XL3525Z

The XL3525 series pulse width modulator ICs are designed to offer improved performance and reduced external component count when designing various switching power supplies. The on-chip +5.1V reference is trimmed to ±1% accuracy, and the error amplifier input common-mode range includes the reference voltage, eliminating the need for external resistors. The oscillator's sync input allows multiple units to be synchronized together, or a single unit to be synchronized to an external system clock. A single resistor between the CT and discharge terminals provides wide-range dead-time adjustment. These devices also feature a built-in soft-start circuit requiring only one external timing capacitor. The shutdown terminal controls both the soft-start circuit and the output stage, providing instantaneous shutdown via the PWM latch during pulse turnoff, and a soft-start cycle under an extended shutdown command. These functions are also governed by an undervoltage lockout circuit, which disables the outputs and discharges the soft-start capacitor when the input voltage falls below normal. The lockout circuit incorporates approximately 500mV of hysteresis for jitter-free operation. Another feature of these PWM circuits is a latch following the comparator. Once a PWM pulse is terminated for any reason, the output remains off for the entire cycle. The latch resets on each clock pulse. The output stage is a totem-pole design capable of sourcing or sinking in excess of 200mA. The XL3525K output stage uses NOR logic, with the output low in the shutdown state.

Key features

• 8 to 35V operating voltage
• 5.1V reference voltage with ±1% accuracy
• 100Hz to 500KHz oscillator range
• Dedicated oscillator sync terminal
• Adjustable dead-time control
• Pulse-by-pulse shutdown
• Input undervoltage lockout with hysteresis
• Latching PWM for multi-pulse prevention
• Dual source/sink output drivers