this is preliminary information on a new product now in dev elopment or undergoing evaluati on. details are subject to change without notice. october 2014 docid026996 rev 1 1/59 R6986 38 v 2 a synchronous step-down switching regulator with 30 a quiescent current datasheet - preliminary data features ? general features ? 2 a dc output current ? 4 v to 38 v operating input voltage ? large ambient temperature range: -40 c to 125 c ? low consumption mode or low noise mode ? 30 a iq at light load (lcm v out = 3.3 v) ?8 a i q-shtdwn ? adjustable f sw (250 khz - 2 mhz) ? output voltage adjustable from 0.85 v to v in ? embedded output voltage supervisor ? synchronization ? adjustable soft-start time ? internal current limiting ? overvoltage protection ? output voltage sequencing ? peak current mode architecture ?r dson hs = 180 m ? , r dson ls = 110 m ? ? thermal shutdown ? aerospace and defense features ? suitable for use in aerospace and defense applications ? dedicated traceabilit y and part marking ? production parts approval documents available ? adapted extended life time and obsolescence management ? extended product change notification process ? designed and manufactured to meet sub- ppm quality goals ? advanced mold and frame designs for superior resilience in harsh environments (acceleration, emi, thermal, humidity) ? extended screening ca pability on request applications ? designed for aerospace applications ? battery powered applications description the R6986 device is a step-down monolithic switching regulator able to deliver up to 2 a dc. the output voltage adju stability ranges from 0.85 v to v in . the 100% duty cycle, the wide input voltage range and the large ambient temperature range make it ideal for aerospace and defense applications. the ?low consumption mode? (lcm) is designed for always-on applications, so it maximizes the efficiency at light load with controlled output voltage ripple. the ?low noise mode? (lnm ) makes the switching frequency constant and minimizes the output voltage ripple overload current range. the output voltage supervisor manages the reset phase for any digital load (c, fpga.). the rst open collector output can also implement output voltage sequencing during the power-up phase. the synchronous rectification, designed for high efficiency at medium - heavy load, and the high switching frequency capab ility make the size of the application compact. pulse by pulse current sensing on both power elements implements an effective constant current protection. htssop16 (r th = 40 c/w) www.st.com
contents R6986 2/59 docid026996 rev 1 contents 1 application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.4 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.5 esd protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4 datasheet parameters over the temperatur e range . . . . . . . . . . . . . . . 13 5 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1 power supply and voltage reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 switchover feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.2 voltages monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.3 soft-start and inhibit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.3.1 ratiometric startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.3.2 output voltage sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.4 error amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.5 light load operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.5.1 low noise mode (lnm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.5.2 low consumption mode (lcm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5.6 switchover feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.6.1 lcm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.6.2 lnm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.7 overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 ocp and switchover feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 5.8 overvoltage protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 5.9 thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
docid026996 rev 1 3/59 R6986 contents 59 6 closing the loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 6.1 g co (s) control to output transfer function . . . . . . . . . . . . . . . . . . . . . . . . 32 6.2 error amplifier compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.3 voltage divider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 6.4 total loop gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 6.5 compensation network design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 7 application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 7.1 output voltage adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 7.2 switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 7.3 mlf pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 7.4 voltage supervisor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 7.5 synchronization (lnm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 7.6 design of the power components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.6.1 input capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.6.2 inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 7.6.3 output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 8 efficiency curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 9 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 10 order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 11 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
application schematic R6986 4/59 docid026996 rev 1 1 application schematic figure 1. application schematic
docid026996 rev 1 5/59 R6986 pin settings 59 2 pin settings 2.1 pin connection figure 2. pin connection (top view) 2.2 pin description 9 % , $ 6 9 , 1 / ; / ; 3 * 1 ' 3 * 1 ' 6 * 1 ' ) % 5 6 7 9 & |