STEVAL-ISA139V1

STEVAL-ISA139V1 350 mA valley current limit adjustable step-down regulator based on the PM6644 Data brief Description This product evaluation board is based on STMicroelectronics' PM6644. The device combines a 350 mA valley current limit step-down regulator with a high accuracy 3.3 V voltage reference in a small DFN10 3x3 package. The switching regulator is based on a CoT (constant on time) architecture that assures fast load transient response. The embedded voltage feed-forward provides nearly constant switching frequency operation. Pulse-skipping is employed to increase efficiency at very light load. The switching frequency can be adjusted from 200 kHz to 600 kHz by means of a simple resistor. Features           4.5 V to 25 V input voltage range Fixed 3.43 V or adjustable 0.9 V to 5 V Reference accuracy = +-1%, Tj=0 °C to 85 °C 380 mA maximum output current Constant on-time control with current sense Programmable switching frequency in PWM mode Pulse skipping mode (skip mode) at light loads Independent EN signal Latched OVP and UVP High accuracy 3.3 V reference voltage August 2014 The switching regulator can be programmed to regulate a fixed value of 3.43 V or it can deliver an adjustable voltage, depending on the FB pin setup. The high precision integrated 3.3 V reference can source up to 5 mA. DocID026819 Rev 1 For further information contact your local STMicroelectronics sales office 1/4 www.st.com Schematic diagram 1 STEVAL-ISA139V1 Schematic diagram Figure 1: STEVAL-ISA139V1 circuit schematic J3 J4 3.3V+ 3.3 VJ2 1 1 1 VIN- - S1 (FB_SE L jumper) shorted to VCC - S2 (EN_SE L jumper) shorted to VIN - S3 (BYP_SE L jumper) shorted to OU T 0 J7 VIN 1 1 0 2 1 0 BY P 3 2 FB_SE L 4 C1 BY P TON VCC GND S1 10n 2M 2 1 3 REF3 FB EN 5 1 EP EP R3 VIN SW 1 2 SW 1u 2 VCC 0 0 1 2 OU T 2 2.2u 1 2 2 C8 1 S3 33u 0 7 VIN 6 10n 1 C4 8 VCC OU T C3 10 9 BY P C5 OU T 3 10n S T PM6644 REF EXT_VCC 2 2 2 1 BYP_SE L C2 1 1 EXT_VCC- J1 VIN+ FB J8 EXT_VCC+ 0 C7 2.2u C6 22u 1 22u 1 VIN 1M 0 R1 2 OU T 0 S2 J10 EXT_VCC FB R4 1M 3 0 J5 EN_SE L 1 J9 J11 SW BY P 1 VOUT+ J6 R2 1 VIN 1 1M 1 1 0 0 3 4 FB SW VOU T- BY P EN SW1 2 1 0 GSPG2808141528SMD 2/4 DocID026819 Rev 1 STEVAL-ISA139V1 2 Revision history Revision history Table 1: Document revision history Date Revision 28-Aug-2014 1 Changes Initial release. DocID026819 Rev 1 3/4 STEVAL-ISA139V1 IMPORTANT NOTICE – PLEASE READ CAREFULLY STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and improvements to ST products and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. ST products are sold pursuant to ST’s terms and conditions of sale in place at the time of order acknowledgement. Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design of Purchasers’ products. No license, express or implied, to any intellectual property right is granted by ST herein. Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product. ST and the ST logo are trademarks of ST. All other product or service names are the property of their respective owners. Information in this document supersedes and replaces information previously supplied in any prior versions of this document. © 2014 STMicroelectronics – All rights reserved 4/4 DocID026819 Rev 1