BQ24180 Datasheet, PDF (16/39 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
Regulation
voltage
Precharge
Phase
Regulation
Current
Current Regulation
Phase
Voltage Regulation
Phase
VSHORT
Charge Voltage
Charge Current
Termination
ISHORT
Precharge
(Linear Charge)
Fast Charge
(PWM Charge )
(a) Without input current limit (default when PSEL = 1)
Precharge
Phase
Regulation
voltage
Current Regulation
Phase
Voltage Regulation
Phase
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VSHORT
Charge Voltage
Charge Current
Termination
ISHORT
Precharge
(Linear Charge)
Fast Charge
(PWM Charge)
(b) With input current limit (default when PSEL = 0)
Figure 27. Typical Charging Profile of bq24180
PWM Controller in Charge Mode
The bq24180 provides an integrated, fixed 3 MHz frequency voltage-mode controller with Feed-Forward function
to regulate charge current or voltage. This type of controller is used to help improve line transient response,
thereby simplifying the compensation network used for both continuous and discontinuous current conduction
operation. The voltage and current loops are internally compensated using a Type-III compensation scheme that
provides enough phase margin for stable operation, allowing the use of small ceramic capacitors with very low
ESR. There is a 0.5V offset on the bottom of the PWM ramp to allow the device to operate between 0% to 99.5%
duty cycles.
The bq24180 has two back to back common-drain N-channel MOSFETs at the high side and one N-channel
MOSFET at low side. An input N-MOSFET (Q1) prevents battery discharge when VBUS is lower than V_{VBUS (MIN)}.
The second high-side N-MOSFET (Q2) behaves as the switching control switch (see Figure 1). A charge pump
circuit is used to provide gate drive for Q1, while a boot strap circuit with external boot-strap capacitor is used to
boost up the gate drive voltage for Q2.
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