What the 49% duty ceiling means for your converter
The LM3524DM is a voltage-mode PWM controller from Texas Instruments that handles both step-up (boost) and step-down (buck) topologies. Its 49% maximum duty cycle means the switch is on for less than half the period — this is a deliberate limit that prevents transformer saturation in push-pull designs and keeps the control loop stable in single-ended converters without slope compensation. The controller operates from an 8 V to 40 V supply rail and drives an external transistor via its single output. Output configuration can be positive or negative, giving flexibility for inverting supplies.
Package and board-fit: 16-SOIC with bulk delivery
The supplier device package is 16-SOIC. It ships in Bulk, so expect tube or tray quantities rather than tape-and-reel — plan your pick-and-place feeder setup accordingly. Operating temperature range is 0°C to 125°C junction — this is a commercial/industrial grade part, not rated for -40°C cold starts. If your design sees freezing ambient, the controller itself may not be the limiter, but verify the external pass transistor's low-temperature performance.
Active lifecycle, but watch the RoHS status
However, the part is RoHS non-compliant. This means it contains lead (Pb) above the 0.1% threshold and cannot be used in products sold into EU RoHS-regulated markets without an exemption. For designs that require RoHS compliance, a lead-free alternative from the same functional family would be needed — the LM3524DM itself is not the drop-in for a green BOM.
Control features and what they let you do
Built-in control features include current limiting, an enable pin, and frequency control. The current limit protects the external switch and load during overloads. The enable pin lets a microcontroller or supervisor shut down the converter without removing the input supply. Frequency control allows the oscillator to be synchronized or adjusted with an external RC — useful for shifting the switching noise away from sensitive analog bands. There is no clock sync input and no synchronous rectifier driver — the LM3524DM is a simpler, lower-cost controller for designs that use a freewheeling diode on the output rather than a second FET.