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| BQ24296_15 Datasheet, PDF (41/55 Pages) Texas Instruments – bq2429x I2C Controlled 3-A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG | |||
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Typical Application (continued)
bq24296, bq24297
SLUSBP6B â SEPTEMBER 2013 â REVISED NOVEMBER 2014
5V USB SDP/DCP
USB
1μF
8.2μF
SYS
bq24297
VBUS
SW
PMID
BTST
D+
REGN
Dâ
PGND
1μH
47nF
4.7μF
SYS: 3.5V-4.35V
10μF 10μF
2.2kW
STAT
SYS
317W(1.5A max)
BAT
VREF
ILIM
QON
10μF
Optional
4.2V
Host
10kW 10kW 10kW
SDA
SCL
INT
TS
OTG
CE
Power Pad
REGN
5.25kW
31.23kW
10kW
Charge Enable (0°C - 45°C)
Figure 41. bq24297 with USB D+/D- Detection, USB On-The-Go (OTG) and Optional BATFET Enable
Interface
10.2.1 Design Requirements
Table 19. Design Requirements
DESIGN PARAMATER
Input voltage range
Input current limit
Fast charge current
Boost mode output current
EXAMPLE VALUE
3.9 V to 6.2 V
3000 mA
3000 mA
1.5 A
10.2.2 Detailed Design Procedure
10.2.2.1 Inductor Selection
The device has 1.5-MHz switching frequency to allow the use of small inductor and capacitor values. The
Inductor saturation current should be higher than the charging current (ICHG) plus half the ripple current (IRIPPLE):
( ) ISAT ³ ICHG + 1/ 2 IRIPPLE
(4)
The inductor ripple current depends on input voltage (VBUS), duty cycle (D = VBAT/VVBUS), switching frequency
(fs) and inductance (L):
IRIPPLE
=
VIN
´ D ´ (1- D)
¦s ´ L
(5)
The maximum inductor ripple current happens with D = 0.5 or close to 0.5. Usually inductor ripple is designed in
the range of (20 â 40%) maximum charging current as a trade-off between inductor size and efficiency for a
practical design.
Copyright © 2013â2014, Texas Instruments Incorporated
Product Folder Links: bq24296 bq24297
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