284xA

Features:

LOW START-UP CURRENT.  (0.5mA max.)
TRIMMED OSCILLATOR DISCHARGE CURRENT.  (See Product Highlight)
  OPTIMIZED FOR OFF-LINE AND DC-TO-DC CONVERTERS.
  AUTOMATIC FEED FORWARD COMPENSATION.
  PULSE-BY-PULSE CURRENT LIMITING.
ENHANCED LOAD RESPONSE CHARACTERISTICS.
UNDER-VOLTAGE LOCKOUT WITH HYSTERESIS.
  DOUBLE PULSE SUPPRESSION.
HIGH-CURRENT TOTEM POLE OUTPUT.
INTERNALLY TRIMMED BANDGAP REFERENCE.
500KHz OPERATION.
 LOW RO ERROR AMPLIFIER.


Application

n n n n ECONOMICAL OFF-LINE FLYBACK OR FORWARD CONVERTERS.
DC-DC BUCK OR BOOST CONVERTERS.
LOW COST DC MOTOR CONTROL.


Pinout




Specifications

Supply Voltage (Low Impedance Source) (V_CC) ............................................................ 30V
Supply Voltage (I_CC < 30mA) .......................................................................... Self Limiting
Output Current ........................................................................................................... ±1A
Output Energy (Capacitive Load) ................................................................................. 5µJ
Analog Inputs (V_FB & I_SENSE) ........................................................................ -0.3V to +6.3V
Error Amp Output Sink Current ................................................................................... 10mA
Power Dissipation at T_A = 25°C (M Package) ................................................................ 1W
Storage Temperature Range .................................................................. -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) ............................................................. 300°C
Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect
to Ground.  Currents are positive into, negative out of the specified terminal. Pin
numbers refer to DIL packages only.


Description

The UC184xA family of control ICs provides all the necessary features to implement off-line fixed-frequency,current-mode switching power supplies with a minimum of external compo-
nents. The current mode architecture demonstrates improved load regulation,pulse-by-pulse current limiting and inherent protection of the power supply output switch. The 284xA IC includes: A
bandgap reference trimmed to ±1% accuracy, an error amplifier, a current sense comparator with internal clamp to 1V, a high current totem pole output stage for fast switching of power

MOSFET's, and an externally program-mable oscillator to set frequency and maximum duty cycle. The under-voltage lock-out is designed to operate with 250µA typ. start-up current,allowing an efficient bootstrap supply oltage design. Available options for this family of 284xA, such as start-up voltage hysteresis and duty cycle, are summarized below in the Available Options section.  The UC184xA family of control ICs is also available in 14-pin SOIC package which makes the Power Output Stage Collector and Ground pinsavailable.