NTE1753 Integrated Circuit Pulse Width Modulator (PWM) Control Circuit Description: The NTE1753 is a fixed-frequency pulse width modulation control circuit in a 14-Lead DIP type package incorporating the primary building blocks required for the control of a switching power supply. An internal-linear sawtooth oscillator frequency is determined by: 1.1 fOSC ^ RT D CT Output pulse width modulation is accomplished by comparison of the positive sawtooth waveform across capacitor CT to either of two control signals. The output is enabled only during that portion of time when the sawtooth voltage is greater than the control signals. Therefore, an increase in control-signal amplitude causes a corresponding linear decrease of output pulse width. The control signals are external inputs that can be fed into the dead-time control, the error amplifier inputs, or the feed-back input. The dead-time control comparator has an effective 120mV input offset which limits the minimum output dead time to approximately the first 4% of the sawtooth-cycle time. This would result in a maximum duty cycle of 96%. Additional dead time may be imposed on the output by setting the dead time-control input to a fixed voltage, ranging between 0 to 3.3V. The pulse width modulator comparator provides a means for the error amplifiers to adjust the output pulse width from the maximum percent on-time, established by the dead time control input, down to zero, as the voltage at the feedback pin varies from 0.5 to 3.5V. Both error amplifiers have a common- mode input range from -0.3V to (VCC -2V), and may be used to sense power supply output voltage and current. The error-amplifier outputs are active high and are 0 red together at the non-inverting input of the pulse-width modulator comparator. With this configuration, the amplifier that demands minimum output on time, dominates control of the loop. The NTE1753 has an internal 5.0V reference capable of sourcing up to 10mA of load currents for external bias circuits. The reference has an internal accuracy of 5% with a typical thermal drift of less than 50mV over an operating temperature range of 0 to +70C. Features: D Complete Pulse Width Modulation Control Circuitry D On-Chip Oscillator with Master or Slave Operation D On-Chip Error Amplifiers D On-Chip 5.0 Volt Reference D Adjustable Dead Time Control D Uncommitted Output Transistor for 200mA Source or Sink Absolute Maximum Ratings: (TA = 0 to +70C unless otherwise specified) Power Supply Voltage, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42V Collector Output Voltage, VC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42V Collector Output Current, IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250mA Amplifier Input Voltage, Vin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VCC +0.3V Power Dissipation (TA 45C), PD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW Operating Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +125C Operating Ambient Temperature Range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to +70C Storage Temperature Range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55 to +125C Thermal Resistance, Junction to Ambient, RJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +80C/W Power Derating Factor, 1/RJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5mW/C Derating Ambient Temperature, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +45C Recommended Operating Conditions: Parameter Symbol Min Typ Max Unit Power Supply Voltage VCC 7.0 15 40 V Collector Output Voltage VC - 30 40 V Collector Output Current IC - - 200 mA Amplifier Input Voltage Vin -0.3 - VCC-2 V Current Into Feedback Terminal If b - - 0.3 mA Reference Output Current Iref - - 10 mA Timing Resistor RT 1.8 47 500 k Timing Capacitor CT 0.0047 0.001 10 F fOSC 1.0 25 200 kHz Oscillator Frequency Electrical Characteristics: (VCC = 15V, CT = 0.01F, RT = 12k. For typical values TA = +25C, for min/max values TA is 0 to +70C unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Unit 4.75 5.0 5.25 V Reference Section Reference Voltage Vref IO = 1mA Line Regulation Regline VCC = 7V to 40V - 2 25 mV Load Regulation Regload IO = 1mA to 10mA - 3 15 mV Vref = 0 15 35 75 mA Short-Circuit Output Current ISC Output Section Collector Off-State Current IC(off) VCE = 40V, VCC = 40V - 2 100 A Emitter Off-State Current IE(off) VCC = VC = 40V, VE = 0 - - -100 A Vsat(C) IC = 200mA, VE = 0, Common Emitter - 1.1 1.3 V Vsat(E) IE = 200mA, VC = 15V, Emitter Follower - 1.5 2.5 V TA = +25C, Common Emitter - 100 200 ns TA = +25C, Emitter Follower - 100 200 ns TA = +25C, Common Emitter - 25 100 ns TA = +25C, Emitter Follower - 40 100 ns Collector-Emitter Saturation Voltage Output Voltage Rise Time Output Voltage Fall Time tr tf Electrical Characteristics (Cont'd): (VCC = 15V, CT = 0.01F, RT = 12k. For typical values TA = +25C, for min/max values TA is 0 to +70C unless otherwise specified.) Parameter Symbol Test Conditions Min Typ Max Unit Error Amplifier Section Input Offset Voltage VIO VO(Pin3) = 2.5V - 2 10 mV Input Offset Current IIO VC(Pin3) = 2.5V - 5 250 nA Input Bias Current IIB VO(Pin3) = 2.5V - -0.1 -1.0 A -0.3 - - V VCC-2 - - V VO = 3V, VO = 0.5V to 3.5V, RL = 2k 70 95 - dB fc VO = 0.5V to 3.5V, RL = 2k - 350 - kHz m VO = 0.5V to 3.5V, RL = 2k - 65 - deg. Common Mode Input Voltage Range Low VICR VCC = 40V, TA = +25C High Open-Loop Voltage Gain Unity Gain Crossover Frequency Phase Margin at Unity Gain AVOL Common Mode Rejection Ratio CMRR VCC = 40V 65 90 - dB Power Supply Rejection Ratio PSRR VCC = 33V, VO = 2.5V, RL = 2k - 100 - dB Output Sink Current IO- VO(Pin3) = 0.7V 0.3 0.7 - mA Output Source Current IO+ VO(Pin3) = 3.5V -2 -4 - mA VTH Zero Duty Cycle - 3.5 4.5 V 0.3 0.7 - mA PWM Comparator Section Input Threshold Voltage Input Sink Current II- V(Pin3) = 0.7V Dead-Time Control Section Input Bias Current (Pin4) IIB(DT) VIN = 0 to 5.25V - -2 -10 A Maximum Output Duty Cycle DCmax VIN = 0, CT = 0.01F, RT = 12k 90 96 100 % VIN = 0, CT = 0.001F, RT = 47k- - 92 100 % Zero Duty Cycle - 2.8 3.3 V Maximum Duty Cycle 0 - - V fOSC CT = 0.001F, RT = 47k - 25 - kHz fOSC CT = 0.001F, RT = 47k - 3 - % - - 12 % - - 12 % - 1 - % VCC = 15V, all other inputs and outputs open - 5.5 10 mA VCC = 40V, all other inputs and outputs open - 7.0 15 mA V(Pin4) = 2V, CT = 0.001F, RT = 47k - 7 - mA Input Threshold Voltage (Pin4) VTH Oscillator Section Frequency Standard Deviation of Frequency Frequency Change with Temperature fOSC(T) 0 TA +70C Frequency Change with Voltage fOSC(V) VCC = 7V to 40V, TA = +25C CT = 0.01F, RT = 12k Total Device Standby Supply Current Average Supply Current ICC IS Note 1. Standard deviation is a measure of the statistical distribution about the mean as derived from the formula: = N 2 S (Xn - X) n=1 N-1 Pin Connection Diagram Non-Inverting Input (1) 1 14 Non-Inverting Input (2) Inverting Input (1) 2 13 Inverting Input (2) Feedback/ PWM Comparator Input 3 12 Vref Dead-Time Control 4 11 N.C. CT 5 10 VCC RT 6 9 Collector 8 Emitter GND 7 14 8 1 7 .300 (7.62) .785 (19.95) Max .200 (5.08) Max .100 (2.45) .600 (15.24) .099 (2.5) Min