Description GM38C4x is fixed frequency, high performance, and cur- Features 40ns output rise and 30ns output fall times rent- mode PWM controllers. Gamma's BiCMOS devices -40° to +85°C temp. range same as standard are pin compatible with standard 384x bipolar devices but 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 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. 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 GM 431 www.gammamicro.com 1 V0.1 Application GM38C42, GM38C43, GM38C44, GM38C45 GM38C4x denotes 8-pin plastic DIP and SOP packages. MARKING INFORMATION & PIN CONFIGURATIONS (TOP VIEW) SOP - 8 VDD VREF DIP - 8 VDD VREF OUT GND 8 7 6 5 8 7 6 5 GM38CXX GM38CXX AYWW AYWW 1 2 3 4 COMP FB OUT GND 1 2 3 4 RT / C T ISNS RT / C T ISNS COMP FB GM38C42, GM38C43, GM38C44, GM38C45 A = Assembly Location Y = Year W W = Weekly 2 ORDERING INFORMATION Ordering Number Package GM38C42S8T SOP - 8 100 Units/ Tube GM38C42S8R SOP - 8 2,500 Units/ Tape & Reel GM38C42D8T DIP-8 60 Units/ Tube GM38C43S8T SOP - 8 100 Units/ Tube GM38C43S8R SOP - 8 2,500 Units/ Tape & Reel GM38C43D8T DIP-8 60 Units/ Tube GM38C44S8T SOP - 8 100 Units/ Tube GM38C44S8R SOP - 8 2,500 Units/ Tape & Reel GM38C44D8T DIP-8 60 Units/ Tube GM38C45S8T SOP - 8 100 Units/ Tube GM38C45S8R SOP - 8 2,500 Units/ Tape & Reel GM38C45D8T DIP-8 60 Units/ Tube * For detail Ordering Number identification, please see last page. Shipping ABSOLUTE MAXIMUM RATINGS SYMBOL VALUE UNIT Zener Current Operation at 16V may require special precautions(Note6) IDD 30 mA Supply Voltage(Note 6) VDD 18 V Switch Supply Voltage VD 18 V Current Sense Voltage PARAMETER VISNS - 0.3 to + 5.5 V Feedback Voltage VFB - 0.3 to + 5.5 V Output Current IOUT 0.5 A TA - 50 to + 150 °C SYMBOL TJ VALUE UNIT 150 °C Storage Temperature OPERATING RATINGS PARAMETER Junction Temperature PIN LEAD FUNCTION FUNCTION Compensation: Connect external Compensation network to modify the error amplifier output. 1 COMP 2 FB Feedback (Input): Error amplifier input .Feedback is 2.5Vat desired output voltage. 3 ISNS 4 RT / C T 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. 5 GND Ground: Combined analog and power ground. 6 OUT Power Output: Totem - pole output. 7 VDD Analog Supply (Input): Controller circuitry supply input. Return to analog ground (AGND). 