UM10782 The NXP LCD driver with on-chip charge pump for the LCD supply voltage generation Rev. 1.00 — 20 February 2014 User manual Document information Info Content Keywords Contrast, LCD driver, charge pump, PCA8547, PCA8543, PCA8537, PCA9620, PCA8538, PCA8539, PCF2119, PCF21219 Abstract The most important parameter to assess the optical performance of a passive monochrome LCD is the display contrast. Therefore the VLCD voltage must be set properly to gain an optimum contrast. UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump Revision history Rev Date Description v.1 20140220 first revision Contact information For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: [email protected] UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 2 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 1. Introduction The most important parameter to assess the optical performance of a passive monochrome LCD is the display contrast. 2. Display contrast Assumed an LCD with a certain resolution, a defined LCD drive mode (commonly called multiplex rate) and a defined LCD bias configuration (commonly called bias system), the display contrast depends on the VLCD voltage, also called operating voltage of the display. For an optimum display contrast, the VLCD voltage must be set in order that the following two conditions are met (see Figure 1): 1. Voff(RMS) Vth where Vth is the threshold voltage of the display, defined as the RMS voltage corresponding to 10 % relative transmission, and Voff is the voltage supplied to drive the pixel OFF; the condition Voff(RMS) Vth means that the pixel is really driven OFF. 2. Voff(RMS) Vsat where Vsat is the saturation voltage of the display, defined as the RMS voltage corresponding to 90 % relative transmission, and Von is the voltage supplied to drive the pixel ON; the condition Von(RMS) Vsat means that the pixel is really driven ON. UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 3 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 7Ȝ 5HODWLYH 7UDQVPLVVLRQ 9WK 9RII506 2)) 6(*0(17 9506>9@ 9VDW 9RQ506 *5(< 6(*0(17 21 6(*0(17 DDD V on RMS = V LCD 2 a bias + 2a bias + n MUX ---------------------------------------------------2 n MUX 1 + a bias V on RMS V th on V off RMS = V LCD 2 –2 a a bias bias + n MUX -------------------------------------------------2 n MUX 1 + a bias V off RMS V th off With abias = 1 for 1⁄2 bias, abias = 2 for 1⁄3 bias etc. and nMUX = 1 for static drive mode, nMUX = 2 for 1:2 multiplex drive mode etc. Fig 1. Proper VRMS values switching a pixel fully on and off Higher values of VLCD lead to a loss of contrast since the pixel cannot be really driven OFF (Voff(RMS) Vth), see Figure 2. UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 4 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 7Ȝ 5HODWLYH 7UDQVPLVVLRQ 9RII506 2)) 6(*0(17 9506>9@ 9VDW 9WK 9RQ506 *5(< 6(*0(17 21 6(*0(17 DDD Fig 2. A too high VLCD causing that Voff(RMS) Vth Lower values of VLCD lead to loss of contrast since the pixel cannot be really driven ON (Von(RMS) Vsat), see Figure 3. 7Ȝ 5HODWLYH 7UDQVPLVVLRQ 9VDW 9WK 9RII506 2)) 6(*0(17 9506>9@ 9RQ506 *5(< 6(*0(17 21 6(*0(17 DDD Fig 3. A too low VLCD causing that Von(RMS) Vsat There is only a strict range of VLCD values that lead to an optimum contrast: the optimum value is that one, that maximizes the product V th – V off V on – V sat . This product has always to be positive. UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 5 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 9WK 9RII9 9RQ 9VDW 9 WK 9RII RQ 9VDW 9 9WK9RII 9 WK9RII 9WK9RIIî9RQ9VDW 9WK9RII 9RQ9VDW 9RQ9VDW 9/&'9 9WK 9RIIî9RQ 9VDW 9 9WK 9RII9RQ 9VDW 9 9WK 9RIIî9RQ 9VDW 9 9WK9RIIî9RQ9VDW 9RQ9VDW 9RQ9VDW 9WK9RII 9WK9RII 9/&'9 DDD Vth = 1.5 V; Vsat = 2.5 V; MUX 1:4; bias 1⁄3. Fig 4. Optimum VLCD value to optimize the display contrast In summary, to optimize the contrast: 1. VLCD must be independent from the VDD supply To be able to select the LCD voltage value and then optimize the display contrast independently from the VDD supply. 2. VLCD must be programmable in a wide range To be able to optimize the display contrast for a wide selection of LCDs with different Vth and Vsat. 3. VLCD must be programmable with a small programming step and very accurate To guarantee that the programmed LCD voltage value is as much as possible close to the optimum value also across process variations. UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 6 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 4. VLCD must be compensated over temperature to keep a high and stable contrast over the temperature range Since the display characteristics change over temperature, VLCD should also change to maintain the best contrast over temperature. Different solutions can be implemented by using discrete components. In order to reduce the BOM and the overall system cost, NXP has developed a wide portfolio of LCD drivers with an integrated charge pump and regulator to generate the VLCD on-chip and allow programming the VLCD value accurately in a wide range, by simply programming a register through the interface. The capacitors of the charge pump are also integrated on-chip, allowing reducing the number of external components to a minimum. Further, NXP has integrated a temperature sensor and a VLCD temperature compensation circuitry in order to compensate the VLCD value with the temperature and to reach an optimum contrast all over the operating temperature range, from 40 C to 85 C for the industrial and consumer LCD drivers and from 40 C to 95 C or even 105 C for the automotive qualified LCD drivers. 76$ 76% 76& 76' 9RIIVHW/&' 7(03(5$785( 0($685(0(17 7'>@ 97>@ 7(03(5$785( &203(16$7,21 9/&'>@ 9SURJ/&' Fig 5. 