BQ24620 Datasheet, PDF (20/30 Pages) Texas Instruments – Stand-Alone Synchronous Switch-Mode Lithium Phosphate Battery Charger with Low Iq

bq24620
SLUS893 – MARCH 2010
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CE (Charge Enable)
The CE digital input is used to disable or enable the charge process. A high-level signal on this pin enables
charge, provided all the other conditions for charge are met (see Enabling and Disabling Charge). A high to low
transition on this pin also resets all timers and fault conditions. There is an internal 1 MΩ pulldown resistor on the
CE pin, so if CE is floated the charge will not turn on.
INDUCTOR, CAPACITOR, AND SENSE RESISTOR SELECTION GUIDELINES
The bq24620 provides internal loop compensation. With this scheme, best stability occurs when the LC resonant
frequency, f_o, is approximately 10kHz – 15kHz per Equation 7:
1
f_o =
2p L_o C_o
(7)
Table 2 provides a summary of typical LC components for various charge currents
Table 2. Typical Inductor, Capacitor, and Sense Resistor Values as a Function of Charge Current
CHARGE CURRENT
Output Inductor Lo
Output Capacitor Co
Sense Resistor
2A
8.2 mH
20 mF
10 mΩ
4A
8.2 mH
20 mF
10 mΩ
6A
5.6 mH
20 mF
10 mΩ
8A
4.7 mH
40 mF
10 mΩ
10A
4.7 mH
40 mF
10 mΩ
CHARGE STATUS OUTPUTS
The open-drain STAT outputs indicate various charger operations as shown in Table 3. 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 3. STAT Pin Definition for bq24620
CHARGE STATE
Charge in progress
Charge complete (PG=LOW)
Sleep mode (PG=HIGH)
Charge suspend, timer fault, ACOV, battery absent
STAT
ON
OFF
OFF
BLINK (0.5 Hz)
20
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