EnFilm™ micro-battery EFL700A39 user guide
Contents
1. Ti AN4085 SLi uenig Application note EnFilm micro battery EFL700A39 user guide Eric Colleoni Introduction STMicroelectronics has developed micro battery products EnFilm with reduced thickness and weight The characteristics and electrical parameters of the product are detailed in the datasheet The EnFilm is easy to use but some design considerations are especially intended to get the maximum performance without damaging the product Figure 1 ELF700A39 micro battery 4y7 CA faa L auo ech ria an 90 ny February 2015 DoclD023052 Rev 2 1 16 www st com Contents AN4085 Contents 1 Handling and assembly of the ELF700A39 000000es 3 2 Charging the EFL700 A39 sosiu iis wwii scien ae eee aw eae Marne a 4 2 1 Charging voltage 42 cricke redid eb ie ee GeeGes PARRY eee eee eeeess 4 2 2 Charging OUIMEM tan tac viens eie se be idee ieee ke pases Pies Vee eRGes 4 2 3 Charging temperature 0 0 0 eee ee 4 3 Discharging the EFL700A39 battery 02202 cece eee 5 3 1 Minimum discharge voltage 0 eee eee 5 3 2 Discharging with continuous current 000000 eee eee 5 3 2 1 Discharging characteristics 0 cece ee eee 5 3 2 2 EFL700A39 survival time in battery disconnect protection mode 6 3 2 3 Recommended maximum load current overtemperature 7 3 3 Discharging with pulsed current 0000 ee 8 3 3 1 Using EF2. Figure 13 shows the EFL700EVALKIT which is including the EFL700PMB board and a load board Its features are e Includes an analogical ammeter and a digital voltmeter to monitor the current delivered by the source the current going through the EFL700A39 battery the battery voltage e Includes a pulsed load emulator with the possibility to adjust the pulsed load cyclic ratio For additional information refer to the STMicroelectronics UM1806 user manual EFL700A39 evaluation board kits and design in board user guide This document is available on the EnFilm Thin film batteries dedicated page of the STMicroelectronics web site http www st com DoclD023052 Rev 2 ky AN4085 Revision history 5 Revision history Table 3 Document revision history Date Revision Changes 11 Jan 2012 1 Initial release 12 Feb 2015 2 Comprehensive content revision DoclD023052 Rev 2 15 16 AN4085 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 choi
3. V 4 5 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 1 1 1 2 Using a buffer capacitor to increase the pulse current For applications in which pulsed current levels are higher than 10 mA and or in which operating temperature are lower than 30 C it is required to add a buffer capacitor in parallel with the EFL700A39 as shown in the Figure 8 Figure 8 Buffer capacitor connection scheme EFL700A39 c The buffer capacitor aims are to keep the battery in a safe operating area to stabilize the output voltage supplied to the application and also to avoid triggering the battery voltage sense and disconnection circuit In order to choose the most adapted buffer capacitor we DoclD023052 Rev 2 9 16 Discharging the EFL700A39 battery AN4085 10 16 recommend to refer to the Figure 9 and the Figure 10 which show various buffer capacitor choices depending on pulsed current characteristics As an example if the application peak pulse current is 20 mA during 4 ms then the buffer capacitor minimum value over the application temperature range should be e 100 UF if the minimum allowed system supply voltage is 3 0 V e 320 UF if the minimum allowed system supply voltage is 3 6 V The Figure 17 provides a suggestion of technology for the buffer capacitor depending of the pulse current characteristics In order to ensure the buffer capacitor is effectively recharged by the EFL700A39 battery between two pulses each