9/&' DDD VLCD generation including temperature compensation UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 7 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 3. LCD drivers with integrated charge pump Table 1. List of LCD drivers with integrated charge pump Product type Maximum resolution Package VLCD programmable range Max. charge pump multiplication factor Temperature range 2.5 V to 9.0 V 3 VDD2 40 C to 95 C Packaged LCD segment drivers PCA8547 4 44 TQFP64 PCA8543 4 60 LQFP80 2.5 V to 9.0 V 3 VDD2 40 C to 105 C PCA8537 8 44 TQFP64 2.5 V to 9.0 V 3 VDD2 40 C to 95 C PCA9620 8 60 LQFP80 2.5 V to 9.0 V 3 VDD2 40 C to 105 C Chip-On-Glass LCD segment drivers PCA8538 9 102 bare die 4.0 V to 12.0 V 5 VDD2 40 C to 105 C PCA8539 18 100 bare die 4.0 V to 16.0 V 4 VDD2 40 C to 105 C Chip-On-Glass LCD character drivers PCA2117 1 line 40 characters or 2 lines 20 characters bare die 4.0 V to 16.0 V 4 VDD2 40 C to 105 C PCF2119 2 lines 20 characters bare die 2.2 V to 6.5 V 4 VDD2 40 C to 85 C PCF21219 2 lines 20 characters bare die 2.5 V to 6.5 V 4 VDD2 40 C to 85 C Choose the NXP LCD drivers with integrated charge pump that allow both, high performance and low cost! UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 8 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 4. References [1] AN10170 — Design guidelines for COG modules with NXP monochrome LCD drivers [2] AN11267 — EMC and system level ESD design guidelines for LCD drivers [3] PCA8547 — 4 x 44 automotive LCD driver with integrated charge pump, product data sheet [4] PCA8543 — 4 x 60 automotive LCD segment driver with integrated charge pump, product data sheet [5] PCA8537 — Automotive LCD driver for multiplex rates up to 1:8, product data sheet [6] PCA9620 — 60 x 8 LCD high-drive segment driver for automotive and industrial, product data sheet [7] PCA8538 — Automotive 102 x 9 Chip-On-Glass LCD segment driver, product data sheet [8] PCA8539 — 100 x 18 Chip-On-Glass automotive LCD dot matrix driver, product data sheet [9] PCF2119 — LCD controllers/drivers, product data sheet [10] PCF21219 — LCD driver for character displays, product data sheet [11] R_10015 — Chip-On-Glass (COG) - a cost-effective and reliable technology for LCD displays UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 9 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 5. Legal information 5.1 Definitions Draft — The document is a draft version 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 have no liability for the consequences of use of such information. 5.2 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. NXP Semiconductors takes no responsibility for the content in this document if provided by an information source outside of NXP Semiconductors. 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 interruption, 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 and its suppliers accept 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 purposes 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 UM10782 User manual 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 for 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 applications and products using NXP Semiconductors products in order to avoid 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. 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 competent authorities. Evaluation products — This product is provided on an “as is” and “with all faults” basis for evaluation purposes only. NXP Semiconductors, its affiliates and their suppliers expressly disclaim all warranties, whether express, implied or statutory, including but not limited to the implied warranties of non-infringement, merchantability and fitness for a particular purpose. The entire risk as to the quality, or arising out of the use or performance, of this product remains with customer. In no event shall NXP Semiconductors, its affiliates or their suppliers be liable to customer for any special, indirect, consequential, punitive or incidental damages (including without limitation damages for loss of business, business interruption, loss of use, loss of data or information, and the like) arising out the use of or inability to use the product, whether or not based on tort (including negligence), strict liability, breach of contract, breach of warranty or any other theory, even if advised of the possibility of such damages. Notwithstanding any damages that customer might incur for any reason whatsoever (including without limitation, all damages referenced above and all direct or general damages), the entire liability of NXP Semiconductors, its affiliates and their suppliers and customer’s exclusive remedy for all of the foregoing shall be limited to actual damages incurred by customer based on reasonable reliance up to the greater of the amount actually paid by customer for the product or five dollars (US$5.00). The foregoing limitations, exclusions and disclaimers shall apply to the maximum extent permitted by applicable law, even if any remedy fails of its essential purpose. Translations — A non-English (translated) version of a document is for reference only. The English version shall prevail in case of any discrepancy between the translated and English versions. 5.3 Trademarks Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 10 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 6. Tables Table 1. List of LCD drivers with integrated charge pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 11 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 7. Figures Fig 1. Fig 2. Fig 3. Fig 4. Fig 5. Proper VRMS values switching a pixel fully on and off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 A too high VLCD causing that Voff(RMS) ³ Vth . . . . . .5 A too low VLCD causing that Von(RMS) £ Vsat . . . . . .5 Optimum VLCD value to optimize the display contrast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 VLCD generation including temperature compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 UM10782 User manual All information provided in this document is subject to legal disclaimers. Rev. 1.00 — 20 February 2014 © NXP B.V. 2014. All rights reserved. 12 of 13 UM10782 NXP Semiconductors The NXP LCD driver with on-chip charge pump 8. Contents 1 2 3 4 5 5.1 5.2 5.3 6 7 8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Display contrast . . . . . . . . . . . . . . . . . . . . . . . . . 3 LCD drivers with integrated charge pump . . . 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Legal information. . . . . . . . . . . . . . . . . . . . . . . 10 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Please be aware that important notices concerning this document and the product(s) described herein, have been included in section ‘Legal information’. © NXP B.V. 2014. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: [email protected] Date of release: 20 February 2014 Document identifier: UM10782