LTC4124 Просмотр технического описания (PDF) - Analog Devices
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LTC4124 Datasheet PDF : 30 Pages
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LTC4124
OPERATION
The LTC4124 is a wireless single cell Li-Ion battery char-
ger. The part has three main components: a wireless
power manager, a full-featured linear battery charger and
an ideal diode PowerPath™ controller.
WIRELESS POWER MANAGER
A complete wireless power transfer system consists of
transmit circuitry with a transmit coil and receive circuitry
with a receive coil (Figure 1). The LTC4124 connected to
an LC tank creates a simple and complete receiver half of
the wireless power transfer system.
LTX LRX
COIL COIL
TRANSMITTER
+– VIN
CIRCUIT
LTC4124
RECEIVER
CIRCUIT
RL
AIR GAP
LOW COUPLING BETWEEN COILS
4124 F01
detection, temperature qualified safe charging and auto-
matic recharge. The charge voltage and charge current are
pin-strap programmable according to Table 2 and Table 3
shown in the Pin Functions section.
Figure 2 and Figure 3 show a typical charging cycle. As
soon as the voltage at the VCC pin reaches 3.4V, the char-
ger attempts to charge the battery and a charge cycle
is initiated. At the beginning of a charge cycle, when
the battery voltage is typically less than the recharge
threshold (97.6% of the final charge voltage), the char-
ger is in CC mode and charges the battery at the full
programmed current.
120
120
100
100
80
80
60
60
Figure 1. Wireless Power Transfer System
40
40
Refer to the Functional Block Diagram for the following
discussion. An external parallel resonant LC tank con-
nected to the ACIN pin allows the LTC4124 to receive
power wirelessly from an alternating magnetic field gener-
ated by a transmit coil. Diode D1 rectifies the AC voltage
at the ACIN pin. Comparator CP1, switch SW1 and switch
SW2 operate together to regulate the rectified voltage on
the VCC pin to between 0.85V and 1.05V above the voltage
on the BAT pin provided BAT ≥ 2.8V.
Operation with an Optional DC Voltage Source
The LTC4124 can alternately be powered from a DC volt-
age source connected to the DCIN pin. Diodes D1 and D2
set VCC to the maximum of the voltage on the DCIN pin
or the peak AC voltage on the ACIN pin. Therefore, the
DCIN pin supplies power to the VCC pin only if its voltage
is higher than instantaneous AC voltage on the ACIN pin.
BATTERY CHARGER
The LTC4124 includes a pin programmable full-featured
CC/CV (Constant Current/Constant Voltage) linear bat-
tery charger with safety timer termination, bad battery
20
20
CHARGE CURRENT
BATTERY VOLTAGE
0
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
TIME (HOURS)
4124 F02
Figure 2. Typical Charging Cycle at 0.5C Rate vs
Time with Pre-Charge Disabled
100
90
80
70
60
50
40
30
20
10
0
50
60
70
80
90
100 110
BATTERY VOLTAGE (% OF FINAL CHARGE VOLTAGE)
4124 F03
Figure 3. Typical Charge Current vs Battery Voltage
in a Charging Cycle with Pre-Charge Disabled
Rev. A
For more information www.analog.com
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