Power Electronics
Switchers Replace LM78xx Linears

Switchers Replace LM78xx Linears

The C&D Technologies series of Datel 78SR switching regulators are suited for cost-sensitive applications where the maximum load current is 0.5 A or less. Rated for +5 V/0.5 A (7805SR), +12 V/0.4 A (7812SR) and +3.3 V/0.5 A (7803SR), the devices are high-efficiency drop-in replacements for the LM78xx linear regulators. These switching regulators are 100% pin- and size-compatible with the industry-standard, TO-220 packages.

Two package styles are available: A standard vertical-mount SIP occupies less than 0.1 in.2 of pc-board real estate and a horizontal-mount version allows for an installed height of less than 0.350 in.

The 78SR Series’ 260-kHz switching frequency produces efficiencies as high as 95% for 12-V models, and 85% for 3.3-V and 5-V models. Full-load operation from 9-V, 12-V, 24-V, 28-V or 36-V supplies—at ambient temperatures as high as +70°C—requires no heatsinks, forced-air cooling, or temperature derating. These benefits make the 78SR a cost-effective alternative in new and existing LM7805/LM7812 designs.

Additionally, the high efficiency can dramatically increase battery life in portable instrumentation and standby-power applications and other applications that require full-load operation at elevated supply voltages and/or elevated temperatures.

The 78SR Series switching regulators offer additional improvements over their linear counterparts, including lower quiescent current (3 mA vs. 5 mA), higher operating input voltage (+36 V vs. +32 V), and significantly tighter output accuracy (±1.5% vs. ±5%). Their excellent line and load regulation of ±0.3% and ±0.2%, respectively, allows operation from poorly-regulated dc supplies. These switchers do not need any external input or output capacitors to provide stable, low-noise outputs.

78SR Series regulators are priced at $9.95 in singles and drop to below $5 in OEM quantities. Small-quantity orders are available from stock. Samples are immediately available.

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