UC3845 UC3845B UC3845BN SOP-8

Description

UC3845 UC3845B UC3845BN SOP-8

The UC3845 family consists of high-performance, fixed-frequency, current-mode PWM controllers optimized for off-line switched-mode power supplies (SMPS) and DC-to-DC converter applications.

• UC3845: The base model number for this current-mode control integrated circuit. It features an Under-Voltage Lockout (UVLO) threshold tailored for lower voltage inputs (8.4V Turn-On / 7.6V Turn-Off) and restricts the maximum duty cycle to 50%.
• UC3845B: The enhanced “B” version offers improved electrical performance over the standard line, including tighter oscillator tolerances and lower startup/operating current characteristics.
• UC3845BN: The “N” suffix traditionally denotes a plastic standard through-hole DIP-8 (Dual In-line Package), rather than surface mount. However, some generic or cross-compatible marketplace listings use these terms interchangeably to designate the core chip functionality.
• SOP-8: Specifies a surface-mount small outline package featuring 8 pins.

• Topology: High-efficiency control optimized for boost, flyback, and forward configurations.
• Frequency: Operates at a high switching frequency up to 500 kHz.
• Output Stage: Features a high-current totem-pole output stage engineered to drive N-channel power MOSFETs natively.
• Protection: Integrated pulse-by-pulse current limiting paired with automatic feed-forward compensation. 

• Pin 1 (COMP): Error amplifier output; utilized for loop compensation.
• Pin 2 (VFB): Inverting error amplifier input; connected to voltage feedback.
• Pin 3 (ISENSE): Current sense input; monitors voltage across a source resistor to handle pulse-by-pulse limits.
• Pin 4 (RT/CT): Oscillator timing; setting node configured by an external resistor and capacitor.
• Pin 5 (GND): Common ground reference.
• Pin 6 (OUTPUT): High-current totem pole driver output hooked directly to the MOSFET gate.
• Pin 7 (VCC): Positive IC operating supply voltage input.
• Pin 8 (VREF): Internally trimmed reference output (5V).