The LM2907 and LM2917 devices are monolithic frequency-to-voltage converters with a high gain op amp designed to operate a relay, lamp, or other load when the input frequency reaches or exceeds a selected rate. The tachometer uses a charge pump technique and offers frequency doubling for low-ripple, full-input protection in two versions (8-pin LM2907 and LM2917), and its output swings to ground for a zero frequency input.

The op amp is fully compatible with the tachometer and has a floating transistor as its output. This feature allows either a ground or supply referred load of up to 50 mA. The collector may be taken above VCCup to a maximum VCEof 28 V.

The two basic configurations offered include an 8-pin device with a input and an internal connection between the tachometer output and the op amp noninverting input. This version is well suited for single speed or frequency switching or fully buffered frequency-to-voltage conversion applications.Read more