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Advanced Regulating Pulse Width Modulators
FEATURES
Dual Uncommitted 40V, 200mA
Output Transistors
1% Accurate 5V Reference
Dual Error Amplifiers
Wide Range, Variable Deadtime
Single-ended or Push-pull
Operation
Under-voltage Lockout With
Hysteresis
Double Pulse Protection
Master or Slave Oscillator
Operation
UC495A: Internal 39V Zener Diode
UC495A: Buffered Steering Control
DESCRIPTION
This entire series of PWM modulators each provide a complete pulse width
modulation system in a single monolithic integrated circuit. These devices in-
clude a 5V reference accurate to
±
1%, two independent amplifiers usable for
both voltage and current sensing, an externally synchronizable oscillator
with its linear ramp generator, and two uncommitted transistor output
switches. These two outputs may be operated either in parallel for single-
ended operation or alternating for push-pull applications with an externally
controlled dead-band. These units are internally protected against double-
pulsing of a single output or from extraneous output signals when the input
supply voltage is below minimum.
The UC495A contains an on-chip 39V zener diode for high-voltage applica-
tions where V
CC
would be greater than 40V, and a buffered output steering
control that overrides the internal control of the pulse steering flip-flop.
The UC494A is packaged in a 16-pin DIP, while the UC495A is packaged in
an 18 pin DIP. The UC494A, UC495A are specified for operation over the full
military temperature range of -55°C to +125°C, while the UC494AC,
UC495AC are designed for industrial applications from 0°C to +70°C.
BLOCK DIAGRAM
UC494A/AC
UC495A/AC
10/93