Product description
The UC3842B is a fixed-frequency current-mode PWM controller designed for off-line and DC-to-DC converter applications. Internal blocks include a precision trimmed bandgap voltage reference, error amplifier with 2.5V reference input, PWM comparator with cycle-by-cycle current limiting, oscillator set by an external resistor and capacitor on the RT/CT pin, and a totem-pole output stage capable of directly driving an N-channel MOSFET gate. The output is actively held low during undervoltage lockout. A trimmed oscillator provides precise frequency control and guaranteed operation at 250 kHz. The UC3842B differs from the UC3843B in UVLO thresholds, making it suited for off-line power supply applications. The BN suffix denotes the Minidip (PDIP-8) package. The UC2842B extends the temperature range to -25°C to +85°C.
- Control mode: peak current mode
- Maximum duty cycle: up to 100%
- UVLO turn-on: 16V, turn-off: 10V (suitable for off-line applications)
- Start-up current: less than 0.5 mA
- Operating supply current: 12 mA typ, 17 mA max
- Oscillator frequency: up to 500 kHz, set by external RT and CT, guaranteed at 250 kHz
- Reference voltage (VREF): 5.0V trimmed (4.90V min, 5.10V max at 25°C)
- Error amplifier reference input: 2.5V, unity gain bandwidth 1 MHz typ
- Current sense maximum input: 1.0V typ
- Output peak current: 1A source and sink
- Supply voltage abs. max: 30V