1. general description the tea1791t is a member of the new gen eration of synchronous rectifier (sr) controller ics for switched mode power supplies. its high level of integration allows the design of a cost-effective powe r supply with a very low number of external components. the tea1791t is a controller ic dedicated to synchronous rectification on the secondary side of discontinuous conduction mode and quasi-resonant flyback converters. the tea1791t is fabricated in a silicon on insulator (soi) process. 2. features and benefits 2.1 distinctive features ? accurate synchronous rect ification functionality ? wide supply voltage range (8.5 v to 38 v) ? high level of integration, resulting in a very low external component count ? high driver output voltage of 10 v to drive all mosfet brands to the lowest r dson 2.2 green features ? low current consumption ? high system efficiency from no load to full load 2.3 protection features ? undervoltage protection 3. applications ? the tea1791t is intended for adapters. the device can also be used in all other discontinuous conduction mode systems and quasi-resonant flyback systems that demand a highly efficient and cost-effective solution. 4. ordering information tea1791t greenchip synchronous rectifier controller rev. 02 ? 7 june 2010 product data sheet table 1. ordering information type number package name description version tea1791t/n1 so8 plastic small outline package; 8 leads; body width 3.9 mm sot96-1
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 2 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 5. block diagram 6. pinning information 6.1 pinning 6.2 pin description fig 1. block diagram v cc 8 3, 5, 6, 7 n.c. 2 gnd srsense 1 4 r s q q ? 55 mv driver control ? 12 mv ? 310 mv timer 2 s 2.2 s 014aaa70 0 fig 2. pin configuration tea1791t srsense v cc gnd n.c. n.c. n.c. driver n.c. 014aaa701 1 2 3 4 6 5 8 7 table 2. pin description symbol pin description srsense 1 synchronous timing input gnd 2 ground n.c. 3 not connected driver 4 driver output for sr mosfet n.c 5 not connected n.c. 6 not connected n.c. 7 not connected v cc 8 supply voltage
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 3 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 7. functional description 7.1 introduction the tea1791t is the controller for synchronou s rectification to be used in discontinuous conduction mode and quasi-resonant flyback converters. 7.2 start-up and underv oltage lockout (uvlo) the ic leaves the undervoltage lockout st ate and activates the synchronous rectifier circuitry as soon as the voltage on the v cc pin is above 8.5 v (typical). when the voltage drops below 8.0 v (typical), the undervoltage lockout state is reentered and the sr driver output is actively kept low. 7.3 synchronous rectification after a negative voltage ( ? 310 mv typical) is sensed on the srsense pin, the driver output voltage is driven high and the external mosfet is switched on. as soon as the srsense voltage rises to ? 55 mv the driver output voltage is regulated to maintain the ? 55 mv on the srsense pin. when the srsense voltage is above ? 12 mv, the driver output is pulled to ground. after switch-on of the sr mosfet, the inpu t signal on the srsense pin is blanked for 2 s (typical). this eliminates false switch-off due to high frequency ringing at the start of the secondary stroke. because the driver output voltage is redu ced when the voltage on the srsense pin is ? 55 mv, the external power switch can be swit ched off quickly when the current through the switch reaches zero. the zero current switch-off remo ves the need for a separate standby mode to maintain high efficiency during the no-load operation. the zero current is detected by sensing a ? 12 mv level on the srsense pin (see figure 3 ).
