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BQ25505EVM-218

BQ25505EVM-218

  • 厂商:

    BURR-BROWN(德州仪器)

  • 封装:

    -

  • 描述:

    BQ25505 - Power Management, Energy Harvesting Evaluation Board

  • 数据手册
  • 价格&库存
BQ25505EVM-218 数据手册
User's Guide SLUUAA8A – September 2013 – Revised August 2014 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting This user’s guide describes the bq25505 evaluation module (EVM), how to perform a stand-alone evaluation and how to allow the EVM to interface with the system and host. The boost charger output is configured to deliver up to 4.2-V maximum voltage to its output, VSTOR, using external resistors. This voltage is applied to the storage element as long as the storage element voltage at VBAT_SEC is above the internally programmed undervoltage of 2 V. The VBAT_OK indicator toggles high when VSTOR ramps up to 3 V and toggles low when VSTOR ramps down to 2.8 V. 5 Contents Introduction ................................................................................................................... 2 1.1 EVM Features ....................................................................................................... 2 1.2 General Description ................................................................................................ 2 1.3 Design and Evaluation Considerations .......................................................................... 3 1.4 bq25505EVM Schematic........................................................................................... 4 1.5 EVM I/O Connections .............................................................................................. 5 EVM Performance Specification Summary ............................................................................... 7 Test and Measurement Summary ......................................................................................... 7 3.1 Test Setups and Results ........................................................................................... 8 Bill of Materials and Board Layout ....................................................................................... 15 4.1 Bill of Materials .................................................................................................... 15 4.2 EVM Board Layout ................................................................................................ 16 PCB Layout Guideline ..................................................................................................... 20 1 bq25505EVM Schematic.................................................................................................... 4 2 Test Setup for Measuring Boost Charger Efficiency .................................................................... 9 3 Charger Efficiency versus Input Voltage .................................................................................. 9 4 Charger Efficiency versus Input Current ................................................................................ 10 5 Test Setup for Measuring Charger Operation .......................................................................... 11 6 Charger Operational Waveforms During Battery Charging ........................................................... 11 7 Test Setup ................................................................................................................... 12 8 Switching from Primary to Secondary Battery .......................................................................... 13 9 Test Setup for Charging a Super Capacitor on VBAT_SEC.......................................................... 13 10 Charging a Super Cap on VBAT_SEC 11 EVM PCB Top Silk ......................................................................................................... 16 12 EVM PCB Top Assembly .................................................................................................. 17 13 EVM PCB Top Layer 1 2 3 4 List of Figures 14 ................................................................................. ...................................................................................................... EVM PCB Bottom Layer ................................................................................................... 14 18 19 List of Tables 1 2 ................................................. 5 Bill of Materials ............................................................................................................. 15 I/O Connections and Configuration for Evaluation of bq25505 EVM SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 1 Introduction 1 Introduction 1.1 EVM Features • • • • • • 1.2 www.ti.com Evaluation module for bq25505 Ultra-low power boost converter/charger with battery management for energy harvester applications Resistor-programmable settings for overvoltage providing flexible battery management Programmable push-pull output indicator for battery status (VBAT_OK) Test points for key signals available for testing purpose – easy probe hook-up Jumpers available – easy to change settings General Description The bq25505 is an integrated energy harvesting Nano-Power management solution that is well suited for meeting the special needs of ultra-low power applications. The product is specifically designed to efficiently acquire and manage the microwatts (µW) to milliwatts (mW) of power generated from a variety of high output impedance (Hi-Z) DC sources like photovoltaic (solar) or thermal electric generators; or with an AC/DC rectifier, a piezoelectric generator. The bq25505 implements a highly efficient, pulse-frequency