BQ24180 Datasheet, PDF (24/39 Pages) Texas Instruments – Fully Integrated Switch-Mode One-Cell Li-Ion Charger with Full USB Compliance and Accessory Power Connection

bq24180
SLUSA02 A – FEBRUARY 2010 – REVISED FEBRUARY 2010
www.ti.com
The bit of RESET in control register is used to reset all the charge parameters. Write ‘1” to RESET bit to
reset all the charge parameters to default values and RESET bit is automatically cleared to zero once the
charge parameters get reset. It is designed for charge parameter reset before charge starts and it is not
recommended to set RESET bit when charging or boosting in progress.
Output Inductor and Capacitor Selection Guidelines
The bq24180 provides internal loop compensation. With this scheme, best stability occurs when LC resonant
frequency, of, is approximately 40 kHz (20 kHz to 80 kHz). Equation 1 can be used to calculate the value of the
output inductor, L_OUT, and output capacitor, C_OUT.
1
¦_o =
2p ´ L_OUT ´ C_OUT
(1)
To reduce the output voltage ripple, a ceramic capacitor with the capacitance between 4.7µF and 47µF is
recommended for C_OUT, refer to the application section for components selection.
Selecting Current Sense Resistor
Both the termination current range and charge current range are depending on the sensing resistor (R_SNS). The
termination current step (I_{OTERM_STEP}) can be calculated using Equation 2:
I_{OTERM_STEP} =
V_{IT ERM 0}
R_SNS
(2)
Table 2 shows the termination current settings with two sensing resistors.
Table 2. Termination Current Settings for 68mΩ and 100mΩ Sense Resistors
BIT
V_ITERM2
V_ITERM1
V_ITERM0
Offset
V_ITERM (mV)
6.8
3.4
1.7
1.7
I_TERM (mA)
R_SNS = 68 mΩ
100
50
25
25
I_TERM (mA)
R_SNS = 100 mΩ
68
43
17
17
The charge current step (I_{OCHARGE_STEP}) can be calculated using Equation 3:
I_{OCHARG E_STEP}
=
V_{ICH R G0}
R _SNS
(3)
Table 3 shows the charge current settings with two sensing resistors.
Table 3. Charge Current Settings for 68 mΩ and 100 mΩ Sense Resistors
BIT
V_ICHRG3
V_ICHRG2
V_ICHRG1
V_ICHRG0
Offset
V_IREG (mV)
54.4
27.2
13.6
6.8
37.4
I_OCHARGE (mA)
R_SNS = 68 mΩ
800
400
200
100
550
I_OCHARGE (mA)
R_SNS = 100 mΩ
544
272
136
68
374
24
Submit Documentation Feedback
Product Folder Link(s): bq24180
Copyright © 2010, Texas Instruments Incorporated