Minimum Duty Cycle Total Standby Current µA mA V GM38C42, GM38C43 GM38C44, GM38C45 94 46 96 50 0 % % 7.0 7.6 8.2 13.5 7.8 8 14.5 8.4 9 15.5 9.0 10 V V ISOURCE = 200mA ISINK = 200mA TA = 25°C, CL = 1nF TA = 25°C, CL = 1nF 20 W 11 40 30 80 60 ns ns TEST CONDITIONS MIN TYP MAX UNIT VDD = 7.5V for GM38C43, GM38C45 Operating Supply Current Zener Voltage (VDD) VFB = VISNS = 0V IDD = 25 mA, Note 6 30 4 37 6 Note 1: These parameters, although guaranteed, are not 100% tested in production. Note 2: Parameter measured at trip point of latch with VEA = 0. Note 3: Gain defined as: A= DVPIN1 ;0 VTH (ISNS) VTH (ISNS) 0.8V Note 4: Adjust VDD above the start threshold before setting at 15V. Note 5: Output frequency equals oscillator frequency for the GM38C42 and GM38C43. Output frequency for the GM38C44, and GM38C45 equals one half the oscillator frequency. Note 6: On 8-pin version, 18V is maximum input on pin 7, as this is also the supply pin for the output stage. GM38C42, GM38C43, GM38C44, GM38C45 5 Start - Up Current VDD = 13V for GM38C42, GM38C44 50 200 TYPICAL PERFORMANCE CHARACTERISTICS 100 200pF 100 OUTPUT DEAD TIME (%) VDD = 15V RT RESISTANCE (kW) 470pF 4.7nF 18nF 10 1.8nF 10nF 4.7nF VDD = 15V 1nF 10 10nF 1nF 470pF 200pF 1 1x104 1x105 OSCILLATOR FREQUENCY (Hz) 5x105 1 1x104 1x105 FREQUENCY (Hz) 1x106 Figure 1. Oscillator Frequency Configuration Figure 2. GM38C42, GM38C43 Output Dead Time vs. Oscillator Frequency 1.2 CURRENT SENSE AMP THRESHOLD (V) 9.0 OSC. DISCHARGE CURRENT(mA) 8.8 8.6 8.4 8.2 8.0 7.8 7.6 7.4 7.2 7.0 -60 -30 0 30 60 90 VDD = 15V VOSC = 2V 1.0 0.8 0.6 0.4 -50°C 125°C 25°C GM38C42, GM38C43, GM38C44, GM38C45 0.2 0.0 120 150 0 2 4 6 8 TEMPERATURE (°C) ERROR AMPLIFIER OUTPUT (V) Figure 3. Oscillator Discharge Current vs. Temperature 120 VREF SHORT CURCUIT CURRENT (mA) VDD = 15V Figure 4. Current Sense Amplifier vs. Error Amplifier Output 25 20 OUTPUT VOLTAGE (V) 100 80 60 40 20 0 -60 15 10 5 0 -5 -10 -15 0.0 VD = 15V CL = 1nF -30 0 30 60 90 120 150 0.2 0.4 0.6 0.8 1.0 TEMPERATURE (°C) TIME (µS) Figure 5. Short - Circuit Reference Current vs. Temperature Figure 6. GM38C4X Output Waveform 6 Application Information Familiarity with 384x converter designs is assumed. GM38C4x has been designed to be compatible with 384xA series controllers. GM38C4x Advantages Start-up Current Start-up current has been reduced to an ultra-low 50µA(typical) permitting higher-valued, lower-wattage, and start-up resistors (power controller during power supply start-up). The reduced resistor wattage reduces cost and printed circuit space. Operating Current Operating current has been reduced to 4mA compared to 11mA for a typical bipolar controller. The controller runs cooler and the VDD hold-up capacitance required during start-up may be reduced. Output Driver Complementary internal P-and N-channel MOSFETs produce rail-to-rail output voltages for better performance driving external power MOSFETs. The driver transistor's low on resistance and high peak current capability can drive gate capacitances of greater than 1000pF. The value of output capacitance which can be driven is determined only by the rise/fall time requirements. Within the restrictions of output capacity and controller power dissipation, maximum switching frequency can approach 500kHz. Design Precautions When operating near 20V, circuit transients can easily exceed 20V absolute maximum rating and permanently damaging the controller's CMOS construction. To reduce transients, use a 0.1µF low-ESR capacitor to next to the controller's supply VDD (or VD for '-1' versions)and ground