CS3524A

The CS3524A PWM control circuit retains the same versatile architecture of the industry standard CS3524 (SG3524) while adding substantial improvements.

The CS3524 is pin-compatible with "non-A" versions, and in most applications can be directly interchanged. The CS3524A, however, eliminates many of the design restrictions which had previously required additional external circuitry.

The CS3524A includes a precision 5V reference trimmed to ±1% accuracy (eliminating the need for potentiometer adjustments), an error amplifier with an output voltage swing extending to 5V, and a current sense amplifier useful in either the ground or power supply output lines. The uncommitted 60V, 200mA NPN output pair greatly enhances the output drive capability.

The CS3524A features an undervoltage lockout circuit which disables all internal circuitry (except the reference) until the input voltage has risen to 8V. This holds standby current low until turnon, and greatly simplifies the design of low power, off-line supplies. The turnon circuit has approximately 600mV of hysteresis for jitter free activation.

Other improvements include a PWM latch that insures freedom from multiple pulsing within a period, even in noisy environments; logic to eliminate double pulsing on a single output, a 200ns external shutdown capability, and automatic thermal protection from
excessive chip temperature. The oscillator circuit iCS3524A s usable to 500kHz and is easier to synchronize with an external clock pulse.