BQ24640 Datasheet, PDF (16/25 Pages) Texas Instruments – High-Efficiency Synchronous Switch-Mode Super Capacitor Charger

bq24640
SLUSA44 – MARCH 2010
www.ti.com
PG OUTPUT
The open drain PG (power good) output indicates when the VCC voltage is present. The open drain FET turns
on whenever bq24640 is not in UVLO mode and not in SLEEP mode (i.e., V(VCC) > V(SRN) and V(VCC) >
V(UVLO)). The PG pin can be used to drive an LED or communicate to the host processor.
CHARGE STATUS OUTPUTS
The open-drain STAT output indicates various charger operations as shown 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
CHARGE STATE
CE high
Sleep mode
Charge Suspend (TS), Input or Output Over-voltage, CE low
STAT
ON
OFF
Blinking
Inductor, Capacitor, and Sense Resistor Selection Guidelines
The bq24640 provides internal loop compensation. With this scheme, best stability occurs when the LC resonant
frequency, f_o, is approximately 12kHz–17kHz. Table 3 provides a summary of typical LC components for various
charge currents.
See INDUCTOR SELECTION section for infomation on controlling ripple current.
Table 3. Typical Inductor, Capacitor, and Sense Resistor Values as a Function of Charge Current
Charge Current
Output Inductor Lo
Output Capacitor Co
Sense Resistor
2A
10 µH
15 µF
10 mΩ
4A
6.8 µH
20 µF
10 mΩ
6A
4.7 µH
30 µF
10 mΩ
8A
3.3 µH
40 µF
10 mΩ
10A
3.3 µH
40 µF
10 mΩ
16
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