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 4 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller if the secondary stroke of the flyback converter is shorter than 2 s (typical), the driver output is disabled. this will guarantee stable operation for very low duty cycles. when the secondary stroke in creases above 2.2 s (typical), the driver output is again enabled. 7.4 supply management all internal reference voltages are derived from a temperature compensated, on-chip band gap circuit. 7.5 driver the driver circuit to the gate of the external power mosfet has a typical source capability of 250 ma and a typical sink capab ility of 2.7 a. this permits fast turn-on and turn-off of the power mosfet for efficient ope ration. the output voltage of the driver is limited to 10 v (typical). this high output voltage will drive all mosfet brands to the minimum on-state resistance. during start-up conditions (v cc tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 5 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 8. limiting values [1] equivalent to discharging a 100 pf capacitor through a 1.5 k series resistor. [2] equivalent to discharging a 200 pf capacitor through a 0.75 h coil and a 10 series resistor. 9. thermal characteristics table 3. limiting values in accordance with the absolute maximum rating system (iec 60134). all voltages are measured with respect to ground (pin 2); positive currents flow into the chip. the voltage ratings and current ratings are valid provided the other ratings are not violated. symbol parameter conditions min max unit voltages v cc supply voltage continuous ? 0.4 +38 v v srsense voltage on pin srsense continuous - 120 v currents i driver current on pin driver duty cycle < 10 % ? 0.8 +3 a i srsense current on pin srsense ? 3- ma general p tot total power dissipation t amb <80 c - 0.45 w t stg storage temperature ? 55 +150 c t j junction temperature ? 40 +150 c v esd electrostatic discharge voltage class 2 human body model [1] - 2000 v machine model [2] -200v charged device model -500v table 4. thermal characteristics symbol parameter conditions typ unit r th(j-a) thermal resistance from junction to ambient in free air 150 k/w r th(j-c) thermal resistance from junction to case 95 k/w
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 6 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 10. characteristics [1] the v cc stop voltage is v startup ? v hys . table 5. characteristics t amb =25 c; v cc = 20 v; all voltages are measured with respect to ground (pin 2); currents are positive when flowing into the ic; unless otherwise specified. symbol parameter conditions min typ max unit supply voltage management (pin v cc ) v startup start-up voltage 8.2 8.5 8.8 v v hys hysteresis voltage [1] -0.5-v i cc(oper) operating supply current v cc =8v (v cc tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 7 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 11. application information a switched mode power supply with the tea1791t consists of a primary side discontinuous conduction mode flyback controller, a transformer, and an output stage with a feedback circuit. a mosfet (q sec ) is used for low conduction lo sses in the output state. this mosfet is controlled by the tea1791t. the timing for the synchronous rectifier switch is derived from the voltage sensed on the srsense pin. the resistor in the srsense connection is needed to protect the tea1791t from excessive voltages. the r srsense resistor should typically be 1 k . higher values might impair co rrect timing, lower values may not provide sufficient protection. fig 4. application diagram high side rectification fig 5. application diagram low side rectification v in tr primary side controller q prim v cc gnd driver tea1791t srsense q sec r srsense v out c out 014aaa70 2 driver srsense v cc v out gnd tea1791t primary side controller v in q sec c out r srsense q prim tr 014aaa8 49
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 8 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 12. package outline fig 6. package outline sot96-1 (so8) unit a max. a 1 a 2 a 3 b p cd (1) e (2) (1) eh e ll p qz y w v references outline version european projection issue date iec jedec jeita mm inches 1.75 0.25 0.10 1.45 1.25 0.25 0.49 0.36 0.25 0.19 5.0 4.8 4.0 3.8 1.27 6.2 5.8 1.05 0.7 0.6 0.7 0.3 8 0 o o 0.25 0.1 0.25 dimensions (inch dimensions are derived from the original mm dimensions) notes 1. plastic or metal protrusions of 0.15 mm (0.006 inch) maximum per side are not included. 2. plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included. 1.0 0.4 sot96-1 x w m a a 1 a 2 b p d h e l p q detail x e z e c l v m a (a ) 3 a 4 5 pin 1 index 1 8 y 076e03 ms-012 0.069 0.010 0.004 0.057 0.049 0.01 0.019 0.014 0.0100 0.0075 0.20 0.19 0.16 0.15 0.05 0.244 0.228 0.028 0.024 0.028 0.012 0.01 0.01 0.041 0.004 0.039 0.016 0 2.5 5 mm scale s o8: plastic small outline package; 8 leads; body width 3.9 mm sot96 -1 99-12-27 03-02-18
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 9 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 13. revision history table 6. revision history document id release date data sheet status change notice supersedes tea1791t v.2 20100607 product data sheet - tea1791t_1 modifications: ? r th(j-c) added to ta b l e 4 . ? figure 5 ? application diagram low side rectification ? , added. ? minimum value junction temperature changed in ta b l e 3 . tea1791t_1 20090203 product data sheet - -
