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NTE1753 Integrated Circuit Pulse Width Modulator (PWM) Control Circuit

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NTE1753 Integrated Circuit Pulse Width Modulator (PWM) Control Circuit Powered By Docstoc
					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 +70°C. 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 +70°C 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 ≤ 45°C), PD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000mW Operating Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +125°C Operating Ambient Temperature Range, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0° to +70°C Storage Temperature Range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –55° to +125°C Thermal Resistance, Junction to Ambient, RΘJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +80°C/W Power Derating Factor, 1/RΘJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5mW/°C Derating Ambient Temperature, TA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +45°C Recommended Operating Conditions:
Parameter Power Supply Voltage Collector Output Voltage Collector Output Current Amplifier Input Voltage Current Into Feedback Terminal Reference Output Current Timing Resistor Timing Capacitor Oscillator Frequency Symbol VCC VC IC Vin If b Iref RT CT fOSC Min 7.0 – – –0.3 – – 1.8 0.0047 1.0 Typ 15 30 – – – – 47 0.001 25 Max 40 40 200 VCC–2 0.3 10 500 10 200 Unit V V mA V mA mA kΩ µF kHz

Electrical Characteristics: (VCC = 15V, CT = 0.01µF, RT = 12kΩ. For typical values TA = +25°C, for min/max values TA is 0° to +70°C unless otherwise specified.)
Parameter Reference Section Reference Voltage Line Regulation Load Regulation Short–Circuit Output Current Output Section Collector Off–State Current Emitter Off–State Current Collector–Emitter Saturation Voltage IC(off) IE(off) Vsat(C) Vsat(E) Output Voltage Rise Time tr tf VCE = 40V, VCC = 40V VCC = VC = 40V, VE = 0 IC = 200mA, VE = 0, Common Emitter IE = 200mA, VC = 15V, Emitter Follower TA = +25°C, Common Emitter TA = +25°C, Emitter Follower Output Voltage Fall Time TA = +25°C, Common Emitter TA = +25°C, Emitter Follower – – – – – – – – 2 – 1.1 1.5 100 100 25 40 100 –100 1.3 2.5 200 200 100 100 µA µA V V ns ns ns ns Vref Regline Regload ISC IO = 1mA VCC = 7V to 40V IO = 1mA to 10mA Vref = 0 4.75 – – 15 5.0 2 3 35 5.25 25 15 75 V mV mV mA Symbol Test Conditions Min Typ Max Unit

Electrical Characteristics (Cont’d): (VCC = 15V, CT = 0.01µF, RT = 12kΩ. For typical values TA = +25°C, for min/max values TA is 0° to +70°C unless otherwise specified.)
Parameter Error Amplifier Section Input Offset Voltage Input Offset Current Input Bias Current Common Mode Input Voltage Range Low High AVOL fc Φm CMRR PSRR IO– IO+ VTH II– IIB(DT) DCmax VTH ∆VO = 3V, VO = 0.5V to 3.5V, RL = 2kΩ VO = 0.5V to 3.5V, RL = 2kΩ VO = 0.5V to 3.5V, RL = 2kΩ VCC = 40V ∆VCC = 33V, VO = 2.5V, RL = 2kΩ VO(Pin3) = 0.7V VO(Pin3) = 3.5V Zero Duty Cycle V(Pin3) = 0.7V VIN = 0 to 5.25V VIN = 0, CT = 0.01µF, RT = 12kΩ VIN = 0, CT = 0.001µF, RT = 47k–Ω Input Threshold Voltage (Pin4) Oscillator Section Frequency Standard Deviation of Frequency Frequency Change with Temperature Frequency Change with Voltage Total Device Standby Supply Current ICC VCC = 15V, all other inputs and outputs open VCC = 40V, all other inputs and outputs open Average Supply Current IS V(Pin4) = 2V, CT = 0.001µF, RT = 47kΩ – – – 5.5 7.0 7 10 15 – mA mA mA fOSC αfOSC CT = 0.001µF, RT = 47kΩ CT = 0.001µF, RT = 47kΩ CT = 0.01µF, RT = 12kΩ ∆fOSC(∆V) VCC = 7V to 40V, TA = +25°C – – – – – 25 3 – – 1 – – 12 12 – kHz % % % % Zero Duty Cycle Maximum Duty Cycle VIO IIO IIB VICR VO(Pin3) = 2.5V VC(Pin3) = 2.5V VO(Pin3) = 2.5V VCC = 40V, TA = +25°C – – – –0.3 VCC–2 70 – – 65 – 0.3 –2 – 0.3 – 90 – – 0 2 5 –0.1 – – 95 350 65 90 100 0.7 –4 3.5 0.7 –2 96 92 2.8 – 10 250 –1.0 – – – – – – – – – 4.5 – –10 100 100 3.3 – mV nA µA V V dB kHz deg. dB dB mA mA V mA µA % % V V Symbol Test Conditions Min Typ Max Unit

Open–Loop Voltage Gain Unity Gain Crossover Frequency Phase Margin at Unity Gain Common Mode Rejection Ratio Power Supply Rejection Ratio Output Sink Current Output Source Current PWM Comparator Section Input Threshold Voltage Input Sink Current Dead–Time Control Section Input Bias Current (Pin4) Maximum Output Duty Cycle

∆fOSC(∆T) 0° ≤ ∆TA ≤ +70°C

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

α=

Pin Connection Diagram

Non–Inverting Input (1) Inverting Input (1) Feedback/ PWM Comparator Input Dead–Time Control

1 2 3 4

14 Non–Inverting Input (2) 13 Inverting Input (2) 12 Vref 11 N.C. 10 VCC 9 8 Collector Emitter

CT 5 RT 6 GND 7

14

8

1

7

.785 (19.95) Max

.300 (7.62)

.200 (5.08) Max

.100 (2.45)

.099 (2.5) Min

.600 (15.24)


				
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Description: NTE1753 Integrated Circuit Pulse Width Modulator (PWM) Control Circuit