8 VREF 5V Reference (Output): Connect external RC network. BLOCK DIAGRAM VDD * 35V 7 5V Reference VREF 8 RT / C T UVLO Oscillator 4 OUTPUT 6 T FB 2 2R - 2.5V + + Q S R Q R + - * COMP 1 GND* 5 GM38C42, GM38C43, GM38C44, GM38C45 PACKAGE PIN DESCRIPTION 3 ISNS 3 * 8 - lead versions only Power Management ELECTRICAL CHARACTERISTICS (TA = -40°C to 85°C, Note 4, VDD = 15V, CT=3.3 nF, RT=10kW, unless otherwise noted ) CHARACTERISTICS TEST CONDITIONS MIN TYP MAX UNIT TA = 25°C, IO = 1mA 4.9 5.0 5.1 V 2 20 mV 1 25 mV Reference Section Output Voltage Line Regulation 12V VDD 16V, IO = 5µA, (Note 6) 1 Load Regulation IO Long Term Stability 0.2 Line, Load, Temp.,Note 1 Total Output Variation Output Noise Voltage 20mA (Note 1) Temp. Stability 10Hz f 4.82 10kHz, TA = 25°C, (Note 1) V µV 50 TA = 125°C, 1000hrs., (Note 1) Output Short Circuit mV / °C 5.18 5 25 mV -30 -80 -180 mA 49 52 55 KHz 1.0 % Oscillator Section Initial Accuracy Voltage Stability 12 Temp. Stability TMIN Clock Ramp Reset Current GM38C42, GM38C43, GM38C44, GM38C45 VDD 16V, (Note 6) 0.2 TA TMAX, (Note 1) 0.04 TA = 25°C, VRT/CT = 2V, TMIN TA TMAX % / °C 7.7 8.4 9.0 7.2 8.4 9.5 VRT/CT (Peak to Peak) 1.9 Input Current VFB = 5V -0.1 -2 Input Voltage VCOMP = 2.5V 2.42 2.5 2.58 Open Loop Voltage Gain 2V VO 4V 65 90 12V VDD 16V 60 Amplitude 4 TA = 25°C, (Note 5) mA Vp-p Error Amplifier Section Power Supply Rejection Ratio Output Sink Current V dB dB VFB = 2.7V, VCOMP = 1.1V 2 14 mA mA VFB = 2.3V, VCOMP = 5V -0.5 -1 High Output Voltage VFB = 2.3V, RL = 15k to GND 5.0 6.6 Low Output Voltage VFB = 2.7V, RL = 15k to VREF Output Source Current µA Unity Gain Bandwidth 0.1 V 1.1 (Note 1) 0.7 1.0 Note 2 and 3 2.85 3.0 3.15 VCOMP = 5V, (Note 2) 0.9 1.0 1.1 V MHz Current Sense Section Gain Maximum Threshold PSRR 12V VDD 16V, (Note 2) 70 V/V V dB Input Bias Current -1.0 -2 µA Delay to Output 120 250 ns ELECTRICAL CHARACTERISTICS (TA = -40°C to 85°C, Note 4, VDD = 15V, CT=3.3 nF, RT=11kW, unless otherwise noted ) CHARACTERISTICS TEST CONDITIONS MIN TYP MAX UNIT Output Section RDS(ON) High ISOURCE = 200mA 20 RDS(ON) Low ISINK = 200mA 11 Rise Time TA = 25°C, CL = 1nF 40 80 ns Fall Time TA = 25°C, CL = 1nF 30 60 ns W Undervoltage Lockout Section GM38C42, GM38C44 13.5 14.5 15.5 GM38C43, GM38C45 7.8 8.4 9.0 GM38C42, GM38C44 8 9 10 GM38C43, GM38C45 7.0 7.6 8.2 GM38C42, GM38C43 94 96 GM38C44, GM38C45 46 50 Start Threshold Minimum Operating Voltage V V PWM Section Maximum Duty Cycle Minimum Duty Cycle % 0 % Start - Up Current VDD = 13V for GM38C42, GM38C44 50 200 VDD = 7.5V for GM38C43, GM38C45 VFB = VISNS = 0V Operating Supply Current Zener Voltage (VDD) IDD = 25 mA, Note 6 4 30 37 6 µA mA V 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 Total Standby Current 5 TYPICAL PERFORMANCE CHARACTERISTICS 100 100 VDD = 15V OUTPUT DEAD TIME (%) RT RESISTANCE (kW) 200pF 470pF 1nF 10 1.8nF 10nF 4.7nF 18nF 10nF 10 1nF 470pF 200pF 4.7nF VDD = 15V 1 1x104 1x105 1 1x104 5x105 OSCILLATOR