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 10 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller 14. legal information 14.1 data sheet status [1] please consult the most recently issued document before initiating or completing a design. [2] the term ?short data sheet? is explained in section ?definitions?. [3] the product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple device s. the latest product status information is available on the internet at url http://www.nxp.com . 14.2 definitions draft ? the document is a draft versi on only. the content is still under internal review and subject to formal approval, which may result in modifications or additions. nxp semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall hav e no liability for the consequences of use of such information. short data sheet ? a short data sheet is an extract from a full data sheet with the same product type number(s) and title. a short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. for detailed and full information see the relevant full data sheet, which is available on request vi a the local nxp semiconductors sales office. in case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail. product specification ? the information and data provided in a product data sheet shall define the specification of the product as agreed between nxp semiconductors and its customer , unless nxp semiconductors and customer have explicitly agreed otherwis e in writing. in no event however, shall an agreement be valid in which the nxp semiconductors product is deemed to offer functions and qualities beyond those described in the product data sheet. 14.3 disclaimers limited warranty and liability ? information in this document is believed to be accurate and reliable. however, nxp semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. in no event shall nxp semiconductors be liable for any indirect, incidental, punitive, special or consequential damages (including - without limitation - lost profits, lost savings, business interrupt ion, costs related to the removal or replacement of any products or rework charges) whether or not such damages are based on tort (including negligence), warranty, breach of contract or any other legal theory. notwithstanding any damages that customer might incur for any reason whatsoever, nxp semiconductors? aggregate and cumulative liability towards customer for the products described herein shall be limited in accordance with the terms and conditions of commercial sale of nxp semiconductors. right to make changes ? nxp semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. this document supersedes and replaces all information supplied prior to the publication hereof. suitability for use ? nxp semiconductors products are not designed, authorized or warranted to be suitable for use in life support, life-critical or safety-critical systems or equipment, nor in applications where failure or malfunction of an nxp semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. nxp semiconductors accepts no liability for inclusion and/or use of nxp semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer?s own risk. applications ? applications that are described herein for any of these products are for illustrative purpos es only. nxp semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. customers are responsible for the design and operation of their applications and products using nxp semiconductors products, and nxp semiconductors accepts no liability for any assistance with applications or customer product design. it is customer?s sole responsibility to determine whether the nxp semiconductors product is suitable and fit for the customer?s applications and products planned, as well as fo r the planned application and use of customer?s third party customer(s). customers should provide appropriate design and operating safeguards to minimize the risks associated with their applications and products. nxp semiconductors does not accept any liability related to any default, damage, costs or problem which is based on any weakness or default in the customer?s applications or products, or the application or use by customer?s third party customer(s). customer is responsible for doing all necessary testing for the customer?s applic ations and products using nxp semiconductors products in order to av oid a default of the applications and the products or of the application or use by customer?s third party customer(s). nxp does not accept any liability in this respect. limiting values ? stress above one or more limiting values (as defined in the absolute maximum ratings system of iec 60134) will cause permanent damage to the device. limiting values are stress ratings only and (proper) operation of the device at these or any other conditions above those given in the recommended operating conditions section (if present) or the characteristics sections of this document is not warranted. constant or repeated exposure to limiting values will permanently and irreversibly affect the quality and reliability of the device. terms and conditions of commercial sale ? nxp semiconductors products are sold subject to the gener al terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms , unless otherwise agreed in a valid written individual agreement. in case an individual agreement is concluded only the terms and conditions of the respective agreement shall apply. nxp semiconductors hereby expressly objects to applying the customer?s general terms and conditions with regard to the purchase of nxp semiconducto rs products by customer. no offer to sell or license ? nothing in this document may be interpreted or construed as an offer to sell products t hat is open for acceptance or the grant, conveyance or implication of any lic ense under any copyrights, patents or other industrial or intellectual property rights. export control ? this document as well as the item(s) described herein may be subject to export control regulations. export might require a prior authorization from national authorities. document status [1] [2] product status [3] definition objective [short] data sheet development this document contains data from the objecti ve specification for product development. preliminary [short] data sheet qualification this document contains data from the preliminary specification. product [short] data sheet production this docu ment contains the product specification.
