NTE1721
Integrated Circuit Pulse Width Modulator (PWM) Regulator

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See also >>> NTE1723

Description:
The NTE1721 and NTE1723 are pulse width modulator control-circuits designed to offer improved performance and lowered external parts count when implemented for controlling all types of switching power supplies. The no-chip +5.1V reference is trimmed to ±1% and the input common-mode range of the errror amplifier includes the reference voltage, thus eliminating the need for external divider resistors. A sync input to the oscillator enables multiple units to be slaved or a single unit to be synchronized to an external system clock. A wide range of dead time can be programmed by a single resistor connected between the CT and the Discharge pins. These devices also feature a built-in soft-start circuitry, requiring only an external timing capacitor. A shutdown pin controls both the soft- start circuitry and the output stages, provided instantaneous turn-off through the PWM latch with pulsed shutdown, as well as soft-start recycle with longer shutdown commands. The under voltage lockout inhibits the outputs and the changing of the soft-start capacitor when VCC is below nominal. The output stages are totem-pole design capable of sinking and sourcing in excess of 200mA. The output stages of the NTE1721 features NOR logic resulting in a low output for an off state while the NTE1723 utilizes OR logic which gives a high output when off.

Features:
- 8V to 35V Operation
- +5.1V ±1% Trimmed Reference
- 100Hz to 400kHz Oscillator Range
- Separate Oscillator Sync Pin
- Adjustable Dead Time Control
- Input Undervoltage Lockout
- Latching PWM to Prevent Multiple Pulses
- Pulse-by-Pulse Shutdown
- Dual Source/Sink Outputs: ±400mA Peak

Absolute Maximum Ratings: (Note 1)
Supply Voltage, VCC.............................................................. +40V
Collector Supply Voltage, VC........................................................ +40V
Logic Inputs.............................................................-0.3V to +5.5V
Analog Inputs.............................................................. -0.3V to VCC
Output Current, Source or Sink, IO................................................ ±500mA
Reference Output Current, Iref.....................................................50mA
Oscillator Charging Current.........................................................5mA
Power Dissipation (TA = +25°C), PD.............................................1000mW
Derate Above 50°C...................................................... 10mW/°C
Power Dissipation (TC = +25°C), PD.............................................2000mW
Derate Above 25°C...................................................... 16mW/°C
Operating Junction Temperature, TJ...............................................+150°C
Storage Temperature Range, Tstg.......................................... -55° to +125°C
Thermal Resistance, Junction-to-Ambient, RthJA.................................. 100°C/W
Thermal Resistance, Junction-to-Case, RthJC...................................... 60°C/W
Lead Temperature (During Soldering, 10sec), TL.................................... +300°C

Note 1 Values beyond which damage may occur


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