4. below 3 0 V Nevertheless this dynamic voltage drop shall remain above 2 0 V and the battery cut off voltage shall recover a minimum of 3 0 V after the pulse as shown in the Figure 3 Figure 3 Minimum discharge voltage K l uLse gt 5 MA g He 5 i re He y fi PE i a it a j ji gt o if Vourorr_pc 3 0V i ee eeE _ _ es ss SS Se SS E ee O gt gt fad be ar 19 a 7 T gt y 7 time i tpurse lt 100ms Below those minimum cut off voltage values of 3 0 V under DC conditions and 2 0 V under pulsed conditions the EnFilm battery can be irretrievably damaged Battery charger devices integrating an over discharge protection feature or any custom discrete protection circuit can be used to secure the minimum battery discharge voltage Discharging with continuous current Discharging characteristics The Figure 4 shows the typical discharge characteristics of the EFL700A39 battery for different discharge current values from 1 A up to 5 mA These battery discharge curves DoclD023052 Rev 2 5 16 Discharging the EFL700A39 battery AN4085 3 2 2 6 16 were performed at 30 C on 4 2 V fully charged batteries and with a cut off protection set to 3 0 V The initial EnFilm micro battery voltage value is 4 2 V for a battery at full charge in open circuit conditions OCV When a load is connected
5. pulse must be followed by a steady state This constraint steps the transmit interval for the load The minimum transmit interval can be easily calculated from the battery resistance R and the value of the buffer capacitance C calculated previously First it is needed to pick the battery resistance R at the minimum application temperature in the Figure 6 Then the minimum transmit interval between 2 pulses is equal to 3 R C Figure 9 Buffer capacitor sizing versus pulse duration and peak pulse current for a minimum 3 0 V supply voltage during the pulse 1 0E 04 tpulse 16ms tpulse 32ms tpulse 64ms tpulse 100ms 1 0E 01 z nae Output capacitor minimum value for Vcap 3 0V MIN _ 1 0E 02 tpulse 1ms S 1 0E 03 tpulse 2ms 5 tpulse 4ms 2 tpulse 8ms o S 5 2 5 O 1 0E 05 1 0E 06 0 10 20 30 40 50 60 70 80 90 100 Peak Pulse Current mA Figure 10 Buffer capacitor sizing versus pulse duration and peak pulse current for a minimum 3 6 V supply voltage during the pulse 1 0E 01 Output capacitor minimum value for Vcap 3 6V MN 1 0E 02 tpulse 1ms 1 0E 03 tpulse 2ms 5 tpulse 4ms Q tpulse 8ms 1 0E 04 tpulse 16ms 3 tpulse 32ms O 1 0E 05 tpulse 64ms tpulse 100ms 1 0E 06 0 10 20 30 40 50 60 70 80 90 100 Peak Pulse Current mA DoclD023052 Rev 2 ky AN4085 Discharging the EFL700A39 battery 4 Fi
6. L700A39 in stand alone configuration 9 3 3 2 Using a buffer capacitor to increase the pulse current 9 4 Available power management IC s and tools 2005 12 4 1 STMicroelectronics SPV1050 IC s 0 2 0 00 ce ees 12 4 2 STMicroelectronics EFL700A39 evaluation boards 12 5 Revision history wecga caw eee eee de taw ddd dee eRe Ew aals o 15 2 16 DoclD023052 Rev 2 ky AN4085 Handling and assembly of the ELF700A39 1 Handling and assembly of the ELF700A39 Refer to both STMicroelectronics Application Note e AN4046 EnFilmTM micro battery EFL700A39 recommendations for manual assembly on PCB e AN4351 EnFilmTM micro battery EFL700A39 automatic or semi automatic mounting on PCB Those documents are describing all needed information and recommendation for proper handling and assembly on PCB of the ST EnFilm micro battery They are available on the EnFilm Thin film batteries dedicated page of the STMicroelectronics web site http www st com ky DoclD023052 Rev 2 3 16 Charging the EFL700A39 AN4085 2 2 1 2 2 2 3 4 16 Charging the EFL700A39 Charging voltage The EFL700A39 can be easily charged from a 4 2 V 1 constant voltage source with or without current limit More than 90 of the total capacity is recharged when the charge current falls below 100 pA For better life duration it is recommended to limit the charge volt
7. additional information are available on STMicroelectronics web site http www st com STMicroelectronics EFL700A39 evaluation boards Two boards have been developed for training and supporting the design of the solid state thin film battery EnFilm EFL700A39 The Evaluation kit Order Number EFL700EVALKIT allows to discover the operation of the EFL700A39 and to monitor the voltage and the dynamic charge discharge current in real use case condition The power management board order number EFL700PMB is rather a design in board including all the necessary power management circuit around the EFL700A39 and can be directly connected and used in the application for a fast evaluation 4 DoclD023052 Rev 2 AN4085 Available power management IC s and tools Figure 12 EFL700A39 power management board EFL700PMB EnFilm The Energy of Things Refer to UM1806 for EFL700EVALKIT description and how to use details Figure 13 EFL700A39 evaluation kit EFL700EVALKIT EnFiim The Energy of Things ky The Figure 12 shows the EFL700PMB board Its features are Management of the charge and the voltage regulation of the EFL700A39 Battery protection against deep discharge Recharge possibility through an external energy harvesting Includes a super capacitor to sustain high pulsed discharge current DoclD023052 Rev 2 13 16 Available power management IC s and tools AN4085 14 16 The
