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 docid026994 rev 1 1/10 R6902D up to 1 a step-down switching regu lator with adjustable current limit for aerospace applications datasheet - preliminary data features ? general features ? up to 1 a dc output current ? operating input voltage from 8 v to 36 v ? output voltage adjustable from 1.235 v to 35 v ? precise 3.3 v ( 2%) reference voltage ? 250 khz internally fixed frequency ? voltage feedforward ? zero load current operation ? internal current limiting ? protection against feedback disconnection ? 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 ? aerospace applications ? adjustable current generator ? simple step-down converters with adjustable current limit so-8 figure 1. application schematic www.st.com
contents R6902D 2/10 docid026994 rev 1 contents 1 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1 pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2 thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
docid026994 rev 1 3/10 R6902D description 10 1 description the R6902D is a complete and simple step-down switching regulator with an adjustable current limit. based on a voltage mode structure it integrates a current error amplifier to have a constant voltage and constant current control. by means of an on-board current sense resistor and the availabilit y of the current sense pins ( both compatible to vcc and for cs- compatible with gnd too) current limit progra mming is very simple and accurate. moreover constant cu rrent control can be used to char ge nimh and nicd batteries. the device can be used as a standard dc/dc conver ter with the adjustable current limit (set by using the external sense resistor). the internal robust p-channel dmos transistor with a typical of 250 m ? assures high efficiency and a minimum dropout even at a high output current level. the internal limit ing current (latched function) of typical value of 2.5 a protects the device from an accidental output short-circuit avoiding dangerous loads damage. if the temperature of the chip goes higher than a fixed internal threshold (150 c with 20 c hysteresis), the power stage is turned off. the large ambient temperature range makes it ideal for aerospace and defense applications. other protections beside the thermal shutdown complete the device for a safe and reliable application: overvoltage protection, frequ ency foldback overcurrent protection and protection vs. feedback disconnection. the inte rnal fixed switching frequency of 250 khz, and the so-8 package pin allow to built an ultra compact dc/dc converter with a minimum board space.
pin connection R6902D 4/10 docid026994 rev 1 2 pin connection 2.1 pin connection figure 2. pin connection (top view) 2.2 pin description $ 0 2 8 7 & 6 & 6 & 2 0 3 9 & & * 1 ' 9 5 ( ) ) % table 1. pin description no. pin description 1 out regulator output. 2 cs+ current error amplifier input (c urrent sense at higher voltage) 3 cs- current error amplifier input (current sense at lower voltage) 4 comp e/a output for frequency compensation. 5fb feedback input. connecting directly to this pin results in an output voltage of 1.23 v. an external re sistive divider is required for higher output voltages. 6v ref 3.3 v reference voltage. no cap is need for stability. 7 gnd ground. 8 vcc unregulated dc input voltage.
docid026994 rev 1 5/10 R6902D electrical data 10 3 electrical data 3.1 maximum ratings 3.2 thermal data table 2. absolute maximum ratings symbol parameter value unit v 8 input voltage 40 v v 1 out pin dc voltage out pin peak voltage at ? t = 0.1 ? s -1 to 40 -5 to 40 v v i 1 maximum output current int. limit. v 4 , v 5 analog pins 4 v v 2 , v 3 analog pins -0.3 to v cc v p tot power dissipation at t a ?? 70 c 0.7 w t j operating junction temperature range -40 to 150 c t stg storage temperature range -55 to 150 c table 3. thermal data symbol parameter so-8 unit r thja maximum thermal resistance junction ambient 110 (1) 1. package mounted on board. c/w
electrical characteristics R6902D 6/10 docid026994 rev 1 4 electrical characteristics t j = -40 to 125 c, v cc = 12 v, unless otherwise specified. table 4. electrical characteristics symbol parameter test conditions min. typ. max. unit v cc operating input voltage range v 0 = 1.235 v; i 0 = 2 a 8 36 v r ds(on) mosfet on resistance 0.250 0.5 ? i l maximum limiting current (1) v cc = 8.5 v 1.8 2.5 3.2 a v cc = 8.5 v, t j = 25 c 2 2.5 3.2 f sw switching frequency 212 250 280 khz duty cycle 0 100 % dynamic characteristics v 5 voltage feedback 8 v < v cc < 36 v, 20 ma < i 0 < 1 a 1.198 1.235 1.272 v ? efficiency v 0 = 5 v, v cc = 12 v 90 % dc characteristics i qop total operating quiescent current 35ma i q quiescent current duty cycle = 0; v fb = 1.5 v 2.7 ma error amplifier v oh high level output voltage v fb =1 v 3.6 v v ol low level output voltage v fb =1.5 v 0.4 v i o source source output current v comp = 1.9 v; v fb = 1 v 160 300 ? a i o sink sink output current v comp = 1.9 v; v fb = 1.5 v 1 1.5 ma i b source bias current 2.5 4 ? a dc open loop gain r l = 50 58 db gm transconductance i comp = -0.1 ma to 0.1 ma; v comp = 1.9 v 2.3 ms v offs input offset voltage v cs- = 1.8 v; v cs+ = v comp 90 100 110 mv i cs+ cs+ output current i 0 = 1 a; r sense = 100 m ? ; v out < v cc - 2 v 1.5 3 ? a i cs- cs- output current i 0 = 1 a; r sense = 100 m ? ; v out < v cc - 2 v 1.5 3 ? a reference section reference voltage i ref = 0 to 5 ma, v cc = 8 v to 36 v 3.2 3.3 3.399 v line regulation i ref = 0ma, v cc = 8 v to 36 v 5 10 mv load regulation i ref = 0 to 5 ma 8 15 mv short-circuit current 5 18 35 ma 1. with t j = 85 c, i lim_min = 2 a, assured by design, characte rization and statistical correlation. 8
docid026994 rev 1 7/10 R6902D package information 10 5 package information in order to meet environmental requirements, st offers these devices in different grades of ecopack ? packages, depending on their level of environmental compliance. ecopack specifications, grade definitions a nd product status are available at: www.st.com . ecopack is an st trademark.
package information R6902D 8/10 docid026994 rev 1 figure 3. so-8 package outline table 5. so-8 package mechanical data symbol dimensions (mm) dimensions (inch) min. typ. max. min. typ. max. a 1.35 1.75 0.053 0.069 a1 0.10 0.25 0.004 0.010 a2 1.10 1.65 0.043 0.065 b 0.33 0.51 0.013 0.020 c 0.19 0.25 0.007 0.010 d (1) 1. 1. dimension ?d? does not include mold flash, prot rusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.15 mm (0.006 inch) in total (both sides). 4.80 5.00 0.189 0.197 e 3.80 4.00 0.15 0.157 e 1.27 0.050 h 5.80 6.20 0.228 0.244 h 0.25 0.50 0.010 0.020 l 0.40 1.27 0.016 0.050 k0 (min), 8 (max) ddd 0.10 0.004
docid026994 rev 1 9/10 R6902D order codes 10 6 order codes 7 revision history table 6. ordering information order codes package packaging R6902D so-8 tube R6902D13tr tape and reel table 7. document revision history date revision changes 06-oct-2014 1 in itial release.
R6902D 10/10 docid026994 rev 1 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 in formation 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 o rder 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
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