modulated (PFM) boost converter/charger targeted toward products and systems, such as wireless sensor networks (WSN) which have stringent power and operational demands. Assuming a depleted storage element has been attached, the bq25505 DC-DC boost converter/charger that requires only microwatts of power to begin operating in cold-start mode. Once the boost converter output, VSTOR, reaches ~1.8 V and can now power the converter, the main boost converter can now more efficiently extract power from low voltage output harvesters such as thermoelectric generators (TEGs) or single- and dual-cell solar panels. For example, assuming the Hi-Z input source can provide at least 5 µW typical and the load on VSTOR (including the storage element leakage current) is less than 1 µA of leakage current, the boost converter can be started with VIN_DC as low as 330 mV typical, and once VSTOR reaches 1.8 V, can continue to harvest energy down to VIN_DC ≃ 120 mV. Hi-Z DC sources have a maximum output power point (MPP) that varies with ambient conditions. For example, a solar panel's MPP varies with the amount of light on the panel and with temperature. The MPP is listed by the harvesting source manufacturer as a percentage of its open circuit (OC) voltage. Therefore, the bq25505 implements a programmable maximum power point tracking (MPPT) sampling network to optimize the transfer of power into the device. The bq25505 periodically samples the open circuit input voltage every 16 seconds by disabling the boost converter for 256 ms and stores the programmed MPP ratio of the OC voltage on the external reference capacitor (C2) at VREF_SAMP. Typically, solar cells are at their MPP when loaded to ~70–80% of their OC voltage and TEGs at ~50%. While the storage element is less than the user programmed maximum voltage (VBAT_OV), the boost converter loads the harvesting source until VIN_DC reaches the MPP (voltage at VREF_SAMP). This results in the boost charger regulating the input voltage of the converter until the output reaches VBAT_SEC_OV, thus transferring the maximum amount of power currently available per ambient conditions to the output. The battery undervoltage, VBAT_UV, threshold is checked continuously to ensure that the internal battery FET, connecting VSTOR to VBAT_SEC, does not turn on until VSTOR is above the VBAT_UV threshold (2 V).The overvoltage (VBAT_OV) setting initially is lower than the programmed value at startup (varies on conditions) and is updated after the first ~32 ms. Subsequent updates are every ~64 ms. The VBAT_OV threshold sets maximum voltage on VSTOR and the boost converter stops switching when the voltage on VSTOR reaches the VBAT_OV threshold. The open circuit input voltage (VIN_OC) is measured every ~16 seconds in order for the Maximum Power Point Tracking (MPPT) circuit to sample and hold the input regulation voltage. This periodic update continually optimizes maximum power delivery based on the harvesting conditions. PowerPAD is a trademark of Texas Instruments. 2 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Introduction www.ti.com The bq25505 was designed with the flexibility to support a variety of energy storage elements. The availability of the sources from which harvesters extract their energy can often be sporadic or timevarying. Systems will typically need some type of energy storage element, such as a re-chargeable battery, super capacitor, or conventional capacitor. The storage element will make certain constant power is available when needed for the systems. In general, the storage element also allows the system to handle any peak currents that can not directly come from the input source. It is important to remember that batteries and super capacitors can have significant leakage currents that need to be included with determining the loading on VSTOR. To prevent damage to a customer’s storage element, both maximum and minimum voltages are monitored against the internally programmed undervoltage (VBAT_UV) and user programmed overvoltage (VBAT_OV) levels. To further assist users in the strict management of their energy budgets, the bq25505 toggles a user programmable battery good flag (VBAT_OK), checked every 64 ms, to signal the microprocessor when the voltage on an energy storage element or capacitor has risen above (OK_HYST threshold) or dropped below (OK_PROG threshold) a pre-set critical level. To prevent the system from entering an undervoltage condition or if starting up into a depleted storage element, it is recommended to isolate the system load from VSTOR by using an NFET to invert the BAT_OK signal so that it drives the gate of PFET, which isolates the system load from VSTOR. For details, see bq25505 data sheet (SLUSBJ3). 1.3 Design and Evaluation Considerations This user's guide is not a replacement for the data sheet. Reading the data sheet first will help in understanding the operations and features of this IC. In this document, “secondary rechargeable battery” or "VBAT_SEC" will be used but one could substitute any appropriate storage element. System Design Tips Compared to designing systems powered from an AC/DC converter or large battery (for example, low impedance sources), designing systems powered by Hi-Z sources requires that the system load-per-unit time (for example, per day for solar panel) be compared to the expected loading per the same time unit. Often there is not enough real time input harvested power (for example, at night for a solar panel) to run the system in full operation. Therefore, the energy harvesting circuit collects more energy than being drawn by the system