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User's Guide

SLUU654A–October 2011– Revised October 2011

bq25504 EVM – Ultra Low Power Boost Converter with

Battery Management for Energy Harvester Applications

This user’s guide describes the bq25504 evaluation module (EVM), how to perform a stand-alone

evaluation and allows the EVM to interface with the system and host. This EVM is programmed from the

factory for settings compatible with most MCU’s and 3V coin cell batteries. The EVM is programmed to

deliver a 3.1VDC maximum voltage (OV) for charging the storage element and the under voltage is

programmed to 2.2VDC. The VBAT_OK indicator toggles high when VSTOR ramps up to 2.8VDC and

toggles low when VSTOR ramps down to 2.4VDC.

Contents

1 Introduction .................................................................................................................. 2

1.1 EVM Features ...................................................................................................... 2

1.2 General Description ................................................................................................ 2

1.3 Design and Evaluation Considerations .......................................................................... 3

2 Performance Specification Summary ..................................................................................... 4

3 Test Summary ............................................................................................................... 4

3.1 Equipment ........................................................................................................... 4

3.2 Equipment and EVM Setup ....................................................................................... 4

3.3 Test procedures .................................................................................................... 5

4 PCB Layout Guideline .................................................................................................... 11

5 Bill of Materials, Board Layout and Schematics ....................................................................... 12

5.1 Bill of Materials .................................................................................................... 12

5.2 EVM Board Layout ............................................................................................... 13

5.3 EVM Schematic ................................................................................................... 15

List of Figures

1 Test Setup for HPA674A (bq25504 EVM) ............................................................................... 5

2 Startup with no Battery and 10k Load.................................................................................... 6

3 Startup with Battery Less Than UV....................................................................................... 7

4 Powering up with a Battery above UV ................................................................................... 7

5 BAT_OK High/Low 2.8V/2.34V – Ramping Battery from 0V to 3.1V (OV) and Down to 1.8V. ................... 8

6 Basic Switching Converter, Vin = 1V, Vbat = 2.5V ..................................................................... 9

7 EVM Operation Near OV With 100-Ω Battery Impedance ........................................................... 10

8 EVM PCB Top Assembly................................................................................................. 13

9 EVM PCB Top Layer ..................................................................................................... 13

10 EVM PCB Bottom Layer.................................................................................................. 14

11 EVM Schematic............................................................................................................ 15

List of Tables

1 I/O Connections and Configuration for Evaluation of bq25504 EVM................................................. 4

2 Bill of Materials............................................................................................................. 12

SLUU654A–October 2011–Revised October 2011 bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for

Energy Harvester Applications

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Summary of content (17 pages)

PAGE 1
User's Guide SLUU654A – October 2011 – Revised October 2011 bq25504 EVM – Ultra Low Power Boost Converter with Battery Management for Energy Harvester Applications This user’s guide describes the bq25504 evaluation module (EVM), how to perform a stand-alone evaluation and allows the EVM to interface with the system and host. This EVM is programmed from the factory for settings compatible with most MCU’s and 3V coin cell batteries. The EVM is programmed to deliver a 3.
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Introduction 1 Introduction 1.1 EVM Features • • • • • • 1.2 www.ti.
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Introduction www.ti.com 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. Be sure to make note of the capacitor selection section when designing the EVM. Many of the IC's pin names start with a "V" and this "V" is removed on the EVM connector's label. The names are interchangeable.
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Performance Specification Summary 2 www.ti.com Performance Specification Summary See Data Sheet “Recommended Operating Conditions” for component adjustments. For details about the resistor programmable settings, see bq25504 data sheet (SLUSAH0). MIN NOM DC input voltage into VIN_DC VIN_Start-up(DC) DC minimum Start-up Voltage VOV Over Voltage – Sets maximum output voltage 2.9 3.1 3.3 V VUV Under voltage setting for shorting VSTOR to VBAT 2.1 2.2 2.
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Test Summary www.ti.com Load # 1 _ Meter # 4 + Meter # 2 - + Meter # 3 + - - + Meter # 1 P/S # 1 + - Jumper Figure 1. Test Setup for HPA674A (bq25504 EVM) 3.3 3.3.1 Test procedures Power-up With No Battery and 10kΩ Load on STOR 1. Connect a 20Ω resistor to J1-1, 10k resistor between J6-1 and J6-3 and place shunt on JP1-DIV. Connect meters and scope probes to monitor CH1→CH4: VPHASE(TP16), VSTOR, VP/S #1, VBAT.
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Test Summary www.ti.com Vstor Vbat Vphase Vp/s#1 Figure 2. Startup with no Battery and 10k Load 3.3.2 Power-up with Battery less than UV (less than a diode drop below UV) 1. Same setup, as 3.3.1, except move the probe on VBAT to VIN and apply a charge element set to 1.9VDC between BAT and GND. Arm scope to trigger on VP/S #1. 2. Set PS#1 to 1VDC and hot plug to input with 20Ω series resistor, see Figure 3.
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Test Summary www.ti.com Vstor Vin Vp/s#1 Vphase Figure 3. Startup with Battery Less Than UV 3.3.3 Power-up with Battery more than UV (2.3V to 3V), BAT FET ON 1. Same setup as 3.3.1, except change the charge element set to 2.4VDC between BAT and GND. Set scope to 2sec/div and to roll. 2. Set PS#1 to 1VDC and hot plug to input with 10Ω series resistor, see Figure 4. Note in Figure 4 that the BAT FET is on and the STOR output is powered prior to the input being applied.
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Test Summary 3.3.4 www.ti.com BAT_OK Indication as Battery Charges/Discharges 1. Connect scope probes CHI→CH4: VPHASE(TP16), VSTOR, VBAT_OK, VBAT and vary charge element from zero voltage to 3.15V and back down to 1.8V and observe the BAT_OK signal. Initially P/S#1 is set to 1V and the battery is adjusted to OV (simulated battery), which clamps VSTOR to ~0.5V (lower body diode drop due to lower current). As the battery voltage is swept higher one can see the different phases discussed earlier.
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Test Summary www.ti.com Vstor Vsource Vin Vphase Figure 6. Basic Switching Converter, Vin = 1V, Vbat = 2.5V Note here that VIN is regulating at the MPPT threshold so the boost circuit is delivering the maximum power that the source can deliver. The user can see after about 4 pulses that the switching waveforms stops which cause the inductor to go discontinuous and ring.
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Test Summary 3.3.6 www.ti.com Operation Near OV With 100-Ω Battery Impedance 1. Connect scope probes CHI→CH4: VPH(TP16), VSTOR, VIN, VBAT; set VP/S#1 to 1.3 VDC and VBAT to 3.00 VDC. Connect the power sources with their respective source impedance to the EVM. VIN source impedance should be 20Ω and the battery impedance should be 100Ω. Set VSTOR and VBAT to 20mVDC/div and 3.135VDC offset (3.135VDC was the average VBAT [OV] measurement), 1 ms/div. Turn on sources. 2.
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PCB Layout Guideline www.ti.com 4 PCB Layout Guideline 1. As with all switching power supplies, the 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 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.
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Bill of Materials, Board Layout and Schematics www.ti.com 5 Bill of Materials, Board Layout and Schematics 5.1 Bill of Materials Table 2. Bill of Materials Count RefDes Value Description Size Part Number MFR 2 C1, C2** 4.7uF Capacitor, Ceramic, 10V, X5R, 10% 0805 GRM219R61A475KE19D Murata 1 C3** 100uF Capacitor, Ceramic, 6.3V, X5R, 20% 1812 GRM43SR60J107ME20L Murata 2 C4, C6 0.1uF Capacitor, Ceramic, 50V, X7R, 10% 0603 Std Std 1 C5** 0.
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Bill of Materials, Board Layout and Schematics www.ti.com 5.2 EVM Board Layout TEXAS INSTRUMENTS Figure 8. EVM PCB Top Assembly Figure 9.
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Bill of Materials, Board Layout and Schematics www.ti.com Figure 10.
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Bill of Materials, Board Layout and Schematics www.ti.com 5.3 EVM Schematic Figure 11.
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Evaluation Board/Kit Important Notice Texas Instruments (TI) provides the enclosed product(s) under the following conditions: This evaluation board/kit is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY and is not considered by TI to be a finished end-product fit for general consumer use. Persons handling the product(s) must have electronics training and observe good engineering practice standards.
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IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.