OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

LTC4125EUFD#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28
LTC4125
7
4125f
For more information www.linear.com/LTC4125
pin FuncTions
STAT (Pin 8): Open Drain Status Pin. This pin pulls low
when the part is delivering power. When connected to an
LED, this pin provides a visual indicator that the LTC4125 is
delivering power to a valid resonant receiver. The STAT pin
is high-impedance during a fault condition or if no receiver
is detected during the most recent transmit power sweep.
FTH (Pin 9): Frequency Threshold Input. This pin is used
to program the primary foreign object detection method.
Connect this pin to the center tap point of a resistor di
-
vider between IN and GND to set the maximum expected
transmit LC resonant frequency value (see Applications
Information for programming details). A resonant driving
frequency exceeding the programmed value indicates the
presence of a large conductive object in the field space
generated by the transmit coil. Such a condition reduces
the apparent inductance of the LC tank resulting in a higher
driving frequency. Transmitting into a foreign conductive
object may result in TX power overload and/or exces
-
sive heating of the foreign object. If a frequency fault is
detected, power delivery will immediately stop until the
next transmit power search.
PTH2 (Pin 10): Pulse Width Threshold Two Pin. The posi
-
tive pulse width waveform on the SW2 pin is proportional
to the voltage on this pin.
PTH1
(Pin 11): Pulse Width Threshold One Pin. The posi
-
tive pulse width waveform on the SW1 pin is proportional
to the voltage on this pin.
PTHM (Pin 12): Minimum Driver Pulse Width Input. The
voltage value on this pin determines the minimum driver
pulse width value used in the transmit power search. The
driver pulse width corresponds to transmit power. Shorting
this pin to GND sets the pulse width of the first step in the
search to 1/32 of the natural period of the transmitting LC
tank. A faster transmit power search can be implemented
when it is known that low transmit power (corresponding
to the 1/32 period pulse width) is not sufficient to meet
the requirements of the receiver load. Connect the pin to
the center tap point of a resistor divider between IN and
GND (See Applications Information) to program a larger
minimum pulse width.
FB (Pin 13): Resonance Feedback Voltage. Connect this
pin to the center tap point of a resistor divider between
the rectified peak voltage generated in the series LC tank
and GND (see Applications Information). The voltage on
the FB pin is monitored during the transmit power search
to determine when the load requirements of the receiver
have been met or exceeded. Short this pin to GND to dis
-
able the internal auto load detection feature.
CTD (Pin 14):
Transmit Power Search Delay Time Capacitor.
Attach a capacitor from the CTD pin to GND to program
the delay time between each cycle of an optimum transmit
power search. Recommended delay times are typically 1s
or greater. See Applications Information for programming
instructions. Short to GND to stop search after the first
cycle or leave open to default to a minimum delay time
(~20ms) between search intervals.
EN (Pin 15): Enable Input Pin. Drive this pin above 1.22V
(typ) to disable the AutoResonant driver. The SW1 and
SW2 pins default low when driver is disabled. Leave the
EN pin open or shorted to GND when disable function is
not used.
GND (Pin 16, Exposed Pad Pin 21): Device Ground.
Connect this ground pin to a suitable PCB copper ground
plane for proper electrical operation and rated thermal
performance.
IN2 (Pin 17): Input Supply Voltage: 3V to 5.5V. Supplies
power to the second half of the full bridge drivers. A local
47µF bypass capacitor to GND is recommended on this pin.
SW2 (Pin 18): Switch 2 Pin. This pin is the center node
of the second half of the full bridge switches. Connect a
series LC network between this pin and the SW1 pin for
full bridge operation.
SW1 (Pin 19): Switch 1 Pin. This pin is the center node of
the first half of the full bridge switches. Connect a series LC
network between this pin and the SW2 pin for full bridge
operation. Connect a series LC network between this
pin and GND when only half bridge operation is desired.
