BQ24650 Datasheet, PDF (17/33 Pages) Texas Instruments – Synchronous Switch-Mode Battery Charge Controller for Solar Power With Maximum Power Point Tracking

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RT1 =
V_{VR EF}
V_{LT F}
-1
1
1
+
RT2 RTH_{CO LD}
VREF
bq24650
TS
RT1
RT2
RTH
103AT
bq24650
SLUSA75 – JULY 2010
(8)
Figure 18. TS Resistor Network
CHARGE ENABLE
MPPSET is used to disable or enable the charge process. A voltage above 175mV on this pin enables charge,
provided all other conditions for charge are met (see the Enabling and Disabling Charge section). A voltage
below 75mV on this pin also resets all timers and fault conditions.
INDUCTOR, CAPACITOR, AND SENSE RESISTOR SELECTION GUIDELINES
The bq24650 provides internal loop compensation. With this scheme, the best stability occurs when the LC
resonant frequency, f_o, is approximately 12kHz – 17kHz for the bq24650.
Table 1 provides a summary of typical LC components for various charge currents.
Table 1. Typical Inductor, Capacitor, and Sense Resistor Values as a Function of Charge Current
CHARGE CURRENT
Output inductor low
Output capacitor C_O
Sense resistor
0.5A
22 µH
7 µF
80 mΩ
1A
15 µH
10 µF
40 mΩ
2A
10 µH
15 µF
20 mΩ
4A
6.8 µH
20 µF
10 mΩ
8A
3.3 µH
40 µF
5 mΩ
10A
3.3 µH
40 µF
4 mΩ
CHARGE STATUS OUTPUTS
The open-drain STAT1 and STAT2 outputs indicate various charger operations as listed in Table 2. These status
pins can be used to drive LEDs or communicate with the host processor. Note that OFF indicates that the
open-drain transistor is turned off.
Table 2. STAT Pin Definition for bq24650
CHARGE STATE
Charge in progress
Charge complete
Charge suspend, over-voltage, sleep mode, battery absent
STAT1
ON
OFF
OFF
STAT2
OFF
ON
OFF
Copyright © 2010, Texas Instruments Incorporated
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