A2557

• 300 mA output current per channel
• Independent overcurrent protection and thermal limiting for each driver
• Output voltage to 60 V
• Output SOA protection
• Fault-detection circuitry for open or shorted load
• Low quiescent current Sleep Mode
• Integral output flyback/clamp diodes
• TTL- and 5 V CMOS-compatible inputs

Description

The A2557 has been specifically designed to provide costeffective solutions to relay-driving applications with up to 300 mA drive current per channel. They may also be used for driving incandescent lamps in applications where turn-on time is not a concern. Each of the four outputs will sink 300 mA in the on state. The outputs of A2557 have a minimum breakdown voltage of 60 V and a sustaining voltage of 40 V. A low-power Sleep Mode is activated with either ENABLE low or all inputs low. In this mode, the supply current drops to below 100 µA.

Overcurrent protection for each channel has been designed into A2557 and is activated at a nominal 500 mA. It protects each output from short circuits with supply voltages up to 32 V. When an output experiences a short circuit, the output current of A2557 is limited at the 500 mA current clamp. In addition, foldback circuitry decreases the current limit if an excessive voltage is present across the output and assists in keeping the A2557 within its SOA (safe operating area). An exclusive-OR circuit compares the input and output state of each driver. If either a short or open load condition is detected, a single FAULT output is turned on (active low).

Continuous or multiple overload conditions causing the channel temperature to reach approximately 165°C will result in an additional linear decrease in the output current of the affected driver. If the fault condition is corrected, the output stage of A2557 will return to its normal saturated condition.

The packages offer fused leads for enhanced thermal dissipation. Package B of A2557 is a 16-pin power DIP with exposed tabs, EB is a 28-lead power PLCC, and LB is a 16-lead power wide-body SOIC for surface-mount applications. The lead (Pb) free versions have 100% matte tin leadframe plating.