when ambient conditions allow and stores that energy in a storage element for later use to power the system. See SLUC461 for an example spreadsheet on how to design a real solar-panelpowered system in three easy steps: 1. Referring the system rail power back to VSTOR 2. Referring the required VSTOR power back to bq255xx input power 3. Computing the minimum solar panel area from the input power requirement As demonstrated in the spreadsheet, for any boost converter, you must perform a power balance: POUT / PIN = (VSTOR × ISTOR) / (VIN × IIN) = η (1) where η is the estimated efficiency for the same or similar configuration in order to determine the minimum input power needed to supply the desired output power. This IC is a highly efficient charger for a storage element such as a battery or super capacitor. The main difference between a battery and a super capacitor is the capacity curve. The battery typically has little or no capacity below a certain voltage, whereas the capacitor does have capacity at lower voltages. Both can have significant leakage currents that will appear as a DC load on VSTOR/VBAT_SEC. SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 3 Introduction 1.4 www.ti.com bq25505EVM Schematic Figure 1 is the schematic for this EVM. VSTOR VSTOR TP4 VIN1 J4 VSTOR VSTOR C4 C5 R4 + GND C8 0.1uF 4.7uF 10M J5 DNP VOC_SAMP JP1 GND BAT_SEC 4.99M J6 80% 50% VIN 2.0V-5.5V JP4 JP1 to R3-R5 R5 L1 C3 J11 3 4 18 16 17 NC NC VBAT_SEC 15 14 VOC_SAMP VBAT_OK 13 VREF_SAMP OK_PROG 12 OK_HYST 11 6 VRDIV VB_SEC_ON VB_PRI_ON EN 8 5 VSS 9 TP3 4.7uF 1 2.1V - 5.5V J9 VBAT_PRI GND C9 GND DNP GND J12 BAT_OK GND VSTOR Q1-A Q1-B J13 VSTOR U1 C11 10 C6 0.1uF 19 21 PWPD 4.7uF + C10 VBAT_PRI BQ25505RGR NC C1 DNP VIN_DC VBAT_OV C7 VSS 2 7 VOC_SAMP + 1 VSTOR TP1 LBOOST GND 20 22uH J3 1 GND TP8 J10 LBOOST VIN1 4.2V (Adj up to 5.5V) BAT_SEC VBAT_PRI 100uF VBAT_PRI GND J7 J8 TP6 TP2 J2 VIN BAT_SEC TP5 VOC_SAMP J1 4.2V (Adj up to 5.5V) 1 R3 4.99M VRDIV 1 VB_PRI_ON VB_SEC_ON VB_SEC_ON TP7 VRDIV R6 887K VREF_SAMP GND VRDIV JP3 C2 R7 6.98M R1 7.5M 2 VBAT_PRI 0.01uF Q2-A Q2-B C13 1uF R2 5.76M R8 5.36M BAT_SEC C12 VB_PRI_ON 1 BAT_SEC JP2 /EN 1 Not Installed J16 J15 J14 GND VOR GND GND VOR Figure 1. bq25505EVM Schematic white white 4 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Introduction www.ti.com 1.5 EVM I/O Connections Table 1. I/O Connections and Configuration for Evaluation of bq25505 EVM REFERENCE DESIGNATOR DESCRIPTION COMMENTS / DEFAULT SETTINGS HEADERS AND TERMINALS J1 – VIN Input source (+) If VIN_DC is higher than VSTOR and VSTOR is equal to VBAT_OV, the input VIN_DC is pulled to ground through a small resistance to stop further charging of the attached battery or capacitor. It is critical that if this case is expected, the impedance of the source attached to VIN_DC be higher than 20 Ω and not a low impedance source. J2 – VIN/GND Input source terminal block J3 – GND Input source return (–) J4 – VSTOR Boost charger output (+) J5 – VSTOR/GND Boost charger output terminal block J6 – GND Boost charger return (–) J7– BAT_SEC Rechargeable storage element connection (+) J8 – BAT_SEC/GND Rechargeable storage element terminal block J9 – GND Rechargeable storage element connection return (–) J10 – VBAT_PRI Non-rechargeable storage element connection (+) J11 – VBAT_PRI/GND Non-rechargeable storage element connection terminal block J12 – GND Non-rechargeable storage element connection return (–) J13 – BAT_OK/GND Battery Status Indicator (+/–) J14 – VOR Output of multiplexing switches, either VSTOR or VBAT_PRI (+) J15 – VOR/GND Output of multiplexing switches terminal block J16 – GND Return for output of multiplexing switches (–) VBAT_PRI is an optional non-rechargeable battery that switches in to the power the system when BAT_SEC drops below the VBAT_OK threshold. TEST POINTS TP1 Input source, VIN_DC (+) TP2 Boost charger switching node TP3 Buck converter switching node TP4 Boost charger output, VSTOR (+) TP5 Rechargeable storage element, VBAT_SEC (+) TP6 Non-rechargeable storage element, VBAT_PRI(+) TP7 VRDIV node TP8 Output return (–) TP9 Input return (–) CAUTION: Providing an additional low impedance current path in parallel with the feedback resistors , for example, with a 10-MΩ scope probe attached, will degrade regulation accuracy. WHITE SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 5 Introduction www.ti.com Table 1. I/O Connections and Configuration for Evaluation of bq25505 EVM (continued) REFERENCE DESIGNATOR DESCRIPTION COMMENTS / DEFAULT SETTINGS JP1 – VOC_SAMP VOC_SAMP = external resistors sized to configure the IC to regulate VIN to 75% of VINOC. Uninstalled (NOTE: Do not install if JP4 shunt is installed) JP2 - EN EN = GND enables the IC. EN = BAT_SEC disables the IC. EN = GND JP3 - VREF_SAMP to GND VREF_SAMP = GND Uninstalled (NOTE: Providing an additional leakage path for the VREF_SAMP capacitor for example, through a 10-MΩ scope probe attached to VREF_SAMP, will degrade input voltage regulation performance). JP4 - VOC_SAMP VOC_SAMP = 80% configures the IC to regulate VIN to 80% of VIN_OC. VOC_SAMP = 50% configures the IC to regulate VIN to 50% of VIN_OC. JP4 = 80% (NOTE: Do not install if JP1 shunt is installed) JUMPERS 6 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback EVM Performance Specification Summary www.ti.com 2 EVM Performance Specification Summary See Data Sheet “Recommended Operating Conditions” for component adjustments. For details about the resistor programmable settings, see bq25505 data sheet (SLUSBJ3). MIN VIN(DC) DC input voltage into VIN_DC 0.13 VIN_STARTUP(D DC minimum start-up voltage into depleted storage element, no load attached C) to VSTOR or VOUT and IBAT(LEAK) ≤ 1 µA VBAT_OV VBAT_OK NOM MAX 4.0 330 UNIT V mV Battery overvoltage Threshold –min and max values include ±2% set point accuracy and ±1% resistor tolerance but excludes effects of output ripple 4.04 4.18 4.32 V OK_HYST indication toggles high when VSTOR ramps up - min and max values include ±2% set point accuracy and ±1% resistor tolerance 2.70 2.79 2.88 V OK_PROG indication toggles low when VSTOR ramps down - min and max values include ±2% set point accuracy and ±1% resistor tolerance 2.89 2.99 3.09 V MPPT Maximum Power Point Tracking, Resistor Programmed % of Open Circuit Voltage CBAT A 100-µF low leakage ceramic capacitor is installed on the EVM as the minimum recommended equivalent battery capacitance. 