BQ25060_1 Datasheet, PDF (17/24 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion Battery Charger with 50-mA LDO, and External Power Path Control

bq25060
www.ti.com
SLUSA32 – MAY 2010
APPLICATION INFORMATION
Selection of Input/ Output Capacitors
In most applications, all that is needed is a high-frequency decoupling capacitor on the input power pin. For
normal charging applications, a 0.1µF ceramic capacitor, placed in close proximity to the IN pin and GND pad
works best. In some applications, depending on the power supply characteristics and cable length, it may be
necessary to increase the input filter capacitor to avoid exceeding the OVP voltage threshold during adapter hot
plug events where the ringing exceeds the deglitch time.
The charger in the bq25060 requires a capacitor from OUT to GND for loop stability. Connect a 1µF ceramic
capacitor from OUT to GND close to the pins for best results. More output capacitance may be required to
minimize the output droop during large load transients. Connect a 0.1µF ceramic capacitor from BAT to GND to
eliminate the potential ESD strike.
The LDO also requires an output capacitor for loop stability. Connect a 0.1µF ceramic capacitor from LDO to
GND close to the pins. For improved transient response, this capacitor may be increased.
bq25060 Charger Design Example
The following sections provide an example for determining the component values for use with the bq25060.
Requirements: Refer to Figure 1 and Figure 2 for Schematics of the Design Example.
• Supply voltage = 4.35~10.2V
• Input current limit is 0.5A
• Set 0°C~45°C operating range
Calculations
Input Current Limit Control (EN): Drive EN low to program the input current limit to the user defined value
programmed using ISET. See Table 1 for other detail EN pin options.
Program the input current Iimit (ISET): Connect a resistor, RISET, from ISET to VSS to program the input
current. The RISET is determined by:
R_ISET
=
K_ISET
I_{IN_LIMIT}
= ^{1000A ´ W}
I_{IN_LIMIT}
= 2000W
(5)
Set 0°C to 45°C charger operating temperature range (TS): The value of R1 and R2 are:
R2 =
-RHOT ´ RCOLD ´ (0.125 - 0.250)
= 11.3kW
RHOT ´ 0.250 ´ (0.125 - 1) + RCOLD´ 0.125 ´ (1 - 0.250)
(6)
R1 = ^{-R2 ´ RHOT ´ (0.125 - 1)} = 24.0kW
0.125 ´ (R2 + RHOT)
(7)
RHOT: 4.911kΩ, the resistor value of Semitec NTC 103AT-2 at 45°C;
RCOLD: 27.28kΩ, the resistor value of Semitec NTC 103AT-2 at 0°C.
External FET Controller (BGATE): On Figure 1, BGATE drives an external P-channel FET that connects the
battery to the system output. When power is first applied to either VBAT or VIN, the device sources a typical
50µA small current out of BGATE and monitors the voltage. If BGATE voltage is higher than logic high in first
1ms and stays high for at least 2ms, the external power path control feature is enabled and VLOWV is set to
2.9V. The OUT pin maintains voltage at VOUT(REG).
In Figure 2, BGATE is connected to Vss. The external power path control feature is disabled and VLOWV is set
to 2.5V. The OUT pin shorts to BAT.
Status Indicators (CHG): The CHG pin is open drain output. If used, CHG pin should be pulled up via a resistor
and possibly a LED to a power source. If monitored by a host, the host pull-up power source should be used.
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): bq25060
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