8. age between 4 0 V and 4 2 V Charging current A constant current charge is possible provided the maximum charge voltage does not exceed 4 2 V Switch mode pulse mode or linear battery charger devices can be used to secure the maximum battery charge voltage Charging temperature The higher the ambient temperature is the faster the charge is but meanwhile the faster is the aging of the EFL700A39 The Figure 2 shows the typical curve of the charge capacity versus the charge time duration for a 30 C ambient temperature As shown in this figure the EFL700A39 can be recharged from 0 State of Charge SoC up to 80 SoC in 20 minutes Figure 2 ELF700A39 typical charge curve Charge capacity 100 90 80 Typical charge curve under constant 4 2V voltage 70 at 30 C 60 50 40 30 Charge time min DoclD023052 Rev 2 ky AN4085 Discharging the EFL700A39 battery 3 3 1 3 2 3 2 1 Discharging the EFL700A39 battery Minimum discharge voltage The cut off voltage is the minimum open circuit voltage OCV across the EnFilm battery Under DC conditions when discharging with a constant current lower than 5 mA the EFL700A39 cut off voltage value should never be lower than 3 0 V During a pulse current above 5 mA with a pulse duration lower than 100 ms to compensate the internal ohmic resistance of the EnFilm battery the EFL700A39 voltage can decay
9. ce 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 2015 STMicroelectronics All rights reserved 3 16 16 DoclD023052 Rev 2
10. connect protection mode The EFL700A39 open circuit voltage should not go below 3 0 V in continuous discharge operating conditions DoclD023052 Rev 2 ky AN4085 Discharging the EFL700A39 battery To prevent deep discharge damage a battery voltage sense and disconnection circuit with a threshold voltage higher than 3 0 V has to be put in place using a battery management IC such as ST SPV1050 device These ICs must have a very low leakage current drawn from the battery specifically when the battery is disconnected The Table 1 provides some example of allowable elapse time in battery disconnect mode for different settings of battery disconnect threshold voltage and different settings of leakage current of the battery management IC For each case of the Table 1 if the duration of the battery disconnection is longer than these values the voltage of the EnFilm can drop down below 3 0 V with a risk of unrecoverable damage Table 1 EFL700A39 elapsed time from battery disconnect until 3 0 V maximum discharge level for different leakage current at 30 C temperature Battery disconnect IC leakage current in battery disconnect mode threshold voltage inA 10nA 100nA 3 80V 3 years 9 months 36 days 3 60V 17 months 4 months 17 days 3 40V 8 months 2 months 8 days 3 20V 2 months 19 days 2 days For example referring to the product datasheet of the ST SPV1050 IC the leakage is specified below 1 nA as shown in t
11. gure 11 Technology of buffer capacitor proposed versus current need Output capacitance F 1 0E 01 5 1 0E 02 utput capacitor minimum value for Vcap 3 0V MIN compact super cap 1 0E 03 1 0E 04 1 0E 05 1 0E 06 tpulse ims tpulse 2ms tpulse 4ms tpulse 8ms tpulse 16ms tpulse 32ms aNntahum eaj 10 20 30 40 50 60 Peak Pulse current mA tpulse 64ms tpulse 100ms 70 80 90 100 DoclD023052 Rev 2 11 16 Available power management IC s and tools AN4085 4 4 1 4 2 12 16 Available power management IC s and tools STMicroelectronics SPV1050 IC s The SPV1050 is an ultra low power energy harvester and battery charger with embedded MPPT and LDOs Its main features are e Thermoelectric generators and PV modules energy harvester e High efficiency for all harvesting sources PV cells and TEG e Up to 70 mA maximum battery current e Fully integrated buck boost DC DC converter 2 5 V to 5 3 V e Trimmable battery charge voltage level 1 accuracy 2 1 V to 3 6 V e Trimmable battery discharge voltage level 1 accuracy e Two fully independent LDOs 1 8 V and 3 3 V output e Enable disable LDO control pins e Battery disconnect function for battery protection e Battery connected and ongoing charge logic open drain indication pins e Programmable MPPT by external resistors The product datasheet and