80% 100 µF See SLUC484 spreadsheet tool to assist with modifying the MPPT, VBAT_OV and VBAT_OK resistors for your application. CAUTION If changing the board resistors or the capacitor on VREF_SAMP (C2), it is important to remember that residual solder flux on a board has a resistivity in the 1–20 MΩ range. Therefore, flux remaining in parallel with changed 1–20 MΩ resistors can result in a lower effective resistances, which will produce different operating thresholds than expected. Similarly, flux remaining in parallel with the VREF_SAMP capacitor provides an additional leakage path, which results in the input voltage regulation set point drooping during the 16-s MPPT cycle. Therefore, it is highly recommended that boards be thoroughly cleaned twice, once after removing the old components and again after installing the new components. If possible, the boards should be cleaned until the wash solution measures ionic contamination greater than 50 MΩ. 3 Test and Measurement Summary Test Setup Tips Energy harvesting power sources are high impedance sources. A source-meter configured as a current source with voltage compliance set to the harvester's open circuit voltage is the best way to simulate the harvester. When simulating a Hi-Z energy harvester with low output impedance lab power supply, it is necessary to simulate the harvester's impedance with a physical resistor between the supply, VPS, and VIN_DC of the EVM. When the MPPT sampling circuit is active, VIN_DC = VPS = the harvester open circuit voltage (VIN_OC) because there is no input current to create a drop across the simulated impedance (that is, open circuit); therefore, VPS should be set to the intended harvester's open circuit voltage. When the boost converter is running, it draws only enough current until the voltage at VIN_DC droops to the MPPT's sampled voltage that is stored at VREF_SAMP. SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 7 Test and Measurement Summary www.ti.com The battery (storage element) can be replaced with a simulated battery. Often electronic 4 quadrant loads give erratic results with a “battery charger” due to the charger changing states (fast-charge to termination and refresh) while the electronic load is changing loads to maintain the “battery” voltage. The charging and loading get out of phase and create a large signal oscillation which is due to the 4 quadrant meter. A simple circuit can be used to simulate a battery and can be adjusted for voltage. It consists of load resistor (~10 Ω, 2 W) to pull the output down to some minimum storage voltage (sinking current part of battery) and a lab supply connected to the BAT pin via a diode. The lab supply biases up the battery voltage to the desired level. It may be necessary to add more capacitance across R1. D1 C A BAT+ R1 GND 3.1 3.1.1 Test Setups and Results Boost Charger Efficiency The test setup is shown in Figure 2. The specific equipment used for the test results in Figure 3 and Figure 4 is listed below: 1. VIN_DC was connected to a Keithley 2420 source-meter configured as a current source with voltage compliance (clamp) set to the open circuit voltage. 2. VSTOR was connected a Keithley 2420 source-meter configured as a voltage source set to the VSTOR voltage. The current sunk by the source-meter was the output current of the charger. 3. VREF_SAMP was connected to a power supply configured to output the desired input voltage regulation point (that is, the MPPT% times the HiZ source's VOC). No jumper is required on JP4. 8 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Test and Measurement Summary www.ti.com SM2 SM2 + + Source (Sink) meter configured as voltage source - SM1 SM1 Source meter configured as current source + - - + Power Supply set to desired input voltage regulation point (that is, MPPT% × VOC) Figure 2. Test Setup for Measuring Boost Charger Efficiency 100 90 80 Efficiency (%) 70 IIN = 100 PA 60 50 40 30 VSTOR = 2.0 V VSTOR = 3.0 V VSTOR = 5.5 V 20 10 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 Input Voltage (V) Figure 3. Charger Efficiency versus Input Voltage SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 9 Test and Measurement Summary www.ti.com 100 90 VIN = 0.5 V Efficiency (%) 80 70 60 50 40 VSTOR = 1.8 V VSTOR = 3.0 V VSTOR = 5.5 V 30 20 0.01 0.1 1 10 100 Input Current (mA) Figure 4. Charger Efficiency versus Input Current Because the boost converter regulates input voltage instead of output voltage, uses PFM switching, operates at very low currents, and has MPPT, efficiency cannot be measured using the same test setup as for an output regulating, higher power, fixed-frequency PWM switching boost converter. The VSTOR output must be held at a fixed voltage (below VBAT_OV threshold) by an external source that is capable of sinking current, with that sunk current