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User's Guide

SLVU473–May 2011

1A, Single Cell LiFePO

Linear Battery Charger with 4.9 V,

50 mA LDO

This user’s guide describes the bq25070 evaluation module (EVM), how to perform a stand-alone

evaluation or interface with a host or system. The converter is designed to deliver up to 1 A of continuous

current to the battery and/or system. The device has a 4.9 VDC, 50 mA max internal LDO that can be

used for USB applications or any other need.

Contents

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

2 Considerations With Evaluating the bq25070 ........................................................................... 2

3 Performance Specification Summary ..................................................................................... 2

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

4.1 Equipment ........................................................................................................... 3

4.2 Equipment and EVM Setup ....................................................................................... 3

4.3 Test Procedure ..................................................................................................... 5

5 Schematic, Physical Layouts and Bill of Materials ..................................................................... 7

5.1 Schematic ........................................................................................................... 7

5.2 Physical Layouts ................................................................................................... 9

5.3 Bill of Materials .................................................................................................... 11

List of Figures

1 EVM Schematic and Evaluation SetupTop Schematic: Application CircuitBottom Circuit: Hardware

Evaluation/Test Circuit to Generate Pulses to Program IC, done by host in Typical Application................. 4

2 Pulse Programming – CH2: 11 pulses; CH1: V

OUT

IR change due to increased charge current.................. 6

3 Battery cell Replacement – Allows quick battery adjustment ......................................................... 6

4 bq25070 EVM Board Schematic (Sheet 1 of 2)......................................................................... 7

5 bq25070 EVM Board Schematic (Sheet 2 of 2)......................................................................... 8

6 Assembly Layer ............................................................................................................. 9

7 Top Layer .................................................................................................................... 9

8 Bottom Layer............................................................................................................... 10

SLVU473–May 2011 1A, Single Cell LiFePO

Linear Battery Charger with 4.9 V, 50 mA LDO

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Summary of content (13 pages)

PAGE 1
User's Guide SLVU473 – May 2011 1A, Single Cell LiFePO4 Linear Battery Charger with 4.9 V, 50 mA LDO This user’s guide describes the bq25070 evaluation module (EVM), how to perform a stand-alone evaluation or interface with a host or system. The converter is designed to deliver up to 1 A of continuous current to the battery and/or system. The device has a 4.9 VDC, 50 mA max internal LDO that can be used for USB applications or any other need. 1 2 3 4 5 Contents Introduction ............................
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Introduction 1 www.ti.com Introduction The bq25070 is a highly integrated LiFePO4 linear battery charger targeted at space-limited portable applications. It operates from either a USB port or AC Adapter and charges a single-cell LiFePO4 battery with up to 1 A of charge current. The 30 V maximum input voltage rating with 10.5 V input overvoltage protections supports low-cost unregulated adapters. The bq25070 has a single power output that charges the battery and powers the system.
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Test Summary www.ti.com 4 Test Summary The bq25070EVM-740 board requires an adjustable 5 VDC, ≥ 1250 mA Current Limited power source to provide input power and a LiFePO4 battery as a load. The test setup connections and jumper settings selections are configured for a stand-alone evaluation, but can be changed to interface with external hardware such as a microcontroller. 4.1 Equipment • • • • • 4.2 Adjustable dc power supply with current meter, set between 5.1 V and 5.
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Test Summary www.ti.com Connect the meters, scope probes, output loads, shunt, and input power supply as listed in Table 1 and set scope to 2 ms/div, single sequence positive trigger; CH1 set to 500 mV/div and CH2 to 2 V/div; DC coupled on CH1 and CH2. The circuit on this sheet is typically not part of the charger design. This circuit generates the pulses to program the charge, which is normally done by the host. Use only one Shunt on JP101 through JP113. Place shunt according to desired program pluses.
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Test Summary www.ti.com 4.3 Test Procedure 1. Make sure that the EVM is set up according to Table 1 and Figure 1, and the power supply is preset to 5.1 VDC at ~1250 mA current limit. 2. Turn on input supply and verify the power supply current meter is between 0.26 A and 0.31 A. Note that this is a linear charger so the input current is approximately the output current minus any current going to VLDO.
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Test Summary www.ti.com V_Out CTRL_Pulses Figure 2. Pulse Programming – CH2: 11 pulses; CH1: VOUT IR change due to increased charge current. Figure 3. Battery cell Replacement – Allows quick battery adjustment The P/S input to the right sets the BAT+ to BAT– voltage one diode drop below V_P/S, R1 and R2 typically sink more than the charge current allowing the BAT+ voltage to drop unless pulled up by the P/S source thus allowing the P/S to set the battery voltage.
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Schematic, Physical Layouts and Bill of Materials www.ti.com 5 Schematic, Physical Layouts and Bill of Materials 5.1 Schematic Figure 4. bq25070 EVM Board Schematic (Sheet 1 of 2) SLVU473 – May 2011 Submit Documentation Feedback 1A, Single Cell LiFePO4 Linear Battery Charger with 4.
PAGE 8
Schematic, Physical Layouts and Bill of Materials www.ti.com The circuit on this sheet is typically not part of the charger design. This circuit generates the pulses to program the charge, which is normally done by the host. Use only one Shunt on JP101 through JP113. Place shunt according to desired program pluses. The 100 numbered components are part of the hardware for creating the programming pulses and are not typically part of an application. Figure 5.
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Schematic, Physical Layouts and Bill of Materials www.ti.com 5.2 Physical Layouts Figure 6. Assembly Layer Figure 7. Top Layer SLVU473 – May 2011 Submit Documentation Feedback 1A, Single Cell LiFePO4 Linear Battery Charger with 4.
PAGE 10
Schematic, Physical Layouts and Bill of Materials www.ti.com Figure 8. Bottom Layer 10 1A, Single Cell LiFePO4 Linear Battery Charger with 4.
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Schematic, Physical Layouts and Bill of Materials www.ti.com 5.3 Bill of Materials Table 2. HPA740A Bill of Materials Count RefDes Value Description Size Part Number MFR 2 C1, C5 0.1 µF Capacitor, Ceramic, 25V, X7R, 10% 1206 Std Std 0 C2, C4 Open Capacitor, Ceramic, 25V, X7R, 10% 1206 Std Std 1 C3 1 µF Capacitor, Ceramic, 6.3V, X5R, 20% 0805 Std Std 1 C6 0.
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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.