connections. Film type capacitors, such as Wima MKS2, are recommended. When designing high -frequency converters, avoid capacitive and inductive coupling of the switching waveform into high impedance circuitry such as the error amplifier, oscillator, and current sense amplifier. Avoid long printed-circuit traces and component leads. Locate oscillator and compensation circuitry neat the IC. Use high frequency decoupling capacitors on VERF, and if necessary, on VDD. Return high di/dt currents directly to their source and use large ground planes. Buck Converter Refer to Figure 7. When at lest 26V is applied to the input, C5 is charged through R2 until the voltage VDD is greater than 14.5V(the undervoltage lockout value of the GM38C42), output switching begins when Q1is turned on by the gate drive transformer T1 and charging the output filter capacitor C3 through L1. D5 supplies a regulated +12V to VDD once the circuit is running. Current sense transformer CT1 provides current feedback to ISNS for current-mode operation and cycle-by-cycle current limiting. This is more efficient than a high- power sense resistor and provides the required groundreferenced level shift. When Q1 turns off, current flow continues from ground through D1 and L1 until Q1 is turned on again. The 100V Schottky diode D1 reduces the forward voltage drop in the main current path, resulting in higher efficiency than could be accomplished by using an ultra-fast recovery diode. R1 and C2 suppress parasitic oscillations from D1. Using a high-value inductance for L1 and a low-ESR capacitor for C3 permits small capacitance with minimum output ripple. This inductance value also improves circuit efficiency by reducing the flux swing in L1. Magnetic components are carefully chosen for minimal loss at 500kHz. GM38C42, GM38C43, GM38C44, GM38C45 7 VIN 26V to 40V R2 68k D2 M17Z105 1/4W D3 MBR030 6.8k 0.22µF CT1 Q1 IRF820 D4 1N765B R1 10 1/2W L1 48µH 31DQ10 C3 D1 VOUT 12V, 2A C4 0.1µF 3.3µF 0.1µF* MKS2 100k GM38C42 VREF 8 1 COMP 2 3 4 FB ISNS RT/CT VDD OUT GND C5 + 4.7W 4.7µF 0.1µF C2 1000pF 7 6 5 C8 0.1µF 0.1µF T1 D5 1N4001 6.19k 1% 1.62k 1% R4 18 C7 200pF R5 16k * Locate near GM38C42 supply pins Figure 7. 500kHz, 25W, Buck Converter Test Line Regulation Conditions VIN= 26V to 80V, IO= 2A VIN= 48V, IO= 0.2A to 2A VIN= 48V, IO= 2A VIN= 48V, IO= 2A (20MHz BW) Results 0.5% 0.6% 90% 100mV GM38C42, GM38C43, GM38C44, GM38C45 Load Regulation Efficiency Output Ripple 8 SOP-8 PACKAGE OUTLINE DIMENSIONS 0.008 +0.0018 -0.0005 0° ~ 8° 0.028 +0.013 -0.022 +0.33 -0.56 0.200 +0.05 -0.01 P ad Layout 0.060 1.52 0.710 0.236 ± 0.008 5.990 +0.21 -0.20 +0.003 -0.004 0.275 7.0 0.155 4.0 0.154 P IN INDENT 3.91 ± 0.1 0.024 0.6 0.050 1.270 Inches ( mm ) 0.191 +0.002 -0.004 +0.05 -0.10 4.850 0.063 ± 0.005 1.600 ± 0.130 0.057 NOM 1.450 NOM ( Inches ) mm 0.007 ± 0.003 0.175 ± 0.075 0.050 NOM 1.270 NOM 0.016 +0.004 -0.003 +0.10 -0.08 0.410 DIP-8 PACKAGE OUTLINE DIMENSIONS 0.26 ± 0.006 6.60 +0.15 -0.16 0.30 7.62 +0.010 -0.015 +0.25 -0.38 0.36 ± 0.01 9.14 +0.25 -0.26 0.01 0.25 0.365 ± 0.02 9.27 ± 0.51 0.13 3.30 +0.002 -0.006 +0.05 -0.15 +0.002 -0.003 +0.05 -0.08 0.180 MAX 4.570 MAX 0.015 MIN 0.380 MIN 0.125 MIN 3.180 MIN 0.018 ± 0.004 0.46 ± 0.10 0.039 ± 0.07 0.99 ± 0.18 0.06 ± 0.01 1.52 +0.26 -0.25 0.100 NOM 2.540 NOM 0.021 ± 0.005 0.53 +0.12 -0.13 ( Inches ) mm GM38C42, GM38C43, GM38C44, GM38C45 9 ORDERING NUMBER GM 38 C 4X S8 R Gamma Micro. Shipping T: Tube R: Tape & Reel Circuit Type BiCOMS Process Package S8: SOP-8 D8: DIP-8 GM38C42, GM38C43, GM38C44, GM38C45 10 11 GM38C42, GM38C43, GM38C44, GM38C45