being the measured output current. In addition to filtering bursts of current due to PFM switching and the ripple voltage on VIN_DC due to input voltage regulation, the series input current meter and input voltage meter must be set to filtering/averaging which will result in longer than usual measurement times, but not longer than the 16-s MPPT sample time. Measurements for both VIN and IN will be most accurate when taken at the midpoint of the 16-s MPPT period. Remote sensing by the source-meters is possible but, on the input side, the source-meter output regulation loop and the charger MPPT input regulation loop may interfere with each other and cause the input voltage to oscillate. Adding a large capacitor across VIN_DC and GND will eliminate this oscillation but the capacitor's leakage current will inflate the input current measurement and result in lower efficiency. See SLUA691 for a detailed explanation on how to take these and other measurements with sourcemeters. 3.1.2 Boost Charger Operation during Battery Charging The test setup is shown in Figure 5. The specific equipment used for the test results in Figure 6 is listed below: 1. VIN_DC and VBAT_SEC are configured as shown in Section 3.1.2. 2. The boost charger inductor current (IL) was measured by using an oscilloscope current probe across a current loop that was inserted in series with inductor L1. 3. VSTOR's ripple voltage was measured using an oscilloscope voltage probe placed directly across the VSTOR capacitor (C5). The scope probe's standard ground lead was replaced with short lead. 4. VIN_DC and the LBOOST pin (switching node of the boost charger) were measured by oscilloscope voltage probes connected to TP1 and TP2. 10 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Test and Measurement Summary www.ti.com 0.5 F 75 75 : : + 1.5 - Figure 5. Test Setup for Measuring Charger Operation Figure 6. Charger Operational Waveforms During Battery Charging SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 11 Test and Measurement Summary 3.1.3 www.ti.com Switching Between Primary and Secondary Batteries The test setup is shown in Figure 5. The specific equipment used for the test results in Figure 8 is listed below: 1. VIN_DC, VBAT_SEC and VBAT_PRI are configured as shown in Section 3.1.2. 2. The function generator and power amplifier simulated VSTOR charging up and discharging. 3. VBAT_SEC, VBAT_PRI, VBAT_OK and VOR were measured with oscilloscope voltage probes at TP5, TP6, J13 and J14, respectively. Function Generator Power Amplifier - PS + 1 k: Figure 7. Test Setup 12 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Test and Measurement Summary www.ti.com Figure 8. Switching from Primary to Secondary Battery Charging a Super Capacitor on VBAT_SEC The test setup is shown in Figure 9. The specific equipment used for the test results in Figure 10 is listed below: 1. VIN_DC was connected to a Keithley 2420 configured as a 1.0-mA current source with 1.2-V voltage compliance. 2. VBAT_SEC was connected to a 120-mF super capacitor. There were no other loads on VSTOR or VBAT_SEC. 3. VIN_DC, VSTOR and VBAT_SEC were measured with oscilloscope voltage probes connected at TP1, TP4 and TP5 respectively. Keithley 2420 120mF IOUT =1.0 mA COMP=1.2 V Figure 9. Test Setup for Charging a Super Capacitor on VBAT_SEC SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 13 Test and Measurement Summary www.ti.com Figure 10. Charging a Super Cap on VBAT_SEC Tips for other Tests and Measurements The quiescent current during main boost operation, which is basically the current from the battery to the IC, is measured at the VSTOR pin. If a source-meter is not available to make the measurement, connect a 100-kΩ resistor to VSTOR and connect a 3-V supply from the other end of this resistor to the ground of the EVM. A 10-MΩ meter can be used to measure the voltage drop across the resistor and calculate the current. No other connections should be made to the EVM and the measurement should be taken after steady state conditions are reached (may take a few minutes). The reading should be much less than 100 nA. 14 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Bill of Materials and Board Layout www.ti.com 4 Bill of Materials and Board Layout This section contains the bq25505 bill of materials (BOM) and PCB board layout. 4.1 Bill of Materials Table 2 lists the BOM for the bq25505EVM. Table 2. Bill of Materials COUNT RefDes Value Description Size Part Number MFR 1 C1 4.7uF Capacitor, Ceramic Chip, 6.3V, X7R, ±10% 805 C0805C475K9RACTU Kemet 1 C10 4.7uF Capacitor, Ceramic Chip, 6.3V, X5R, ±20% 603 GRM188R60J475ME19D Murata 0 C11-12 DNP Capacitor, Ceramic Chip, 6.3V, X5R, ±20% 603 Engineering Only n/a 1 C2 0.01u Capacitor, Ceramic, 50V, X7R, 10% 0603 GRM188R71H103KA01D Murata 1 C3 100u Capacitor, Ceramic Chip, 6.3V, X5R, 20% 1812 GRM43SR60J107ME20L Murata 2 C4 C6 0.1u Capacitor, Ceramic Chip, 6.3V, X5R, 10% 603 06036D104KAT2A AVX 1 C5 4.7uF Capacitor, Ceramic Chip, 10V, X7R, ±10% 805 LMK212B7475KG-T Taiyo Yuden 0 C7-9 DNP Capacitor, Electrolytic, Snap Mt., vvV 7343 (D) Engineering Only n/a 1 C13 1.0uF Capacitor, Ceramic Chip, 10V, X5R, ±20% 603 GRM188R61A105MA61D Murata 11 J1 J3-4 J6-7 J910 J12-14 J16 PEC02SAAN Header, Male 2-pin, 100mil spacing, 0.100 inch x 2 PEC02SAAN Sullins 5 J2 J5 J8 J11 J15 ED555/2DS Terminal Block, 2-pin, 6-A, 3.5mm 0.27 x 0.25 inch ED555/2DS OST 2 JP1 JP3 PEC02SAAN Header, Male 2-pin, 100mil spacing, 0.100 inch x 2 PEC02SAAN Sullins 2 JP2 JP4 PEC03SAAN Header, Male 3-pin, 100mil spacing, 0.100 inch x 3 PEC03SAAN Sullins 1 L1 22uH Inductor, SMT, 0.65A, 360mΩ Inductor SMT, 0.36A, 410mΩ 4.0mm x4.0mm x1.80mm 3.8mm x3.8mm x1.65mm LPS4018-223M 744031220 Coilcraft Wurth Elektronik 2 Q1-2 CSD75205W1015 MOSFET, Dual PChan, -20V, 1.2A, 190 milliOhm CSP 1x1.5mm CSD75205W1015 TI 1 R1 7.5M Resistor, Chip, 1/16W, 1% 603 CRCW06037M50FKEA Vishay Dale 1 R2 5.76M Resistor, Chip, 1/16W, 1% 603 CRCW06035M76FKEA Vishay Dale 2 R3 R5 4.99M Resistor, Chip, 1/16W, 1% 603 CRCW06034M99FKEA Vishay Dale 1 R4 10M Resistor, Chip, 1/16W, 1% 603 CRCW060310M0FKEA Vishay Dale 1 R6 887K Resistor, Chip, 1/16W, 1% 603 CRCW0603887KFKEA Vishay Dale 1 R7 6.98M Resistor, Chip, 1/16W, 1% 603 CRCW06036M98FKEA Vishay Dale 1 R8 5.36M Resistor, Chip, 1/16W, 1% 603 CRCW06035M36FKEA Vishay Dale 4 TP1 TP4-6 5002 Test Point, White, Thru Hole Color Keyed 0.100 x 0.100 inch 5002 Keystone 0 TP2 TP7 DNP Test Point, 0.020 Hole 0.100 x 0.100 inch n/a n/a 2 TP3 TP8 5001 Test Point, Black, Thru Hole Color Keyed 0.100 x 0.100 inch 5001 Keystone 1 U1 BQ25505RGR IC, Ultra-Low Power Harvester Charger VQFN BQ25505RGR TI Shunt, 100-mil, Black 0.1 929950-00 3M PWR218 Any 2 1 -- SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback PCB, 2.5212 in x 2.6039 in User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 15 Bill of Materials and Board Layout 4.2 www.ti.com EVM Board Layout Figure 12 through Figure 14 are the board layouts for this EVM. J5 TP4 J8 GND VSTOR TP1 J9 J6 J4 J7 GND BAT_SEC TP8 + C3 C8 J1 VIN TP2 LBOOST + C7 J12 C5 C4 C9 L1 GND C10 C1 C6 J2 TP5 J11 TP3 VREF_SAMP GND JP2 GND JP3 /EN J10 BAT_PRI R5 R6 R7 R8 50% U1 JP1 R2 R1 GND VOC_SAMP R3 R4 C2 J3 JP4 80% + 1 TP7 VRDIV C11 1 Q1 BAT_SEC C12 Q2 C13 2013 PWR218 REV A J14 1 GND J13 BAT_OK GND VOR bq25505EVM-218 TP6 J16 J15 Figure 11. EVM PCB Top Silk 16 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Bill of Materials and Board Layout www.ti.com J5 J4 TP1 J6 J8 J9 J7 + TP5 C8 TP8 J12 J1 C3 TP4 + TP2 L1 C9 J11 C1 C6 C2 1 U1 R2 R1 R6 R7 R8 J10 + R3 R4 R5 C7 JP4 JP1 C4 C10 J3 J2 C5 TP6 TP7 JP2 C11 C12 JP3 TP3 1Q1 J13 1Q2 J16 J14 C13 J15 Figure 12. EVM PCB Top Assembly SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 17 Bill of Materials and Board Layout www.ti.com Figure 13. EVM PCB Top Layer 18 User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated Bill of Materials and Board Layout www.ti.com Figure 14. EVM PCB Bottom Layer SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback User's Guide for bq25505 Battery Charger Evaluation Module for Energy Harvesting Copyright © 2013–2014, Texas Instruments Incorporated 19 PCB Layout Guideline 5 www.ti.com PCB Layout Guideline As for all switching power supplies, the PCB layout is an important step in the design, especially at high peak currents and high switching frequencies. If the layout is not carefully done, the boost converter/charger and buck converter could show stability problems as well as EMI problems. Therefore, use wide and short traces for the main current path and for the power ground paths. The input and output capacitors as well as the inductors should be placed as close as possible to the IC. For the boost charger, the first priority are the output capacitors, including the 0.1-µF bypass capacitor (CBYP), followed by CSTOR, which should be placed as close as possible between VSTOR, pin 19, and VSS, pin 1. Next, the input capacitor, CIN, should be placed as close as possible between VIN_DC, pin 2, and VSS, pin 1. Last in priority is the boost converter inductor, L1, which should be placed close to LBOOST, pin 20, and VIN_DC, pin 2. It is best to use vias and bottom traces for connecting the inductors to their respective pins instead of the capacitors. To minimize noise pickup by the high impedance voltage setting nodes (VBAT_OV, OK_PROG, and OK_HYST), the external resistors should be placed so that the traces connecting the midpoints of each divider to their respective pins are as short as possible. When laying out the non-power ground return paths (for example from resistors and CREF), it is recommended to use short traces as well, separated from the power ground traces and connected to VSS pin 15. This avoids ground shift problems, which can occur due to superimposition of power ground current and control ground current. The PowerPAD™ should not be used as a power ground return path. The remaining pins are either NC pins, that should be connected to the PowerPad as shown below, or digital signals with minimal layout restrictions. In order to maximize efficiency at light load, the use of voltage level setting resistors > 1 MΩ is recommended. However, during board assembly, contaminants such as solder flux and even some board cleaning agents can leave residue that may form parasitic resistors across the physical resistors or from one end of a resistor to ground, especially in humid, fast airflow environments. This can result in the voltage regulation and threshold levels changing significantly from those expected per the installed resistor values. Therefore, it is recommended that no ground planes be poured near the voltage setting resistors. In addition, the boards must be carefully cleaned, possibly rotated at least once during cleaning, and then rinsed with de-ionized water until the ionic contamination of that water is well above 50 Ω. If this is not feasible, then it is recommended that the sum of the voltage setting resistors be reduced to at least 5X below the measured ionic contamination. Revision History Changes from Original (September 2013) to A Revision ............................................................................................... Page • Changed contents in the bill of materials ............................................................................................. 