L7987 61 V 3 A asynchronous step-down switching regulator with adjustable current limitation Datasheet - production data Description The L7987 device is a step-down monolithic switching regulator able to deliver up to 3 A DC. The output voltage adjustability ranges from 0.8 V to V . The wide input voltage range and the IN HTSSOP16 (R = 40 C/W) 100% duty cycle capability meet the fail safe TH specifications for industrial systems. The embedded switchover feature on the V pin BIAS maximizes the efficiency at light load. The Features adjustable current limitation, designed to select the inductor RMS current accordingly with the 3 A DC output current nominal output current, and the high switching 4.5 V to 61 V operating input voltage frequency capability make the size of the application compact. Pulse-by-pulse current R = 250 m typ. DS,ON sensing with digital frequency foldback Adjustable f (250 kHz - 1.5 MHz) SW implements an effective constant current Low IQ-SHD (11 A typ. from V ) protection over the different application IN conditions. The peak current foldback decreases Low IQ (1 mA typ. - V 24 V - V 3.3 V) IN OUT the stress of the power components in heavy Output voltage adjustable from 0.8 V to V IN short-circuit condition. The PGOOD open Synchronization collector output can also implement output voltage sequencing during the power-up phase. Adjustable soft-start time Multiple devices can be synchronized sharing the Adjustable current limitation SYNCH pin to prevent beating noise in low noise Low dropout operation (12 s max.) applications like sensors with A/D conversion. V improves efficiency at light load BIAS PGOOD open collector output Output voltage sequencing Digital frequency foldback in short-circuit Peak current foldback in short-circuit Auto-recovery thermal shutdown Applications Designed for 24 V bus Fail safe tolerant system Programmable logic controllers (PLCs) March 2015 DocID025589 Rev 3 1/37 This is information on a product in full production. www.st.comContents L7987 Contents 1 Application schematic and block diagram . 4 2 Pin settings 5 2.1 Pin connection 5 2.2 Pin description 6 2.3 Maximum ratings 7 2.4 Thermal data . 7 2.5 ESD protection 7 3 Electrical characteristics . 8 4 Functional description 11 4.1 Oscillator and synchronization 11 4.2 Soft-start 15 4.3 Error amplifier and light-load management . 16 4.4 Low VIN operation 17 4.5 Overcurrent protection . 17 4.6 Overtemperature protection . 19 5 Application information . 20 5.1 Input capacitor selection 20 5.2 Output capacitor selection 21 5.3 Inductor selection . 22 5.4 Compensation network . 23 5.4.1 Type II compensation network 25 5.4.2 Type III compensation network . 26 5.5 Thermal considerations 29 5.6 Layout considerations . 30 6 Demonstration board . 31 7 Package information 34 2/37 DocID025589 Rev 3