AN2726
Application note
Evaluation board user guidelines for the
STw4102 single Li-Ion cell battery charger including gas gauge
1
Introduction
This application note describes the STEVAL-ISB006V1, an evaluation board specifically
designed for the STw4102 battery management integrated circuit.
This document provides:
●
a brief description of the STw4102
●
a description of the evaluation board
●
a detailed bill of materials of the evaluation board
●
the layout of the evaluation board.
Figure 1.
July 2008
STw4102 evaluation board
Rev 1
1/10
www.st.com
About the STw4102
2
AN2726
About the STw4102
The STw4102 is a standalone constant-current, constant-voltage (CCCV) linear charger
dedicated to Li-Ion batteries. The device has a dual charging capability that uses the main
input adaptor (wall or car adapter) or a USB cable with no external component.
The STw4102 offers a programmable fast-charge current using an external resistor. The
thermal regulation circuitry limits the charge current so that the die junction temperature
never exceeds the maximum specified value. An end-of-charge output pin indicates the
charge termination when the fast charge current drops below 10% of the programmed
current value.The STw4102 contains an accurate gas-gauge based on a 13-bit AD
converter. An external resistor is used between the battery and ground pin to sense a
charge/discharge current. With a typical 30 mΩ resistor, the current can be up to 2.5 A and
the 24-bit accumulator system provides a capacity of up to 914 mA.h.
The STw4102 has the following key features.
■
Constant-current constant-voltage (CCCV) linear charger.
■
Common or separate USB/wall adapter inputs.
■
Fast-charge current control up to 1 A for wall adapters and up to 500 mA for USB.
■
Support for currents higher than 1 A using external components.
■
Programmable charge voltage (4.1 V, 4.2 V, 4.3 V, 4.35 V) with 1% accuracy.
■
Thermal regulation.
■
Trickle-charge mode at low battery voltage.
■
Wall adapter voltage up to 13 V.
■
Battery over-voltage protection at 4.7 V.
■
Gas gauge with 13-bit AD converter.
■
Battery voltage monitor with 7- to 12-bit AD converter.
■
I²C interface for device monitoring and control.
■
Charge status output pin.
■
Power detection output pin.
■
Programmable watchdog security timer.
■
4.7 V LDO regulator (with external power MOSFET).
Figure 2 describes the application schematics, with the typical connections and peripheral
components surrounding the charger IC.
2/10
AN2726
About the STw4102
Figure 2.
Typical application for the STw4102
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Refer to the datasheet for more detailed information on the STw4102.
3/10
Description of the demonstration board
3
AN2726
Description of the demonstration board
The STEVAL-ISB006V1 is a demonstration board designed to help you evaluate the
performances of the STw4102.
This section explains how to evaluate the battery charger and the current gauge in a typical
application configuration.
Figure 3.
Demonstration board schematic diagram
1
MAIN
DRV
C5
100nF/16V/X7R
IC1
1
3
1
MAIN
VOUT
Driver
USB
4
1
USBPWR
SENSE
24
1
R2
BATT
1
10K
22
8
BATTSENSE
EOCHG
ISET
CVREF
C2
1uF/6.3V/X5R
6
16
SDA
M2A
STS2DPFS20V
1
15
R4
10K
RST
STDBY
SDA
RESETN
Epad
1
ICG+
1
PHONE
1
C3
22uF/6.3V/X5R
4/10
M1
STT4PF20V
ICG-
1
BSENSE
7
10
1
GNDBATT
13
14
1
1
11
12
1
C32
STBY
CG+
R3
R033 +/-1% 0805
1
TEST
C4
22uF/6.3V/X5R
ISET
R1
12K +/-1%
S2
0R
1
GND
1
21
SCL
TEST
17
1
VIO
23
SCL
18
BATT
C1
1uF/6.3V/X5R
C32kHz
C7
100nF/16V/X7R
SENSE
20
LDOFB
1
GND
VIO
1
LDODRV
9
M2B
STS2DPFS20V
19
1
STw4102
CV IS
5
VOUT
Vbat
PWRDETECTN
Vbat
EOCH
1
S1
0R
C6
100nF/16V/X7R
PWRDT
2
CG-
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Table 1.
Description of the demonstration board
Evaluation board bill of materials
Component
Part type
Footprint
Description
Manufacturer
Reference
IC1
STw4102
QFN24
Dual-source Li-Ion charger
with gas gauge
STMicroelectronics STw4102
C1
1µF/6.3V/X5R
0402
Internal supply decoupling
capacitor
Taiyo Yuden
JMK105BJ105KV
C2
1µF/6.3V/X5R
0402
Voltage reference decoupling
Taiyo Yuden
capacitor
JMK105BJ105KV
C3
22µF/6.3V/X5R
0805
Phone supply decoupling
capacitor
Taiyo Yuden
JMK212BJ226KG
C4
22µF/6.3V/X5R
0805
Battery decoupling capacitor Taiyo Yuden
JMK212BJ226KG
C5
100nF/16V/X7R 0402
Main supply decoupling
capacitor
Taiyo Yuden
EMK105BJ104KV
C6
100nF/16V/X7R 0402
USB supply decoupling
capacitor
Taiyo Yuden
EMK105BJ104KV
C7
100nF/16V/X7R 0402
Digital supply decoupling
capacitor
Taiyo Yuden
EMK105BJ104KV
M1
STT4PF20V
External LDO P-Mosfet
STMicroelectronics STT4PF20V
M2
STS2DPFS20V SO8
External LDO P-Mosfet and
Schottky diode
STMicroelectronics STS2DPFS20V
R1
12K ±1%
0402
Rset resistor for fast charge
current setting
R2
10K ±1%
0402
PWRDETECTN pull-up
resistor
R3
R033 ±1%
0805
Gas gauge shunt resistor
R4
10K ±1%
0402
RESETN pull-up resistor
S1
0R
0402
Strap
S2
0R
0402
Strap
Note:
SOT23-6
Phycomp
235051117330
The M1 and M2 components (two external P-Mosfets plus a Schottky diode) are not
mounted on the standard configuration of the demoboard. They can be added at a later
stage to test the external LDO feature.
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Evaluation board layout
4
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Evaluation board layout
The evaluation board’s printed circuit board has the following characteristics.
●
Board dimensions: 22.7 mm x 17 mm.
STw4102 and peripheral components PCB area: 12.4 mm x 7.5 mm (0.93 cm2or
0.14 inch2):
●
4-layer PCB, FR4 material
●
PCB thickness: 0.8 mm, copper thickness: 18 µm
These standards are similar to the ones used by portable equipment manufacturers.
6/10
Figure 4.
Demonstration board (top view)
Figure 5.
Demonstration board (bottom view)
AN2726
Evaluation board layout
Figure 6.
Internal layers of the demonstration board
Figure 7.
Single-connector application typical schematic
Power Detected
Charging
(if R1 removed)
VBUS
Vio
System
Controller
| Battery +
Gnd
Gnd
7/10
Evaluation board layout
Figure 8.
AN2726
Dual-connector application typical schematic
Power Detected
Charging
(if R1 removed)
VBUS
Gnd
Vio
System
Controller
8/10
Gnd
| Battery +
Vdc
Gnd
Adapter
(5V DC)
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5
Revision history
Revision history
Table 2.
Document revision history
Date
Revision
10-Jul-2008
1
Changes
Initial release.
9/10
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