15 NOTE: Page numbers for previous revisions may differ from page numbers in the current version. 20 Revision History SLUUAA8A – September 2013 – Revised August 2014 Submit Documentation Feedback Copyright © 2013–2014, Texas Instruments Incorporated ADDITIONAL TERMS AND CONDITIONS, WARNINGS, RESTRICTIONS, AND DISCLAIMERS FOR EVALUATION MODULES Texas Instruments Incorporated (TI) markets, sells, and loans all evaluation boards, kits, and/or modules (EVMs) pursuant to, and user expressly acknowledges, represents, and agrees, and takes sole responsibility and risk with respect to, the following: 1. User agrees and acknowledges that EVMs are intended to be handled and used for feasibility evaluation only in laboratory and/or development environments. Notwithstanding the foregoing, in certain instances, TI makes certain EVMs available to users that do not handle and use EVMs solely for feasibility evaluation only in laboratory and/or development environments, but may use EVMs in a hobbyist environment. All EVMs made available to hobbyist users are FCC certified, as applicable. Hobbyist users acknowledge, agree, and shall comply with all applicable terms, conditions, warnings, and restrictions in this document and are subject to the disclaimer and indemnity provisions included in this document. 2. Unless otherwise indicated, EVMs are not finished products and not intended for consumer use. EVMs are intended solely for use by technically qualified electronics experts who are familiar with the dangers and application risks associated with handling electrical mechanical components, systems, and subsystems. 3. User agrees that EVMs shall not be used as, or incorporated into, all or any part of a finished product. 4. User agrees and acknowledges that certain EVMs may not be designed or manufactured by TI. 5. User must read the user's guide and all other documentation accompanying EVMs, including without limitation any warning or restriction notices, prior to handling and/or using EVMs. Such notices contain important safety information related to, for example, temperatures and voltages. For additional information on TI's environmental and/or safety programs, please visit www.ti.com/esh or contact TI. 6. User assumes all responsibility, obligation, and any corresponding liability for proper and safe handling and use of EVMs. 7. Should any EVM not meet the specifications indicated in the user’s guide or other documentation accompanying such EVM, the EVM may be returned to TI within 30 days from the date of delivery for a full refund. THE FOREGOING LIMITED WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY TI TO USER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. TI SHALL NOT BE LIABLE TO USER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES RELATED TO THE HANDLING OR USE OF ANY EVM. 8. No license is granted under any patent right or other intellectual property right of TI covering or relating to any machine, process, or combination in which EVMs might be or are used. TI currently deals with a variety of customers, and therefore TI’s arrangement with the user is not exclusive. TI assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or services with respect to the handling or use of EVMs. 9. User assumes sole responsibility to determine whether EVMs may be subject to any applicable federal, state, or local laws and regulatory requirements (including but not limited to U.S. Food and Drug Administration regulations, if applicable) related to its handling and use of EVMs and, if applicable, compliance in all respects with such laws and regulations. 10. User has sole responsibility to ensure the safety of any activities to be conducted by it and its employees, affiliates, contractors or designees, with respect to handling and using EVMs. Further, user is responsible to ensure that any interfaces (electronic and/or mechanical) between EVMs and any human body are designed with suitable isolation and means to safely limit accessible leakage currents to minimize the risk of electrical shock hazard. 11. 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Any loads applied outside of the specified output range may result in unintended and/or inaccurate operation and/or possible permanent damage to the EVM and/or interface electronics. Please consult the applicable EVM user's guide prior to connecting any load to the EVM output. If there is uncertainty as to the load specification, please contact a TI field representative. During normal operation, some circuit components may have case temperatures greater than 60°C as long as the input and output are maintained at a normal ambient operating temperature. These components include but are not limited to linear regulators, switching transistors, pass transistors, and current sense resistors which can be identified using EVMs’ schematics located in the applicable EVM user's guide. When placing measurement probes near EVMs during normal operation, please be aware that EVMs may become very warm. As with all electronic evaluation tools, only qualified personnel knowledgeable in electronic measurement and diagnostics normally found in development environments should use EVMs. Agreement to Defend, Indemnify and Hold Harmless. User agrees to defend, indemnify, and hold TI, its directors, officers, employees, agents, representatives, affiliates, licensors and their representatives harmless from and against any and all claims, damages, losses, expenses, costs and liabilities (collectively, "Claims") arising