Maximum transmit power available is higher with full
bridge operation.
IN1 (Pin 20): Input Supply Voltage: 3V to 5.5V. Supplies
power to the first half of the full bridge drivers. A local
47µF bypass capacitor to GND is recommended on this pin.
LTC4125
8
4125f
For more information www.linear.com/LTC4125
FuncTional block DiagraM
C
TS
C
TD
C
IN
R
FB2
C
FB2
C
FB1
3V TO 5.5V
V
IN
R
STAT
V
IN
LOGIC
SW
DRIVER
4125 BD
+
–
+
–
+
–
A/D
A/D
A1
A2
A3
A5
A4
D/A
D/A
+
–
TOO HOT
V
IN
V
IN
V
IN
A/D
V
IN
V
IN
V
IN
V
IN
10MΩ
V
IN
10MΩ
10MΩ
FB
MAXREF
RESONANT
FEEDBACK
INT OSC
DIE TEMP
SENSOR
BG
STARTUP
EXT OSC
PULSE WIDTH
MODULATOR
FREQUENCY
TO VOLTAGE
CONVERTER
I
LIMREF
V
IN
R
DTH1
R
DTH2
V
IN
V
IN
R
FTH1
R
FTH2
V
IN
R
NTC1
R
NTC2
V
TANK
R
FB1
10MΩ
C
IMON
R
IMON
C
IF
R
IS
R
IN
V
TANK
C
TX
C
IN1
L
TX
D
C
B
A
C
IN2
R
PTHM1
R
PTHM2
V
IN
I
LIMREF
D
FB
11
PTH1
9
FTH
20
IN1
19
SW1
18
SW2
17
IN2
10
PTH2
13
FB
15
EN
8
STAT
16
GND
12
PTHM
7
DTH
6
NTC
5
IMON
4
IS
+
3
IS
–
2
CTS
14
CTD
1
IN
A6
I
IN
LTC4125
9
4125f
For more information www.linear.com/LTC4125
operaTion
INTRODUCTION
A wireless power system is composed of two parts sepa-
rated by an air gap: transmit circuitry with a transmit coil,
and receive cir
cuitr
y with a receive coil. The LTC4125 is the
power controller for a simple but versatile wireless power
transmitter. The LTC4125 enhances a basic wireless power
transmitter by providing three key features: an AutoReso
-
nant function that maximizes available receiver power, an
Optimum Power Sear
ch algorithm that maximizes overall
wireless power system efficiency and foreign object detec
-
tion to ensure safe and reliable operation when working
in the
presence of conductive foreign objects. In order to
understand these features, an overview of wireless power
systems is required.
In a typical wireless power system, an AC magnetic field
is generated by a transmit coil which then induces an
AC current in the receive coil—like a typical transformer
system. The main difference between a transformer sys
-
tem and a wireless power system is that an air gap (or
other non-magnetic material gap
)
separates the primary
(transmitter) and secondary (receiver). Furthermore, the
coupling between the transmit and the receive coils is typi
-
cally very low. Whereas a coupling of 0.95 to 1 is common
in a transformer system,
the coupling coefficient in the
wireless power system varies from 0.8 to as low as 0.05.
+
–
R
L
V
IN
L
TX
COIL
L
RX
COIL
LTC4125
TRANSMITTER
CIRCUIT
RECEIVER
CIRCUIT
4125 F01
AIR GAP
LOW COUPLING BETWEEN COILS
Figure1. Typical Wireless Power System Setup
In order to induce enough AC current in the receive coil
with such low coupling, a strong magnetic field is needed.
Since the magnetic field generated by the transmit coil is
proportional to the current flowing in the coil, a large AC
current needs to be generated in the transmit coil.
There are various ways of producing a large AC current in
an inductor from a DC voltage. The LTC4125 is designed
to employ one of the simplest and most efficient methods
using a series LC resonant circuit.
SERIES RLC
R
C
V
a
sinωt V
L
L
I
L
4125 F2
I
a
sin(ωt + θ)
+
–
Figure2. Simple Series Resonant RLC Circuit
Figure2 shows a simple series resonant circuit. When
driven with a sinusoid voltage at the resonant frequency
the impedance of the inductor and the capacitor cancels
leaving a pure resistance R. The resonant frequency can
be calculated as:
f
n
=
1
2
π
LC
Therefore at resonance the amplitude of current developed
in the inductor is simply:
I
a
=
V
a
R
Notice that at resonance, with a low enough R value, a
significant amount of inductor current can be generated.
Furthermore, the inductor voltage is proportional to the
driving voltage:
V
L
= I
a
• ω
n
L = V
a
•
ω
n
L
R
= QV
a
where Q is the familiar quality factor of the series tank.
The LTC4125 enables a series LC to be driven at exactly
its resonant frequency with ease. It uses a patent pending
AutoResonant method to automatically detect the resonant
frequency of the series LC connected to its switch pins
and drive it at that frequency.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P28

LTC4125EUFD#PBF

Mfr. #:
Buy LTC4125EUFD#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Wireless Charging ICs 5W AutoResonant Wireless Pwr Transmitter
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet