Extended Temperature Performance –40°C to 125 °C Optimized for Offline and DC-to-DC Converters Low Startup Current (<0.5 mA) Tuned Oscillator Discharge Current Automatic Feedforward Compensation Pulse Current Limit Pulse Enhanced Load Response Characteristics Voltage Locked Double Pulse Rejection High Current Totem Pole Output Internally Trimmed Bandgap Reference 500 kHz Operation Low Reverse Osmosis Error Amplifier Description The UC2842A /3A/4A/5A series of control ICs are pin-compatible improved versions of the UC2842/3/4/5. family. Providing the necessary functions to control current mode switching power supplies, this series has features that follow improvements. The startup current is guaranteed to be less than 0.5 mA. Oscillator discharge trimmed to 8.3 mA. During undervoltage lockout, the output stage can drop at least 10 mA if VCC exceeds 1.2 V. 5 volts.

Note: 1.A=DIL-8 pins. B=SO-14 stitches. Step two. Toggle triggers are only used in the 2844A and 2845A.

Absolute Maximum Ratings Over Operating Free Air Temperature Range (unless otherwise stated) VCC voltage (low impedance source) 30 VVCC voltage (ICC MA) Self-limiting output current, IO ± 1 A
Output Energy (Capacitive Load) 5. Micro-J Analog Inputs (Pins 3, 5) – 0.3V to 6.3V Error Amplifier Output Receiver Current 10 mA ATA < +25C (Package D) Power Dissipation 1 W Component Thermal Impedance, θja (See Note 1): D (8-pin) assemblies 97°C/W storage temperature range, TSTG – 65C to 150C lead temperature solder 1.6 mm (1/16 inch) from case 10 seconds at 260.

Stresses in excess of the Absolute Maximum Ratings may cause permanent damage to the device. These are pressure ratings only, and do not imply functional operation of the equipment under the conditions shown under "Recommended Operating Conditions" or any other conditions. Exposure to absolute maximum rated conditions for extended periods may affect device reliability. Unless otherwise stated, voltage is referenced to ground and current is the positive and negative inputs and outputs to the designated terminals.

The error amplifier can source and sink currents up to 0.5 mA and sink currents up to 2 mA.
Figure 1. Bad AMP configuration

Parameter measurement information

The peak current (is) is determined by the following formula: Ismax 1.0 volts may require a small RC filter to suppress switching transients.
Figure 3. Current Sense Circuit

application information

The high peak currents associated with capacitive loads require careful grounding techniques. Timing and bypass capacitors should be connected close to pin 5 in a single point ground. Sample the oscillator waveform using a transistor and a 5K potentiometer and apply an adjustable ramp to pin 3.
Figure 7. Open Loop Lab Text Fixture

A portion of the oscillator ramp can be resistively summed. Use the current sense signal to provide slope compensation for converters with a duty cycle greater than 50%. Note that capacitor c forms a filter with r2 to suppress leading edge switch peaks.
Figure 8. Slope failure

application information

Power Specifications
1. Input voltage 95Vac to 130Vac (50Hz/60Hz)
2. The second step. Line isolation 3750V
three. Switching frequency 40 kHz
Chapter Four. Efficiency, 70% full load
5. Output voltage:
A.+5V, ±5%; 1A to 4A load
B. +12V, ±3%; 0.1A to 0.3A load ripple voltage: 100 mV pp max
C.–12V, ±3%; 0.1A to 0.3A load ripple voltage: 100 mV pp max
Figure 9. Offline Flyback Regulator