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PDF L6924D Data sheet ( Hoja de datos )
| Número de pieza | L6924D | |
| Descripción | Battery charger system | |
| Fabricantes | STMicroelectronics | |
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L6924D
Battery charger system with integrated
power switch for Li-Ion/Li-Polymer
Features
■ Fully integrated solution, with a power
MOSFET, reverse blocking diode, sense
resistor, and thermal protection
■ Ideal for coke and graphite anode single-cell LI-
ION packs
■ Both linear and quasi-pulse operation
■ Closed loop thermal control
■ USB BUS-compatible
■ Programmable charge current up to 1 A
■ Programmable pre-charge current
■ Programmable end-of-charge current
■ Programmable pre-charge voltage threshold
■ Programmable charge timer
■ Programmable output voltage at 4.1 V and 4.2
V, with ± 1 % output voltage accuracy
■ (NTC) or (PTC) thermistor interface for battery
temperature monitoring and protection
■ Flexible charge process termination
■ Status outputs to drive LEDs or to interface
with a host processor
■ Small VFQFPN 16-leads package (3 x 3 mm)
Applications
■ PDAs
■ Handheld devices
■ Cellular phones
■ Digital cameras
■ Standalone chargers
■ USB-powered chargers
Table 1. Device summary
Order code
L6924D
L6924D013TR
Package
VFQFPN16
September 2010
Doc ID 11908 Rev 9
VFQFPN16
Packaging
Tube
Tape and reel
1/38
www.st.com
38
1 page  
L6924D
Pins description and connection diagrams
2 Pins description and connection diagrams
Figure 3. Pins connection (top view)
IPRE IPRG VPRE IEND
VIN
V
INSNS
ST2
ST1
VREF
VOUT
VOSNS
VOPRG
TPRG GND SD TH
2.1 Pin description
Table 2. Pin functions
Pin I/O Name
Pin description
1I
VIN Input pin of the power stage.
2
I
VINSNS
Supply voltage pin of the signal circuitry.
The operating input voltage ranges from 2.5 V to 12 V and the start-up threshold is 4 V.
3-4 O ST2-ST1 Open-collector status pins.
Maximum charging time program pin.
5 I TPRG It must be connected with a capacitor to GND to fix the maximum charging time, see
Chapter 7.8: Maximum charging time on page 20
6 - GND Ground pin.
7I
SD
Shutdown pin.
When connected to GND enables the device; when floating disables the device.
8I
Temperature monitor pin.
TH
It must be connected to a resistor divider including an NTC or PTC resistor. The charge
process is disabled if the battery temperature (sensed through the NTC or PTC) is out of the
programmable temperature window see Chapter 8.1: NTC thermistor on page 23.
9
I
VOPRG
Output voltage selection pin.
VOUT = 4.1 V if left floating. VOUT = 4.2 V if connected to GND.
10
I
VOSNS
Output voltage sense pin.
It senses the battery voltage to control the voltage regulation loop.
11 O VOUT Output pin. (connected to the battery)
Doc ID 11908 Rev 9
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5 Page 
L6924D
6 Operation description
Operation description
The L6924D is a fully integrated battery charger that allows a very compact battery
management system for space limited applications. It integrates in a small package, all the
power elements: power MOSFET, reverse blocking diode and the sense resistor.
It normally works as a linear charger when powered from an external voltage regulated
adapter. However, thanks to its very low minimum input voltage (down to 2.5 V) the L6924D
can also work as a Quasi-Pulse charger when powered from a current limited adapter. To
work in this condition, is enough to set the device’s charging current higher than the
adapter’s one (Chapter 7.4 on page 18). The advantage of the linear charging approach is
that the device has a direct control of the charging current and so the designer needn’t to
rely on the upstream adapter. However, the advantage of the Quasi-Pulse approach is that
the power dissipated inside the portable equipment is dramatically reduced.
The L6924D charges the battery in three phases:
● Pre-Charge constant current: in this phase (active when the battery is deeply
discharged) the battery is charged with a low current.
● Fast-Charge constant current: in this phase the device charges the battery with the
maximum current.
● Constant Voltage: when the battery voltage reaches the selected output voltage, the
device starts to reduce the current, until the charge termination is done.
The full flexibility is provided by:
● Programmable pre-charging current and voltage thresholds (IPRETH and VPRETH)
(Chapter 7.2 on page 17, Chapter 7.3 on page 17).
● Programmable fast-charging current (ICHG) (Chapter 7.4 on page 18).
● Programmable end of charge current threshold (IENDTH) (Chapter 7.5 on page 19).
● Programmable end of charge timer (TMAXCH) (Chapter 7.8 on page 20).
If the full flexibility is not required and a smaller number of external components is preferred,
default values of IPRETH and VPRETH are available leaving the respective pins floating.
● If a PTC or NTC resistor is used, the device can monitor the battery temperature in
order to protect the battery from operating in unsafe thermal conditions.
● Beside the good thermal behavior guaranteed by low thermal resistance of the
package, additional safety is provided by the built-in temperature control loop. The IC
monitors continuously its junction temperature. When the temperature reaches
approximately 120°C, the thermal control loop starts working, and reduces the charging
current, in order to keep the IC junction temperature at 120°C.
● Two open collector outputs are available for diagnostic purpose (status pins ST1 and
ST2). They can be also used to drive external LEDs or to interface with a
microcontroller.
The voltage across the resistor connected between IEND and GND gives information about
the actual charging current (working as a Gas Gauge), and it can be easily fed into a µC
ADC.
Doc ID 11908 Rev 9
11/38
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet L6924D.PDF ] | |
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