out of, or in connection with, any handling and/or use of EVMs. User’s indemnity shall apply whether Claims arise under law of tort or contract or any other legal theory, and even if EVMs fail to perform as described or expected. Safety-Critical or Life-Critical Applications. If user intends to use EVMs in evaluations of safety critical applications (such as life support), and a failure of a TI product considered for purchase by user for use in user’s product would reasonably be expected to cause severe personal injury or death such as devices which are classified as FDA Class III or similar classification, then user must specifically notify TI of such intent and enter into a separate Assurance and Indemnity Agreement. RADIO FREQUENCY REGULATORY COMPLIANCE INFORMATION FOR EVALUATION MODULES Texas Instruments Incorporated (TI) evaluation boards, kits, and/or modules (EVMs) and/or accompanying hardware that is marketed, sold, or loaned to users may or may not be subject to radio frequency regulations in specific countries. 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General Statement for EVMs including a radio User Power/Frequency Use Obligations: For EVMs including a radio, the radio included in such EVMs is intended for development and/or professional use only in legally allocated frequency and power limits. Any use of radio frequencies and/or power availability in such EVMs and their development application(s) must comply with local laws governing radio spectrum allocation and power limits for such EVMs. It is the user’s sole responsibility to only operate this radio in legally acceptable frequency space and within legally mandated power limitations. Any exceptions to this are strictly prohibited and unauthorized by TI unless user has obtained appropriate experimental and/or development licenses from local regulatory authorities, which is the sole responsibility of the user, including its acceptable authorization. U.S. Federal Communications Commission Compliance For EVMs Annotated as FCC – FEDERAL COMMUNICATIONS COMMISSION Part 15 Compliant Caution This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation. Changes or modifications could void the user's authority to operate the equipment. FCC Interference Statement for Class A EVM devices This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at its own expense. FCC Interference Statement for Class B EVM devices This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures: • Reorient or relocate the receiving antenna. • Increase the separation between the equipment and receiver. • Connect the equipment into an outlet on a circuit different from that to which the receiver is connected. • Consult the dealer or an experienced radio/TV technician for help. Industry Canada Compliance (English) For EVMs Annotated as IC – INDUSTRY CANADA Compliant: This Class A or B digital apparatus complies with Canadian ICES-003. Changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment. Concerning EVMs Including Radio Transmitters This device complies with Industry Canada licence-exempt RSS standard(s). Operation is subject to the following two conditions: (1) this device may not cause interference, and (2) this device must accept any interference, including interference that may cause undesired operation of the device. Concerning EVMs Including Detachable Antennas Under Industry Canada regulations, this radio transmitter may only operate using an antenna of a type and maximum (or lesser) gain approved for the transmitter by Industry Canada. To reduce potential radio interference to other users, the antenna type and its gain should be so chosen that the equivalent isotropically radiated power (e.i.r.p.) is not more than that necessary for successful communication. This radio transmitter has been approved by Industry Canada to operate with the antenna types listed in the user guide with the maximum permissible gain and required antenna impedance for each antenna type indicated. Antenna types not included in this list, having a gain greater than the maximum gain indicated for that type, are strictly prohibited for use with this device. Canada Industry Canada Compliance (French) Cet appareil numérique de la classe A ou B est conforme à la norme NMB-003 du Canada Les changements ou les modifications pas expressément approuvés par la partie responsable de la conformité ont pu vider l’autorité de l'utilisateur pour actionner l'équipement. Concernant les EVMs avec appareils radio Le présent appareil est conforme aux CNR d'Industrie Canada applicables aux appareils radio exempts de licence. L'exploitation est autorisée aux deux conditions suivantes : (1) l'appareil ne doit pas produire de brouillage, et (2) l'utilisateur de l'appareil doit accepter tout brouillage radioélectrique subi, même si le brouillage est susceptible d'en compromettre le fonctionnement. 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Use EVMs in a shielded room or any other test facility as defined in the notification #173 issued by Ministry of Internal Affairs and Communications on March 28, 2006, based on Sub-section 1.1 of Article 6 of the Ministry’s Rule for Enforcement of Radio Law of Japan, Use EVMs only after user obtains the license of Test Radio Station as provided in Radio Law of Japan with respect to EVMs, or Use of EVMs only after user obtains the Technical Regulations Conformity Certification as provided in Radio Law of Japan with respect to EVMs. Also, do not transfer EVMs, unless user gives the same notice above to the transferee. 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