tea1791t all information provided in this document is subject to legal disclaimers. ? nxp b.v. 2010. all rights reserved. product data sheet rev. 02 ? 7 june 2010 11 of 12 nxp semiconductors tea1791t greenchip synchronous rectifier controller non-automotive qualified products ? unless this data sheet expressly states that this specific nxp semicon ductors product is automotive qualified, the product is not suitable for automotive use. it is neither qualified nor tested in accordance with automotive testing or application requirements. nxp semiconductors accepts no liabili ty for inclusion and/or use of non-automotive qualified products in automotive equipment or applications. in the event that customer uses t he product for design-in and use in automotive applications to automotive s pecifications and standards, customer (a) shall use the product without nxp semiconductors? warranty of the product for such automotive applicat ions, use and specifications, and (b) whenever customer uses the product for automotive applications beyond nxp semiconductors? specifications such use shall be solely at customer?s own risk, and (c) customer fully indemnifies nxp semiconductors for any liability, damages or failed product claims resulting from customer design and use of the product for automotive app lications beyond nxp semiconductors? standard warranty and nxp semiconduct ors? product specifications. 14.4 trademarks notice: all referenced brands, produc t names, service names and trademarks are the property of their respective owners. greenchip ? is a trademark of nxp b.v. 15. contact information for more information, please visit: http://www.nxp.com for sales office addresses, please send an email to: salesaddresses@nxp.com
nxp semiconductors tea1791t greenchip synchronous rectifier controller ? nxp b.v. 2010. all rights reserved. for more information, please visit: http://www.nxp.com for sales office addresses, please se nd an email to: salesaddresses@nxp.com date of release: 7 june 2010 document identifier: tea1791t please be aware that important notices concerning this document and the product(s) described herein, have been included in section ?legal information?. 16. contents 1 general description . . . . . . . . . . . . . . . . . . . . . . 1 2 features and benefits . . . . . . . . . . . . . . . . . . . . 1 2.1 distinctive features . . . . . . . . . . . . . . . . . . . . . . 1 2.2 green features . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.3 protection features . . . . . . . . . . . . . . . . . . . . . . 1 3 applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 4 ordering information . . . . . . . . . . . . . . . . . . . . . 1 5 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6 pinning information . . . . . . . . . . . . . . . . . . . . . . 2 6.1 pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6.2 pin description . . . . . . . . . . . . . . . . . . . . . . . . . 2 7 functional description . . . . . . . . . . . . . . . . . . . 3 7.1 introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 7.2 start-up and undervoltage lockout (uvlo) . . 3 7.3 synchronous rectification . . . . . . . . . . . . . . . . . 3 7.4 supply management. . . . . . . . . . . . . . . . . . . . . 4 7.5 driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8 limiting values. . . . . . . . . . . . . . . . . . . . . . . . . . 5 9 thermal characteristics . . . . . . . . . . . . . . . . . . 5 10 characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 6 11 application information. . . . . . . . . . . . . . . . . . . 7 12 package outline . . . . . . . . . . . . . . . . . . . . . . . . . 8 13 revision history . . . . . . . . . . . . . . . . . . . . . . . . . 9 14 legal information. . . . . . . . . . . . . . . . . . . . . . . 10 14.1 data sheet status . . . . . . . . . . . . . . . . . . . . . . 10 14.2 definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 14.3 disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 14.4 trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 11 15 contact information. . . . . . . . . . . . . . . . . . . . . 11 16 contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
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