FREQUENCY (Hz) FREQUENCY (Hz) Figure 2. GM38C42, GM38C43 Output Dead Time vs. Oscillator Frequency 1.2 8.6 8.4 8.2 8.0 7.8 7.6 7.4 VDD = 15V VOSC = 2V 7.2 -30 0 30 60 90 120 CURRENT SENSE AMP THRESHOLD (V) OSC. DISCHARGE CURRENT(mA) 8.8 7.0 -60 1.0 0.8 125°C 25°C 0.6 0.4 -50°C 0.2 0.0 150 0 2 4 6 TEMPERATURE (°C) ERROR AMPLIFIER OUTPUT (V) Figure 3. Oscillator Discharge Current vs. Temperature Figure 4. Current Sense Amplifier vs. Error Amplifier Output 120 20 100 80 60 40 20 0 -60 8 25 VDD = 15V OUTPUT VOLTAGE (V) VREF SHORT CURCUIT CURRENT (mA) GM38C42, GM38C43, GM38C44, GM38C45 1x106 Figure 1. Oscillator Frequency Configuration 9.0 6 1x105 15 10 5 0 -5 -10 -30 0 30 60 90 120 150 TEMPERATURE (°C) Figure 5. Short - Circuit Reference Current vs. Temperature -15 0.0 VD = 15V CL = 1nF 0.2 0.4 0.6 0.8 TIME (µS) Figure 6. GM38C4X Output Waveform 1.0 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. 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 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. 7 VIN 26V to 40V Q1 IRF820 CT1 R1 10 1/2W D4 1N765B R2 68k D2 M17Z105 1/4W 0.1µF* 6.8k D3 MBR030 0.22µF R4 18 MKS2 100k GM38C42 VREF 8 1 COMP 2 FB VDD 7 3 ISNS OUT 6 4 RT/CT GND C7 200pF R5 16k VOUT 12V, 2A L1 48µH 31DQ10 C3 D1 3.3µF C4 0.1µF C2 1000pF C5 + 4.7W 4.7µF 0.1µF D5 T1 1N4001 C8 0.1µF 5 6.19k 1% 1.62k 1% 0.1µF * Locate near GM38C42 supply pins GM38C42, GM38C43, GM38C44, GM38C45 Figure 7. 500kHz, 25W, Buck Converter 8 Test Conditions Results Line Regulation VIN= 26V to 80V, IO= 2A 0.5% Load Regulation VIN= 48V, IO= 0.2A to 2A 0.6% VIN= 48V, IO= 2A 90% VIN= 48V, IO= 2A (20MHz BW) 100mV Efficiency Output Ripple SOP-8 PACKAGE OUTLINE DIMENSIONS 0.008 +0.0018 -0.0005 0.200 +0.05 -0.01 0 ° ~ 8° 0.028 0.710 +0.013 -0.022 Pad Layout 0.060 +0.33 -0.56 1.52 0.236 ± 0.008 5.990 +0.21 -0.20 0.154 +0.003 -0.004 0.275 0.155 7.0 4.0 PIN INDENT 3.91 ± 0.1 0.024 0.050 0.6 1.270 Inches ( mm ) 0.191 +0.002 -0.004 4.850 +0.05 -0.10 0.057 NOM 1.450 NOM 0.063 ± 0.005 1.600 ± 0.130 0.007 ± 0.003 0.175 ± 0.075 0.050 NOM 1.270 NOM 0.016 +0.004 -0.003 0.410 +0.10 -0.08 DIP-8 PACKAGE OUTLINE DIMENSIONS 0.26 ± 0.006 6.60 +0.15 -0.16 0.30 +0.010 -0.015 7.62 +0.25 -0.38 0.36 ± 0.01 9.14 +0.25 -0.26 0.365 ± 0.02 9.27 ± 0.51 0.13 +0.002 -0.006 3.30 +0.05 -0.15 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 0.01 +0.002 -0.003 0.25 +0.05 -0.08 GM38C42, GM38C43, GM38C44, GM38C45 ( Inches ) mm 9 ORDERING NUMBER GM 38 C 4X S8 R Gamma Micro. Shipping T: Tube R: Tape & Reel Circuit Type BiCOMS Process GM38C42, GM38C43, GM38C44, GM38C45 Package S8: SOP-8 D8: DIP-8 10 11 GM38C42, GM38C43, GM38C44, GM38C45