12. he Table 2 and the cut off voltage is adjustable from 2 1 V up to 3 6 V 2 1 V TO 3 6 V trimmable battery under voltage protection level Table 2 ST SPV1050 datasheet extract for leakage current in battery disconnect mode 3 2 3 Sumbol Parameter Test condition Min Typ Max Unit Static current consumption Shut down mode ics Shutdown current ach first startup or BATT_CONN r nA TAMB lt 60 Choosing a 3 60 V cut off voltage setup ensures according to the Table 1 17 months of EFL700A39 micro battery survival time It means that once the battery is disconnected a source of energy like a harvester has to charge the EFL700A39 before 17 months 1 4 years Recommended maximum load current overtemperature The Figure 5 provides the characteristics of the EFL700A39 internal resistance on the battery operating temperature range The battery internal resistance is decreasing when the temperature is rising The Figure 6 shows the maximum load current available over the ambient temperature for safe operating cut off voltages of 3 0V minimum 3 2 V 3 4V and 3 6 V DoclD023052 Rev 2 7 16 Discharging the EFL700A39 battery AN4085 3 3 8 16 For example at 30 C ambient temperature and considering a 3 2 V cut off voltage a maximum DC load current of 5 0 mA can be drawn This maximum continuous current capability is decreasing to 1 8 mA if the minimum ambient temperature of the applicat
13. ion is 10 If the EFL700A39 is protected by a battery management IC with a cut off voltage set at 3 6 V then the maximum load current will be 2 9 mA at 30 C 0 8 mA at 10 C and the maximum 5 mA DC current capability will be achieved for a temperature higher than 40 C Figure 5 EFL700A39 internal resistance variation vs temperature Recommended maximum load current vs Temperature 20 C 10 C 0 C 10 C 20 C 30 C 40 C 50 C 60 C Cut off voltage 3 0V Cut off voltage 3 2V Cut off voltage 3 4V Cut off voltage 3 6V Discharging with pulsed current Some application may exhibit pulsed load current consumption with low steady state current and high pulsed current alternatively This type of load is typical of a wireless sensor network where current pulses are generated by RF transmissions DoclD023052 Rev 2 ky AN4085 Discharging the EFL700A39 battery 3 3 1 3 3 2 Using EFL700A339 in stand alone configuration The EFL700A39 micro battery is able to withstand pulsed current discharges The Figure 7 shows a typical discharge curve for pulsed current discharge application with following conditions applied on a stand alone EFL700A339 battery e ON state toy 100 ms Ion 10 mA cut off voltage during pulse 2 0 V e OFF state topp 900 ms loff 0 no load current e Tamb 30 C Figure 7 EFL700A39 typical pulsed discharge curve Voltage
14. the battery voltage drops to a lower value the higher is the load current the higher is the drop voltage and progressively the battery discharges until the voltage decreases down to the protection cut off level In any case the cut off voltage must not be fixed below 3 0 V Figure 4 curves show that when the discharged capacity increases the EFL700A39 terminal voltage decreases Figure 4 EFL700A39 typical discharge curves PEEL AW i ee eee Mie N i t1mA 0 7 mA i 350 pA 70 pA 3 4 10 pA 1 yA 3 2 i Typical Discharge Curve at 30 C Voltage V 30 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 Discharge Capacity mA h The time between the beginning and the end of a discharge depends on e the initial state of charge e the discharge current e the temperature e the minimum operating voltage of the application cut off voltage setup For example extracting information from the Figure 4 with a constant load current of 1 mA the charge used by the load starts at 0 mA h and reaches a maximum of 0 81 mA h This means that 1 mA was supplied to the load by the battery during 0 81 h 48 min 36 s before the 3 0 V cut off threshold voltage was reached For a 3 5 mA load current the cut off occurs at 0 68 mA h The discharge duration can then be calculated as follow 0 68 3 5 0 19 h 11 min 40 s EFL700A39 survival time in battery dis
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